As a climate-sensitive region， precipitation over the Qinghai-Xizang （Tibetan） Plateau significantly impacts the water cycle and the climate of East Asia.Therefore， it is important to study its changes.Precipitation is an important variable in the global hydrological cycle and one of the major climate systems affected by climate change.To investigate the ability of the global climate models to simulate precipitation over the Qinghai-Xizang （Tibetan） Plateau and examine possible changes in future precipitation under the new model and scenarios， this paper uses the latest monthly precipitation data from the 31 climate models of the Coupled Model Intercomparison Project 6 （CMIP6） and the CN05.1 precipitation observation data set provided by the National Climate Center to evaluate the ability of the CMIP6 model to simulate precipitation over the Qinghai-Xizang （Tibetan） Plateau.Furthermore， better models are selected to project the future precipitation of the Qinghai-Xizang （Tibetan） Plateau under different Shared Socioeconomic Pathway （SSP） scenarios.The results show that the model distribution of observed precipitation over the Qinghai-Xizang （Tibetan） Plateau from 1995 to 2014 is characterized by a decrease from southeast to northwest and a summer precipitation concentration.Most of the models can simulate the precipitation distribution and seasonal trend， but almost all of them overestimate the precipitation phenomenon， and the average precipitation of multiple modes is 102% higher than that observed.In general， the latest model of CMIP6 has a poor ability to simulate precipitation over the Qinghai-Xizang （Tibetan） Plateau， and the average relative deviation index of the model from the observation is 102%， indicating that most of the models are not satisfactory， and EC-Earth3-Veg-LR， MPI-ESM1-2-LR， EC-Earth3-Veg， and MRI-ESM2-0 are selected as the better modes after quantitative analysis of all the models， which can roughly reflect the precipitation characteristics of the Qinghai-Xizang （Tibetan） Plateau.Climate models show the slowest increase of precipitation over the Qinghai-Xizang （Tibetan） Plateau under the SSP1-2.6 scenario and the fastest increase under SSP5-8.5.From SSP1-2.6 in the small radiative forcing scenario to SSP5-8.5 in the large scenario， the recent （from 2021 to 2040） precipitation increase on the plateau is difficult to find a large difference in each scenario， but there is a significant increase in the mid （from 2041 to 2060） and late （from 2081 to 2100） scenarios， indicating that carbon emission intensity has a small impact in the short term and a large impact in the long term.The future increase in precipitation mainly occurs in the area south of the Nianqing Tanggula Mountains， from a seasonal point of view， the summer increase is the largest， followed by spring and autumn， the smallest increase is in winter， so we should pay attention to the future summer and spring precipitation changes over the Qinghai-Xizang （Tibetan） Plateau and take coping measures.

Autumn rain in western China is a unique and complex precipitation phenomenon that takes place during the autumn season in the western region of China， which is closely related to various aspects of economy， society and human life.This natural phenomenon has a profound impact on agriculture， transportation and other aspects of social production and life， sometimes even causes the phenomenon of autumn flood， which deserves full attention.Based on the basic understanding of the phenomenon in the 20th century， this paper compares and reviews the main research achievements of autumn rain in western China over the past 20 years from multiple perspectives.First of all， the spatial distribution range and temporal extent and precipitation intensity of autumn rain in West China are thoroughly explored， quantitative criteria and indexes such as ARI （Autumn Rain Index）， DARI （Daily Autumn Rain Index） and MARI （Modified Autumn Rain Index）are also proposed.In addition to this， the significant interannual differences， the "positive - negative - positive" interdecadal variations and the 4~8 years cycle of autumn rain in western China fully demonstrate its complexity and inhomogeneity.Secondly， the different but important influences of atmospheric circulation systems at low， middle， and high latitudes， tropical sea temperature forcing including Pacific Ocean， Indian Ocean， and Atlantic Ocean as well as the Qinghai-Xizang （Tibet） Plateau effect and other aspects on the autumn rain in western China are pointed out.These different factors all play significant roles in the evolution of the phenomenon， but the mechanisms are different.This leads to the recognition of the significance of the multi-system and multi-factor synergistic effect on the anomalous evolution of autumn rain in western China， which enriches the understanding of the autumn rain and its impact.Finally， according to the current cognition of autumn rain in western China， the main problems that exist in the combination of different monsoon systems like Indian monsoon， East Asian monsoon and Plateau monsoon， cold and warm air currents， evolution causes， weather processes， night rain characteristics， regional responses to the global warming and other aspects are pointed out.These problems highlight the challenges that researchers face in studying this complex phenomenon.However， despite the challenges， there are several promising areas for future research.The main development trend in the future about the research of autumn rain in western China is the comprehensive and elaborate analysis of the multi-scale synergy of autumn rain in western China and its physical mechanism under the complex and important topography of Qinghai-Xizang （Tibet） Plateau.

