Plateau Meteorology

Current Issue

28 December 2021, Volume 40 Issue 6   
  • An Overview of the Aerosol and Cloud Properties and Water Vapor Budget over the Qinghai-Xizang Plateau
  • HUANG Jianping, LIU Yuzhi, WANG Tianhe, YAN Horngru, LI Jiming, HE Yongli
  • 2021 Vol. 40 (6): 1225-1240.  DOI:10.7522/j.issn.1000-0534.2021.zk012
  • Abstract ( ) PDF (49747KB) ( )
  • Acting as the “Asian water tower”， the Qinghai-Xizang Plateau （QXP） can significantly influence the East Asian and global climate.This paper introduces some preliminary results of the Strategic Priority Research Program of Chinese Academy of Sciences （Grant No.XDA2006010301）.Focusing on the Pan Third Pole centered by the QXP， the dominant results include： （1） Dust， polluted dust， elevated smoke and polluted continental aerosols are the most important types over the Pan-Third Pole region.Among them， the dust emission and transport can significantly affect the atmospheric thermodynamic structure over the western QXP and the Qaidam Basin.（2） The occurrence frequency of supercooled water clouds and its role in adjusting the energy budget are greater than those of warm water clouds over the QXP.Precipitation is mainly produced by ice clouds and mixed phase clouds， especially in warm season.Although the QXP is warming and wetting， the water vapor arriving from outside the QXP could not effectively replenish the surface water storage， the water cycle over the eastern part of the QXP shows a weakening trend， while the one over the western part indicates opposite trend.（3） Due to the black carbon （BC）， a weak South Asian Summer monsoon is induced， leading less water vapor transported from the Indian Ocean to the QXP.Besides， BC addition can induce an intensified East Asian Summer monsoon significantly， consequently， more water vapor is transported from the east of QXP.Overall， due to the BC， the net water vapor is positive over the QXP， implying a net import of water vapor from the surroundings to the QXP.The eastward movement of convective clouds polluted by dusts over the QXP can merge with the local cloud clustering， leading to an intensified precipitation in the Yangtze River Basin and North China.In general， aerosols can directly affect radiation， or indirectly change the macro and micro characteristics of clouds by acting as cloud condensation nuclei， or by affecting the thermal structure required for cloud formation， thereby further affecting the surface energy budget and atmospheric heating rate profile of QXP.And ultimately affect the circulation system and the water vapor budget of the plateau.Being some parts of the program， the research on above results is beneficial to reveal the physical mechanism of the QXP influencing the surrounding water cycle， to understand the mechanism of aerosol-cloud-interaction affecting the water cycle of TP.Additionally， it may provide some evidence and guidance for the improvement of the efficiency of air water resources development and utilization.
  • The Review of the Observation Experiments on Land-Atmosphere Interaction Progress on the Qinghai-Xizang （Tibetan） Plateau
  • MA Yaoming, HU Zeyong, WANG Binbin, MA Weiqiang, CHEN Xuelong, HAN Cunbo, LI Maoshan, ZHONG Lei, GU Lianglei, SUN Fanglin, LAI Yue, LIU Lian, XIE Zhipeng, HAN Yizhe, YUAN Ling, YAO Nan, SHI Xingdong
  • 2021 Vol. 40 (6): 1241-1262.  DOI:10.7522/j.issn.1000-0534.2021.zk006
  • Abstract ( ) PDF (34425KB) ( )
  • Featured with high topography， the Qinghai-Xizang （Tibetan） Plateau （QXP） shows very significant dynamic and efficient thermal effects， and the land-atmosphere interaction and the atmospheric boundary layer processes are very important for the weather development and climate change over the QXP and its surrounding regions.Since the 1960s， especially after 1979， a series of observation and research programs have been conducted， including "the Qinghai-Xizang Plateau Meteorological Science Experiment （QXPMEX） "， " The Second Tibetan Plateau Scientific Experiment （TIPEX-Ⅱ）"， "the Global Energy and Water Cycle Experiment （GEWEX）， the Asian Monsoon Experiment on the Tibetan Plateau（GAME/Tibet）"， "the Coordinated Enhanced Observing Period （CEOP） Asia-Australia Monsoon Project on the Tibetan Plateau（CAMP/Tibet）"， "the Tibetan Observation and Research Platform （TORP）"， and "The Third Tibetan Plateau Atmospheric Scientific Experiment （TIPEX-Ⅲ）"， where the observation analysis， numerical simulation and satellite application of the land-atmosphere interaction and the atmospheric boundary layer processes are the most important contents.Here， we reviewed the major atmospheric scientific experiments over the QXP in the past 40 years and summarized the observation experiments of the land-atmosphere interaction and the atmospheric boundary layer processes systematically.The relevant results are briefly summarized in 5 aspects， including the land-atmosphere interaction process， the atmospheric boundary layer process， the surface and atmospheric heat sources， satellite application of land evapotranspiration， numerical simulation of land surface processes.
