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    2019,24(6):663-677 , DOI: 10.3878/j.issn.1006-9585.2018.18052
    Abstract:
    The spatial and temporal changes in net primary productivity (NPP) during 1901-2005 were studied using six earth system models. The relationship between NPP changes and the climatic factors of air temperature and precipitation was analyzed. The results show that: (1) In the past 100 years, the global NPP has shown an upward trend. The trend coefficient of the ensemble model average is 0.88, which passes the 99.9% confidence test. The trend in the Northern Hemisphere is more pronounced than in the Southern Hemisphere. (2) In the past 100 years, high NPP values of 800 g(C) m-2 a-1 or higher are mainly distributed in tropical rainforest areas in the equatorial regions of South America, Equatorial Africa, the Indochina Peninsula, and Indonesia. Low NPP values are mainly distributed in the high latitudes of the Northern Hemisphere, Northern Africa, the arid and semi-arid regions of the Asian continent, and the northwestern Tibetan Plateau. (3) The global NPP had a positive correlation with temperature in most of the regions during this century period. This correlation only becomes negative for South America, Africa, and India near the equator, mainly because radiation in these areas is a limiting factor of NPP. The 100-year changes in the global NPP and precipitation are also primarily positively correlated in most regions, but are negatively correlated in the arid and semi-arid regions of Northern Africa and Western Asia. (4) The six earth system models yield relatively consistent NPP and temperature/precipitation changes in most of the 21 regions of the world. In West Africa, the pattern changes are inconsistent where the uncertainty of the NPP simulation is greater, followed by the Mediterranean region. (5) In particular, the evolution of the NPP in the East Asia region and climate is synchronized and highly correlated, which reflects the strong process of atmospheric interaction with vegetation.
    2019,24(6):678-692 , DOI: 10.3878/j.issn.1006-9585.2019.19033
    Abstract:
    The potential vegetation distribution, the net primary production (NPP), net ecosystem production (NEP), burned area, carbon emissions from fires, soil temperature, and soil moisture in Northeast China from 1997 to 2010 was simulated by using a high-resolution climate-driven field and global dynamic vegetation model, i.e., Lund-Potsdam-Jena Wetland Hydrology and Methane (LPJ-WHyMe) model. The LPJ-WHyMe model is characterized by the capability to describe the physical processes of freezing and thawing, as well as the humidity and temperature of multiple layers in the soil. The five main plant functional types in Northeast China are temperate broad-leaved summergreen tree, boreal needle-leaved evergreen tree, boreal needle-leaved summergreen tree, boreal broad-leaved summergreen tree, and C3 perennial grass. During the period under study in Northeast China, the average value of NPP is 376 g(C) m-2, ranging from 324.15 g(C) m-2 to 424.86 g(C) m-2. The introduction of the mechanism of fire further improves the simulation capability of the LPJ-WHyMe model for NEP. The average value of NEP is 42.36 g(C) m-2. The annual average burned area is 0.84% and the carbon emission from fire is 42.41 g(C) m-2 in Northeast China. Overall, the model overestimated the burned area and carbon emission from fire. Moreover, the model still has some limitations in the simulation of fire in Northeast China. A positive correlation between soil and air temperatures is observed in Northeast China, and the correlation in each layer decreases with the increase in depth. A positive correlation between soil moisture and precipitation and a negative correlation between soil moisture and air temperature are observed in Northeast China. These results show that the LPJ-WHyMe model is effective in simulating the potential vegetation distribution and carbon cycle in Northeast China.
    2019,24(6):693-710 , DOI: 10.3878/j.issn.1006-9585.2018.18048
    Abstract:
    Both observations and numerical simulations with bin microphysics indicated that aerosol concentrations and size distributions play an important role in cloud droplet spectrum evolution and precipitation formation. With limited prognostic variables, current bulk microphysics parameterization cannot simulate the cloud droplet spectrum evolution properly because of the abnormal broadening problem during condensation. No studies of the effect of the size distribution of aerosols on cloud droplet spectra with bulk scheme simulations have been conducted. The newly developed triple-moment bulk scheme includes an additional spectrum shape parameter and overcomes the abnormal broadening problem, which can be better applied to simulate the main characteristics of cloud droplet spectrum evolution than double-moment schemes. To analyze the effect of the size distribution of aerosols on the cloud droplet spectrum evolution using triple-moment microphysical bulk scheme IAP-LACS which has been developed by Key Laboratory of Cloud-Precipitation Physics and Severe Storms (LACS) of Insitute of Atmospheric Physics (IAP). This work focuses on the effects of three parameters of the size distribution of aerosols (i.e., number concentration, geometric radius, and standard deviation) on the cloud droplet spectrum evolution using WRF-LES ideal simulations. The results of the numerical sensitivity tests for the three parameters show that the newly developed triple-moment water vapor growth scheme coupled with the explicit aerosol activation process is a powerful tool to simulate the effect of the size distribution of aerosols on the cloud droplet spectrum evolution. Aerosol number concentration significantly affects the shape of the cloud droplet spectrum. A high aerosol number concentration results in a narrow droplet spectrum with activated droplets and small average size. By contrast, a low aerosol number concentration produces less droplets but with large radius. Enlarging the geometric radius, which means moving the aerosol spectrum toward a large particle size, leads to cloud droplets with a large size. Notably, the standard deviation plays a less important role in the cloud droplet spectrum than the aerosol number concentration and geometric radius.
    2019,24(6):711-722 , DOI: 10.3878/j.issn.1006-9585.2019.18066
    Abstract:
    This work aimed to design an observational network of the air-sea boundary layer over the Bohai and the Yellow Sea, China, and further investigate the effects of these observations on a U.S. numerical prediction model (Weather Research and Forecasting model, WRF). Statistical analysis of the regional characteristics of the air-sea elements, model error, and observation system simulation experiments (OSSE) were conducted. Evaluations of the observation network were conducted under different wind and weather conditions and the advantages and disadvantages of each configuration scheme were weighed. The 6-h NCEP/NCAR FNL (NCEP Final Operational Global) reanalysis data, NCEP real-time global daily sea surface temperature (RTG_SST) analysis data, and buoy and oil-platform observational data were used. Results showed that the forecast humidity and wind were greatly affected by the actual direction and velocity of the wind, and humidity was better predicted under easterly and northerly wind conditions. Moreover, in the moderate southerly wind case, the forecast winds were closer to the observations. It was found that the forecast accuracy of temperature could be significantly improved by configuring the station network based on regional characteristics. Based on a comprehensive overview of the model simulations, suggestions for configuring the air-sea observation stations so as to improve numerical forecast accuracy are provided.
    2019,24(6):723-734 , DOI: 10.3878/j.issn.1006-9585.2018.18072
    Abstract:
    The tropical Pacific plays an important role in modulating the global climate. However, large discrepancies remain among the various estimates of the long-term trend in the tropical Pacific under global warming. Using multiple sea surface temperature (SST) and subsurface temperature datasets, this study investigates the long-term trend of SST in the tropical Pacific and the long-term trend of subsurface temperature in the equatorial Pacific based on the Theil-Sen trend estimation method. Our results indicate a cooling trend in the Pacific cold tongue region and a warming trend in the rest of the tropical Pacific under global warming. That is, the long-term trend of oceanic temperature has a La Niña-like pattern. Furthermore, this La Niña-like pattern in the tropical Pacific is induced by the cold tongue mode (CTM). A positive CTM is characterized by the cold temperature anomaly in the Pacific cold tongue region and the warm temperature anomaly in the rest of the tropical Pacific. Moreover, the time series of the CTM mainly exhibits a strong long-term trend, which is induced by the ocean dynamical processes in response to global warming. The La Niña-like pattern of the long-term trend of the SST and subsurface temperature in the equatorial Pacific indicates the different aspects of the CTM.
    2019,24(6):735-740 , DOI: 10.3878/j.issn.1006-9585.2019.18082
    Abstract:
    Utilizing the ground sand concentration net grid products forecasted by the China Meteorological Administration (CMA) Unified Atmospheric Chemistry Environment (CUACE) numerical model, human forecasts of sand-dust rank products, observed ground sand-dust rank, and the observed particulate pollution (PM10), this paper calculated the Threat Score (TS) from 2012 to 2014, which contained a total of 25 processes of sand-dust weather, to select the best observations and radii of circular interpolation for an objective verification of the sand-dust forecast. For the net grid CUACE numerical model products, different radii were chosen by using the circular interpolation to generate the interpolated station sand-dust forecast. Several conclusions were drawn from the studyresults (1) For the sand-dust rank observations, the radii approximately linearly declined with TS in the float dust-dust rank; the TS rarely changed when the radius changed in the sand-dust rank above the sandstorm, and the best radius selected was the minimum radius, i.e., 0.5° (longitude/latitude). For the PM10, the TS changed markedly when the radius changed in the float dust, but rarely changed when the radius changed in the sand rank above the sandstorm, when the best radius selected averaged 3.5°. If the sand was very weak, the radius could be properly decreased to 1°. (2) For the CUACE numerical model product, the usability of the TS of the observed sand-dust rank was better than the observed PM10, while the two were nearly the same in rank above the sandstorm. Thus, the best observation used for the objective verification of the CUACE numerical model product, generally, was observed ground sand rank. For the human sand rank forecast, the TS of the observed ground sand-dust rank was much higher than the PM10, and the best observation for the verification was the observed ground sand rank.
    2019,24(6):741-754 , DOI: 10.3878/j.issn.1006-9585.2019.19085
    Abstract:
    Observations and European Centre for Medium-Range Forecast (ECMWF) reanalysis data were used to compare the ability of ensemble forecast members [with a horizontal resolution of 0.5º(latitude)×0.5º(longitude)] to provide dynamic and thermodynamic factors relating to a cyclone that exploded over the southern Yellow Sea in February 2018. According to validation results for the track and strength of the cyclone and surface wind, two sets of ensemble forecast members were selected as good and bad forecast members, respectively, and the main conclusions were subsequently obtained from a comparative investigation between them as follows: 1) When the cyclone had explosively developed, the trough and vortex at 500 hPa and 850 hPa, respectively, strengthened rapidly, and the southwest jet streams at lower and upper levels simultaneously increased rapidly in association with the rapid strengthening of synoptic systems; this provided a favorable condition for explosive cyclone development. 2) With the rapid strengthening of ascending motion after the cyclone had entered the Yellow Sea, convergence and divergence at lower and upper levels were respectively intensified; this promoted a pressure reduction and the cyclone then explosively developed. Following convergence of water vapor at a mid-low level, latent heat was released under the ascending motion, which promoted divergence and convergence at upper and lower levels, respectively, and then enhanced ascending motion. Therefore, the rapid strengthening of water vapor flux convergence caused the cyclone to explosively develop. The downward transmission of the high potential vorticity (PV) and baroclinicity at a lower level were strengthened, the degree of stability weakened, and cyclonic vorticity was enhanced. These factors were beneficial for explosive cyclone development, and it finally increased to a medium-strength explosive cyclone. 3) Although the forecast fields from the two ensemble sets were both weaker than those of analysis data, the good ensemble members caught the rapid strengthening of the synoptic system at a mid-upper level over the cyclone and the rapid developing processes of these key factors and physical quantities (such as vertical motion, PV, temperature advection, and water vapor). Therefore, the ability of the good members to track the strengthening cyclone was found to be superior to that of bad members.