Using radiosonde and ground mapping data from conventional observations， FNL analysis data （1°×1°） and quality controlled hourly precipitation data of Yunnan regional automatic station， diagnosed the function of the Qinghai-Xizang Plateau’s eastern slope topography in the PLV （plateau vortex） affected precipitation in Yunnan during 2-3 July 2017.While the latest WRFv4.0 numerical model is used to conduct the topographic sensitivity test of this process.The results show that PLV which generated in the Yajiang region of Sichuan province （NO.C1735） is an important system influenced on this heavy rainfall in Yunnan； This low-vortex system maintain warm core structure in the middle and high altitude during the process period， corresponding with remarkable alternately distribution of ascending and descending movements； Distribution of process accumulated rainfall present two obvious NW-SE rain belts parallel to the mountain trend and the precipitation on the rain belt have intensity interlaced fluctuation characteristics； The heavy rainfall mainly occurred within two periods： one from afternoon to evening and other at the first half of the night， and all located besides the terrain slope （the east and south slopes）， especially in areas with steep terrain， large slopes， and trumpet-shaped topography， and then propagates downstream alone with the PLV； The South Asian High， northwest divergent airflow， Western Pacific subtropical high and Yunnan-Myanmar high provides favorable upper flow field for the eastward movement and development of the PLV， besides the position of 500 hPa positive vorticity and 700 hPa water vapor flux convergence can well indicates the heavy rainfall area； There exist β-mesoscale gravity wave during the period of precipitation， which stimulated by the Qinghai-Xizang Plateau’s eastern slope， and propagate between 300~200 hPa； Non geostrophic equilibrium motion and vertical wind shear at high-altitude are beneficial to the occurrence and propagation of gravity wave； The gravity wave propagate downstream before the PLV and precipitation， its wave ridge corresponds to the upward motion and divergence center， whereas the wave trough corresponds to the descending motion and convergence center， the heavy precipitation and the wave ridge are all located at the southwest side of PLV， the area of strong convergence and upward movement； After reduced the terrain height， its mechanical blocking and lifting effect weakened， the gravity wave and PLV disappears， leading to significant changes in the intensity and spatial distribution of the rain belt； Thus， the topography of the eastern slope of the Plateau plays important role both on the formation and development of PLV and precipitation in Yunnan under the influence of PLV.