  • Progress in the Study of Influence of the Qinghai-Xizang Plateau Land Atmosphere Interaction on East Asia Regional Climate
  • LAI Xin;FAN Guangzhou;HUA Wei;DING Xu
  • 2021 Vol. 40 (6): 1263-1277.  DOI:10.7522/j.issn.1000-0534.2021.zk018
  • Abstract ( ) PDF (13248KB) ( )
  • The land atmosphere interaction over the Qinghai-Xizang Plateau （QXP） has important influences on the weather and climate of East Asia， and the climate effect of vegetation and thermodynamic processes over the TP are two major topics.This paper provides a review on variation characteristics of the QXP vegetation and land atmosphere water and heat exchange， influence of the QXP vegetation and thermodynamic processes on the QXP monsoon and East Asian monsoon and regional climate of East Asia.The results show that： （1） The Normalized Difference Vegetation Index （NDVI）， vegetation coverage and Net Primary Production （NPP） over the QXP decreased from southeast to northwest.Generally， in recent decades the NDVI， vegetation coverage and NPP increased over the QXP， Annual Leaf Area Index （LAI） and LAI in the growing season increased over southeast Tibet.（2） The Sensible Heat （SH） flux over the QXP significantly decreased since 1980.The Latent Heat （LE） flux over the QXP significantly increased in summer from 2000 to 2016.（3） The QXP vegetation has significant and positive correlations with QXP surface heat source.The degradation of vegetation to desert over the QXP decreased the net radiation absorbed by the surface， weakening the surface heat source， leading to a westward extending of the south Asia high and a weakening of the western Pacific subtropical high.As a result， Precipitation in southern and northeastern China increased， and precipitation in northern China decreased.（4） When the QXP atmospheric heat source is strong （weak）， the QXP summer monsoon is strong （weak）.The QXP heat source is closely correlated with the establishment and maintenance of the East Asian summer monsoon.QXP heating effect make air column warming from April to mid-May， and it is beneficial to the surrounding air converging to the QXP and tropical warm-moist air proceeding northward， leading to the outbreak of the South China Sea （SCS） summer monsoon.The QXP heating effect is also beneficial to maintaining the SCS summer monsoon.The QXP SH flux decreased in recent decades， making less precipitation in the north and more precipitation in the south over eastern China.The annual mean air temperature in each layer over the QXP and the QXP summer monsoon index has significant correlations.On the interannual and decadal timescales， when the temperature over the QXP increases in the lower to middle-upper troposphere and decreases in the high troposphere， there is more precipitation in the regions south of the Yangtze River and southern China and less precipitation in the northeastern China.
  • The Impact of Land-atmosphere Interaction on the Initiation and Development of Convective Activities： A Review
  • LIU Weicheng, ZHANG Qiang, LIU Xinwei
  • 2021 Vol. 40 (6): 1278-1293.  DOI:10.7522/j.issn.1000-0534.2021.zk0019
  • Abstract ( ) PDF (10786KB) ( )
  • The land-atmosphere interaction will affect the initiation and development of the convective system， which in turn affects the generation and distribution of precipitation.Understanding and clarifying the impact mechanism is crucial to improving the forecasting technology of convective activities.This paper systematically summarizes the influence mechanism of land-atmosphere interaction on the formation， development of convective systems， generalizes the influence sign and intensity of land-atmosphere interaction， and analyzes the complexity of land-atmosphere interaction on convective activities.Finally， key scientific issues that need to be resolved are put forward.In-depth research is needed in the future， including the influence mechanism of the entire composition process of land-atmosphere interaction on convective activities， the influence mechanism of land-atmosphere interaction forced by different weather systems， scientific evaluation and verification of the influence mechanism， parameterization and coupling of land surface processes and boundary layers process， and the mutual feed mechanism of land-atmosphere interaction and convective activities.The study of these issues can profoundly reveal the mechanism of the influence of land-atmosphere interaction on convective activities， with a view to providing theoretical support for improving and enhancing the forecasting capabilities of convective activities.
  • Review of Qinghai-Xizang Plateau Monsoon’s Evolution and Climatic Effects
  • FAN Weiwei;HU Zeyong;XUN Xueyi;YANG Yaoxian;YU Haipeng;FU Chunwei;WU Di
  • 2021 Vol. 40 (6): 1294-1303.  DOI:10.7522/j.issn.1000-0534.2020.zk013
  • Abstract ( ) PDF (19534KB) ( )
  • Qinghai-Xizang Plateau Monsoon （QXPM） is a prevailing wind system with a seasonal reversal of wind direction， which is caused by the thermal effects of the plateau.QXPM plays a vital role in the energy budget and water cycle of the Qinghai-Xizang Plateau （QXP） and thus has profound impacts on the formation and variations of Asian climate and environment.The review on the QXPM and its climatic influence is not only the need for an in-depth understanding of the climatic and environmental of QXP but the requirements of the country's ecological civilization construction and social and economic development.This paper reviews the advances of studies in QXPM， emphasizing its multi-scale variability， factors affecting the QXPM， and its climate and environmental effects.The existing studies show that the formation of QXPM is an important sign of the beginning of Quaternary and related to the uplift of QXP closely.The variation in QXPM is significantly influenced by QXP heating， the tropical sea surface temperature， Atlantic Oscillation， and teleconnection patterns.Existence and variations in the Qinghai-Xizang Plateau Monsoon have notable impacts on the climate of the QXP and its surrounding area， such as Asian monsoon， South Asian high， mid-latitude westerlies， and so on.In the future， the relationship between the water vapor transport condition， thermal characteristics， and dynamic characteristics of the plateau monsoon system needs to be clarified.Studies on the interaction between the complex land surface process and the QXPM need to be strengthened.Moreover， under the background of global climate change， it's also necessary for us to analyze the response of QXPM to QXP warming.
