Plateau Meteorology

Current Issue

28 October 2018, Volume 37 Issue 5   
  • Applicability Evaluation of Merged Soil Moisture in GLDAS-NOAH and CLDAS-V2.0 Products over Qinghai-Tibetan Plateau of 2015 Based on TIPEX Ⅲ Observations
  • CUI Yuanyuan;JING Wenqi;QIN Jun
  • 2018 Vol. 37 (5): 1143-1160.  DOI:10.7522/j.issn.1000-0534.2018.00020
  • Abstract ( ) HTML PDF (25881KB) ( )
  • In-situ soil temperature and soil moisture observations at five layers (5 cm, 10 cm, 20 cm, 50 cm and 100 cm) from the 3rd Qinghai-Tibetan Plateau Atmospheric Scientific Experiment (TIPEX Ⅲ) were used to verify the applicability of two land surface model products, i.e.Global Land Data Assimilation System-NCEP, OSU, Air Force and Office of Hydrology (GLDAS-NOAH) and CMA (China Meteorological Administration) Land Data Assimilation System Version 2.0 (CLDAS-V2.0).This paper calculated the correlation coefficient and deviation between the two land model products and the in-situ soil temperature and soil moisture observations in 2015.In addition, this paper also analyzed the response of the soil temperature and soil moisture products from CLDAS-V2.0 and GLDAS-NOAH.From the two aspects, this study comprehensively evaluated the soil temperature and soil moisture' applicability of the two model products over Qinghai-Tibetan Plateau.Through the above analysis, it is discovered that the correlation (both for soil temperature and soil moisture) between the CLDAS-V2.0 and in-situ observations is better than that of GLDAS-NOAH.The correlation between the land model products (both for CLDAS-V2.0 and GLDAS-NOAH) and in-situ observations in wet season is larger than that in dry season, and shows a decreasing trend with soil depth.The deviation of soil moisture between the CLDAS-V2.0 and in-situ observations is slightly larger than that of GLDAS-NOAH.In addition, in shallow soil layers, the mean relative error (MRE) of soil moisture between the model products (both for CLDAS-V2.0 and GLDAS-NOAH) and in-situ observations during dry season is larger than that of the wet season.The root mean square error (RMSE) between CLDAS-V2.0 soil temperature product and in-situ observations in wet season is larger than that of the dry season, while this inclination of RMSE is opposite for GLDAS-NOAH temperature product during the wet and dry season.Both the CLDAS-V2.0 and GLDAS-NOAH model products can relatively accurate grasp that how the soil temperature and soil moisture response to the precipitation in shallow soil layers.However, the two model products show a lager fluctuation in deep soil layers relative to in-situ observations both in soil temperature and soil moisture.At last, the two model products (CLDAS-V2.0 and GLDAS-NOAH) cannot reproduce the significantly "lag" features that the observed soil temperature and soil moisture show a delayed change with the soil depth.And the daily Peak/valley values appear time of the soil temperature and soil moisture will show a "lag" feature after the precipitation happened which the two model products cannot describe it.
  • The Interannual and Decadal Variation Characteristics of the Surface Sensible Heating at Different Elevations over the Qinghai-Tibetan Plateau and Attribution Analysis
  • YU Wei;LIU Yimin;YANG Xiuqun;WU Guoxiong
  • 2018 Vol. 37 (5): 1161-1176.  DOI:10.7522/j.issn.1000-0534.2018.00027
  • Abstract ( ) HTML PDF (21906KB) ( )
  • Based on the daily regular meteorological observations in the period of 1961-2014 provided by the China Meteorological Administration, the climatological characteristics of the surface sensible heating (SH) over the Qinghai-Tibetan Plateau (QTP) in different seasons and at different elevations have been studied.The impact of the drag coefficient for heat and air density on SH has also been analyzed.Besides, the temporal and spatial distributions of SH over the QTP on different time scales were investigated.Furthermore, the contributions of surface wind speed and ground-air temperature difference to the variation of SH on interannual and decadal time scales were revealed.The results show that the SH calculated by using real density and constant drag coefficient for heat is most reasonable.The SH increases with increasing elevation of the QTP, and the maximum SH scores in spring with the minimum occurs in autumn and winter.The spatial distribution of SH over the QTP is that the southeast (south) part is large (small) while the north part is small (large) in spring (summer).The first leading mode of empirical orthogonal function analyses for spring and summer SH shows an out of phase distribution between south and north on interannual time scale, and between the main body and northeast part on the decadal time scale.Furthermore, SH increases from 1961 to the late (early) 1970s in spring (summer), and then decreases until early 2000s, after that it increases.Besides, the trend of spring and summer SH shows uniform decreasing in the whole QTP with particularly pronounced decreasing in the south part during 1979-2003.The surface wind speed and ground-air temperature difference contribute nearly equal to the variation of SH on the interannual time scale, however the former is larger than the latter on the decadal time scale.
  • Response of Carbon and Water Cycles to Climate Change in the High-Frigid Ecotone: A Case Study of Gannan Zone
  • LIU Shuang;XIE Zhenghui;GAO Junqiang;ZENG Yujin;LIU Bin;LI Ruichao
  • 2018 Vol. 37 (5): 1177-1187.  DOI:10.7522/j.issn.1000-0534.2018.00016
  • Abstract ( ) HTML PDF (4001KB) ( )
  • The high-frigid ecotone is sensitive to climate change and often faced with shortage of water resources and environmental degradation, so quantitative study on its terrestrial ecological and hydrological change is helpful to better understand the impacts of climate.This work took the Gannan Zone as a case, based on a land model coupled with a scheme of the changes in soil freeze-thaw fronts, firstly partitioned the study area into climatological permafrost and seasonally frozen regions and explored the responses of frozen soil, water resource and carbon cycle to climate change from 1979 to 2012.The results show that climatological permafrost and seasonally frozen areas are about 15 000 km2 and 25 000 km2 respectively.The maximum thaw table depth in the permafrost region increased and the maximum frost table depth in the seasonally frozen region decreased.The precipitation was increasing but the warming air temperature made the evapotranspiration increased and reduced the total runoff so that the available water resource tailed off.The amplitude of decreasement was more obvious in the permafrost region.On the aspect of the ecosystem, the northern Gannan is a carbon source and the southern Gannan is a carbon sink.Climate warming promotes the plant growth, which is in favour of more carbon input from atmosphere.However, the carbon use efficiency decreases.Moreover, according to multiple linear regression analysis, it was found that in the permafrost region climate change can explain 66% of the change in NPP and 31% of the change in NEE, while in the seasonally frozen region only 45% of the change in NPP can be explained.