To promote the understanding of precipitation microphysical characteristics and differences in the central and eastern Qinghai-Xizang （Tibetan） Plateau and the Sichuan Basin， disdrometer measurements collected at Naqu， Yushu， Linzhi， Batang， Luding， and Chengdu from July to August 2019 and 2020 are utilized to comprehensively investigate the characteristics and differences of raindrop size distributions （RSDs） among the six different areas.Meanwhile， local empirical relations between the Gamma shape parameter and slope parameter and between the reflectivity factor and rain rate are proposed and compared.The results show that RSDs in the basin and adjacent areas （Chengdu and Luding） are generally wider and have higher number concentrations of medium-to-large raindrops （diameter ≥1.0 mm） than those in the plateau areas （Naqu， Yushu， Linzhi， and Batang） due to the contribution of more strong convective precipitation.In contrast， RSDs in the plateau areas are narrower and possess higher number concentrations of small raindrops （diameter <1.0 mm） due to more occurrences of stratiform and weak-convective precipitation.RSDs gradually become wider with higher number concentrations as the increase of rainfall intensity both in the six observation areas.The RSD differences among the six observation areas can also change with the rain rate.Specifically， when the rain rate exceeds 0.1 mm·h^-1， the increase of the number concentration of small raindrops with increasing rain rate is significantly greater in Naqu and Linzhi than in other areas， and can gradually exceed that in Chengdu.When the rain rate exceeds 5 mm·h^-1， the differences in the number concentrations of medium-to-large raindrops between Chengdu and Luding and other plateau areas also gradually become larger.With the same shape parameters， the slope parameters in Chengdu and Luding are smaller than in other areas， indicating that they possess a slower decreasing rate of raindrop number concentration with increasing particle size than that in other plateau areas.Under the same radar echo intensities （reflectivity factor）， rain rates of stratiform precipitation in Naqu and Linzhi are greater than in other regions.The rain rate of convective precipitation in Linzhi is also greater than that in other areas when the radar echo is below 40 dBZ， but the rain rate of convective precipitation in Naqu can be smaller than that in other areas when the radar echo is greater than 40 dBZ.

Based on the hourly product of CLDAS （CMA Land Data Assimilation System） in 2021， this study is to evaluate the prediction capacity of the global high-resolution deterministic numerical prediction product ECMWF （European Center for Medium Weather Forecasting） for winter mean near-surface 2 m temperature of complex terrain region around the Hengduan mountains in southwest China by starting from winter average temperature， daily variation， and diurnal temperature range.And this study compares the temperature deviation characteristics of near-surface 2 m temperature in different topographic regions by distinguishing between high terrain region （the Western Sichuan Plateau） and low terrain region （the southern Sichuan Basin）.The results show that： （1） The ECMWF model can reasonably predict the spatial distribution characteristics of the winter mean near-surface 2 m temperature around the Hengduan mountains in southwest China， but the deviation distribution is related to the terrain height.With the increase of the terrain height， the prediction deviation tends to increase.（2） The ECMWF model well reproduces the daily variation characteristics of winter mean near-surface 2 m temperature around the Hengduan mountains in southwest China， with the peak time appearing at 14:00 （Beijing Time）.The prediction deviation of temperature at various times varies at different terrain heights.The maximum negative deviation of the western Sichuan Plateau and the Hengduan mountain regions occurs in the afternoon， while the maximum negative deviation of the south Sichuan Basin occurs in the morning.At the same time， the prediction deviation at each moment in high terrain areas is greater than the prediction deviation at each moment in low terrain areas.（3） The ECMWF model can reasonably predict for the spatial distribution of winter mean near-surface 2 m temperature over different terrain at various times during the day， but the deviations have diurnal variation characteristics.Especially in the high terrain region of the Hengduan mountain regions， there are different characteristics of cold and warm deviations at various times.（4） The area with large forecast bias of diurnal temperature range is generally the area with frequent Quasi-stationary front activities in Kunming.For the days （A total of 90 days， from December 1， 2021 to February 28， 2022） with large diurnal temperature range， the prediction deviation of winter mean near-surface 2 m temperature in this area is greater than the days with small diurnal temperature range.What’s more， the prediction deviation of diurnal temperature range is relatively unstable in the area with large forecast bias of diurnal temperature range.