  • Climate Effects of Soil Freeze-Thaw Process over Qinghai-Xizang Plateau： Progress and Perspectives
  • WANG Chenghai;YANG Kai;ZHANG Feimin;BAO Hongyan;CHENG Rong;LI Dengxuan;CUI Zhiqiang;LI Kechen
  • 2021 Vol. 40 (6): 1318-1336.  DOI:10.7522/j.issn.1000-0534.2021.zk021
  • Abstract ( ) PDF (5959KB) ( )
  • The thermal effects of the Qinghai-Xizang Plateau （QXP） on the East Asian and global atmospheric circulation and climate are due to the surface diabatic heating， which is closely related to the land surface processes.This paper reviewed the research progress of soil frozen-thawing process on soil hydrothermal transport， surface diabatic heating over QXP and its climate effects， the main points are as follows： （1） soil frozen-thawing process has "water storage" effect， and the water storage index can reach 0.99 in the whole soil layer.（2） The estimation of surface diabatic heating on QXP is still a challenging problem， and different reanalysis data have large biases， especially in spring， one of the main reasons is the bias of the atmospheric model in simulating the soil frozen-thawing process.（3） The fully coupled water-heat transport scheme and the modified frozen-thawing parameterization scheme can effectively reduce the model biases in the simulation of soil temperature and moisture.（4） Soil moisture anomalies in the previous autumn and winter can persist to spring through the soil frozen-thawing process， causing the surface diabatic heating anomalies in spring， can be a signal of climate prediction.（5） The anomalous thawing of frozen ground in spring over QXP affects the surface diabatic heating by causing soil moisture anomalies， and changes the baroclinicity of the atmosphere on the north and south sides of the QXP， which excites the Rossby wave train， leads the anomalies of atmospheric circulation over the downstream regions， causes summer precipitation anomalies in eastern China.The large biases of the numerical model and reanalysis data in estimation of the surface diabatic heating of QXP limit the deep understanding of the thermal effects of the QXP.How to improve the model parameterization by deepening the understanding of the physical processes of freeze-thaw and snow is a challenging problem and an important part of future research.
  • Recent Progress in the Land Surface Process Studies： A Case Study of CAS-LSM
  • WANG Longhuan;XIE Zhenghui;JIA Binghao;WANG Yan;LI Ruichao;XIE Jinbo;CHEN Si;QIN Peihua;SHI Chunxiang
  • 2021 Vol. 40 (6): 1347-1363.  DOI:10.7522/j.issn.1000-0534.2021.zk016
  • Abstract ( ) PDF (20342KB) ( )
  • Land surface processes are an important part of the climate system， affecting atmospheric circulation and climate change.Reasonable descriptions of human activities， biophysical and biochemical processes in the land surface model are very important for improvint our understanding of land-atmosphere interaction.This paper first reviews the development of the land surface model， which has evolved from the simple box model to consider more complete physical， chemical and biological processes， and is developing toward refinement and integration.Human activities， such as irrigation and agricultural fertilization， discharge， and urban planning， affect terrestrial carbon， nitrogen and water cycle processes and aquatic ecosystems.Processes including groundwater lateral flow and the movement of frost and thaw fronts alter water budget， energy balance， and affect the weather， climate， and environment.Therefore， there is an urgent need to reasonably represent these processes and the effects of human activities in land surface models.Then this work introduces the physical parameterizations of a land surface model of the Chinese Academy of Sciences （CAS-LSM）.The new developed model can be applied to the simulation of inland river basins in arid areas to quantitatively evaluate the ecohydrological effects of stream water transfer.Combined with climate system models， CAS-LSM can monitor river water environment.It can also help quantitatively evaluate weather and climate effects of urban planning.