  • Variations of Extreme Air Temperature Events and Diurnal Temperature Range in Xining, Northeastern Qinghai-Tibetan Plateau from 1955 to 2015
  • CHEN Ruijie;LIU Fenggui;CHEN Qiong;MAO Xufeng;ZHOU Qiang
  • 2018 Vol. 37 (5): 1188-1198.  DOI:10.7522/j.issn.1000-0534.2018.00022
  • Abstract ( ) HTML PDF (3095KB) ( )
  • Based on the daily temperature (maximum, minimum and average) data of Xining station from 1955 to 2015, the methods of linear and correlation analysis were employed to analyze the temporal variability and correlation of climate extremes and diurnal temperature range.The results are as follows:(1) The magnitudes of changes in warm indices show a increasing trend and cold indices show a decreasing trend.The occurrence of summer days, warm nights, warm days, growing season length and warm spell duration days show increasing trends at the rate of 2.07, 0.72, 1.49, 2.57, and 0.87 d·(10a)-1, respectively.The occurrence of ice days, frost days, cold nights, cold days and cold spell duration days has decreased by -2.42, -0.29, -0.33, -1.3 and -0.31 d·(10a)-1, respectively.The tendency rate of monthly minimum value of daily maximum (minimum) temperature and monthly maximum value of daily maximum (minimum) temperature is 0.51, 0.17, 0.35 and 0.15℃·(10a)-1.(2) The occurrence of monthly minimum value of daily maximum temperature, monthly maximum value of daily maximum temperature, ice days, summer days, cold days, warm days, growing season length and warm spell duration days shows statistically significant trends and reach a significant level of 0.01 or 0.05.(3) The magnitudes of changes in warm indices and cold indices, night indices and day indices with symmetrical.(4)The annual diurnal temperature range in Xining has obvious trend with inclining rate of 0.25℃·(10a)-1.In four seasons, the occurrence of spring, summer, autumn and winter show increasing trends at the rate of 0.27, 0.21, 0.15 and 0.36℃·(10a)-1, respectively.The annual diurnal temperature range and the diurnal temperature range in spring, summer, autumn and winter under the influence of extreme temperature events by different degrees.The absolute indices and relative indices has significant effect on the diurnal temperature range.(5) Extreme temperature events and diurnal temperature range in Northeastern Qinghai-Tibetan Plateau has its own particularity, may be affected by a variety of climate control system and special terrain and other factors.
  • Analysis of Flood Season Dry Wet Change Trend on the Accumulated Temperature Dryness Index in the Eastern Yunnan-Guizhou Plateau
  • CHI Zaixiang;XIA Yang;LIU Lijuan;YANG Chunyan;LONG Xianju;PAN Xuyan;SHU Langning;WU Dan
  • 2018 Vol. 37 (5): 1199-1207.  DOI:10.7522/j.issn.1000-0534.2018.00075
  • Abstract ( ) HTML PDF (3008KB) ( )
  • Based on daily meteorological data of 104 meteorological stations in 4~9 months from 1958-2015 years in the eastern Yunnan-Guizhou Plateau, using accumulated temperature dryness index as drought index, the temporal and spatial distribution characteristics of flood season dry wet change trend and their relationship with climate factors were studied.The mutation characteristics of precipitation and temperature drying index were analyzed by Mann-Kendall mutation test method.Mexico hat wavelet transform is used to analysis dry and wet conditions of flood season dry wet in the eastern Yunnan-Guizhou Plateau.The result shows that the precipitation is generally between 800~1 000 mm on flood seasons in the eastern Yunnan-Guizhou Plateau, presenting the spatial distribution characteristics in the decline from south to North.Meanwhile, the standard deviation and the average precipitation are found to be uniform distribution.In recent 60 years, the average accumulated temperature dryness index on flood season in eastern Yunnan-Guizhou Plateau shows an increasing trend, but it has the alternation tendency between dry stage and wet stage.And the climate characteristic is developing towards the partial humidity direction.The spatial distribution of the accumulated temperature drying index is reverse phase of precipitation and its large/small value center is basically the same as that of the small/large.There is a significant correlation (P < 0.01) between the accumulated temperature dryness and the average temperature, maximum temperature, sunshine duration, evaporation, precipitation and relative humidity.There is a significant correlation between the accumulated temperature dryness in the eastern Yunnan-Guizhou Plateau and the meteorological factors in the flood season, which indicates that the dry and wet climate changes are affected by several meteorological factors, and the single meteorological factors are difficult to reflect the changes of dry and wet conditions of the climate.The main reason for the drought in the eastern part of the Yunnan-Guizhou Plateau is the decrease of precipitation, followed by the increase of temperature.The index classification standard used in this study is truly and objective to reflect the degree of drought, and the calculation is simple.It only needs daily mean temperature and daily precipitation data.It can be calculated in a short period or in real time, which is beneficial to large scale application.Based on the above analysis, it is considered that the future climate in the eastern part of the Yunnan-Guizhou Plateau in the rainy season is developing towards a partial wet trend.Because of the complicated geological and geomorphologic conditions in the eastern part of Yunnan-Guizhou Plateau, there are certain limitations in judging the dry and wet climate change by two factors, temperature and precipitation.The complexity of drought formation still needs further study.
  • The Characteristics of Spring Vegetation Cover and Its Response to Spring Drought over the Loess Plateau
  • WANG Danyun;Lü Shihua;HAN Bo;MENG Xianhong;LI Zhaoguo;ZHANG Jingwei
  • 2018 Vol. 37 (5): 1208-1219.  DOI:10.7522/j.issn.1000-0534.2018.00033
  • Abstract ( ) HTML PDF (11860KB) ( )
  • Vegetation always represents the state of land cover change.It plays an indicator role in global change.It is a sensitive index of climate and human factors to environmental impact.And in arid and semi-arid areas, climatic conditions are the direct driving forces and important factors of vegetation growth and development.Vegetation coverage not only reflects the local dry and wet conditions, but also an important indicator of local drought resistance.Based on two kinds of Normalized Difference Vegetation Index (NDVI) data, the temporal and spatial variation of spring vegetation cover over the Loess Plateau has been discussed from 1982 to 2014.The spatial distribution of vegetation coverage in the Loess Plateau is basically consistent with the two NDVI data of GIMMS and MODIS.During 1982-1999, the integral NDVI in the Loess Plateau was increased.The increase rate was even greater in 2000-2014.The linear variation of NDVI and spring precipitation in the Loess Plateau is different.Because the spring precipitation in most area of the Loess Plateau was decreased in 1982-2014, it may not cause the change of spring NDVI.The standardized precipitation evapotranspiration index (SPEI) was used to characterize the spring drought in the Loess Plateau.Before 2000, when a severe spring drought happens, as in 1995 and 2000, the integral NDVI in Loess Plateau decreased significantly; for normal years before 2000, the correlation between NDVI and spring drought was weak.But after 2000, the correlation between NDVI and SPEI become strong and significant, which may be connected to the ecological restoration in Loess Plateau.In the past 2000-2014 years, the most significant increase of NDVI appeared in farmland and grassland, which should be mainly attributed to the ecological recovery project leading by local government in the 1990s, aiming to turn farmland into forest and pasture into natural grassland.Because of the human activity, the response to the spring drought in farmland is usually weaker than in grassland and forest area.In the comparison of interannual variability, the highest degree of correlation between the grassland and forest NDVI and the correlation coefficient of first leading EOF mode of SPEI, followed by the crops, and the last is the shrub.In addition to the drought tolerance of different vegetation, this difference may be related to geographical location.As a result, we can expect a more intensive response of vegetation to spring drought in Loess Plateau if the local ecological environment in Loess Plateau keep improving.