The warm zone blizzard are both infrequent and highly destructive， making their accurate prediction a challenging and crucial focus.This study utilized four distinct cloud microphysics schemes （Lin， Thompson， WDM6， and WSM6） within the WRF mesoscale model to conduct a numerical simulation of a typical warm zone blizzard process in the northern Xinjiang in the middle of November 2016.The research objectives encompassed the evaluation of the model's capacity to simulate the warm zone blizzard， the selection of an optimal parameterization scheme， an analysis of the vertical distribution and evolution of hydrometeors during the snowstorm， and an exploration of the developmental patterns of related mesoscale systems contributing to the snowstorm.The analysis yielded the following key findings： （1） Among the diverse cloud microphysics parameterization schemes tested， the Lin scheme demonstrated the most favorable performance， effectively simulating snowfall magnitudes， spatial distributions， and trends.（2） In the cloud， all kinds of water condensate particles are active in the lower and middle troposphere， with graupel and snow being the most.Ice crystals， snow， cloud water and graupel particles are distributed from the upper layer to the lower layer.Near the windward slope of Altai Mountain is the center of the large concentration of each water condensate particle.The vertical alignment of the high value center of the four kinds of cloud water condensate particles in the strong snowfall area is conducive to the transformation of each particle.（3） High-humidity systems upstream moved westward， with the intensification of low-level southward jet streams resulting in pronounced moisture convergence.The western foothills of the Altai Mountains acted as a barrier， promoting moisture convergence by blocking the windward side； The low-level southerly jet also provides a continuous updraft and unstable condition for the generation of the blizzard.Strong snowfall is located in a wide updraft area between two groups of secondary circulations.The explosive growth of vertical movement is conducive to triggering the release of unstable energy， providing strong dynamic lifting conditions for the development and maintenance of the blizzard.

The NCEP reanalysis data were utilized to diagnose the structural characteristics and evolutionary mechanisms of two plateau vortex processes that moved eastward out of the plateau on June 25-27， 2008 and June 4-10， 2013.The data were also used to explore the structural characteristics of the two long and short track plateau vortex processes and the influencing factors that caused their different life histories.The results show that： （1） During the Zhaduo vortex activity with a short path， the South Asian high pressure is flattened， the upper-level jet stream is southward and the plateau vortex moves out of the plateau in the slump trough.During the Qumalai vortex activity with a long path， the South Asian high pressure has a north arch， the plateau vortex is in the northwest airflow under the South Asian high-pressure ridge， the subtropical high is southward and the plateau vortex is strengthened with the eastward movement of the trough， accompanied by the eastward movement of the southwest vortex.（2） The two plateau vortex processes exhibit distinct structural characteristics， especially when the Zhaduo vortex is strengthened on the plateau and when the Qumalai vortex is strengthened again after coupling with the southwest vortex.The former vortex is in the deeper positive vorticity and upward motion layer at 600~350 hPa and also has the structural characteristics of strong divergence in the upper troposphere.The latter has the structural characteristics of high， middle， and low positive vorticity penetration in the troposphere， ascending movement in the troposphere， and weak divergence in the troposphere.（3） The diagnosis of total vorticity budget shows that the change of divergence term plays a decisive role in the change of total vorticity variability of low vortices.The strength change of Zhaduo vortex is consistent with the divergence term change.The influence of vertical transport term and horizontal advection term are strengthened during the accompaniment of Qumalai vortex with the southwest vortex.（4） Regarding the budget analysis of the 500 hPa positive vorticity variability in the central region of the vortex， the results show that when there is no activity of the southwest vortex， the plateau vortex contributes mainly to the 500 hPa positive vorticity variability of the plateau vortex due to convergence.When there is activity of the southwest vortex， the vertical transport of positive vorticity becomes more important with the superposition and companionship with the southwest vortex in the vertical direction.