  • Uncertainties in the Regional High-Resolution Land Surface Simulations
  • GAO Yanhong;LIU Wei;ZENG Li
  • 2021 Vol. 40 (6): 1364-1376.  DOI:10.7522/j.issn.1000-0534.2021.zk008
  • Abstract ( ) PDF (1921KB) ( )
  • Land is an important part of the earth's climate system and an important place for human life.Water resources， ecosystems and human activities over land are all affected by global climate systems and are sensitively respond to climate changes.At the same time， as the lower boundary for the climate system， land exerts an important feedback on regional weather and climate system.Therefore， accurate， and high-resolution land surface simulation is an important prerequisite for simulating weather climate events and correctly understanding weather climate phenomenon.However， there is still great uncertainty in modern land surface processes simulations.The uncertainty of land surface process simulation comes from three aspects： model physical process， surface characteristic parameters， and meteorological driven data.This study summarizes the sources of uncertainty in high - resolution simulations of land surface processes， especially in high altitude mountains， focusing on the important impact of heterogeneous distribution characteristics of precipitation data on land surface process simulation.Improving land surface process model， providing realistic distribution of surface characteristic parameters， and carrying out dynamical downscaling simulation at convection permitting scale based on the high-resolution land surface statements may be an effective way to improve precipitation simulation for complex terrains.We aim to accurately simulate regional water circulation and realize the ultimate purpose of land surface process and regional climate simulation.
  • Area Averaged Fluxes and Scintillometry
  • WANG Jiemin
  • 2021 Vol. 40 (6): 1377-1393.  DOI:10.7522/j.issn.1000-0534.2021.zk017
  • Abstract ( ) PDF (7147KB) ( )
  • This is a review of the Optical-Microwave Scintillometer （OMS） system newly developed in last two decades， which can measure area averaged sensible and latent heat fluxes over a scale of 1 -10 km， especially over heterogeneous surfaces such as cross a valley or over urban areas.Among the methods of area averaged flux measurements， such as eddy-covariance based multi-point observations， air craft observations， satellite， and surface remote sensing etc.， scintillometry is probably the most feasible technique in getting areal fluxes up to 10 kilometers.The basic theory of scintillometry includes electromagnetic wave propagation， atmosphere turbulence， and micrometeorology， which are more sophisticated than that of the popular eddy covariance （EC） system.Based on the introduction of concepts such as refractive index， structure parameter and turbulence spectra etc.， basic scintillometer theories and equations are presented briefly， including： （1） calculation of structure parameter of refractive index via the variance of received light log-intensities； （2） the understanding of the working scale of scintillometry via the light-path weighting function， the spatial spectral weighting function， and the temporal spectral characteristics； （3） the derivation of structure parameters of temperature and humidity via the structure parameters of refractivity； （4） the calculation of fluxes by using the typical functions of Monin-Obukhov similarity； （5） the footprint analysis of scintillometry.A comparison between scintillometry and EC are presented in three aspects： ‘Characteristics’， ‘Advantages’ and ‘Weakness’.It is clear that a combined use of EC & Scintillometry can provide better area averaged fluxes， and， refined flux aggregation schemes.Then， the application of scintillometry is introduced for rather homogeneous surfaces， complicated surfaces， urban areas， and， the ‘ground truth’ for remote sensing and the application of areal averaged fluxes in atmospheric models.The example utilizations of the OMS systems in the Arou alpine-meadow station and the Zhangye oasis station， of the Heihe River basin， clearly show the advantages of scintillometry over the EC in the measurements of larger scale evapotranspiration.Nowadays there are hundreds flux stations operating over various climate regions and surface states of the world.Upscaling of the spatial representativeness of these stations becomes a key point to better understanding the land surface processes， and improving the spatial matching between land surface models and meso/large scale atmospheric models.Comparatively， the time of development of scintillometry， particularly the microwave scintillometers in measuring water vapor fluxes， are still short.Further improvements of relevant hardware， data sampling， and data processing software etc.are still needed.
  • New Related Progress on Researches of the Vortex Source of Southwest China Vortex
  • LI Yueqing
  • 2021 Vol. 40 (6): 1394-1406.  DOI:10.7522/j.issn.1000-0534.2021.zk005
  • Abstract ( ) PDF (11865KB) ( )
  • Southwest China Vortex （SWCV） and its weather influences are one of the main directions in Plateau Meteorology， and the vortex source of SWCV is a basic scientific problem.Because the interaction between topography and circulation is the important formation mechanism for the vortex source of SWCV， it always has been the focus of attention in SWCV researches.The new related progresses in researches of the vortex source of SWCV system are reviewed in this paper for the last 10 years.In particular， it is recognized that because of the multi-scale effects between the topography and circulation， the vortex source of SWCV has the multi-scale characteristic of its distribution， and there are obviously differences between the structure、 evolution、 cause and influence of SWCV with the different vortex sources.The vortex sources of SWCV have closely connection each other.The upper-reach vortex sources such as Jiulong、 Xiaojin have an important effect on the lower-reach vortex sources such as the Basin.The “effect of upper-reach vortex source” of SWCV， atmospheric gravity wave connecting with the complex topography， internal atmospheric process induced by precipitation， and the anomalous influences of East Asia monsoon are also the formation mechanisms for the vortex source of SWCV.External atmospheric forcing and internal atmospheric process all play an important role for the formation of the vortex source of SWCV.But， for research on the vortex source of SWCV， there are some problems such as being weaker in fine observation and basic data， being unknown for the multi-scale structures of the vortex source and its evolution， being not deep to understand the formation cause of different vortex sources and being incomplete in study of the SWCV evolutions and its effects of different vortex sources.And finally， it is pointed out that high resolution observation-experiment， internal structure and abnormal characteristics， evolution process and formation mechanism， and the effects of regional response to climate change on vortex sources are the future research focuses for the problem of the vortex source of SWCV， which is of important significance for the forecast theory and key technology of SWCV system and its effects.