  • Analysis on the Causes of an Extreme Rainfall Event in the West of Xinjiang
  • ZENG Yong;YANG Lianmei
  • 2018 Vol. 37 (5): 1220-1232.  DOI:10.7522/j.issn.1000-0534.2018.00014
  • Abstract ( ) HTML PDF (24091KB) ( )
  • Based on the conventional observational data, the TBB data of FY-2G satellite, the data of ground encrypted automatic weather stations and the NCEP/NCAR reanalysis data with 0.25°×0.25° spatial resolution, the cause of an extreme torrential rainstorm occurred in the West of Xinjiang from 31 July to 1 August 2016 was studied.The results are as follows:Stable circulation of "two ridges one trough" at 500 hPa and monomorphic South Asia high pressure at 100 hPa were the weather background of the rainstorm, rainstorm area was located in the right side of the entrance area of southwest jet at 200 hPa, the front of low-level east jet at 700 hPa, nearby of southerly jet at 500 hPa and the convergence line at 700 hPa.The water vapor source of the extreme heavy rain were Central Asia low trough carried its own water vapor and low latitude Baya Bay, the South China Sea and the Western Pacific Ocean transporting to the rainstorm area rich water vapor under the extremely advantageous match of the high, medium and low latitude circulation system.Water vapor importations that from the west border, east border and south border played an important role in the rainstorm process, especially the western boundary and the eastern boundary, accounting for 78.4% of the total water vapor input.The match of the high altitude jet and the low altitude jet and the horizontal shear of the meridional wind and the vertical shear of the zonal wind provided favorable conditions for the generation and development of the mesoscale systems of the rainstorm and the convergence rising movement in the rainstorm area.After the formation of the mesoscale convective cloud, moving and developing northward continuously under the action of the pilot airflow, which were the direct systems of heavy rain.Developmental and moving the low-level jet, the shear line, the wind field convergence line and the terrain convergence line and a number of strong ascending branch of the multiple mesoscale vertical circulations from the Tianshan windward slope to distributed northward constantly transported the water vapor and the energy upwards, which were transported northward to the rainstorm area by strong southerly flow of the trough at 500 hPa.All of the warm advection, the wind shear of middle and low level and the Tianshan terrain played an important role in the generation and upward intensive development of the mesoscale system on the windward slope of the Tianshan terrain constantly.
  • Downscaling of Air Temperature in the Yarlung Zangbo River Basin Based on the Random Forest Model
  • REN Meifang;PANG Bo;XU Zongxue;ZHAO Yanjun
  • 2018 Vol. 37 (5): 1241-1253.  DOI:10.7522/j.issn.1000-0534.2018.00026
  • Abstract ( ) HTML PDF (6452KB) ( )
  • Random forest (RF) model was used to downscale the daily air temperature at 20 meteorological stations in and around the Yarlung Zangbo River basin.For the purpose to explore the better downscaling method of air temperature in the study area, three methods were used to compare, namely, the Multiple Linear Regression (MLR), Artificial Neural Network (ANN), and Support Vector Machine (SVM).Principal Component Analysis (PCA) and Partial Correlation Analysis (PAR) were used to select the characteristic variables.The model performance was assessed using four criteria, namely, the NASH coefficient of efficiency (NASH), the root mean squared error (RMSE), the mean absolute error (MAE), and the coefficient of correlation (r).The results showed that the performance of RF model was obviously better than other models; the results obtained by PAR to select characteristic variables were not only better than those used by PCA method, but also more stable.In addition, the NASH efficiency coefficients of various models were all above 0.86 and the correlation coefficients were all above 0.93 in the validation periods.Therefore, all of models used in this study can well simulate the average temperature in the Yarlung Zangbo River basin.The experimental data of two typical extreme concentration paths(Representative Concentration Pathway, RCP)emission scenarios RCP2.6 and RCP8.5 of MPI-ESM-LR model in the future (2016-2050)were chosen to study the future trend of temperature in the Yarlung Zangbo River basin.The results showed increasing trend of daily air temperature both under RCP2.6 and RCP8.5 scenarios in the future years of 2016-2050 in the Yarlung Zangbo River basin.The daily air temperature will increase by 0.14℃ under RCP2.6 scenario, and 0.30℃ under RCP8.5 scenario from 2016 to 2050.
  • Decadal Summer Drought Characteristics over Yangtze-Huaihe River Basin in Recent 30 Years Associated with Abnormal Eurasian Westerly Circulation
  • LIU Shimeng;ZHANG Jie;YU Han
  • 2018 Vol. 37 (5): 1254-1263.  DOI:10.7522/j.issn.1000-0534.2018.00029
  • Abstract ( ) HTML PDF (8211KB) ( )
  • As the main planetary system affecting the precipitation over Yangtze-Huaihe river basin in summer changed in mid-July, this paper investigated the temporal and spatial characteristics of arid in Yangtze-Huaihe river basin and the characteristics of atmospheric abnormal circulation in interdecadal extreme drought years and their possible causes from June 1 to July 15(Meiyu period) and July 16 to August 31(drought period).This research based on daily precipitation data from 501 stations in northern China, the reanalyze data from European Centre for Medium-Range Weather Forecasts (ECMWF) and the sea temperature data from national oceanic and atmospheric administration (NOAA).The results indicate that on the spatial scale, the number of rainless day in the northwest of the Yangtze-Huaihe river basin in the Meiyu period is more than that in the southeast, while there is no significant difference in the number of rainless day in the entire Yangtze-Huaihe river basin during the drought period.On the time scale, the drought in the Jianghuai basin was more severe than in other periods at the end of the 20th century, and there were dry trends during the two periods.The drought in the Yangtze-Huaihe river basin is related to the Eurasian teleconnection in the middle and high latitudes.During the Meiyu period, there is a northeast-southwest anticyclone anomaly in Mongolia with a strong intensity range.Therefore, the Yangtze-Huaihe river basin is affected by the northerly wind and the subsidence movement is maintained, providing a circulation background that is easy to form a drought in this region.During the drought period, there is a positive anomaly at 500 hPa over the eastern Mongolia, which weakens the East Asian trough and causes the west Pacific subtropical high to move northward.This area is controlled by descending airstream, resulting in aridity.In the Meiyu period the 200 hPa wave energy from Eastern Europe propagates eastward and converges in the north of China, which intensifies abnormal anticyclone.Such phenomenon is conducive to the maintenance and development of drought in the Yangtze-Huaihe river basin.During drought period, the 200 hPa origins of wave energy are the North Atlantic and the north of China.Wave energy from North Atlantic propagates eastward, with a small amount transported to East Asia.In the northern China the energy diverges after combining with energy wave forced by surface.The weakened trough in Mongolia leads to the formation of anti-cyclonic abnormal center, which is conducive to the maintenance of drought.The results present the interdecadal characteristics and factors of drought in the Yangtze-Huaihe river basin to some extent, and provide the basis for the study of multi-scale drought mechanism and arid climate prediction.