The variation in precipitation in Motuo is closely associated with the transport of water vapor from the India Ocean and the Bay of Bengal to inland China， the Asia summer monsoon， and the progression of the rain band in eastern China.A rain band with an average annual precipitation of more than 2000 mm has been formed due to the interaction of the distinctive topography of Motuo and the southwest air flow.However， it has been challenging to observe precipitation in Motuo due to the peculiar topography， insufficient electricity， and inadequate traffic conditions.An X-band dual-polarization phased array radar （XPAR） is installed during the Second Qinghai-Xizang Plateau Scientific Expedition and Research Program.The advanced dual-polarization phased array radar is used to continuously observe the precipitation in Motuo and is of great significance to the research of the local ecological environment and cloud water resources， and the impact on downstream.Based on XPAR data collected for the period from June to August 2020， we selected the radial precipitation echoes using a statistical method， and after integrating the precipitation echoes， we created the hybrid elevation angle that tallied with the topography of Motuo.Using DSD data from Motuo in 2019， we calculated radar parameters and obtained the localized QPE （Quantitative Precipitation Estimation） formulas of X-band weather radar.We selected three processes of precipitation with different cumulative precipitation， duration， and average rain rate from July to August 2020， calculated Φ _DP （Differential Propagation Phase Shift） using the linear programming method， K _DP （Differential Propagation Phase Shift Rate） using the ordinary least square method， and corrected Z _H （Reflectivity Factor） using the “ZPHI” rain profiling algorithm.Using Z _H and K _DP as thresholds， we estimated precipitation piecewise utilizing R（Z _H） and R（K _DP）， and contrasted results with the QPE results from the R（Z _H） and R（K _DP） methods， respectively.And explored the relationship between precipitation distribution and the topography of Motuo based on the QPE results.The quality of Z _H and K _DP had been significantly improved.The hybrid elevation angle constructed using a statistical method had a larger echo area than the hybrid elevation angle constructed using STRM1 v3.0 data.The PPI （Plane Position Indicator） diagrams of three precipitation （radar parameters at typical times， and average radar parameters） processes can show the relationship between the variation in precipitation and the topography of Motuo.The QPE formulas and Piecewise Estimation Method （PEM） used in the research functioned well， and each evaluation parameter performed well.The following conclusions are drawn： （1） The hybrid elevation angle constructed using the statistical method outperformed the hybrid elevation angle constructed using topography data in QPE， due to the drastic variation of the topography around the XPAR in Motuo； （2） The data quality control method， the QPE formulas， and the PEM utilized in the research all performed well at precipitation retrieval.The estimation error of the QPE results was significantly reduced， without causing significant changes in CC and RMSE； （3） Precipitation in Motuo may occur and grow as a result of the lifting of the southwest air flow by northern slopes of the valley.Clouds with higher rain rates and smaller drops are found near the level bottom of the valley.

The Yarlung Tsangpo River Grand Canyon region serves as a main water vapor entrance for the Tibetan plateau.However， the region has been experiencing a persistent decline in both water vapor convergence and precipitation since 1979， which has an important impact on the water storage over the Tibetan Plateau.In order to investigate the reasons behind this reduction in water vapor transport in the area， ERA5 hourly reanalysis data were utilized to drive the LAGRANTO model to derive the backwards water vapor transport trajectories in the region during the boreal summer （June to August） of typical dry and wet years， facilitating a comparative analysis of alterations in moisture flux along these trajectories.It was found that the water vapor sources primarily originating from four oceanic regions： the Bay of Bengal in the southern plateau， the Arabian Sea on the southwest side of the plateau， the Indian Ocean around south of the equator， and the South China Sea.The water vapor transportation in these regions is predominantly governed by the South Asian and Indian summer monsoons and influenced by the Somalia cross-equatorial jet.By comparing the characteristics of water vapor transport trajectories in dry and wet years， it is evident that trajectory patterns remain largely unchanged， with the exception of the South China Sea source.Furthermore， moisture flux along these trajectories diminishes as elevation increases， and the moisture loss during wet years consistently proves to be lower than that during dry years.Additionally， the trajectories originating from the Bay of Bengal source are supplemented by water vapor from the ocean surface， resulting in significant increased water vapor flux in wet years.This finding is supported by comparing the evaporation， precipitation， and circulation fields between dry and wet years.Ultimately， during wet years， the moisture flux reaching the boundaries of the Yarlung Tsangpo Grand Canyon region surpasses that of dry years， notably marked by a particularly significant increase in moisture entering through the southern boundary.This highlights that the depletion processes during water vapor transport， in addition to contributions from moisture sources and the influence of large-scale monsoonal circulation， play a critical role in determining the moisture equilibrium within the Yarlung Tsangpo Grand Canyon region.