    2019,24(6):755-768 , DOI: 10.3878/j.issn.1006-9585.2019.19075
    Abstract:
    To investigate the variation characteristics of rainstorms in the middle-lower reaches of the Yangtze River from 1958 to 2017, four rainstorm characteristic variables were defined based on daily precipitation data of 426 stations. The tendency analysis and mutation test were conducted using a linear trend analysis, cumulative anomaly test, sliding t-test, and the Pettitt test. Results showed that: 1) There was a gradual decrease of the average annual rainstorm and rainstorm days from central Jiangxi to the surrounding areas, and a gradual increase of the average annual rainstorm intensity and rainstorm variation coefficient from south to north. The four rainstorm characteristics variables showed evident seasonal differences. Most rainstorms occurred in the order: summer > spring > autumn > winter. However, the largest rainstorm variation coefficient can be found in winter, showing strong volatility in winter. 2) An increasing tendency in average annual rainstorms, rainstorm days, and rainstorm intensity was observed at 74% of all the stations. The linear trend rates of the average annual rainstorms and rainstorm days gradually increase from northwest to southeast. In addition, the ratio of stations having significant increasing (p < 0.05) in the annual rainstorms and rainstorm days were 17.8% and 16.7%, respectively. 3) Results of the cumulative anomaly test, sliding t-test, and Pettitt test indicated that a significant change of rainstorms occurred in 1988 in the middle-lower Yangtze River Valley. Meanwhile, the average and trend rates of three rainstorm characteristic variables significantly increased after 1988.
    2019,24(6):769-784 , DOI: 10.3878/j.issn.1006-9585.2019.19021
    Abstract:
    Based on monthly precipitation data from CRU TS v4.0 (Climatic Research Unit Timeseries version 4.0), output of the CMIP5 (Coupled Model Intercomparison Project Phase 5) historical experiments and RCP4.5 (Representative Concentration Pathway 4.5) scenario from 24 models, a variety of simple and multiple regression methods were designed to bias-correct projected precipitation for China. These included simple regression (SR), simple regression with log-transformed rainfall (SR-Log), simple regression with year-to-year rainfall increment as predictand (SR-Increment), simple regression with year-to-year log-transformed rainfall increment as predictand (SR-Log-Increment), multiple regression (MR), multiple regression with log-transformed rainfall (MR-Log), multiple regression with year-to-year rainfall increment as predictand (MR-Increment), multiple regression with year-to-year log-transformed rainfall increment as predictand (MR-Log-Increment), and simple removal of climate drift (RCD). Bias-corrected results for projected precipitation over mainland China for 2006-2015 showed that univariate regression correction methods were generally better than multi-variate methods and simple RCD. SR-Log performed best, with rate of precipitation anomaly having the same sign with observation (AR) and precipitation anomaly percentage correlation coefficient (APCC) were the highest, reaching 69% and 0.5, respectively. On the other hand, SR-log-Increment obtained the highest correlation coefficient of precipitation anomaly (ACC) among the different methods. The distributions of precipitation anomaly with the same sign with respect to observation, using different bias-correction methods, showed that the SR-Log performed better in the north than in the south. To the contrary, SR-Increment and SR-Log-Increment performed better in the south than in the north. As a result, the AR, ACC and APCC of the SR-Log or MR-Log were lower than those of the SR-Log-Increment and MR-Log-Increment over southern China (east of 95°E and south of 35°N), while the opposite was true for northern and western China. Therefore, the best regression correction method for model precipitation was regional-dependent, possibly reflecting the differences in statistical properties of precipitation in different regions. Using synthesis of regional regression models, i.e., using SR-Increment in the southern region and SR-Log for the rest of China, the AR of projected precipitation for 2006-2015 improved to 72% while ACC and APCC declined slightly, as the increment regression method increased the variance of the projected precipitation. Projected precipitation for 2016-2045 was bias-corrected by the synthesis of regional regressions method. The results showed that, compared with the average of 1976-2005, the precipitation anomaly pattern for the next 30 years would display a “dry in the north and south, wet in the middle” pattern. Precipitation would decrease by 10%-20% in the middle and lower Yangtze River, middle and west of the regions south of the Yangtze River, the northeastern part of southwestern China, and the coastal regions of southern China and Hainan; precipitation would increase by 10%-40% in the Huai River basin, three rivers source regions, and Taiwan. Minimal changes, or slightly less precipitation was projected over the eastern part of northwestern China, northern China, and most of northeastern China. According to the variance of precipitation anomaly percentage, the spread (uncertainty) of the model group was smaller in the east and larger in the west. It indicated that the projected less precipitation areas were more uncertain such as in the central northwestern, and western Qinghai-Tibet Plateau. In addition, the northern part of the Hetao area, the southern part of northern China, and the eastern part of the south of the Yangtze River corresponded to the “obscured areas,” where the precipitation anomaly in the projections and observations showed opposite signs for the verification period 2006-2015. As such, the projected precipitation over these regions may not be of value. Consequently, alternative methods need to be developed in the future for further improvement.
    2019,24(6):785-794 , DOI: 10.3878/j.issn.1006-9585.2019.18153
    Abstract:
    In this study, the relationship between the land surface albedo over the Tibetan Plateau and the plateau summer monsoon are statistically analyzed using a representative plateau monsoon index, i.e., Dynamic Plateau Monsoon Index (DPMI) based on MODIS surface albedo and ECMWF/ERA-Interim reanalysis data from 2000 to 2016. The main results are as follows: 1) There is a close relationship between the land surface albedo over the Tibetan Plateau in November and the onset of plateau summer monsoon. The land surface albedo of the Tibetan Plateau in November is low (high), and the plateau summer monsoon starts early (late) in April of the following year. 2) When the land surface albedo over the Tibetan Plateau in November is low, the sensible heat flux of the main body of the plateau on the atmosphere is strong in the latter period, which significantly strengthens the uplifting movement of the plateau in April. Thus, the plateau becomes conducive to the transfer of heat to the upper air, resulting in enhanced tropospheric heating, increased tropospheric temperature in the plateau, and strengthened plateau monsoon circulation system, eventually leading to the early plateau monsoon seasonal changes, and vice versa.
    Display Method:
    Accept: December 30, 2019                                                      
    Abstract:
    Based on NCEP/NCAR global reanalysis data, ground observation data and automatic station precipitation data, this paper analyzed the circulation anomalies such as winter monsoon circulation and South Branch trough in rare continuous rain and oligoscale weather in Zhejiang in the winter of 2018/2019, and analyzed the causes of local circulation anomalies from such aspects as westerly wind fluctuation and sea temperature forcing. The results showed that: in the winter of 2018/2019, the rainy days and sunshine hours broke the historical record, and the rainfall was significantly more than normal. The main circulation anomalies were the abnormal northerly Western North Pacific anomalous anticyclone (WNPAC). At the same time, the Aleutian low pressure and the Siberian high pressure were also northerly. There was a strong southerly wind anomaly south of 40°N in East Asia, and the winter monsoon was weak. the southern branch trough were stronger than the perennial, ensuring that there was a continuous water vapor and disturbance transport over Zhejiang. In the middle layer of the troposphere, there was a wave energy that propagated along Europe to East Asia and the Western Pacific. Wave energy had spread southwards to the south of 20°N in East Asia, which might lead to a significant North lift of WNPAC and the strengthening of the southern branch trough. The ENSO warm phase caused abnormal convective cooling in the maritime continent, while the convection over Zhejiang strengthened, and ENSO also had a significant effect on the activity intensity of the southern branch trough. The high sea surface temperature in the offshore waters of China was an important factor for WNPAC and the Aleutian low to significantly jump north. The abnormal circulation in the northern hemisphere in the winter of 2018/2019 might be caused by ENSO and China's offshore sea temperature collaborative forcing.
    Accept: December 03, 2019                                                      
    Abstract:
    Long-term snow-depth observations at AerShan station is used to evaluate the application of snow-depth products retrieved from AMSR-E and AMSR-2 microwave data and Chinese snow-depth dataset developed by Chinese researchers, and to establish new snow-depth retrieval algorithm. The statistical snow-cover days and the maximum snow-depth records derived from 35-year Chinese snow-depth dataset and station observations are more consistent, especial after 2000. The snow-depth variation trend estimated from the snow-depth products of AMER-E and AMSR-2 is agree with that from the station observations, with the correlation coefficient greater than 0.6, however, the variation range of snow-depth products is much higher than that of station observations so that the root mean square error(RMSE) of both snow-depth is higher about 13 cm. The Chinese long-term snow-depth dataset at AerShan station shows higher correlation coefficient 0.65 and reduced RMSE (6.3 cm) compared with the station observations. To better estimate snow in AerShan region, the new snow-depth retrieval method is developed using both space-born passive microwave brightness temperature and observed snow-depth data at AerShan station. The validation shows that the retrieved snow-depth from new method is higher correction with the observation about 0.77 and less RMSE about 4.68 cm, better than the three snow-depth products from AMSR-E and AMSR-2 as well as the Chinese snow-depth dataset used in this paper.
    Accept: November 26, 2019                                                      
    Abstract:
    Using 324 stations in the central and eastern China during 1980 – 2014, we analyze the spatial and temporal variations of persistent haze events and their related impact factors. The results show that the annual average frequency of persistent haze events and their contributions to total haze events increase year by year, with growth rates of 0.79 t (10 a)-1 and 2.7% (10 a) -1, respectively. It is represented by three large-value areas: The North China Plain (including Shanxi Province, Beijing-Tianjin-Hebei region), the Yangtze River Delta, and the eastern Sichuan Basin. The most significant increase appears mainly in Huang-Huai area, with a growth rate of 6.3 t·(10a)-1and 13.95 d·(10a)-1. At the same time, persistent haze events show obvious seasonal and monthly changes. January is the highest incidence month with 2.56 d, meanwhile high frequency appears in summer and autumn, with a growth rate of 0.38 t·(10a)-1 and 0.46 t·(10a)-1. Unfavorable meteorological conditions, such as increasing windless days, decreasing wind speed and gale days, and adverse circulation situations, such as the weakening of the East Asian winter monsoon, have resulted in an increase in persistent hazy days and its abnormal maintenance.
    Accept: November 22, 2019                                                      
    Abstract:
    Using the National Center for Atmospheric Research Community Atmosphere Model version 3 (CAM3) outputs and European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Re-analysis (ERA-Interim) data, the roles of the orography (Tibetan Plateau and Iranian Plateau) on modulating the sources of stationary wave energy are investigated in this study. There are two areas of stationary wave energy sources in the troposphere during winter, one is in the East Asia north of the Plateau, and the other is in the Western Pacific downstream the Plateau. When orography uplifts, the baroclinic development weaken over East Asia north of the Plateau, and enhance over Western Pacific downstream the Plateau in the troposphere. The location of the barotropic development of stationary wave energy is similar to that of baroclinic development, while the intensity is weaker in the troposphere. When the orography heights uplift, the barotropic development of stationary wave energy weaken first and then enhance over East Asia north of the Plateau, while it enhance over Western Pacific downstream the Plateau in the troposphere. In the troposphere during winter, the total stationary wave energy development is consistent with the baroclinic development of stationary wave energy, which means that the baroclinic development stationary wave energy plays important role in the development of stationary wave.
    Accept: November 21, 2019                                                      
    Abstract:
    Temperate grasslands are important components of terrestrial ecosystems and play an important role in the global carbon cycles. Studying the grassland carbon exchange processes and their impact factors is essential to assess variations in terrestrial ecosystems carbon source-sink and their responses to future climate change. Based on the eddy covariance measurements of carbon fluxes at Tongyu meadow steppe during 2011-2017 and at Maodeng typical steppe during 2013-2017, we analyzed the diurnal variation in carbon fluxes and its responses to environmental factors. The results showed that both grasslands had the strongest carbon uptake in July. The monthly peaks of gross primary production (GPP), ecosystem respiration (Re) and net ecosystem exchange (NEE) of the meadow steppe were greater than those of typical steppe. The diurnal variation of NEE is dominated by unimodal pattern. However, when the saturated vapor pressure difference was high in July and August, GPP decreased around noon, leading to a bimodal pattern of NEE. Photosynthetically active radiation was the key factor in the diurnal variation of NEE in meadow steppe, while in the typical steppe diurnal variation of NEE was also susceptible to shallow soil water content (5 cm). Water deficit led to significant decrease in NEE at both grasslands. However, the meadow steppe carbon sequestration rate was more sensitive to water deficit than the typical steppe. Meanwhile, water deficit modified the responses of GPP, Re and NEE to temperature and photosynthetically active radiation.