  • Abnormal High Precipitation on the Southwestern Qinghai-Xizang （Tibet） Plateau during the Mid-Holocene Compared with Present Day
  • HUANG Lingxin, ZHANG Shuai, CHEN Jie, HUANG Wei, YANG Kun, CHEN Fahu
  • 2021 Vol. 40 (6): 1407-1418.  DOI:10.7522/j.issn.1000-0534.2021.zk022
  • Abstract ( ) PDF (23987KB) ( )
  • The ancient lake shorelines in the western Qinghai-Xizang （Tibet） Plateau reveals that there may be more precipitation than present day（PD）during the mid-Holocene（MH）， especially in the Ngari.Thus， we compared the precipitation between the MH and the PD using the high-resolution precipitation of the WorldClim dataset and then applied the ERA5 dataset to explore the underlying mechanisms of the precipitation over the southwestern Qinghai-Xizang （Tibet） Plateau.The results show that precipitation in the MH over the western Qinghai-Xizang （Tibet） Plateau was much higher than that in the PD， with the strongest precipitation occurring over the southwestern Qinghai-Xizang （Tibet） Plateau.When the precipitation over the southwestern Qinghai-Xizang （Tibet） Plateau enhanced in the PD， the Indian summer monsoon（ISM）also strengthened.The enhanced ISM could strengthen low pressure in the lower troposphere and deep convection over the Indian subcontinent.These could increase the water vapor transport to the southwestern Qinghai-Xizang （Tibet） Plateau.Meanwhile， the increased condensation latent heat released by the increased precipitation over northern India enhanced and northwestward moved the South Asian High， leading to the increased ascending motion and precipitation over the southwestern Qinghai-Xizang （Tibet） Plateau in the PD.Compared with PD， the ISM during the MH was stronger， and the low pressure over the Indian subcontinent may be stronger.The related condensation latent heat may also increase， which could further result in the increased precipitation over the southwestern Qinghai-Xizang （Tibet） Plateau during the MH.
  • Intraseasonal Oscillation of Atmospheric Heat Source over the Qinghai- Xizang Plateau in Boreal Spring and Its Maintaining Mechanism
  • LIU Boqi;DUAN Yanan;LI Jianying;MAO Jiangyu
  • 2021 Vol. 40 (6): 1419-1431.  DOI:10.7522/j.issn.1000-0534.2021.zk020
  • Abstract ( ) PDF (17871KB) ( )
  • The formation of atmospheric heat source over the Qinghai-Xizang Plateau （QXP） in boreal spring indicates the beginning of the QXP thermal forcing on regional and global weather and climate.Based on the JRA-55 atmospheric reanalysis and station-based observation data from 1981 to 2010， the present study investigated the spatial and intraseasonal variations of the spring atmospheric heat source over the QXP.A significant 10-20-day intraseasonal oscillation （ISO） was found in the atmospheric heat source over the QXP in boreal spring.It featured an alternation between zonal dipole and monopole mode of the spring atmospheric heat source over the QXP.The dipole mode was characterized by the inverse change of anomalous condensation latent heat between the northwestern and southeastern QXP.While the monopole mode exhibited a predominantly positive or negative sensible heat anomalies over the QXP.In the phases with the dominant monopole mode， the anomalous sensible heat over the QXP could produce the low-level circulation anomaly.It gave rise to the distinct water vapor transport between the eastern and western QXP， inducing the opposite variation of the local precipitation and condensation latent heat anomaly over the eastern and western QXP.The ISO thus entered its zonal dipole mode.As the atmospheric response to the anomalous condensation latent heat in the zonal dipole mode， the near-surface zonal wind was changed to facilitate the sensible heat anomaly over the QXP.In turn， the water vapor transport was altered over the eastern and western QXP but reversed its original property.As a result， the condensation latent heat anomaly decreased gradually over the QXP.On the one hand， the zonal dipole mode started to weaken.On the other hand， the response of the near-surface wind to the zonally asymmetric condensation heat anomaly could enhance the anomalous sensible heat over the QXP.Therefore， the atmospheric heat source over the QXP returned to the monopole mode with the homogeneous sensible heat anomaly.Finally， the interaction among sensible heat， condensation latent heat and local circulation maintained the quasi-biweekly ISO of the atmospheric heat source over the QXP in boreal spring.In addition， the zonal dipole mode of the quasi-biweekly ISO of the atmospheric heat source over the QXP led the significant anomaly of spring rainfall to the south of the Yangtze River by one phase （about 3 days）.It implicated that the biweekly ISO over the QXP could be treated as a potential subseasonal predicting precursor of the spring rainfall over East China.