As we know， the atmosphere is mainly characterized by its baroclinicity and stratification.The vertical coordinate is crucial for the description of 3D atmospheric motion and thermal-dynamic condition of the static atmosphere.Furthermore， the vertical coordinate is foundation of numerical prediction model construction.Different atmospheric dynamic cores， such as height， pressure and potential temperature-based frames are usually established depending on different vertical coordinate modes.The development of vertical coordinates always contributes to major version update and considerable upgrade of the numerical prediction model.In this paper， we briefly review the history of vertical coordinates for the numerical model.Then， we mainly demonstrate the design art for hybrid vertical coordinates in some operational non-hydrostatic models at home and abroad.Additionally， this paper presents some suggestions on how to select model vertical resolution and prediction variables vertical distribution style.Finally， the progress on arrangement and application of the vertical coordinate for numerical prediction models is summarized and its development tendency is also illustrated.

Based on NCEP/NCAR reanalysis data and the daily precipitation data from 105 meteorological stations in the central and eastern Qinghai-Xizang Plateau from 1982 to 2020， we investigate the spatiotemporal anomalous characteristics and major falling areas of warm season extreme precipitation and typical circulation of large-scale extreme precipitation in the central and eastern Qinghai-Xizang Plateau.The results show that： （1） Total precipitation of central and eastern Tibetan Plateau in the warm season shows statistically significant increasing at the rate of 10.7 mm·（10a）^-1 （P<0.05） during 1982 -2020， but there are obvious interdecadal trend shifts in the late 1990s and late 2000s.The increase in extreme precipitation of central and eastern Qinghai-Xizang Plateau is most prominent after 2009， and the climate tendency rate is of 4~5 times greater than that of during 1982 -2020.In terms of the distribution of spatial climate tendency rates， the trend of extreme precipitation in the southern Qinghai-Xizang Plateau is opposite to that in the central and northern Qinghai-Xizang Plateau in the three periods.The increase of extreme precipitation in the northern Qinghai-Xizang Plateau is the most prominent during 1998 -2009， and the extreme precipitation in the southern Qinghai-Xizang Plateau experiences the interdecadal trend shifts of significant increase， significant decrease and significant increase.（2） The small-scale extreme precipitation in central and eastern Qinghai-Xizang Plateau shows statistically significant decreasing trend （P<0.1）， while the large-scale extreme precipitation exhibits statistically significant increasing trend （P<0.05） during 1982 -2020.According to the locations of precipitation center， the level 4 large-scale extreme precipitation can be divided into three types， that is， northeast type （A type）， southern type （B type） and southeastern type （C type）.（3） The difference of location and intensity of the West Pacific Subtropical High is the main factor， which leads to the difference of water vapor sources and the locations of large-scale extreme precipitation falling areas.When the A-type large-scale extreme precipitation occurs， the West Pacific Subtropical High is anomaly weaker and eastward， which leads to the water vapor mainly transported from the Pacific Ocean and the westerlies.When the B-type occurs， the West Pacific Subtropical High is anomaly stronger and extending westward and southward， consequently， the water vapor mainly transported from the Indian Ocean and the Bay of Bengal.When the C-type occurs， the West Pacific Subtropical High is anomaly stronger， extending from the westward and northward， resulting in the water vapor mainly transported from the northwest Pacific Ocean， the South China Sea and the Bay of Bengal.