  • Different PNA and NAO Configurations and Their Relationship with China Precipitation in Boreal Winter
  • WANG Bo;RAO Jian;WANG Huazhao;SHENG Chen
  • 2018 Vol. 37 (5): 1264-1276.  DOI:10.7522/j.issn.1000-0534.2018.00012
  • Abstract ( ) HTML PDF (15900KB) ( )
  • By using the National Center for Environmental Prediction-National Center for Atmospheric Research (NECP/NCAR) monthly reanalysis data, the Global Precipitation Climatology Centre (GPCC) rainfall data, and the station precipitation data provided by the China Meteorological Administration, the four configurations of the extreme Pacific-North America (PNA) pattern and North Atlantic Oscillation (NAO) and their relationship with China precipitation were investigated.It is revealed that the PNA and NAO are nearly independent of each other on the interannual time scale with a correlation coefficient of -0.13 during 1950-2015.We classified PNA and NAO into four configurations:Extremely positive PNA and NAO (configuration I), positive PNA and negative NAO (configuration Ⅱ), extremely negative PNA and NAO (configuration Ⅲ), and negative PNA and positive NAO (configuration IV).Compared with the circulation anomalies related to one factor (PNA or NAO), those during different extreme configurations of PNA and NAO are relatively larger, which in turn induces different spatial patterns of the winter rainfall anomalies in China.Both GPCC and station precipitation data showed that, in configuration I, more rainfall appears in the south coastal China and the southeastern of Qinghai-Tibetan Plateau; while the Huaihe Valley is anomalously dry.In configuration Ⅱ, it is dry from the southwest China to the south coastal China, while the east coastal China is anomalously wet.In configuration Ⅲ, a nationwide drought is seen, especially of south to the Yellow River.However, when PNA and NAO are in their configuration IV, a large part of east China is anomalously wet, while the southwest China is significantly dry.
  • Causation Analysis of a Short-Time Strong Rainfall Triggered by Cold Front at the Northern Piedmont of Qinling Mountains
  • WANG Nan;ZHAO Qiang;JING Yu;ZHANG Xiaowen
  • 2018 Vol. 37 (5): 1277-1288.  DOI:10.7522/j.issn.1000-0534.2017.00070
  • Abstract ( ) HTML PDF (19163KB) ( )
  • On August 3, 2015, a short time heavy rainfall suddenly occurred at the northern piedmont of Qinling Mountains, whose intensity has been rarely seen in recent years, triggered floods and caused casualties.Based on the analysis of aerological sounding data, intense surface observation data, NCEP reanalysis data, wind profile data and Doppler radar data, it was found that the precipitation process has good convective potential and humidity condition, and it was triggered by the cold front system.The structural features of the cold front system include:thewater vapor content was greater than 18 g·kg-1 near surface in front of the front zone, the frontal rising motion located above the sinking movement and below the free convection level, there was significant convection instability ahead of the front and so on, which are all favorable conditions for the occurrence of convective strong precipitation.The calculation result of frontogenetical function showed that strong frontogenesis(up to 20×10-10 K·s-1·m-1) of this process mainly occured in the middle and lower troposphere.The main reason is that the cold front system was accompanied by strong cold advection at 850 hPa which caused the horizontal frontogenesis; convective instability and the ascending motion caused vertical frontogenesis.In addition, the strong cold advection at 850 hPa caused shallow temperature inversion of the layer, so that convective instability energy can be concentrated, that is another favorable factor for the development of strong convection in the afternoon.The wind shifted to the west and formed ultra low level strong westerly wind with feedback of heavy rainfall after the cold front passed due to the blockage of Qinling Mountains.The westerly winds combining with the windward slope of Qinling Mountains made amplitude effect to the precipitation and brought low level water vapour transportation for the precipitation area, but the presence of the ultra low westerly wind causes the environment wind appeared negative vertical wind shear and was consistent with the moving direction of the storm.Under the influence of such wind field, the bottom of the storm which has just been established moving eastward faster than the top, and the vertical structure of the storm is difficult to maintain for a long time.The wind profile radar can detect the fine vertical wind structure of the cold front system, which reflects the vertical structure information of the cold front and predict weather system development much earlier than the other meteorological elements, which has a good indicative significance for the forecast.
  • Application Research of Two Types of Dynamical Factors in a Vortex Rainstorm in Sichuan Basin
  • SONG Wenwen;LI Guoping;LONG Keji;GUO Jie
  • 2018 Vol. 37 (5): 1289-1303.  DOI:10.7522/j.issn.1000-0534.2018.00015
  • Abstract ( ) HTML PDF (7402KB) ( )
  • By using the conventional observation data, the FY-2E satellite Black Body Temperature (TBB) data, the 0.25°×0.25° data of European Center, and based on the chosen dynamical factors including mass divergence, vertical helicity, mass vertical helicity, moisture vertical helicity, divergence vertical flux, density divergence vertical flux and moisture divergence flux, diagnostic analysis was performed for a rainstorm process occurred in Sichuan Basin during 16-18 August 2015. The results showed that:(1) the rainstorm event was caused by the southwest vortex formed and maintained in the central Sichuan Basin. The southwest vortex was because of the eastward movement of plateau vortex and plateau shear lines toward Sichuan Basin. (2) Following the eastward movement and weakening of the plateau low-pressure systems (plateau vortex and plateau shear lines), and the producing and development of the southwest vortex, the convective cloud cluster went through the process of "reinforce-combine-weaken-regeneration-reinforce-weaken". (3) Dynamical factors had good indication significance for the development and evolution of the rainstorm. The high value area of the dynamical factors basically covered the strong precipitation area. At the beginning while southwest vortex formed, the distribution of the dynamical factors and the plateau shear line were the same, and the rainfall center which located at the high value area of the dynamical factors and the right side of the plateau shear line was the same as the center of the southwest vortex. At the strong stage of the southwest vortex, the high value area of the dynamical factors, the center of the southwest vortex and the rainfall center coincided. The precipitation area had profound positive vorticity column and upward movement, but the convergence layer was too shallow. The mass divergence convergence, vertical upward transportation and convergence upward movement of cyclonic vorticity and moisture flux vorticity appeared above the precipitation area. Due to the vorticity effect of the vortex-type influence system was more obvious than divergence effect, the vertical structure of three helicity-type dynamical factors including vertical helicity, mass vertical helicity and moisture vertical helicity was very significant from the lower layer to the upper layer.