  • Impact of the Lower-Tropospheric Warm Core over the Qinghai-Xizang Plateau on Central Asian-Tibetan Plateau Precipitation in Spring
  • SHANG Ke;LIU Xiaodong
  • 2021 Vol. 40 (6): 1443-1454.  DOI:10.7522/j.issn.1000-0534.2021.zk015
  • Abstract ( ) PDF (52798KB) ( )
  • The frequent occurrence of tropospheric warm cores over the Qinghai-Xizang Plateau （QXP） is an unique climate phenomenon in East Asia and is closely associated with the QXP heating effect.By using the six-hourly ERA-interim reanalysis data from 1979 to 2018， the modulation effect of the springtime intensity of the low-level warm core （LLWC） on the dipole pattern of precipitation in Central Asia-Tibetan Plateau （CA-TP） is investigated on the basis of the warm core event statistics and singular variance decomposition （SVD）.At the interannual time scale， significantly enhanced （reduced） rainfall in Central Asia （from Pamirs Plateau to northeastern Iranian Plateau） and suppressed （enhanced） rainfall over the eastern QXP and northern India are observed in strong （weak） LLWC years.The linkages between the LLWC and the associated lower-tropospheric temperature variation， the atmospheric circulation and the corresponding water vapor transport are revealed through diagnostic analyses.The results indicate that the anomalously strong LLWC significantly changes the meridional and zonal temperature gradients， which further trigger the barotropic anticyclonic circulation anomalies at the middle and upper tropospheric levels over the QXP.Strong sinking flows overwhelm the interior of the anticyclone and suppress the convective precipitation development.In addition， the anomalous northerly and easterly winds on the eastern and southern sides of the anticyclone restrain the water vapor transport.These conditions favor the decreased rainfall over the eastern QXP and northern India.Meanwhile， powerful southwesterly flow， prevailing in the northwestern side of the anticyclone， carries abundant moisture and converges in Central Asia， consequently leading to surplus rainfall from Pamir Plateau to northeastern Iranian Plateau.The anomalously weak LLWC triggers the cyclonic circulation anomaly at the middle and upper tropospheric levels and results in the opposite precipitation anomaly pattern.
  • Evaluation and Projection of CMIP6 Models for Climate over the Qinghai-Xizang （Tibetan） Plateau
  • CHEN Wei;JIANG Dabang;WANG Xiaoxin
  • 2021 Vol. 40 (6): 1455-1469.  DOI:10.7522/j.issn.1000-0534.2021.zk003
  • Abstract ( ) PDF (8928KB) ( )
  • Based on the numerical experiments undertaken by 45 Coupled Model Intercomparison Project Phase 6 （CMIP6） global climate models， we first evaluate the model performance in simulating the temperature and precipitation climatology over the Qinghai-Xizang （Tibetan） Plateau for the period 1985 -2014.Results show that the CMIP6 models can reasonably reproduce the climatological spatial patterns of annual and seasonal temperatures.Most models underestimate annual and seasonal temperatures， with an average of -2.1 ℃ for the annual mean and greater cold biases for winter and spring.The CMIP6 models perform poorly in reproducing annual and seasonal precipitation.They can reasonably reproduce the climatological spatial pattern of annual and seasonal precipitation， but obvious overestimation exists， especially for spring and summer， with a value of 397.8 mm a-1 for the annual mean.Furthermore， based on the preferred models， annual temperature over the Qinghai-Xizang （Tibetan） Plateau is projected to increase by 2.5 ℃ in the 2090s relative to 1995 -2014， with a trend of 0.28 ℃ per decade during 2015 -2100 under the Shared Society-economic Pathways （SSPs） 2 -4.5 scenario.Larger warming occurs in autumn and winter， and this holds for the high-altitude areas.Annual precipitation increases by 12.8% in the 2090s， with a trend of 1.56% per decade during 2015 -2100 under SSP2-4.5.Generally， larger increase in precipitation occurs in spring and in the northern border area of the Tibetan Plateau throughout the 21st century.Comparatively， annual and seasonal temperatures and precipitation have larger increases under the SSP5-8.5 scenario， and the corresponding magnitudes are 5.1 ℃ and 30.2% in the end of the 21st century， with a trend of 0.64 ℃ and 3.80% per decade， respectively.Overall， the inter-model uncertainty of the projected temperature and precipitation changes increases over time.