The snow cover in winter and spring on the Qinghai-Xizang （Tibetan） Plateau has a significant inter-annual variation， which has a certain indicative significance for the prediction of summer precipitation in eastern China.Due to the special complex terrain， the distribution of meteorological stations on the Tibetan Plateau is sparse and uneven.The uncertainty of the plateau snow cover information provided by reanalysis data and satellite data is a key issue affecting and constraining the study of snow variability and its weather-climate effects.Based on the multi-source snow data from station observations， reanalysis （ERA5 and NOAA-V3）， and satellite inversion （MODIS snow cover and IMS snow cover） on the Qinghai-Xizang （Tibetan） Plateau， this paper highlights the uncertainties of the multi-source plateau snow data in characterizing the inter-annual variability of the snow cover by means of multivariate statistical methods such as bias analysis， root-mean-square error and correlation analysis.By comparing the spatio-temporal distribution and variation characteristics of various snow data， we aim to improve the knowledge of the applicability of multi-source plateau snow data and provide meaningful references for subsequent related studies.The results show that： （1） In terms of the snow data given by the reanalysis data， the ERA5 snow depth exhibits a better depiction of the observed snow depth at the plateau stations compared to the NOAA -V3 snow depth.The mean bias and root-mean-square error of the ERA5 snow depth data are relatively small， except for some stations in the central-eastern part of the plateau， while NOAA-V3 snow depth is to some extent overestimated throughout the plateau； （2） Both reanalysis （ERA5 and NOAA-V3） and satellite inversion （MODIS as well as IMS snow cover） snow data and the station-observed snow depth on the plateau show good consistency in terms of interannual variability characteristics； Where the ERA5 reanalysis is more similar to the observed snow data on the plateau station in terms of long-term trend； In addition， decadal trend in Northern Hemisphere snow cover and station-observed snow depth appear more similar； （3） The spatial discrepancies in the distribution of snow depth and snow cover on the plateau was observed in the reanalysis data （ERA5， NOAA-V3）， in which the large value areas of NOAA-V3 in the years of more and less snow are located in the southern and northern margins of the plateau and in the central-eastern part of the plateau， while the large value of ERA5 are mainly distributed in the central-eastern， western and southern margins of the plateau.However， the differences between the respective snow depth and snow cover for each reanalysis data are relatively small， and the difference distribution between the snow anomalies years is relatively consistent， with the positive anomaly areas located in the central， western and southern margins of the plateau and the negative anomaly areas in the northern part of the plateau for both snow depth and snow cover； （4） The large value areas of snow cover for all three satellites in snowy years are located in the central-eastern and southern part of the plateau as well as in the western region.The difference distribution of snow cover in the increased anomalies years is also consistent for each type of satellite data， but the negative anomalies at the northern edge of the plateau reflected in the reanalysis data are not reflected in the satellite snow cover data， which may be related to the short coverage time of the satellite inversion snow data and different processing methods.

The inland arid zone of northwestern China has two climate regimes， monsoon-dominated and westerly-dominated， and is also an area of monsoon-westerly interaction.The study of climate and environment in this region is of great theoretical and practical significance， and it is also a frontier issue that has attracted much attention in global change research.This paper summarized the research progress on the definition of the monsoon zone， the westerly belt and their boundary zones， the progress on the climatic impacts of these two circulations and their interactions as indicated by instrumental measurements and proxies.Future research needs to focus on the westerly-dominated climate regime and its interaction with the monsoon， spatial definition， and driving mechanisms at high resolution and large spatial and temporal scales.These studies can promote research on the response to global change and its dynamic mechanism， and provide scientific support and theoretical basis for regional desertification management and national ecological security guarantee in arid northwestern China.