    Accept: November 13, 2019                                                      
    Abstract:
    Based on the observed outgoing longwave radiation (OLR) data and other reanalysis datasets during 1979-2018, we found that there are three categories of significant inter-monthly variations of the warm pool convection in the western Pacific. For the first category, there is a negative OLR anomaly in June and August and a positive one in July. By contrast, the second category shows an opposite anomaly to the first one. For the third category, there is a positive OLR anomaly in June and July and a negative one in August. All categories of inter-monthly variations are related to the ENSO background. The first and second category occur in relatively weak La Ni?a years and El Ni?o developing years, which are closely associated with sea surface temperature (SST) anomaly in spring over the warm pool. When the SST is higher in the preceding month, convection in the next month is enhanced along with a reduced SST. Consequently, convection is suppressed due to the reduced SST in the preceding month. The local air-sea interaction in the warm pool plays a key role in the first and second categories. Different from the former two categories, the third category occurs in El Ni?o decaying years, which is related to a higher SST in spring over the tropical Indian Ocean. During June and July, convection near India is enhanced due to a higher SST in the tropical Indian Ocean. By exciting a Kelvin wave propagating eastward, convection in the warm pool is suppressed. In the meantime, the enhanced convection near India reduces the local SST and suppresses convection in August, when the influence from the Indian Ocean on the warm pool convection is largely weakened. On the other hand, the warm pool SST in August tends to rise due to suppressed convection in June and July. As a result, the warm pool convection is enhanced in August. Therefore, the third category results from the combined effects of the tropical Indian Ocean forcing and local air-sea interaction in the warm pool.
    Accept: November 13, 2019                                                      
    Abstract:
    Using the level-2 product data of Aqua MODIS and CloudSat from 2013 to 2016, the precipitating and non-precipitating ice clouds occurred in the summer of Beijing-Tianjin-Hebei region were counted. Based on this, cloud feature parameters, cloud layer numbers and cloud phase of the two types of ice clouds are compared and analyzed. The differences between the two in the vertical structure are studied, and the relative size of the cloud parameters in different channels are explored. The results show that precipitating ice clouds are dominated by deep convective clouds and nimbostratus, accounting for 48.63% and 34.65% respectively. The mean cloud top temperature, cloud top height, cloud optical thickness, cloud-water path and effective particle radius are 230.99K, 10.90km, 53.26, 937.98 and 31.45, respectively. Non-precipitating ice clouds are dominated by altocumulus and cirrus clouds, accounting for 55.62% and 31.58% respectively. The mean cloud top temperature, cloud top height, cloud optical thickness, cloud water path and effective particle radius are 236.17K, 10.10km, 12.81, 209.00 and 27.54, respectively. Precipitating ice clouds mainly consist of single-layer clouds (80.39%), but double-layer clouds still account for a large proportion (18.75%) and are higher than non-precipitating ice clouds; non-precipitation ice clouds still consist of single-layer clouds (85.35%) and double-layer clouds (14.38%). Compared with non-precipitating ice clouds, the position of cirrus and altocumulus in precipitating ice clouds is higher, which are higher 1~9km and 0~1.5km respectively, while the position of altostratus and deep convective are lower, which are lower 0~0.5km and 0.5~3km respectively. The ice water content of non-precipitating ice clouds varies with height as a double peak structure, while that of precipitating ice cloud is a single peak structure; the particle number concentration of precipitating and non-precipitating ice clouds varies little with height; the particle effective radius of non-precipitating ice clouds varies little with height from 5 to 7.5 km, while precipitating ice clouds decrease with height. The ratio of the cloud water path, optical thickness and particle effective radius of the precipitating ice clouds b_n 16>b_n 21≥b_n 37mode (b_n16、b_n21、b_n37respectively represent the values of the cloud parameters in 1.6, 2.1, 3.7μm. When n=1, 2, and 3, they represent the optical thickness (b_1), the total amount of integrated cloud water (b_2), and the effective radius(b_3).) are higher than non-precipitating ice clouds, and the ratio of the two parameters in the cloud parameter b_n 21≥b_n 16≥b_n 37 mode is different.
    Accept: October 22, 2019                                                      
    Abstract:
    A regional air quality model system (RAQMS) drivern by WRF is applied to investigate the distribution and evolution of aerosol components in Beijing in spring 2014. The synoptic condition, meteorological variables, characteristics of aerosol chemical components are comparatively analyzed and the impacts of heterogeneous reactions on dust and anthropogenic aerosol surface on chemical compositions during the dust (17 and 19 March) and haze periods (25-27 March) are quantified and compared. The comparison with observations exhibits that the model is capable of reproducing meteorological variables, PM2.5, PM10 and their chemical component concentrations during the study period, and the inclusion of heterogeneous reactions apparently improve the prediction accuracy of PM (primary particulate) and secondary aerosol concentrations. In dust days, dust is the dominant component of PM10 mass (50.7%), and its percentage contribution to PM2.5 is comparable to nitrate and PPM (primary particulate matter). In haze days, nitrate (25.6%) and OM (23.6%) contribute most to PM2.5 mass, whereas in PM10, the fractions of nitrate, PPM and OM in PM10 are comparable. The fraction of coarse particle increases significantly in dust days with the mean fraction being 45.5% in PM10. In haze days, fine particle dominates PM10 mass, with a fraction of 85.6%. The heterogeneous reactions increase sulfate and nitrate concentrations by 16.9% and 83.8% in dust days, and by 14.5% and 45.0% in haze days, respectively. On average, the heterogeneous reactions lead to changes in near surface SO2, NO2, O3, sulfate, ammonium and nitrate concentrations by -2.5%, -5.7%, -3.4%, 11.7%, 18.6% and 58.5%, respectively, in Beijing in March 2014, highlighting the important role of heterogeneous reactions in secondary aerosol formation.
    Accept: October 17, 2019                                                      
    Abstract:
    In this paper, the NCEP-FNL data-sets are used as the initial field and boundary field of the WRF model, six planetary boundary layer parameterization schemes are applied in the model for Xinjiang regions with 10km horizontal resolution, the spatial distribution and temporal evolution of the meteorological elements are focused. The analysis results showed that: 1) WRF model with six Planetary Boundary Layer Parameterization Schemes (PBLPS) can simulate the seasonal circulation of monthly precipitation and the spatial pattern of annual and rainy seasonal precipitation. 2) For Xinjiang region, the deviation of rainy season precipitation between simulated with Grenier-Bretherton-McCaa (GBM) scheme and observed which within ±30%. For the Tianshan area, the deviation of annual precipitation between simulated with Bougeault-Lacarrere (BouLac) scheme and observed which is -19.13%. The TS score of moderate rain and heavy rain are 0.37 and 0.33 in the test result of daily precipitation simulated with GBM scheme. For the different types of underlying surface in the Tianshan area, the day and night precipitation can be well simulated by model with GBM scheme with the deviation of precipitation is within 5mm during larger precipitation days. 3) WRF model with BouLac PBLPS can simulate the annual spatial and temporal distribution characteristics of annual precipitation in the Tianshan area, and the rainy seasonal precipitation can be simulated well by model with GBM scheme in Xinjiang. Therefore, planetary boundary layer parameterization schemes with WRF model in the Xinjiang region should be well considered.
    Accept: October 16, 2019                                                      
    Abstract:
    Numerical simulation on wind environment in a neighborhood with super-high resolution has been a hot research area of urban meteorology. This paper utilized a computational fluid dynamics (CFD) model based on large-eddy simulation to simulate the climatic wind environment in Longhu Community in Chongqing, and investigate the impacts of local building configurations on fine-scale structures of wind field. The results showed that complex underlying surfaces played an important role in regulating local circulations. The strong winds were mainly found over open spaces and at broad streets parallel to background inflow. The overall wind speed in summer was larger than other seasons, and can reach a magnitude of 0.8 m/s. Different building configurations would lead to different patterns of local wind field. The isolated tall building resulted in strong downward motions and winding flows at windward side of the building, where strong winds frequently occurred. The scattered low buildings had little impact on local inflow, thus the wind field was in a homogeneous pattern. The densely-built tall complex with a enclosing shape would block the wind greatly, which led to relatively weak wind speed in the vicinity and was unfavorable for the pollutant dispersion.
    Accept: October 12, 2019                                                      
    Abstract:
    Nowadays, the dynamical climate models are inefficient to meet the real need of the climate prediction, it is one of the effective methods that the combination between dynamical and statistical model, that is the application of the large-scale circulation information from the dynamical models into the statistical model to improve the predicted skill. Based on the higher prediction skill for summer large scale circulation variable of climate models and the significant relationship between the preceding ENSO signal and summer precipitation in China, a hybrid statistical downscaling prediction method for summer precipitation anomaly prediction in China was proposed in this paper. The cross validation of seasonal prediction for the summer precipitation in China was performed and the results showed that the downscaling method improved the multi-year average of anomaly correlation coefficient significantly. In the real application, the average PS score can reach 71.5/72.7 during 2013-2018/2015-2018, which is higher than the original model and the operational predictions issued by Beijing Climate Center. This statistical downscaling model, which has stable predictive skill, is one of the effective references for operational seasonal prediction in China.
    Accept: September 26, 2019                                                      
    Abstract:
    The wetland has an important function in local microclimate regulation. Studying the characteristics of the wetland microclimate effect can specifically understand the impact of the wetland on the local microclimate. In this paper, we chose the Hengshui Lake in Hengshui City of Hebei Province as the study area, and analyzes the microclimate effects of Hengshui Lake in different seasons by comparing the meteorological elements between outside the lake and the lake. The data comes from 11 conventional meteorological stations in Hengshui City. Results show that: 1) The Hengshui Lake has a remarkable cold island effect, wet island effect and wind island effect, which can adjust the surrounding climate characteristics. 2) The microclimate effect of Hengshui Lake has an obvious seasonal characteristic. The order of average cold island effect in four seasons is spring > winter > autumn > summer; the order of wet island effect is spring > summer > winter > autumn; and the order of wind island effect is spring > summer > winter > autumn. The microclimate effect is intense in spring. 3) The Hengshui Lake shows an obvious circadian rhythm for its microclimate effect. The cold island and wet island effect are stronger during the night than at day, while the wind island effect during the day is stronger than at night.
    Accept: September 25, 2019                                                      
    Abstract:
    According to the topography and historical seismic information of the South China Sea, many scholars at home and abroad have studied the source area of possible earthquakes and tsunamis in the South China Sea. In this paper, based on those research results, the authors analyze the areas that may cause tsunamis, choose a group of typical tsunami sources, simulate them with the COMCOT model, and study the damage to coastal area and reefs of the South China Sea from the aspects of tsunami propagation time, wave height, and energy distribution, etc. It is confirmed by the sensitivity test that the intensity of the tsunami wave is greatly influenced by the magnitude of the earthquake. If a local tsunami is triggered by strong earthquakes, it will cause great damage to the different parts of coastal and reefs of the South China Sea.