  • The Leading Modes of Summertime Precipitation Anomalies over the Yangtze River Basin and Possible Causes
  • XIAO Zhixiang;TAN Jianghong
  • 2018 Vol. 37 (5): 1304-1312.  DOI:10.7522/j.issn.1000-0534.2018.00019
  • Abstract ( ) HTML PDF (19543KB) ( )
  • Based on the daily mean rainfall data at 202 stations within Yangtze River basin, the daily gridded precipitation, with a horizontal resolution of 0.5°×0.5° for the China domain from National Meteorological Information Center in version 2, and the JRA-55 reanalysis datasets, the leading modes of summertime precipitation anomalies over the Yangtze River basin were investigated with Empirical Orthogonal Function (EOF) and its possible causes were revealed. The analysis showed that there are two dominant modes of the summertime precipitation over Yangtze River basin. The first EOF mode (EOF1) depicts a characteristic of unified spatial distribution with obvious interannual variation, representing the typical drought and flood events of the summer precipitation over the Yangtze River basin. And the second EOF model (EOF2) exhibits a characteristic of meridional dipole pattern with obvious interdecadal variability overlay on interannual variability. Moreover, results also showed that the EOF2 pattern is closely associated with the anti-cyclone anomaly over the Scandinavian Peninsula, which stimulates a teleconnection wave-train at 200 hPa, making the South Asian High shrinks westward and the western Pacific subtropical high shifts eastward. Thus, water vapor transportation shifts eastward and southward over Eastern China, favoring moisture convergent and divergent over the southern and northern part of the Yangtze River basin, respectively. And then the seesaw precipitation anomaly pattern forms over the southern and northern part of the Yangtze River basin.
  • Sensitivity of High-Resolution Simulations of the Warm-Sector Rainstorm in Eastern Hubei to Planetary Boundary Layer Schemes
  • XU Jianyu
  • 2018 Vol. 37 (5): 1313-1324.  DOI:10.7522/j.issn.1000-0534.2018.00003
  • Abstract ( ) HTML PDF (32780KB) ( )
  • A typical warm-sector rainstorm occurred in eastern Hubei during 5-6 July 2016, causing severe flooding and damage. This heavy rainfall event, associated with an unusual environment to trigger convection, happened on the edge of subtropical high. The Weather Research and Forecast (WRF) model is used to simulate this event in cloud-resolving resolution (3 km). Experiments are conducted to examine the sensitivity of the simulation to the use of three different planetary boundary layer schemes, including the asymmetric convective models like version 2 (ACM2), Yonsei University (YSU), and Mellor-Yamada-Janjic (MYJ) schemes. Numerical results show a significant sensitivity of the short-time heavy rainfall to planetary boundary layer schemes, with the YSU and MYJ schemes produce stronger rainstorm in the development stage of precipitation and weaker rainstorm in the extinction stage compared to the ACM2 scheme, which is mainly due to the earlier triggering and earlier extinction of the strong convection in the simulations with the YSU and MYJ schemes. Specifically, before convection triggering, the eddy diffusivity coefficients simulated by the YSU and MYJ schemes are much less than the ACM2 scheme, and the meridional wind tendencies due to planetary boundary layer processes are much weaker, so the deceleration of the low-level south wind is less, leading to the enhanced convergence of south wind and the earlier triggering of strong convection. While in the extinction stage of precipitation, convections simulated by the YSU and MYJ schemes disappear quickly, comparing with the new convections initiated continuously on the low level shear line which is more obvious in the simulation with the ACM2 scheme. Furthermore, a sensitivity test is carried out with the latent heating from the microphysical processes turned off during the extinction stage of precipitation, which shows that the generation of the low level shear line is mainly due to the regulation of the mesoscale environment by the latent heat release from precipitation in the development stage, while the effect of planetary boundary layer processes is relatively small. On the other hand, detailed analysis of the impact of planetary boundary layer schemes on cloud microphysics and resulting precipitation shows that, the formation of the short-time heavy rainfall is related to the dominant role played by the melting graupel in the cold-cloud precipitation. Compared to the ACM2 scheme, simulations with the YSU and MYJ schemes produce more graupel in the development stage of precipitation and less graupel in the extinction stage, which is corresponding to the characteristics of the short-time heavy rainfall.
  • Analysis of the Cloud Characteristic and the Mechanism of an Extreme Rainfall-snowfall Event Associated with Cyclones over Changjiang-Huaihe River Basin
  • ZHAO Yu;LAN Xin;YANG Chengfang
  • 2018 Vol. 37 (5): 1325-1340.  DOI:10.7522/j.issn.1000-0534.2018.00024
  • Abstract ( ) HTML PDF (39389KB) ( )
  • An extreme rainfall-snowfall event that occurred in Shandong province from 12 to 13 February 2016 was contributed to the Cyclones over Changjiang-Huaihe River Basin. The precipitation of 48 stations in Shandong province broke the historic record of the same period. The characteristics of the cloud evolution and mesoscale wind field as well as precipitation mechanism were analyzed by using multiple observation and NCEP/NCAR 1°×1° reanalysis data. The main results show that:(1) Meso-β cloud mass constantly moved northeastward into Shandong province from Jiangsu and Anhui provinces, and the precipitation was contributed to four meso-β cloud mass. The comma head of Cyclones over Changjiang-Huaihe River Basin developed from four banded echoes. In the initial phase of the cyclone, the warm front cloud was dominated by stratiform clouds with scattered convective clouds, while the cold front clouds in the tail of comma cloud were more convective and then weakened after moving into the sea. When the cyclone formed, the radar echo had a cyclonic rotation and elongation, forming a number of strong mesoscale rain bands. (2) The water vapor conditions were very helpful to the precipitation. The low-level jet originating from southwesterly path and southeasterly path transported ample moisture. During the rainfall period, there was moisture transmission by the southeasterly ultra-low level jet, while the transmission was weak in the boundary layer in the snowfall period. (3) The northeast cold air mattress in the low level was shallow in the rainfall period, while it was much thicker in the snowfall period. The southeaster layer above the cold mattress experienced attenuation to becoming invisible, which is a sign of the phase transition from rain to snow. Both heavy rainfall and snowfall occurred in the strongest period of southerly low-level jet. (4) The convergence between northeast and southeast winds near the shear line in front of the low vortex, warm advection, warm frontogenesis and the release of the conditionally unstable energy, are the forcing mechanism of ascending motion, which result in heavy precipitation. The observations of wind profile radar and laser raindrop spectrograph are helpful to judge the precipitation phase in weather forecast.