  • An Evaluation for Impacts of the Horizontal Resolution of CMIP6 Models on Simulating Extreme Summer Rainfall over Southwest China
  • HUANG Zili;WU Xiaofei;MAO Jiangyu
  • 2021 Vol. 40 (6): 1470-1483.  DOI:10.7522/j.issn.1000-0534.2021.zk010
  • Abstract ( ) PDF (47075KB) ( )
  • Due to complex topography in Southwest China （SWC）， state-of-the-art climate models cannot capture sufficiently the distribution and intensity of summer precipitation， especially extreme rainfall （ER） over SWC.Thus， this study is to evaluate how well the current climate models could reproduce the climate mean summer precipitation and to what extend the horizontal resolutions might impact the ER simulations over SWC， based on daily rain-gauge station-observed， satellite-observed and ERA5-reanalysed rainfall datasets and 12 models available from CMIP6 High-Resolution Model Inter-comparison Project （HighResMIP）.Each HighResMIP model contains one high-resolution and one low-resolution simulation with the same suite of physical processes and external forcing.Results show that almost all models can reproduce the climate-mean state of summer rainfall over SWC， with an area correlation coefficient （ACC） greater than 0.75 between the rain-gauge observed rainfall and simulated rainfall by each model.Over， the performance of CMIP6 HighResMIP models is better than that of CMIP5 models， but over half of the CMIP6 HighResMIP models still underestimate the summer rain amount over the Sichuan Basin.As the model resolution increased， the intensity and spatial pattern of the simulated summer rainfall over the Hengduan mountains are much closer to the observational dataset， especially to the ERA5 reanalysis.However， the underestimating biases over Sichuan Basin are not improved obviously with a higher horizontal resolution.In terms of ER， large spreads exist in the ER intensity and occurrence frequency over SWC among CMIP6 HighResMIP models.The four models， including CNRM-CM6、 FGOALS-f3、 GFDL-CM4 and HadGEM-GC31， exhibit better performances in capturing ER days and percentage.Even so， the first three of the above four models underestimate the ER days over SWC， but HadGEM-GC31 overestimates ER intensity over Guangxi Province.In contrast， the ER frequency is much lower than that of observation in the models ECMWF-IFS， EC-Earth3P， IPSL-CM6A， MPI-ESM1-2 and MRI-AGCM3-2.The higher resolution simulations can improve the simulation in the rainfall intensity to a certain degree， manifesting mainly in enhancing the rainfall intensity over the mountainous region rather than the flat-terrain area such as the Sichuan Basin.
  • Characteristics of the Three-Dimensional Circulation and Dynamic Structure of Jiulong Vortex of Southwest China Vortex
  • QU Ding;LI Yueqing
  • 2021 Vol. 40 (6): 1497-1512.  DOI:10.7522/j.issn.1000-0534.2021.zk002
  • Abstract ( ) PDF (39126KB) ( )
  • Affected by multi-scale processes， the structure of Jiulong Vortex （JLV） of Southwest China vortex is complex and changeable.In order to study the climatic characteristics of the three-dimensional structure of JLV， using ERA-interim reanalysis data， and on the basis of subdividing JLV’s generating area into subregion 1 and subregion 2， the characteristics of three-dimensional circulation and dynamic structure were deeply studied for the four types of JLV （the unmoved： local type and the moved： eastward type， northeastward type， and southward type） during the summers of 1989 -2018 by observation statistics， synthetic analysis and physical diagnosis.The results show that： （1） There are totally 249 cases of JLV for the past 30 summers.The local type， the eastward type， the northeastward type and the southward type account for 75.5%， 13.7%， 7.2%， 3.6%， respectively.And the four types of JLV all have different regional high-frequency generating centers.JLV moves mainly along the direction of 500 hPa dominant wind above the generating area and nearby.The total number of JLV and the numbers of different four types in subregion 1 are significantly more than that in subregion 2， and JLV in subregion 1 is easier to move out to the northeast and south than it in subregion 2.But， the probabilities of the eastward type are almost equal in subregion 1 and subregion 2.（2） The horizontal scale of JLV is 300~500 km in subregion 1， and 200~400 km in subregion 2.The temperature above JLV is abnormal distribution of "warm below and cold above"， the warm layer is deep and can reach more than 200 hPa， the negative abnormal area of height at lower layer is shallow and can only reach 500 hPa.The positive vorticity extends deeply and can reach more than 500 hPa， and it expands eastward at lower layer.The positive abnormal area of height above JLV in subregion 1 slopes vertically to the north obviously， but the positive temperature anomaly of JLV in subregion 2 slopes vertically to the south， and its intensity and range are greater than that in subregion 1.The positive vorticity extension thickness of moved type is deeper than that of unmoved type.（3） The strong convection area of JLV is asymmetrically distributed， mostly in the east and the north along its center.The local type and eastward type have weaker convection development in subregion 1， but they have stronger convection development in subregion 2.And the convergent-divergent structure of JLV corresponds to its convection， the more vigorous the convection is， the stronger the low-level convergence and high-level divergence are.（4） There are obvious differences in the structure and evolution of JLV for the different regions and paths， which depend on the different physical characteristics of different local topography， movement modes， and development stages， and they are the results of the multi-scale interaction of topography and circulation under the different-latitude atmospheric coupling effect between the westerly belt to the north of the Qinghai-Xizang Plateau， the subtropical belt to the east of it， and the tropical belt to the south of it.