    Accept: September 25, 2019                                                      
    Abstract:
    This paper uses a high-resolution climate driving field and global dynamic vegetation model LPJ-WhyMe (Lund-Potsdam-Jena-Wetland Hydrology and Methane) to simulate the potential vegetation distribution and estimate the net primary production (NPP), net ecosystem production (NEP), burn area, fire carbon emissions, soil temperature and soil moisture in Northeast China from 1997 to 2010. LPJ-WhyMe is characterized by the ability to describe the physical processes of freezing and thawing, as well as the humidity and temperature of multiple layers in the soil. It is shown that there are five main plant functional types (PFTs) in Northeastern China, that is temperate broadleaved summergreen tree, boreal needleleaved evergreen tree, boreal needleleaved summergreen tree, boreal broadleaved summergreen tree and C3 perennial grass. During the period under study in Northeast China, the average value of NPP is 376 g C.m-2, ranging from 324.15 g C.m-2 to 424.86 g C.m-2. The introduction of the fire mechanism further improves the simulation capability of the LPJ-WHyMe model for NEP. And the average value of NEP is 42.36 g C.m-2. The annual average of burned area is 0.84%, and the carbon emission by fires is 42.41g C.m-2 in Northeast China. Overall, the model overestimates the burned area and the carbon emission by fires, and the model still has some limitations in the simulation of fires in Northeast China. There is a positive correlation between soil temperature and temperature in Northeast China, and the correlation in each layer decreases with increasing depth. There is a positive correlation between soil moisture and precipitation, and an anti-correlation between soil moisture and temperature in Northeast China. The above results show that LPJ-WhyMe model is effective in simulating the potential vegetation distribution and carbon cycle in Northeast China.
    Accept: September 20, 2019                                                      
    Abstract:
    The explosive extratropical cyclone will lead to meteorological disasters such as strong winds and storm surges at sea, which will pose a serious threat to ships' navigation and operations at sea. Based on the observations and the ECMWF (European Centre for Medium-Range Forecast) reanalysis data and ensemble forecast data with a horizontal resolution of 0.5o 0.5o, the dynamic and thermodynamics factors are comparatively investigated when a cyclone exploded over south part of yellow sea in February 2018. According to the validation results on the track and strength of cyclone and the surface wind, two sets of ensemble forecast members are selected as a set of good members and a set of bad members. Main conclusions are made by the comparative investigation between the good forecast members and bad forecast members. (1) When the cyclone was explosively developed, the trough at 500hPa and the vortex at 850hPa strengthened rapidly, and the southwest jet streams at low and upper level increased rapidly at the same time, associated with the rapid strengthen of synoptic systems, which provide a favorable condition for the explosive development of cyclone. (2) With the rapid strengthen of ascending motion after the cyclone entering the yellow sea, the convergence at low level and the divergence at upper level were intensified, it is beneficial to the pressure reduction and then the cyclone developed explosively. After the convergence of water vapor at mid-low level, latent heat release under ascending motion are benefit to divergence at upper level and convergence at low level, and then enhance ascending motion. So that the rapid strengthen of water vapor flux convergence cause the cyclone developing explosively. Down transmission of the high potential vorticity (PV) is strengthened, the baroclinicity at low level gets stronger, the degree of stability is weaker, and the cyclonic vorticity is enhanced. These factors are convenient for the cyclone’s explosive development, and the cyclone finally increased to a medium-strength explosive cyclone. (3) Although the forecasted fields from the two ensemble sets are both weaker than those from the analysis data, the good ensemble members caught the repaid strengthen of synoptic system at mid-upper level over the cyclone, and the rapid developing processes of these key factors, such as the vertical motion, PV, the temperature advection, and the water vapor, so the track and strength of cyclone forecasted by the good members are much better than those forecasted by the bad members.
    Accept: September 16, 2019                                                      
    Abstract:
    Meteorological forecasting is the key to affecting the accuracy of atmospheric heavy pollution prediction. In response to a heavy pollution process in Beijing from December 16 to 21, 2016, this paper carried out a sensitivity test for the parameterization scheme of the mesoscale meteorological model WRF. Combining microphysical processes, long-wave radiation processes, short-wave radiation processes, land surface processes, boundary layer processes, near-surface processes, and cumulus convective parameterization processes, a total of 50 sets of parameterization schemes were designed to analyze the simulation accuracy and sensitivity of temperature, relative humidity and 10m wind speed of 8 meteorological stations in Beijing under different simulation schemes. The test results show that the temperature simulation is the most sensitive to the long-wave process parameterization scheme, the set dispersion is 2.4-7.4℃, followed by the short-wave process parameterization scheme; the relative humidity simulation is also the most sensitive to the long-wave process parameterization scheme, followed by the land surface process; the wind speed simulation has little difference in sensitivity to different process parameterization schemes. By comparing the statistical results of the simulation results with the observations, we prefer the combination of the smallest simulation error: Lin microphysical scheme, RRTMG long-wave scheme, RRTMG short-wave scheme, Tiedtke cumulus convection scheme, Noah land surface scheme, MYNN 3rd boundary layer scheme and MYNN near-surface scheme, and compare the best scheme to the ensemble mean and baseline scheme. For the ensemble mean, the correlation coefficient between temperature simulation and observation is 0.69, which is higher than the baseline scheme. The simulated deviation and root mean square error are 25% and 11% lower than the baseline scheme; the ensemble mean relative humidity and wind speed simulation are less variable than the baseline scheme. Compared with the ensemble mean, the best scheme can simultaneously improve the temperature, relative humidity and wind speed simulation, so that the temperature simulation deviation and root mean square error decreased by 35% and 17% compared with the baseline scheme, and the relative humidity simulation deviation and root mean square error decreased by 43% and 13%, and the wind speed simulation deviation and root mean square error decreased by 33% and 24%. The above results show that the sensitivity test and optimization of the parameterization scheme can significantly reduce the simulation error of meteorological elements during heavy pollution. The improvement of heavy pollution prediction needs to focus on the uncertainty of the parametric scheme simulation. This study also found that the MYNN 3rd boundary layer scheme has good performance in the simulation of meteorological elements in this heavy pollution process, which can provide reference for future improvement of heavy pollution forecasting.
    Accept: September 16, 2019                                                      
    Abstract:
    Earth system model (ESM) is an important tool for studying global climate and ecological environment changes. Aerosol and Atmospheric Chemistry Model (AACM) provides the simulation of gases and aerosols associated with climate effect for the Atmospheric General Circulation Model (AGCM). Based on the Global Nested Grid Air Quality Prediction Model System, AACM of the Institute of Atmospheric Physics (IAP-AACM) suitable for ESM of the Chinese Academy of Sciences (CAS-ESM) was developed, using a simplified gas phase chemical mechanism. Not only anthropogenic aerosols, but also natural aerosols (e.g. sea salt, dust and Dimethyl sulfide) emitting online are considered. The evaluation of the simplified version of IAP-AACM showed that IAP-AGCM can capture the spatial characteristics of meteorological elements well. IAP-AACM with simplified mechanism showed reasonable spatial distribution of aerosols and precursor gases ant the difference from the version with CBM-Z mechanism is small. The comparison with the observation shows that the simplified version captured the spatial distribution of the aerosol and its precursors well, and provide a reliable aerosol simulation for IAP-AGCM. Furthermore, the simplified version can effectively improve the calculation efficiency, and it can save 14 times for the same computing task. In order to provide a more comprehensive aerosol simulation in the research of global climate change, nitrogen chemical mechanisms and stratospheric chemistry of ozone will be taken into account in IAP-AACM in the future.
    Accept: September 06, 2019                                                      
    Abstract:
    The relationship between the land surface albedo over the Tibetan Plateau and the plateau monsoon are statistically analyzed using the representative plateau monsoon index —DPMI in the present study based on MODIS surface albedo and ECMWF/ERA-Interim reanalysis data from 2000 to 2016. The main results are as follows: (1) The land surface albedo over the Tibetan Plateau in November has certain implications for the onset of Plateau Summer Monsoon. The land surface albedo of the plateau in November is low (high), and the plateau summer monsoon break out early (late) in April of the following year. (2) When the land surface albedo over the plateau is low (high) in November, the sensible heating effect of the main body of the plateau on the atmosphere is strong (weak) in the latter period, which causes the uplifting movement of the plateau to be significantly strengthened (weakened) in April, and there is (not) conducive to the transfer of heat to the upper air, resulting in enhanced (weakened) tropospheric heating, high (low) tropospheric temperature in the plateau, making the plateau monsoon circulation system strengthened (weakened), eventually leading to the Plateau Monsoon Seasonal changes in advance (postponed).
    Accept: September 06, 2019                                                      
    Abstract:
    In order to reveal the variation characteristics of rainstorms in the middle-lower Reaches of Yangtze River, four rainstorm characteristic variables were defined based on the daily precipitation data of 426 stations from 1958 to 2017. Tendency analysis and mutation test were performed by linear trend analysis, cumulative anomaly test, sliding t-test and Pettitt test. The results show that: (1) The average annual rainstorm and average annual rainstorm days decrease from the central Jiangxi to the surrounding. The average annual rainstorm intensity and average annual rainstorm variation coefficient increase gradually from south to north. There are obvious seasonal differences for four rainstorm characteristics variables. Summer is the main contributor to the rainstorms throughout the year, spring and autumn rank second and the former is more than the latter, winter has less proportion. However, the average annual rainstorm variation coefficient of winter is the largest, which indicate the volatility is strong. (2) The trend rate of the average annual rainstorms, average annual rainstorm days and average annual rainstorm intensity gradually increase from northwest to southeast, and most of the regions show an increasing trend, accounting for 74%. Besides, the station ratio passing the 95% significance test exceeds 16%. (3) Based on cumulative anomaly test, sliding t-test and Pettitt test, result show that 1988 is a significant change point of rainstorms in the middle-lower Yangtze River Valley for nearly 60 years. Comparing to 1988 ago, the average and the trend rate of three rainstorm characteristic variables increase significantly after 1988.
    Accept: August 26, 2019                                                      
    Abstract:
    Based on observations of monthly mean temperature, precipitation and relative humidity at Lhasa, Shigatse, Zedang and Jiangzi stations over the Yarlung Zangbo River valley in the hinterland of the Tibetan Plateau in the past 57 years (1961~2017), theevolution characteristics of interannual and interdecadal of the climate series in the region are analyzed. With the relationships among each climate series and the connections of that related to total cloud cover and surface water vapor pressure during the same period on the interannual and interdecadal scales discussed as well. The results show that: (1) In the past 57 years the summer climate in the region has a trend of warming and drying, The temperature (relative humidity) increased (decreased) significantly, and the precipitation trend is not obvious. (2) There exists a close relationship between the summer climate factors in the region and the interannual and interdecadal variations: there is a significant negative correlation between temperature and relative humidity ( precipitation ), while here is a significant positive correlation between precipitation and relative humidity.(3) Interannual and interdecadal variations of summer climatic factors in the region are related to total cloud cover and surface water vapor changes over the same period. The continuous reduction of total cloud cover in the past 57 years is one of the main reasons for the significant increase in temperature; while the significant increase in temperature and the change in precipitation do not significantly cause a significant decrease in relative humidity.
    Accept: August 26, 2019                                                      
    Abstract:
    Using WRF-Chem model, a large-scale PM2.5 heavy pollution process in northern China from November 25 to December 2, 2015 was simulated. Comparison with the observation shows that the model can realistically capture the magnitude and variation of PM2.5 concentration and meteorological factors, and can be used for the mechanism analysis of this pollution event. The paper further analyzed the mechanism of the strong pollution event from the aspects of dynamics, thermo-meteorological conditions and chemical transformation. The results show that the dynamic factors mainly affect the pollution event through the weakening of surface wind and vertical wind shear. The thermal factors such as boundary layer inversion promote the enhancement of atmospheric stability, which is not conducive to pollutant diffusion. Through the analysis of the composition of PM2.5, it can be seen that nitrate, sulfate and organic carbon are increased in this event, indicating that secondary aerosol formation caused by vehicle exhaust and coal combustion contributes greatly to PM2.5 pollution. In order to identify the main factors causing this pollution event, we used multiple linear regression and relative contribution rate accounting methods to quantify the multi-factor analysis. The results show that thermal factors play a major role in the pollution process, with variance contribution of 52%, dynamic factor of 34%, and chemical transformation variance contribution of 14%, indicating that adverse meteorological conditions, especially thermal conditions, are the main causes of the pollution event.