  • Low-Frequency Features during the Two Typical Extreme Cold Events in China
  • LI Yan;ZHANG Jinyu;LI Xu;MA Baisheng;WANG Yafang
  • 2018 Vol. 37 (5): 1341-1352.  DOI:10.7522/j.issn.1000-0534.2018.00035
  • Abstract ( ) HTML PDF (20175KB) ( )
  • Keeping oscillation of low frequency of 30~60 days, Butterworth band-pass filter method was used to process the NCEP/NCAR reanalysis data. Based on the application of the low-frequency synoptic map (LFSM), low frequency features of the two extreme low temperature events including durative low temperature, snow fall and freezing weather in early 2008 and "overlord"-level cold wave in 2016 were analyzed in order to reveal the characteristics, forming and evolution of the low frequency systems during these two events. The results are as follows:During durative low temperature, snow fall and freezing weather in early 2008, large-scale atmospheric systems including blocking-high and upper-level jet stream all featured a distinct 30~60 days oscillation. The positive (negative) anomaly of geopotential height was closely coincided with the low frequency high (low) pressure of the low frequency systems, and the center of positive zonal wind anomaly was consistent with the high value center of low frequency zonal wind. During this event, the positive phase of the Arctic Oscillation (AO) favored the strengthening of the Middle East jet and the maintenance of the blocking high, resulting in durative low temperature in south China. The 30~60 days oscillation features of the weather systems including upper-level jet and blocking high were not so obvious during "overlord"-level cold wave in 2016 as that during early 2008. However, the low pressure of low frequency can describe the generating and developing of the polar vortex. Meanwhile the low-frequency synoptic map reflected the phase transition of AO before and after the cold wave. The phase of AO was positive in later December 2015 while negative in early January 2016, which led to the weakened latitudinal circulations of the middle latitudes and the strengthen longitudinal circulations. Then under north air stream at the front of blocking high ridge guidance, the strong cold air in the middle of polar vortex invaded southern China. These can be concluded as the main cause of the sharp drop in temperature. Although the position distribution of low-frequency low pressure, high pressure and the south path of cold air are different, the low-frequency flow field showed the phase transition of AO lagging behind the synoptic flow field about two days during the two events. By tracking and estimate the path of such low-frequency signal in the LFSM. This result can provide reference for extended-range weather forecast of similar extreme cold events by using the numerical forecast products.
  • The Analysis of Spatiotemporal Climate Change in the Western Hexi Region
  • LIU Qiong;ZHANG Xiaoping;ZHANG Zhibin;ZHANG Bo
  • 2018 Vol. 37 (5): 1353-1363.  DOI:10.7522/j.issn.1000-0534.2018.00031
  • Abstract ( ) HTML PDF (3449KB) ( )
  • Climate change has become a hot issue in the world, which has a profound impact on human survival, economic and social development. This paper is concerned with the spatiotemporal climate change of the western Hexi Region. The spatiotemporal characteristics of temperature, precipitation, relative humidity and wind speed in the western Hexi Region were systematically analyzed by multiple linear regression model, the methods of inverse distance weighted interpolation and Mann-Kendall abrupt change test, based on the data collected from 14 meteorological stations from 1958 to 2013. It aims to reveal the laws of climate change and provide theoretical references for local government making related policies. The results showed that from the time point of view, there is a significant increasing trend in temperature and the inter-annual rate of change is 0.25℃·(10a)-1. The average temperature of each season shows a same trend and the trend of spring is the most evident. It can be found that the abrupt change of temperature is mainly detected in 1989. From the space point of view, the average temperature is high in midland and low in the north and south. The analysis leaded us to the conclusion that the precipitation is also in an increasing trend and its inter-annual rate of change is 1.30 mm·(10a)-1. Concretely, there is a downward trend in spring while there are opposite trends in summer, autumn as well as winter and the change rate of autumn is more obvious than others. From Mann-Kendall abrupt change test of the study area, it is found that there is no significant abrupt change in precipitation. The spatial variation of precipitation is distinct and the precipitation of northwest is low while southeast is high. Temporal analysis revealed that the annual average relative humidity slightly increases in fluctuation from 1958 to 2013. At the same time it decreases in spring and summer while increases in autumn and winter. The relative humidity indicated that there is an ascending tendency from west to east in space. The change of wind speed shows obvious stage. The Data analysis demonstrated that the abrupt change occurred around 1985 and the trend was more evident after 1991. After abrupt change, the mean is 0.56 m·s-1 that lower than before the abrupt change. The change trends of the average wind speed in the four seasons are similar to the trend of the annual average wind speed, all of which have gone through the three stages that are rising, falling rapidly and rising slowly. Compared to other seasons, the difference in the mean value of winter is significant higher. The average wind speed has a descending tendency from north to south.
  • The Environmental Conditions and Radar Echo Characteristics of the Super Cell Storm under the Background of the Northeast Cold Vortex
  • ZHANG Guilian;CHANG Xin;HUANG Xiaolu;ZI Yaohai;LI Ruiqing;LIANG Fengjuan
  • 2018 Vol. 37 (5): 1364-1374.  DOI:10.7522/j.issn.1000-0534.2018.00068
  • Abstract ( ) HTML PDF (21337KB) ( )
  • Based on the conventional observational data, automatic weather station data, Doppler radar data and NCEP (1°×1°)every six hours reanalysis data, the strong convective weather such as strong hail and thunderstorm wind induced by super cell storm in southeastern Inner Mongolia on 16 August 2016 was analyzed. The main conclusions are as follows:The super cell storm occurred in the background of strong unstable conditions caused by the northeast cold vortex in the high altitude and the warm-wet shear line in the low level. The rich water vapor in the low level, medium intensity of CAPE and large deep vertical wind shear provides a very favorable environmental condition for the strong convective weather. The coupling and strengthening of the surface meso-scale convergent line and dew point front is the trigger mechanism of convective storm. The features of a supercell storm can be found, such as the hook echo, WER, overhang echo, echo wall, and mesocyclone in the reflectivity products. Besides, the WER and overhang echo have large intensity gradient, which is tilting toward low-level inflow side from low to high; The mid-level of the storm maintained a relatively strong cyclonic convergence, and the top of the storm showed significant cyclonic divergence. TBSS (Three-Body Scatter Spike) exists and the core of reflectivity above 50 dBZ extends above -20℃, which is a typical echo structure of hail. The ratio of the VIL (Vertical Integrated Liquid Water Content) and the top height of the storm which means the density of VIL reaching to 5 g·m-3 that also a predictor of hail.