  • Comparative Analysis of the Characteristics of Annual and Seasonal Extreme Precipitation in South China during 1961 -2018
  • WEI Zhigang;LI Xianru;LIU Yujia;WANG Huan
  • 2021 Vol. 40 (6): 1513-1530.  DOI:10.7522/j.issn.1000-0534.2021.zk001
  • Abstract ( ) PDF (56427KB) ( )
  • Using a 0.25°×0.25° gridded daily temperature and daily precipitation observation data set CN05.1， we investigated characteristics of annual and seasonal extreme precipitation in South China.Based on spatial distribution and trends， the nine kinds of extreme precipitation in South China are classified into four categories： the category 1 is the extremely wet days （R99P）， the very wet days （R95P）， the maximum 1-day precipitation amount （RX1day） and the maximum 5-day precipitation amount （RX5day）.The category 2 is the number of heavy precipitation days （R10day）， the number of very heavy precipitation days （R20day） and the simple daily intensity index （SDII）.The category 3 and 4 is the consecutive wet days （CWDday） and the consecutive dry days （CDDday）， respectively.For 1961 -2018， the regional average extreme precipitation of the category 1 and 2 in South China increased except in spring.R99P， R95P， R10day and R20day increased significantly in summer.RX1day and RX5day increased significantly in winter and SDII in winter and summer.The CWDday increased significantly in spring， however， the annual and seasonal CDDday showed a downward trend， CDDday decreased significantly in winter.Except for CWDday， there is no significant trend of extreme precipitation in spring.Taking R95P， R20day， CWDday and CDDday as examples， the temporal and spatial changes and general trends of annual and seasonal extreme precipitation were further compared and analyzed by EOF decomposition.The results show that the extreme precipitation in South China is mainly the consistent variation in the whole region， the second is the variation of the north-south reverse phase or the east-west reverse phase.The north and south are roughly bounded by 23°N （Western South China） -25°N（ Eastern South China）， reflecting the reverse phase changes in coastal areas and northern mountainous areas in South China.East and west are roughly bounded by 114°E.The consistent variation in winter is the strongest， and the main component accounts for the largest proportion of variance.In addition， the spatial distribution characteristics of the trends of these four kinds of annual and seasonal extreme precipitation are analyzed and compared in detail.
  • Study on the Charge Structure in the Stratiform Region of a Mesoscale Convective System based on in-situ Electric Field Observation
  • ZHANG Hongbo;QIE Xiushu;LIU Mingyuan;JIANG Rubin;LU Gaopeng;CHEN Zhixiong;SUN Zhuling;LIU Ruiting;LI Jinliang;ZHENG Tianxue;CHEN Hongbin
  • 2021 Vol. 40 (6): 1531-1541.  DOI:10.7522/j.issn.1000-0534.2021.zk004
  • Abstract ( ) PDF (9702KB) ( )
  • Based on the in-situ observation of double-metal-sphere three-dimensional （3-D） electric field sonde and the comprehensive data of surface electric field， weather radar and lightning location， the electric field （E-field） and corresponding charge structure inside the stratiform region of a mesoscale convective system （MCS） in the North China Plain on 19 August 2016 were studied.The sounding system was released at 04： 30 （Beijing time） when the storm was at mature stage.The surface E-field was relatively weak （about +1.7 kV·m-1） compared to that of other overhead strong thunderstorms （>5 kV·m-1）.The lightning frequency of the whole MCS presented an obvious unimodal distribution and the peak occurred at about 06： 00.However， almost all lightning occurred in the convection region， while there was a few lightning within the stratiform.The complete sounding data during the ascent stage showed that there were six charge layers in the stratiform and the charge polarity altered in the vertical direction.The main positive charge region was at 8.2-9.5 km （-20~-14 ℃） and the main negative charge region was at 7.4~8.2 km （-14~-10 ℃）.A thin positive layer was just below， and a negative shielding charge region was near the top of thunderstorm.There were one positive and one negative charge layer near 0 ℃.The total net charge of the six layers was weakly positive （about +0.22 nC·m-2）， that may be caused by the positive particles advected from the convection based on the 3-D dynamic field simulation of the MCS.The local electrification mechanism may also contribute to the charge layers near 0 ℃， that need more observation and simulation to study.When the sounding system flew down （about 1 hour later）， it still went through the stratiform region that was at the mature stage.The available sounding data between 4.6 to 9.0 km showed the maximum E-field was about +70 kV·m-1， larger than that in the ascent stage， and four charge layers existed.The distribution of charge structure corresponded roughly to with that during the ascent stage， while the heights， thicknesses and charge densities of the charge layers were different.The differences may be caused by the changes of the sounding position relative to the thunderstorm， the development status， and the dynamic and microphysical field inside cloud.

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