    Accept: August 22, 2019                                                      
    Abstract:
    Based on the meteorological satellite data and reanalysis data from 2006 to 2017, the convection activities and surface sensible heating flux in North China and its surrounding areas from May to August are analyzed statistically. The results show that the daytime average sensible heating flux is closely related to the topography in North China and its surrounding areas. The sensible heating flux is stronger in the central and southeastern Inner Mongolia, the northern and the western mountainous area of North China. The strongest sensible heating flux occurs in May and June, and weakens obviously in July and August. Corresponding to the intensity of sensible heating flux, the higher convection frequency also occurs in May and June. In May, most of the convections are weak. The deep convections are most active in the north-central part of North China in June, and the deep convections are relatively frequent in the area around the Bohai Sea from June to July. The trend of daily average sensible heating flux and convection frequency from May to August shows a consistent weakening corresponding relationship. In the morning, sensible heating causes convergence and warming in different degrees in the lower troposphere below 700hPa at Western and Northern Hebei province. The ascending motion reaches the middle troposphere, and the compensating descending motions occur in the eastern plains. The warming up and ascending motion triggers convection which can develop rapidly when it moves eastward under favorable conditions. The diurnal variation of convection frequencies in different months and regions is obvious different. The diurnal variation of convection frequencies in June is remarkable, and is weakest in August. The diurnal variation of convection frequencies in mountainous areas is remarkable and is weakest in the eastern Bohai Sea and its surrounding areas. Both of the monthly mean distribution and diurnal variation of convection frequency have a close relationship with surface sensible heating flux caused by the topography.
    Accept: July 10, 2019                                                      
    Abstract:
    In order to deeply understand the influence of temperature and relative humidity in the boundary layer on the vertical distribution of PM2.5 and near-surface pollution, In this paper, a UAV equipped with multi-parameter atmospheric environment detector was used for vertical observation of PM2.5 concentration, temperature and relative humidity in Nanjing from December 3 to 4 and December 23 to 24, 2017. Combined with the analysis of meteorological data and the application of HYSPLIT4 trajectory calculation model, the vertical distribution characteristics of PM2.5 and the causes of pollution process in these two times were analyzed. The results showed that there was a significant positive correlation between PM2.5 concentration and relative humidity, and the average correlation coefficient reached 0.96 in the six observations from December 23 to 24. Under the inversion layer, PM2.5 concentration and relative humidity are high and the vertical difference is small. Above the inversion layer, PM2.5 concentration and relative humidity rapidly decrease as the height increases. Due to the poor atmospheric diffusion conditions, PM2.5 continuously accumulates in the south of the north China plain, and then moves to the south and southeast under the influence of the high-pressure system. Both PM2.5 pollution processes were significantly affected by external transport. Atmospheric inversion significantly inhibited the upward transport of PM2.5 and water vapor, the external transport and local inversion were the main causes of these two PM2.5 pollution.
    Accept: June 24, 2019                                                      
    Abstract:
    The characteristics and mechanisms of sub-seasonal evolution of Northwest Pacific Anomalous Anticyclone (NWPAC) during the El Ni?o decaying summer were analyzed based on a variety of reanalysis data and observation data. The results show that NWPAC has a northern shift and increased intensity in both July and August compared with that in June during the El Ni?o decaying summer. NWPAC affects the precipitation in East Asia during boreal summer by influencing the divergence of water vapor fluxes in the low-level troposphere. The abnormal rain belt in East Asia shifts northward accompanied with NWPAC jumping northwards. The anomalous precipitation decline and incidental solar short-wave radiant fluxes increasement in the ridge of the NWPAC can result in positive surface air temperature anomalies in the Indochina Peninsula, the Philippines, and southern China during the El Ni?o decaying summer. With the northward shift of NWPAC, the positive surface air temperature anomalies in East Asia also shift northwards. Local air-sea interaction process may be one of the causes of NWPAC&quot;s northern jump during the El Ni?o decaying summer. Increased short-wave radiant fluxes and reduced upward sensible and latent heat fluxes in the southern side of NWPAC can cause anomalous positive Sea Surface Temperature anomalies (SSTAs), and positive SSTAs in turn could be detrimental to NWPAC&quot;s maintenance via inducing convective instability. In contrast, weakened short-wave radiation fluxes and increased upward sensible and latent heat fluxes in the northern side of NWPAC can cause negative anomalous SSTAs, which favors the maintenance of NWPAC.
    Accept: June 17, 2019                                                      
    Abstract:
    The influence of external forcing changes over time on non-stationary systems is very important. How to reconstruct or extract external forcing features from non-stationary systems becomes the key. In this paper, based on the Slow Feature Analysis (SFA), the continuous system (the changed Lorenz system) is used as the reference model. We discuss the ability of slow feature analysis to extract different forced signals in the model under the conditions of periodic forcing, weakened periodic forcing, exponential decay forcing, and periodic forcing with exponential decay. The results show that the slow feature analysis can extract the external forcing information acting on the continuous system, and its extraction effect is related to the intensity of the external forcing, noise and embedding dimension m: For the weaker external forcing or the stronger the noise interference, the worse the extraction effect, the false high frequency fluctuation will appear in the extracted signal; the increase of the embedded dimension m can improve the extraction effect of the external forcing signal to a certain extent. The experiment also shows that the external forcing acting on a single variable embeds its driving information in the system, and SFA can extract the external forcing signal from other variables.
    Accept: June 12, 2019                                                      
    Abstract:
    Based on microwave radiometer, wind profiler radar, four-component radiometer, sonic anemometer-thermometer, satellite images, buoys, conventional surface observation, and FNL (Final) reanalysis data, a heavy fog occurred around Bohai Sea on 17 December 2016 was investigated. The synoptic system for fog formation and vertical characteristics of radiation and turbulence were studied as key analysis points. The results show that: (1) the fog appeared in the front of low pressure and the back of high pressure, and the warm-wet advection accompanied by strong low-level jet provided stable inversion and continuous water vapor accumulation in the fog area, which was very helpful to the formation of fog. (2) The water vapor flux was closely related to the movement of the low-level jet. The growth rate of near-surface specific humidity was proportional to the intensity of low-level jet. (3) Water vapor transport humidified the lower boundary layer atmosphere around the Bohai Sea, which enhanced the attenuation effect of atmospheric radiation, leading to the decrease of short-wave radiation and increase of long-wave radiation. When fog formed, the net radiation was approaching zero. (4) Inversion effectively inhibited the development of turbulent. the turbulence kinetic energy and friction velocity in the near-surface layer were weak.
    Accept: May 29, 2019                                                      
    Abstract:
    Aerosol lidar and radio sounding are two main methods to detect the height of boundary layer at home and abroad. In this paper, based on three consecutive months of lidar data and radiosonde data from November 2017 to January 2018 in Beijing area, the detection methods and calculation results of atmospheric boundary layer height are analyzed and compared according to three weather conditions: clear day, pollution and cloudy day. The results show that the three methods based on extinction coefficient of lidar, gradient method, standard deviation method and wavelet method, can extract the boundary layer height well. The boundary layer height calculated by clean sky standard deviation method is higher than that calculated by gradient method and wavelet method. The average boundary layer height obtained by radio sounding at 08:00 and 20:00 are 1176 m and 1224 m, respectively. In polluted days, the calculated results of standard deviation method are lower than those of gradient method and wavelet method. The average height of boundary layer obtained by radio sounding in polluted days is about 956 m, which decreases by more than 200 m compared with clean days. In heavy polluted days, the lowest is 562 M. The inverse correlation between inversion height and PM2.5 concentration is obvious. In cloudy weather, the boundary layer height determined by gradient method and wavelet method is very close to the cloud height, and the result calculated by standard deviation method is slightly lower. The height of boundary layer calculated by aerosol lidar has no obvious decreasing trend with the increase of pollution level. At 08:00, the height of boundary layer is almost around 900 M. At 20:00, the height of boundary layer decreases slightly with the increase of pollution level, but increases under severe pollution. This may be due to the continuous accumulation of pollutants. Standard deviation method is not susceptible to the influence of pollutant transport process, and the height of boundary layer determined by gradient method is susceptible to the influence of pollutant transport process, slightly higher than the height of inversion layer. When the height of the boundary layer determined by lidar is affected by the residual layer, it will also be higher than the inversion layer.
    Accept: May 28, 2019                                                      
    Abstract:
    Abstract Using C-band dual-polarization radar (C-POL) datasets from the Third Tibetan Plateau Atmospheric Scientific Experiment, EAR-interim 0.125°×0.125° reanalysis data, conventional meteorological radiosonde data, diagnostic analysis and radar echo features of a hailstorm severe convective weather process in the Naqu area of Tibet on the afternoon of July 30, 2014 are carried out. Results show: (1) The hail process occurred during the eastward movement of a plateau vortex-shear line. The forward-tilting shear line at the rear of the vortex provided favorable energy and water vapor for this hail process. (2) The water vapor provided for the severe convective weather mainly comes from the Bay of Bengal, India and Nepal, which strengthens significantly before the severe convective weather. Water vapor in the lower layer was concentrated below 400hPa, with obvious convergence of water vapor and vertical upward transportation. (3) The layer below 400hPa of Naqu, the overlap area of pseudo-equivalent potential temperature decreasing with height, the negative vertical velocity and the negative divergence, has obvious convective instability energy and dynamic conditions. (4) It can be found on radar echo images that the severe convective weather is obviously local, mainly caused by multiple γ mesoscale isolated convection cells,the moving path of which is consistent with the southwest airflow in front of the shear line. Most of cells have small horizontal scales and short life, but some cells are stronger and have long life. Local small scale velocity convergence can lead to new cells, and the occurrence, development and maintenance of cells depend on the low-level airflow convergence to provide dynamic conditions. (5) It shows on the RHI map the characteristics of a weak hail cloud without obvious strong overhang echo, with the top reaching around 16km but not reaching the top of the troposphere, higher than the general convective clouds in plain areas, and the 0°C layer is much lower than that on the plain area. The cloud indicates the deep strong convective precipitation, and the precipitation center is located in the bottom of the cloud, including precipitation and hail dominated by radon particles. There are strong inflows and updrafts in the vertical direction. The suspended echoes appear above the inflowing updraft, the airflow sinking zone below the middle-level convergence zone corresponds to the hail zone. The combination of the middle-level convergence zone and the high-altitude divergence zone leads to vertical growth and strong development of convective storms.
    Accept: May 24, 2019                                                      
    Abstract:
    The MJO simulation ability of the numerical experiments from CNRM General Circulation Models(GCMs) participated in the MJOTF/GASS are evaluated by tracking the eastward propagating positive equatorial precipitation anomalies. The GCMs include a fully coupled simulation (CNRM-CM), a half-coupled simulation (CNRM-ACM) and uncoupled simulation (CNRM-AM) during 1991-2010. The possible impacts of air-sea coupling on the MJO simulation are investigated. CNRM-CM shows the highest skill in simulating the MJO characteristics, in terms of the occurrence frequency, amplitude and the propagation range. The climatological Sea Surface Temperature (SST) of CNRM-CM and CNRM-ACM shows distinct cold bias over the Indo-Pacific warm pool region compared with the CNRM-AM. Such cold bias does not impact the MJO simulation ability too much when compare the MJO simulation abilities between CNRM-ACM and CNRM-AM. The zonal gradient of the intraseasonal SST is obvious in CNRM-CM with strong positive intraseasonal SST anomaly to the east of the MJO convection center and negative intraseasonal SST anomaly to the west of the MJO convection center when MJO is over the Indian Ocean, while such gradient is lost in CNRM-ACM and CNRM-AM. The results indicate the impact of the air-sea coupling on the MJO simulations by the CNRM GCMs mainly through the influences on the intraseasonal SST variability.