  • Structural Characteristics of the Advance, Retreat and Maintenance of Kunming Quasi-Stationary Front in January
  • ZHANG Yanan;DUAN Xu
  • 2018 Vol. 37 (5): 1375-1387.  DOI:10.7522/j.issn.1000-0534.2018.00011
  • Abstract ( ) HTML PDF (21462KB) ( )
  • Based on the ground meteorological elements data, interim daily reanalysis data and DEM data, this paper discussed the structure of Kunming Quasi-Stationary Front (KQSF) when it moved westward, gone eastward and kept sustaining. The movements of KQSF are closely related to the weather of Yunnan, Guizhou and south Sichuan in winter, so it is important to study its frontal structure and shift mechanism. By using synthetic analysis and disusing the circulation features, meteorological factors and frontogenesis function terms, we can draw some mainly conclusions:When the isotherm between lower atmosphere and ground presents "V" distribution, and the frontal secondary circulation is relatively deep, the front is easy to move westward; when the lower atmosphere presents deep inversion layer, and the frontal secondary circulation is very thin, the front is tend to move eastward; when the inversion layer only exists in lower atmosphere, and there is a cold center in surface layer, the front tends to sustain. For the vertical structure of the u wind, when the border of east and west wind is on the left side of the front, the front tends to move westward, on the contrary it tends to go eastward; when the border is basically coincident with front, it's likely to sustain. When there exists continuous transmission of east wind behind of the front, undulating topography can change the vertical distribution of wind near ground, which leads to the multiple centers of rising and sinking. For the vertical motion tilting term, there is a strong phenomenon of frontolysis in the windward slope near 105°E when the font goes westward, and there is a weak phenomenon of frontogenesis when the font goes eastward or keeps still. For the horizontal divergence term, it is related to the gradient of equivalent potential temperature and horizontal divergence, and it contributes much to frontogenesis. Horizontal divergence term is predictable to front's movement, when the strong frontogenetical area is on the left side of front, the front tends to go westward; when the strong frontogenetical area is on the right side of the front, and the phenomenon of frontogenesis is weak, the front tends to go eastward; when the strong frontogenesis is basically coincident with frontal zone, the front tends to sustain. For the horizontal deformation term, it consists of tilting term and deformation term, and tilting term is more important to frontogenesis. For the expansion deformation term, there is a stronger phenomenon of frontolysis in the east of 104°E because of the interaction between cold air mass and windward slope.
  • Large Eddy Simulation of Flow Field over the Xiaohaituo Mountain Division for the 24th Winter Olympic Games
  • LIU Yujue;MIAO Shiguang;HU Fei;LIU Yubao
  • 2018 Vol. 37 (5): 1388-1401.  DOI:10.7522/j.issn.1000-0534.2018.00034
  • Abstract ( ) HTML PDF (37133KB) ( )
  • Competitions for luge, bobsleigh and alpine skiing of the 24th Winter Olympic Games in February 2022 will be held in Xiaohaituo Mountain area northwest of Beijing, 90 kilometers away from the downtown. The outdoor events are very strict on the near-surface wind fields. Therefore, it is necessary to provide wind field prediction within 100 meters resolution. At present, the widely used mesoscale models, limited by their grid resolution (>1 km), cannot meet the needs. This paper described a multi-scale weather modeling system, WRF-LES, which employs large-eddy simulation (LES) with the WRF model. The system was employed to simulate real-world conditions of a typical clear day with strong winds over Xiaohaituo mountain area. With four nested domains, the horizontal grid spacing is decreased from 1 km to 37 m. Through a group of sensitivity tests of horizontal, vertical, terrain resolution and boundary layer schemes, the applicability of WRF-LES has been evaluated and tested against in-situ observation from MOUNTOAM (Mountain Terrain Atmospheric Observations and Modeling) filed campaign. Compared to ordinary mesoscale model, 100 meters or higher resolution WRF-LES results were found to capture more microscale flows owing to its explicit resolving of large atmospheric turbulence eddies, and obtain wind field flow more resemble the real atmosphere. For accurate simulation, the topographygraphic data should be matched with the model horizontal resolution, and the vertical grid spacing needs to be carefully set. For this case, WRF-LES has the potential and value for the ultra-high-resolution simulation of the near-surface wind field over complex mountainous area. It shows high forecasting ability, and can provide technical support for fine weather service in Winter Olympic Games.
  • The Correction of Wind Speed Forecasted of Wind Farms under Complex Topographic Conditions using Kalman Filtering
  • LI Zhaorong;DA Xuanfang;WANG Yousheng;ZHAO Wenjing;YAN Xiaomin
  • 2018 Vol. 37 (5): 1402-1412.  DOI:10.7522/j.issn.1000-0534.2018.00025
  • Abstract ( ) HTML PDF (9285KB) ( )
  • The distribution characteristics of wind speed and direction at 70 m and prediction errors of forecast wind speed of three typical wind farms (i. e., Nanqiu, Heiyazi, and Ganhekou) with complex topographic conditions in Gansu were analyzed. A correction model based on Kalman filtering was established to correct wind speed forecasted by Beijing Rapid Updated Cycling Analysis and Forecast System (BJ-RUC). Results show that:The percentage of effective wind speed hours of the total year is 90.9% in Nanqiu, 85.06% in Heiyazi, and 82.93% in Ganhekou, respectively. Significant differences of the percentage of effective wind speed hours exist in different seasons for each wind farm. Specifically, percentages of effective wind speed hours are higher in summer and autumn, and can reach up to 29.65%, 27.19%, 23.24% in Nanqiu, Heiyazi and Ganhekou, respectively. In summer, the diurnal variation of wind speed in Nanqiu has two or three peaks while in Heiyazi is characterized by a single peak and in Ganhekou is performed as double peaks and single valley. From summer to autumn, the prevailing wind direction in Nanqiu is southeast, the leading wind direction in Heiyazi shifts from east to west and the dominant wind direction in Ganhekou persistently keeps easterly persistently. The gustiness of wind speed varies from season to season. The Weibull distribution indicates that the wind speed in september is more volatile than wind speed in June in Heiyazi and Ganhekou. On the contrary, wind speed in June is more volatile than that in september in Nanqiu. Limitations in forecasting wind speed by BJ-RUC are mainly two aspects:one is that the gustiness of prediction wind speed is relatively weaker; The other one is that the wind speed forecasted by model is relatively larger than measured one. However, with the correction by Kalman Filtering method, the capability of forecasting gustiness of wind speed based on numerical weather model has been improved; Weibull distribution shape and scale parameters of the corrected wind speed are approximation to those of measured wind speed. The correlation coefficient of observed speed and corrected speed can be increased by 15%; the absolute error and root mean square error have also been improved significantly, which drop to 1.30 m·s-1 and 1.66 m·s-1.