    Accept: May 13, 2019                                                      
    Abstract:
    Based on the hourly geostationary satellite TBB data provided by Kochi University, two types of mesoscale convective systems (MCSs) generated over the eastern Tibetan Plateau (TP) during 16 consecutive warm seasons were identified and tracked by an automatic tracking algorithm. After verifying the automatic tracking results manually, statistical and comparative analyses on these two types of MCSs were conducted using NOAA&amp;#39;&amp;#39;s CMORPH precipitation data and NCEP&amp;#39;&amp;#39;s CFSR reanalysis data. Main results show that, July and August were the most active months for MCSs’ generation over the eastern section of the plateau, but they underwent minima in the proportions that vacated the TP. In May, the MCSs experienced a minimum in MCSs’ generation number, but up to nearly 40% MCSs could vacate the TP. Compared to the MCSs that could not vacate the TP (N-MCS), the MCSs that could vacate the TP (C-MCS) usually had longer lifespan, earlier triggering time, and lower proportion of short lifespan cases. During the study period, compared to the N-MCSs, the C-MCSs were usually faster in development and stronger in intensity. However, due to the much lower occurrence frequency of C-MCSs, their contribution to the local precipitation was only about 15%, which was approximately a half of that of the N-MCSs. The composite circulation features of the C-MCSs and N-MCSs generated over the eastern plateau were significantly different. The shortwave trough and stronger westerly wind in the middle troposphere as well as the cyclonic wind shear in the lower troposphere provided more favorable conditions for the C-MCSs’ occurrence, maintenance and eastward displacement. In contrast, the divergence conditions in the upper troposphere were more conducive to the N-MCSs (the South Asia high associated with them was stronger).
    Accept: May 09, 2019                                                      
    Abstract:
    The aims of this work are to design the observation station network of the air-sea boundary layer over the Bohai Sea and the Yellow Sea and further investigate its effect on the numerical prediction model (WRF: Weather Research and Forecasting model). The statistical analysis of regional characteristics of the ocean-meteorological elements, along with the model error and the observation system simulation experiments (OSSE) approaches are adopted. The evaluations on the observation station network are conducted under different wind and weather conditions and the advantages and disadvantages are weighed for each configuration scheme. The 6-hourly NCEP/NCAR FNL reanalysis data (1°×1°), NCEP real-time global daily sea surface temperature (RTG_SST) analysis data (0.5°×0.5°) and buoy and oil-platform observational data are used. The results show that the forecast humidity and wind are greatly affected by the actual direction and velocity of wind, and the humidity is better predicted with easterly and northerly wind conditions. Moreover, in the moderate southerly wind case, the forecast winds are closer to the observations. The forecast accuracy rate of temperature can be significantly improved with the configuration of station network determined by the regional characteristics. Based on the comprehensive overview of the model simulations, suggestions for configuring the air-sea observation stations to improve the accuracy of numerical forecasts are provided.
    Accept: May 09, 2019                                                      
    Abstract:
    The strong precipitation caused by the typhoon Fung-Wong landing in 2008 was simulated by using WRF WDM6 double-moment cloud microphysics scheme. The model simulations are evaluated by statistical methods using cloud top brightness temperature TBB and precipitation radar reflectivity data from MTSAT-1R, TRMM satellite and the Satellite Data Simulator Unit. Reduce the difference between simulation results and satellite observations through sensitivity experiments including autoconversion rate of cloud water to rain, ice nucleation, the terminal velocity and the slope parameter of snow and graupel. The results show that the precipitation, the strong convective cloud system and the convective columnar radar echo simulated by the WDM6 scheme are agreed with observation, but the simulation results are stronger at some area. The WDM6 scheme simulation produced more shallow convective clouds and underestimated the frequency of convective cloud systems. The radar echoes simulated by different cloud types are all strong, and the vertical distribution of convective cloud radar echoes is close to observation. The sensitivity experiments results show that modifying the production rate for autoconversion of cloud water to rain in the WDM6 scheme effectively improves the simulation results. At the same time, it is found that the concentration of initial cloud droplets affects the production rate for autoconversion of cloud water to rain and finally affects the simulation results of cloud structure and radar reflectivity. High concentration of initial cloud droplets will make the simulation result worse.
    Accept: May 09, 2019                                                      
    Abstract:
    West China (25 &amp;amp;amp;amp;amp;amp;#176; N - 35 &amp;amp;amp;amp;amp;amp;#176; N, 100 &amp;amp;amp;amp;amp;amp;#176; E - 110 &amp;amp;amp;amp;amp;amp;#176; E) is one of the main regions of autumn precipitation in China. This paper studies the interdecadal trend of autumn precipitation in west China from 1961 to 2014 and its relationship with atmospheric circulation and SST. The research results show that: west China precipitation had a significant interdecadal transition from 1961 to 2014, accompanied by corresponding interannual changes. From 1960 to the mid - late 1980s, west China precipitation was unusually frequent and showed a significant downward trend. During the period from 1990 to 2010, west China precipitation was unusually low and accompanied by an upward trend, the turning point of the trend appeared roughly around 1998. The period of P1 (1964 - 1998) showed a downward trend, while the period of P2 (1998 - 2014) showed an upward trend. The atmospheric potential height fields at 850hPa and 500hPa during P1 were configured as positive anomalies in the west and negative anomalies in the east. The circulation field affects the quasi-latitudinal wave train in east Asia from the Atlantic to the arctic baron-kara sea, a negative anomaly center was formed in the northeast of the study area, water vapor is transported from the northward continental region by northward flow, the wave train reflects the modulation of the NAO negative phase in the upstream, autumn rain shows a downward trend; the height field configuration in time period of P2 is opposite to that in time period of P1, the part of wave line in Eurasia is northwest - southeast, the whole train is to the west which formed a negative anomaly center in the northwestern side of the study area, this causes the study area to be controlled by the southwest airflow, the wave train reflects the modulation of the NAO positive phase in the upstream, autumn rain shows a upward trend. The key regions that affect the change of autumn rain trends are located in the tropical middle eastern Pacific and tropical Indian Ocean. There is a positive correlation between the tropical middle eastern Pacific Ocean and the autumn precipitation trend in west China during the period of P1, and the weak correlation of the previous winter gradually evolved to the strong correlation of the same period (autumn), there is also a positive correlation between the Indian Ocean and autumn precipitation in west China. During the period of P2, the tropical middle eastern Pacific also affected the annual change of autumn rain, showing a negative correlation between them, however, the pre-winter corresponding to the different period of P1 showed a significant negative correlation, and the influence of the tropical middle eastern Pacific gradually weakened in the summer and autumn season, the significant correlation region is not only located in the cold tongue region of the eastern Pacific Ocean, the northwest Pacific presents an inverse correlation with the middle eastern Pacific, and the tropical Indian Ocean changed from negative correlation to positive correlation.
    Display Method:
    Available online:November 05, 2019, DOI: 10.3878/j.issn.1006-9585.2019.19026
    Abstract:
    Abstract: Based on the annual averaged surface air temperature data from eight meteorological stations in the source region of the Yellow River using the Ensemble Empirical Mode Decomposition (EEMD) approach, the multi-timescale temperature features of meteorological stations with Madoi as a representative during 1953-2017 and their contributions to the temperature variations are revealed. The correlations between different time-scale temperature oscillations with the SST indices are analyzed, particularly with the Atlantic Multidecadal Oscillation (AMO). The results demonstrated that: (1) a long-term temperature trend was 0.31℃/10a during 1953-2017 in the source region of the Yellow River, and the warming started in the late 1980s and accelerated in the late 1990s. (2) There were 3-year, 6-year, 11-year, 25-year, 64-year and 65-year quasi-cycle oscillations for the temperature during 1953-2017. Among them, the 3-year and 65-year quasi-cycle oscillations were significant. The amplitude of 3-year time-scale oscillation was large before the 21st century and decreased after the 21st century, while the amplitude of 65-year oscillation was enhanced after the 21st century. (3) The 3-year quasi-cycle oscillation occupied a dominant position during the period of 1953-1997, and the contribution of 65-year oscillation increased nearly five times which was equivalent to the contribution of the 3-year oscillation during the rapid warming period since 1998. (4) The correlations between temperature with Nino3.4 and PDO indices were not significant, but the maximum significant correlation was found when the temperature led PDO 22 years. Unlike PDO, the maximum significant correlation was found when AMO led the original temperature and its three inter-decadal components 0 and 3-7 years which supported that AMO had a significant impact on the temperature variation in the source region of the Yellow River. (5) The positive warm phase of AMO corresponded to the warming of the East Asia including China, and the source region of the Yellow River was only a part of that area. The negative cold phase of AMO from the early 1960s to the middle and late 1990s and the positive warm phase of AMO from the early 1990s to the present corresponded to the negative and positive phases of the temperature in the source region of the Yellow River. The AMO highly correlated with the 65-year oscillation. These results supported that AMO was an important climatic oscillation affecting the temperature variation especially on the inter-decadal time scales in the source region of the Yellow River.
    Display Method:
    2017,22(3):253-270, DOI: 10.3878/j.issn.1006-9585.2016.16104
    [Abstract] (3223) [HTML] (0) [PDF 12.34 M] (15861)
    Abstract:
    Based on the remote sensing data from National Snow and ICE Data Center (NSIDC), the performance of CMIP5 (Coupled Model Inter-comparison Project) models in reproducing the winter snow water equivalent (SWE) in the Eurasian continent during 1981-2005 was evaluated first, and the multi-model ensemble (MME) technique was then applied to project the SWE changes over Eurasian continent in the 21st century under the conditions of two different representative concentration pathways (RCP4.5 and RCP8.5) using eight good CMIP models out of total 26 models. The results show that the models were able to reproduce the spatial pattern of winter mean SWE in the Eurasia, i.e. the 25-year average of SWE increased from south to north and SWE in the Tibetan Plateau was much higher than those in other regions of the same latitude. However, some errors still existed in the models. For example, almost all models underestimated the maximum SWE in central Siberia, and SWE in northeastern China was also underestimated. It was found that SWE to the west of Ural Mountains and over northern part of China and Mongolia was overestimated when compared with observation. Meanwhile, only a subset of the models could produce the maximum SWE on the eastern Tibetan Plateau, and the spurious maximum SWE could be found on the western Tibetan Plateau in most CMIP5 models. The spatial and temporal characteristics of winter SWE from CMIP5 model simulations and observations were further analyzed using the Empirical Orthogonal Function (EOF) analysis, and the results suggested that only a small number of CMIP5 models could reproduce main features of the first eigenvector that reflects the decadal variation of SWE over the whole Eurasia. The second mode reflects the annual variation of SWE over the Eurasia, and only a few models (e.g., INMCM4) could reproduce the spatial and temporal characteristics of the second mode to some extent. With respect to the reference period 1981-2005, projection of SWE by the MME under the RCP4.5 shows that SWE in the northeastern Eurasia continent would increase significantly with an increase of 4.1 mm for the 25-year averaged winter SWE in the early stage of the 21st century, followed by 5.4-mm and 6.8-mm increases in the middle and late 21st century, respectively. In contrast, there would exist a decrease of SWE in continental Europe to the west of 90°E and over the Tibetan Plateau and the decrease would become more severe with time. In terms of percentage change of SWE, the region with large magnitudes was found in the northeastern Eurasian continent, where the increase of SWE could be around 5%-10%. However, no maximum centers were found in the Tibetan Plateau, Scandinavian Peninsula and East European Plain possibly because of the large values of winter SWE in these regions. Projection of SWE changes by the MME under the high emission scenario RCP8.5 shows a similar pattern with results under the emission scenario RCP4.5, but with larger amplitudes of changes in snow water equivalence.
    2010,15(6):743-755, DOI: 10.3878/j.issn.1006-9585.2010.06.04
    [Abstract] (3044) [HTML] (0) [PDF 11.35 M] (13306)
    Abstract:
    利用区域气候模式(RegCM3)敏感性数值试验模拟“三江源”地区湿地变化对区域气候的影响。依据2000年美国EOS/MODIS遥感数据解译结果以及1990年1∶100万青海省土地利用2种资料中三江源区湿地资源的分布状况,敏感性数值试验采用R1、R2两种湿地覆盖情景,分别代表三江源地区湿地资源较广布和湿地面积锐减后的两种情景,对三江源地区的降水和气温进行了长达15年的积分试验。结果表明,湿地减少对三江源区气温和降水的总体效应是使降水减少、气温升高。区域空间分布的分析表明:年降水量减少幅度较大的区域位于三江源区西部,15年平均减少40~90 mm左右;年平均气温升高幅度最大的区域位于三江源区西北部,15年平均升高0.4 ℃以上。15年积分结果的时间序列分析结果表明:湿地减少后三江源区的增温效应会随着时间进程缓慢扩大,但降水在模拟的后6年不再有明显差异。
    2010,15(4):443-450, DOI: 10.3878/j.issn.1006-9585.2010.04.12
    [Abstract] (3771) [HTML] (0) [PDF 5.42 M] (12079)
    Abstract:
    利用国家气象信息中心提供的华南89个代表站1969~2008年逐日降水资料, 研究了近40年我国华南前汛期(4~6月)极端降水时空演变特征,主要结论是:(1)华南前汛期降水强度、强降水量和暴雨日数的空间分布与总降水量的空间分布基本一致;(2)极端降水指数随时间的变化对华南整个区域前汛期总降水量的变化有很好的指示意义, 特别是强降水量、强降水频率和暴雨日数;90年代以来华南前汛期总降水量的显著增加与强降水量、强降水频率以及暴雨日数显著增加密切相关,且极端强降水量异常程度明显增强。
    2010,15(4):462-469, DOI: 10.3878/j.issn.1006-9585.2010.04.14
    [Abstract] (2950) [HTML] (0) [PDF 7.97 M] (11335)
    Abstract:
    利用江西省17个国家级台站1960~2008年逐日降水量资料,对日降水量超过绝对阈值(25 mm和50 mm)和百分位数阈值(95%和99%)的极端降水变化情况进行了分析。结果表明,江西省近50年极端降水频率和强度均呈波动上升趋势,大雨和强降水频率的增加最为迅速,暴雨和极端强降水事件强度增加最大;夏季各种极端降水事件频率均有明显升高;冬季大雨和强降水事件频率也有显著增加;春季和秋季极端降水强度有明显增加,特别是暴雨和极端强降水事件强度增加迅速;夏季暴雨和极端强降水强度有所降低或略有增加;江西省极端降水的频率和强度变化趋势较为一致,特别是1990年代;极端降水的增加以发生频数的增加为主,降水强度的增加并不显著;近50年江西省大部分地区的极端降水事件频率和强度均有增加,但高值区的分布有较大的差异。极端强降水事件强度在鄱阳湖平原附近减小,而在周边的大部分地区呈增长趋势。进一步的分析发现,极端降水强度的变化与地形有显著的正相关关系。
    2010,15(4):395-404, DOI: 10.3878/j.issn.1006-9585.2010.04.07
    [Abstract] (3943) [HTML] (0) [PDF 9.95 M] (10806)
    Abstract:
    2009年10月底到11月底,包括北京在内的华北地区连续出现2次较强冷空气过程,造成大范围的低温、雨雪天气。利用北京地区11个气象站近50年逐日气温、降水资料,对全市历年11月低温雨雪事件的演变特征进行了分析。结果表明,2009年11月全市月平均气温、月平均最低气温均突破了50年的最低记录,月平均最高气温位列1981年11月之后,接近历史极值;2009年11月降雪量也位列有记录以来第一位,冰冻日数历史排位第三;从气温和降水极端事件发生的频次来看,2009年11月日平均气温、日最高气温和日最低气温通过5%分位值标准的极端低温事件频次都明显偏多,在50年中居于第2位,降水量通过95%分位值标准的极端强事件频次在50年中居于第四位。2009年11月的严重低温雨雪事件出现在区域气温总体变暖、低温事件频率总体下降的气候趋势背景下,在一定程度上放大了负面影响。亚洲中高纬地区500 hPa高度场经向度异常加大、冷暖气流交换活跃,是造成2009年11月极端低温和大雪的直接环流因子。
    2010,15(3):311-321, DOI: 10.3878/j.issn.1006-9585.2010.03.11
    [Abstract] (4677) [HTML] (0) [PDF 5.96 M] (10595)
    Abstract:
    The decadal variation of precipitation in March over South China and its relationship with PDO(Pacific Decadal Oscillation) are analyzed by using the observational rainfall data, PDO index, and NCEP reanalysis data. The Mann-Kendall test performed on precipitation in March over South China shows that the turning year for decadal change in about 1978, precipitation experienced a notable low to high transition. In the decadal period of low rainfall, PDO is in negative phase (high sea surface temperature in the North Pacific, low sea surface temperature in the middle East Pacific), sea level pressure and height at 500 hPa in North Pacific are high, sea level pressure and height at 500 hPa on the Asian continent are low, the troposphere atmosphere in East Asia is warm, the western Pacific subtropical high is easterly, East Asian upper tropospheric jet stream is northerly, Hadley circulation in East Asian is weak. In the decadal period of high rainfall, PDO is in positive phase, the situation is completely the opposite. The variability of the precipitation in March has a very significant correlation with PDO index in February and March, the correlation coefficients between them were positive at 99% confidence level. It can be summed up the changes of precipitation in March over South China is closely related to the changes of sea surface temperature in the North Pacific Ocean on decadal time scales, and a possible mechanism is proposed about how the PDO influences the precipitation anomaly over South China in March.
    2011,16(2):209-220, DOI: 10.3878/j.issn.1006-9585.2011.02.10
    [Abstract] (3277) [HTML] (0) [PDF 11.11 M] (8810)
    Abstract:
    The main weather processes and their related circulations in summer 2009, including the South China Sea monsoon and the precipitation features over South China, the Yangtze Huaihe River basin, and northeast China, are discussed. There were not wide area floods, but serious heat wave and drought were reported over southern China. The South China Sea monsoon began at the fourth pentad of May. The Indian Monsoon was extremely abnormal than usual which may influenced the variation of rainband in China. The typical circulation and the related strong precipitation during the Meiyu period over the Yangtze River basin did not appeared, however, the westerlies troughs and landing typhoons brought several rainfall processes to the Yangtze Huaihe River basin. The total precipitation over North China was below normal. The vortices over northeastern China were very active in the summer of 2009, which resulted in the more precipitation and low temperature in that area. In addition, the heat wave and drought occurred in southern China during 8 to 24 July and 15 August to 14 September, and both of the periods were associated with the western Pacific subtropical high.
    2017,22(2):115-133, DOI: 10.3878/j.issn.1006-9585.2016.16085
    [Abstract] (3291) [HTML] (0) [PDF 32.99 M] (7616)
    Abstract:
    The performance of IAP (Institute of Atmospheric Physics) Atmospheric General Circulation Model Version 4.0 (IAP AGCM4.0) in simulating the Madden-Julian Oscillation (MJO) is examined in this paper using the 30-year model integration results during 1979-2008. It is found that the IAP AGCM4.0 can reproduce the observed wave number-frequency power spectrum of MJO to some extent, with dominant spectrum power at wavenumber 1 and periods of 30-80 days. Meanwhile, the IAP AGCM4.0 can generally reproduce the observed coherent eastward propagating signals at the intraseasonal time scale, with the power of eastward moving waves much stronger than that of the westward moving waves. The RMM (Real-time Multivariate MJO) index is further applied to evaluate the simulated MJO structure. It is found that IAP AGCM4.0 can well reproduce the observed intraseasonal signals of 850 hPa and 200 hPa zonal winds and the enhanced convection structure of MJO in the tropical regions. However, the simulated eastward propagation is generally too fast, and the simulated westward propagation is stronger than the observation. IAP AGCM4.0 also splits the intraseasonal convective anomalies into two centers straddling the equator, and produces weaker convection. The vertical profile of diabatic heating simulated by the IAP AGCM4.0 has a similar structure to the observation, but in the Indian Ocean and western Pacific Ocean, positive maximum heating occurs later than the observation in phases. Numerical experiments are conducted by using different RHc (relative humidity criterion) values of 85%, 90%, 95%, and 100% for triggering the convection. It is found that the vertical diabatic heating profiles for experiments with different RHc vary considerably, which can lead to differences in the simulated MJO features. Comparison of results further shows that both the main features of MJO and vertical diabatic heating profiles are best simulated when RHc is set to 90%. This suggests that proper specifications of the values for key parameters in the convective parameterization scheme might help improve the model capability in simulating the observed features of MJO.
    2005,10(4):701-716, DOI: 10.3878/j.issn.1006-9585.2005.04.01
    Abstract:
    总结了"十五"攻关课题有关中国温度变化研究的若干进展.在资料质量控制和序列非均一性检验及订正的基础上,更新了中国地面近50年、100年和1 000年气温序列.研究表明,不论是近54年还是近100年全国年平均地面气温升高趋势一般比原来分析结果表明的要强,分别达到0.25℃/10 a和0.08℃/10 a.中国现代增暖最明显的地区包括东北、华北、西北和青藏高原北部,最显著的季节在冬季和春季.近50多年中国近地面气候变暖主要是平均最低气温明显上升的结果,全国范围内极端最低气温也显著升高,而极端最高气温升高不多.中国与温度相关的极端气候事件强度和频率一般呈降低趋势或稳定态势.研究发现,城市化因素对中国地面平均气温记录具有显著影响,但在现有的全国和区域平均温度变化分析中一般没有考虑,因此需要在将来的研究中给予密切关注.在增温明显的华北地区,1961~2000年间城市化引起的年平均气温增加值达到0.44℃,占全部增温的38%,城市化引起的增温速率为0.11℃/10 a.中国其他地区的增温趋势中也或多或少反映出增强的城市热岛效应影响.20世纪60年代初以来中国对流层中下层温度变化趋势不明显,仅为0.05℃/10 a,比地面气温变化小一个量级;对流层上层和平流层底层年平均温度呈明显下降趋势,变化速率分别为-0.17℃/10 a和-0.22℃/10 a;整个对流层平均温度呈微弱下降趋势.中国对流层温度与地面气温变化趋势存在明显的差异,但这种差异在20世纪80年代初以后趋于减小.近千年来中国地面气温变化史上可能确存在"中世纪温暖期"和"小冰期"等特征性气候阶段,但"中世纪温暖期"的温暖程度似乎没有过去认为的那样明显.从全国范围看,11世纪末和13世纪中的温暖程度可能均超过了20世纪30~40年代暖期,表明20世纪的增暖可能并非史无前例.中国20世纪气候增暖的原因目前还不能给出明确回答.一些迹象表明,人类活动可能已经对中国的地面气温变化产生了影响,但太阳活动及气候系统内部的低频振动对现代气候变暖可能也具有重要影响.
    2000,5(3):329-332, DOI: 10.3878/j.issn.1006-9585.2000.03.13
    Abstract:
    阐述了当前全球温室气体浓度的增加及其引起的气候效应,讨论了气候变化研究中存在的许多不确定性,如未来温室气体的浓度如何变化,未来气候如何变化,以及气候影响的评价问题等.最后,强调了未来气候变化基础研究中需要注意的问题.