  • Numerical Simulation and Character Analysis of Wind Field in Complex Terrain in Hami Xinjiang
  • ZHOU Rongwei;HE Xiaofeng
  • 2018 Vol. 37 (5): 1413-1427.  DOI:10.7522/j.issn.1000-0534.2018.00021
  • Abstract ( ) HTML PDF (45542KB) ( )
  • For numerical simulation and character of wind field with high resolution in complex terrain, mesoscale meteorological model WRF with data assimilation technology of nudging was used to realize numerical simulation of wind field with 1 km horizontal resolution in Hami area where terrain is very complex. By comparison with mast observation data, the simulation result after assimilation was close to observation data, the absolute error of wind speed simulation results decrease 0.25 m·s-1. The simulation results corrected the problem that overestimate wind speed in breeze condition and underestimated in high wind condition. And simulation results of wind profile was also more consistent with observations. Through analysis of simulation results of wind field in Hami complex terrain by 1 km horizontal resolution with 10 min interval output, some conclusions were draw as the followings:(1) As terrain is very complex in Hami area, the wind speed distribution is very different. In April, the high wind area is mainly distributed in the north area of mountain and the pass area that is south of mountain in west region. While in July, the high wind area is located in the south area of pass in west region and north region. (2) Wind shear was negative in breeze condition under complex terrain, and the smaller the wind speed, the larger the negative shear value, and negative shear value was higher in more complex terrain. While in high wind condition, the vertical shear was positive even in complex terrain, but the positive value was less than that in flat area. And the positive value was greater with wind speed increasing in flat area. (3) The temporal and spatial distribution of the proportion in full-load wind condition was very different when wind speed is between 12 and 25 m·s-1 as terrain is complex in Hami area. The wind speed was high in April, the proportion of full-load wind speed was more than 20% in most areas, especially in north area and pass area in west region, the proportion was even more than 50%, the average wind speed of full-load at 80 m was higher 0.60~0.80 m·s-1 than that at 60 m, and the difference was larger than that of monthly average wind speed. (4) The variation of wind direction with 10 min interval was not obvious in high wind condition, while in breeze condition, the variation was bigger. The variation value was bigger in flat area than that in complex area. (5) The vertical variation of wind direction was more consistent with wind speed. The smaller the wind speed, the greater the vertical variation of wind direction, and terrain will be more complex, the vertical variation will be greater.
  • Profiling of Dust Aerosol Mass Concentration over Dunhuang: Case Studies
  • HUA Wenli;HAN Ying;QIAO Hanyang;WANG Tianhe;HUANG Zhongwei;BI Jianrong;ZHOU Tian
  • 2018 Vol. 37 (5): 1428-1439.  DOI:10.7522/j.issn.1000-0534.2018.00017
  • Abstract ( ) HTML PDF (6744KB) ( )
  • Dunhuang is located in the dust source area and also heavy industry base, natural dust events and pollution dust weather are its typical weather process. Therefore, this paper aims at the typical characteristics of dust weather in Dunhuang, using the data of Micro Pulse Lidar (MPL) and Photometer CE318 based on intensify observation of Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) in Dunhuang. Applying the detection advantages of laser lidar polarization technology, combining local weather character, two cases of typical dust weather in spring 2012 were chosen to be quantitatively analyzed. According to dust depolarization ratio from observation, coarse particle (dust aerosol) and fine particle (background aerosol) were separated to retrieve their extinction coefficients and mass concentrations vertical distribution. In natural dust day, represented by 26 April 2012, appearing a strong dust layer, the particle depolarization ratio profile totally larger than 30% with the strong asphericity. Due to the influence of aerosol particle size distribution and its composition, the aerosol lidar ratio gradually decreases in the whole period. At 18:45 on 26 April 2012, the extinction coefficient and mass concentration profile both appeared the single-peakstructure and the maximum value of were Mm-1 and 1 070 μg·m-3 at 1.5 km. In polluted dust day, represented by 6 April 2012, three parent vertical aerosol layers were observed demonstrating obvious aerosol stratification and mixing. At 16:55 on 6 April 2012, the particle depolarization ratio was 5%~20% and the mass concentration was 2~45 μg·m-3. On the bottom aerosol layer, local pollution contributed most and fine aerosol mass concentration was about 17 μg·m-3 at 1.5 km; dust from long distance transport contributed most in middle (2.5~3.7 km) and top (5.5~7.2 km) aerosol layer, and dust mass concentration were 29 μg·m-3 and 18 μg·m-3. Compared with the natural dust weather, there is a strong heterogeneity in polluted dust day. Because of local pollution and aerosol mixture during transport, dust mass-specific extinction coefficients of polluted dust day (0.79 m2·g-1) was bigger than dust day (0.48 m2·g-1). The depolarization ratio from lidar detection reflects the proportion of dust aerosols in the atmosphere to a certain extent, which exhibit that the method combined with particle depolarization ratio to separating coarse and fine particles applied well in the dust and anthropogenic aerosol mixed area, which could benefit the characteristics study of dust and fine particles under different atmospheric conditions. Therefore, effectively separating dust and fine aerosol are significant to evaluate optical and physical characteristics as extinction coefficient and mass concentration of dust aerosol.
  • A Review of Future Climate Change Based on Regional Climate Models
  • ZHANG Lei;WANG Chunyan;PAN Xiaoduo
  • 2018 Vol. 37 (5): 1440-1448.  DOI:10.7522/j.issn.1000-0534.2018.00018
  • Abstract ( ) HTML PDF (541KB) ( )
  • Regional climate differentiation is becoming more and more obvious with global climate change, regional climate tends to be extreme. Droughts, heavy rainfall, heat waves, snow, super typhoons and other extreme weather events that have brought huge losses all over the world every year are very frequent across the global. Research on small-scale regional climate using the global climate models can't meet the requirements of spatial scale, temporal scale, the regional scale assessment of climate change and adaptation research. The global climate model reproduce climatic characteristics from large scale and it can't finely show the local information at different elevations. A full understanding of the inter-regional climate differences is very important for a more accurate prediction of future climate change. As the regional climate models have a more complete physical mechanism and higher spatial resolution, it has made a great deal of improvement over the global climate model and can solve the problem the global climate model faced and has been widely used in regional climate research, notable results have been achieved. In this paper, we sketched the development of the regional climate model, summarized the latest research progress in the regional climate model, the world's major regional climate models, and the development of climate scenarios. And we also summarized the general trend of climate change in different regions of the world from temperature and precipitation, research findings in different regions can help to have a better understanding of future climate change and also can help policymakers develop appropriate applicability strategies that will reduce the loss caused by climate change. Although the models used by the researchers may be different, the precipitation estimates are not the same, and there are significant regional characteristics in different region, almost all studies agree that in the future the world will continue to experience a process of sustained warming. Based on a summary of future climate change in different regions, then we discussed the current problems of the regional climate model, including the uncertainty of the model itself, the uncertainty of emissions scenarios and the complexity of the earth-atmosphere system. Finally, for the problems in the regional climate model, we summarized the solutions in term of current regional climate models, and looked forward to the development of the regional climate model and give the trend of the future regional climate model in China.

NewsDownloadMore+More+

DynamicsVideo InformationMore+More+

Links E-journal More+ More+

Official Wechat

QQ Group Chat

The system is designed and developed by Beijing magtec Technology Development Co., Ltd. with technical support: support@magtech.com.cn