    2006,11(6):772-780, DOI: 10.3878/j.issn.1006-9585.2006.06.12
    Abstract:
    从云雾降水物理学的角度学习和分析了一些中国古诗词。内容有:1)分析和统计了唐诗300首和毛泽东诗词中用到云雾雨雪等字的百分比,其分别占总首数的45%和66%;2)列举和分析了描述自然过程、大气过程有云雨雪等字的诗(词)句;3)从现代科学观出发,分析了在一些古诗词中有关云、雨、霜、露等的理解,并作了一些评述;4)对古诗词中直接描述云、雾、雨、雪的内容进行了评论。
    2009,14(1):9-20, DOI: 10.3878/j.issn.1006-9585.2009.01.02
    [Abstract] (5324) [HTML] (0) [PDF 11.28 M] (6787)
    Abstract:
    利用1951~2000年我国西北干旱、半干旱区地温、气温和表面风场逐日4个时次(北京时间2、8、14和20时)的台站观测资料,以及NCEP/NCAR和ERA-40再分析资料,计算并比较了在我国西北地区春夏季感热输送的差异。分析结果表明:NCEP/NCAR和ERA-40的感热输送再分析资料都能显示出我国西北地区是欧亚大陆上的感热中心之一。从年代际时间尺度上,ERA-40再分析资料的感热资料更接近于实际台站观测资料计算得到的感热资料。
    2014,19(4):419-436, DOI: 10.3878/j.issn.1006-9585.2013.13041
    [Abstract] (3555) [HTML] (0) [PDF 11.62 M] (6530)
    Abstract:
    The uncertainties regarding these hydrological simulation results were further examined by three sets of numerical simulations using different precipitation forcing. It's found that the streamflow simulation using CFSR precipitation forcing exhibited a larger bias than simulations using EAG (East Asia Grid data) precipitation forcing. These results demonstrate the importance of the precipitation forcing chosen for hydrological simulation. Further comparative analysis suggests that the temporal disaggregation method for precipitation forcing preserves the strong diurnal variation, and is therefore also important when conducting hydrological simulations over the Huaihe River basin."
    2014,19(2):153-163, DOI: 10.3878/j.issn.1006-9585.2014.13231
    [Abstract] (7136) [HTML] (0) [PDF 12.48 M] (6420)
    Abstract:
    An aerosol-optical module based on Mie scattering theory has been implemented in the Nested Air Quality Prediction Modeling System (NAQPMS), and a new coupler has been developed to deal with the interaction between the mesoscale meteorology model WRF (Weather Research and Forecasting Model) and NAQPMS. The one-way off-line and two-way coupled WRF-NAQPMS models are compared to simulate the severe haze in the Beijing-Tianjin-Hebei area from 27 September to 1 October 2013. The results show that the simulated meteorological elements and PM2.5 concentrations from the two-way coupled model with the aerosol direct radiation effect are more consistent with observations. During the haze period, the boundary layer meteorological elements change significantly because of the aerosol direct radiation effect over the Beijing-Tianjin-Hebei area: Incoming solar radiation is reduced by 25%, the 2-m temperature decreases by 1 ℃, the turbulent kinetic energy is reduced by 25%, the 10-m wind speed decreases by up to 0.2 m/s, and the planetary boundary layer (PBL) height is reduced by 25%. These changes make the atmospheric boundary layer more stable and further exacerbate air pollution over the areas where it is already severe, for example, the PM2.5 concentration increases by up to 30% over Shijiazhuang City. The analysis indicates that there is a positive feedback mechanism between haze and boundary layer meteorology, and the two-way coupled model incorporating this feedback is helpful for accurate simulation and forecasting of haze pollution processes.
    2010,15(4):425-432, DOI: 10.3878/j.issn.1006-9585.2010.04.11
    [Abstract] (2899) [HTML] (0) [PDF 12.43 M] (6059)
    Abstract:
    利用NCAR/NCEP再分析日资料计算了影响山西省区域的季风强度指数,并以山西省1960~2005年逐日降水资料为基础,采用线性趋势分析、小波分析等数理统计方法,分析了46年来山西省主汛期极端降水的变化特征。结果表明: 考虑到季风在山西建立和撤退的多年平均日期,山西省的主汛期定为7月上旬到8月中旬更为恰当;山西省大部分地区主汛期降水量均呈下降趋势,但日降水大于30 mm和50 mm降水量却有所增加,尤以中部地区增多为主;20世纪60年代以来全山西省主汛期小雨日数明显减少;进入21世纪后,山西省主汛期降水虽然在减少,但极端强降水的次数有所增加,主要表现在中部地区大于30 mm、大于50 mm降水的日数和强度均有增加或增强的趋势。在多暴雨年份,500 hPa位势高度异常场上在乌拉尔山附近地区易产生稳定的、强大的高压形势或阻塞形势,贝加尔湖至巴尔咯什湖一带有强低压槽,西太平洋副热带高压加强且北抬西伸,山西处于强低压槽的东南侧与副高西北侧的交汇带,且850 hPa风场异常显示华北地区被一致的偏南气流控制,且与蒙古异常气旋南部的异常西风相遇,极有利于山西产生极端强降水。
    2004,9(2):261-277, DOI: 10.3878/j.issn.1006-9585.2004.02.04
    Abstract:
    如何把离散的气象台站资料通过合适的空间内插方法转变成规则的网格数据,对于气候变化分析和模拟研究具有重要的意义.作者利用中国区域160个常用台站10年降水观测资料为例,分别采用克里格(Kriging)插值、反距离加权、Delaunay三角剖分线性插值、双谐样条(Biharmonic Spline)插值和Cressman客观分析等几种常见的空间内插方法,较为系统地分析和比较了这几种内插方法插值结果之间的异同,对其优缺点和适用范围进行了适当讨论,并采用不同的网格分辨率和影响半径对Cressman客观分析方法做了进一步分析比较.结果表明:在台站分布密集的区域不同空间内插方法之间差异较小,在台站分布稀疏的区域则差异较大;与更加密集的台站观测资料的比较显示,自动调节影响半径的Cressman客观分析方法与双谐样条插值方法误差相对较小.
    2011,16(4):505-512, DOI: 10.3878/j.issn.1006-9585.2011.04.11
    [Abstract] (4707) [HTML] (0) [PDF 4.74 M] (6011)
    Abstract:
    The characteristics of vegetation and its response to climate change were explored using NOAA/AVHRR(NOAA/Advanced Very High Resolution Radiometer) (1982-2001) and EOS/MODIS (Earth Observation System/Moderate Resolution Imaging Spectroradiometer)(2000-2008) NDVI (Normalized Difference Vegetation Index) products, monthly air temperature and precipitation of Maqu, Madoi, and Xinghai meteorology stations over the source region of the Yellow River. The results showed: The vegetation of Madoi region generally revealed a decreasing trend in the time and space scale; the vegetation of Maqu region, which is the source region of the up stream Yellow River, revealed an increasing trend before 2000 and appeared to degenerate after that; The vegetation revealed a decreasing (increasing) trend before (after) 2000 in the north of the source region of the up stream Yellow River. The NDVI appeared to decrease during 1982-1990 in the spatial scale, this occurred in the east region of the Ngoring Lake. The areas with decreasing trend of vegetation further enlarged during 1991-2000. Du ring 2000-2008, an evident degeneration occurred in Maqu area, while the vegetation of Xinghai region generally increased. The responding relationship of the vegetation to climate change implied: The air temperature was the most sensitive factor to vegetation variation in the source region of the Yellow River, an exponential relationship existed between them, the NDVI had a little variation when the air temperature was lower than 0.0 ℃, and the NDVI increased fast with the air temperature when the air temperature was greater than 5.0 ℃. Local precipitation had great contribution to the early growing of the vegetation, when the vegetation saturated and the NDVI reached maximum, local precipitation was not sensitive to vegetation variation anymore.
    2006,11(6):683-690, DOI: 10.3878/j.issn.1006-9585.2006.06.02
    Abstract:
    利用“中国西北干旱区陆气相互作用观测试验(NWC-LAIEX)”所获取一年的地面辐射观测资料(2000年5月~2001年4月),比较分析了我国典型干旱区敦煌戈壁、临泽沙漠和藏北高原五道梁地区地表辐射能量的收支特征。结果表明:3个地区各辐射分量季节变化明显,春季一般为跳跃式增加,而秋季则急剧减小,敦煌和临泽地区总辐射月总量几乎全年都小于藏北高原的五道梁地区,冬季最为明显。五道梁和临泽地区的地表反照率有较明显的季节变化和日变化,季节变化是夏季较小,冬季大;而敦煌戈壁地区的反照率不论是季节变化还是日变化,都比较平缓;3个地区相比,临泽沙漠地区的反照率最大,五道梁地区次之,敦煌戈壁地区最小。敦煌戈壁和临泽沙漠地区的地面向上长波辐射和大气逆辐射都比藏北高原的五道梁地区大。地面有效辐射在敦煌戈壁和临泽沙漠地区是夏季大,冬季小;而在藏北高原的五道梁地区则是春秋季大,冬夏季小。地面有效辐射与地面吸收辐射之比敦煌戈壁和临泽沙漠地区量值相近,藏北高原的五道梁地区较小,夏季尤为突出。在夏季,五道梁的地表净辐射要远远大于其他两个地区,冬季3个地区量值相当。与地表净辐射相对应,五道梁地区的地面热源强度在夏季大于敦煌戈壁地区,在冬季相差不大。
    2011,16(6):679-689, DOI: 10.3878/j.issn.1006-9585.2011.06.01
    [Abstract] (4079) [HTML] (0) [PDF 13.62 M] (5843)
    Abstract:
    The Weather Research and Forecasting (WRF) model coupled with a single layer Urban Canopy Model (UCM) is used to simulate the Urban Heat Island (UHI) features in Shanghai and Nanjing, two different cities in China. Results show that the horizontal distribution of UHI is determined by large scale surface wind, which causes high air temperature of downstream rural area. Cross sections of the difference of air temperature between the urban and rural surfaces are analyzed, the model suggests that more heat is transported from the land to the air over urban area, which leads to the continuous transportation of heat to the downstream rural surface under the control of the steady large scale wind. It is concluded that the effect of large scale surface wind on UHI can increase the downstream rural air temperature, which shouldn’t be ignored.
    2011,16(2):231-242, DOI: 10.3878/j.issn.1006-9585.2011.02.12
    [Abstract] (4560) [HTML] (0) [PDF 13.03 M] (5772)
    Abstract:
    Relationship between the East Asia Westerly Jet (EAWJ) and the Huaihe River Valley (HRV) summer rainfall was investigated month by month, using the NCEP/NCAR reanalysis data and the monthly rainfall data at 160 stations in China from 1979 to 2008. It was found that the HRV summer rainfall is closely related to the monthly variation of the EAWJ. In the years with more rainfall over the HRV, the EAWJ is located northward than normal and the circulation pattern exhibits two ridges and one trough in mid high latitudes of Asia in June. The cold air activities are weak and the HRV is controlled by anomalous southerlies, which favors more precipitation there. The situation is almost opposite in the years with less rainfall. In the years with more rainfall over the HRV, the EAWJ moves southward to its climatic location, the South Asia high is located eastward than normal, and the western Pacific subtropical high is stronger and is located westward than normal, resulting in more precipitation in the HRV during July and August, and vice versa. The analyses indicate that in June, the change in the intensity and location of the EAWJ is more influenced by the mid high latitude circulations of Asia. However, in July and August, the intensity and location of the EAWJ is more affected by the variation of the tropical and subtropical circulations.

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