In order to solve the problem of the traditional remote sensing drought index focuses on the monitoring of a single response factor and lacks a complete analysis of drought.In this paper， we selected TVDI， RVI， PDI， and GVMI daily products estimated from remote sensing data as independent variables， and MCI calculated from meteorological data at the adjacent moments of satellite transit as dependent variables， and uses the Random Forest Regression （RFR） model to construct a integrated remote sensing drought monitoring model.The results show that the accuracy of RFR model is better than that of the Ordinary Least Squares （OLS） model in bothtraining data and test data.The R value of the RFR training data is 0.97， the RMSE is 0.33， the R value of the RFR test data is 0.90， and the RMSE is 0.53.The R value of the OLS training data is 0.78， the RMSE value is 0.73， the R value of the OLS test data is 0.76， and the RMSE value is 0.79.The comparisons of RFR and OLS model in R and RMSE show that the RFR model is superior than the OLS model in the characterization of regional drought.In the application of drought monitoring in Southwest China in 2022， the RFR results are consistent with the spatiotemporal distribution of the MCI index， which can better characterize the spatial and temporal dynamics of the regional drought， reflecting the practicality of the RFR model in the actual drought monitoring process.However， the accuracy of RFR model is related to the number of regional stations and the spatial distribution of stations， and the accuracy of the RFR model is higher in areas with a large number of stations and uniform distribution of stations.

Based on the daily summer precipitation data of 99 national stations in Shaanxi Province and the ERA5 reanalysis data from 1979 to 2021， the temporal and spatial variations of extreme summer precipitation and the corresponding large-scale circulation characteristics in Shaanxi Province were studied， and the water vapor tracking analysis was conducted on the typical regions.The results showed that the extreme summer precipitation in shannxi Province exhibits more in the south and less in the north， with increasing trend in the central part of northern shannxi and the eastern part of Guanzhong.The variation trend of extreme precipitation in northern Shaanxi， Guanzhong and southern Shannxi is 0.36 mm·a^-1， 0.35 mm·a^-1 and 0.11 mm·a^-1 respectively based on REOF analysis.In summer， there are three main paths for water vapor sources that affect Shaanxi Province.The northern branch comes from the high latitude region of Eurasia， the eastern branch comes from inland river basins， and the southern branch comes from the South China Sea and the Bay of Bengal.In addition， the increase of extreme summer precipitation in Shaanxi Province after 2005 was the result of the combined effects of the high， middle， and low-level atmospheric circulation.The enhanced divergence in the high atmosphere is conducive to the upward movement， and the water vapor is more likely to enter the inland due to the westward extension of the west Pacific subtropical high in the middle atmosphere.The anomalous easterly wind in the south side of the Mongolian anticyclone and the anomalous southeast wind in the lower atmosphere are more conducive to the transport of water vapor to the northwest region.

El Ni?o-Southern Oscillation （ENSO） is the most prominent interannual climate mode over the tropical Pacific， which is characterized by a periodic and phase-locked evolution of sea surface temperature anomalies （SSTA）.From the perspective of ENSO cycle， this study objectively classified the SSTA evolution of ENSO from 1961 to 2021 into two results using K-means clustering method （KMA）： 3 or 5 types of ENSO cycle.When it is classified into 3 types， the basic characteristics of ENSO cycle are warm-developing， warm-decaying， and cold-persistence.When it is classified into 5 types， the discrepancies of intensity and zonal distribution of the development and decay processes between super-strong and normal events are highlighted.To further explain these discrepancies， this study employed a KMA considering the Principal Component Analysis （Empirical Orthogonal Function）.Based on the two EOF leading modes which reflects the zonal symmetric and asymmetric development modes， the zonally symmetric and asymmetric development processes of the ENSO cycle are divided.Combined with the KMA clustering analysis， it is further found that zonally asymmetric development mode together with the zonally consistent development mode jointly lead to the zonal asymmetric development speed of ENSO cycle.Reconstruction of the zonally homogeneous and asymmetric evolution modes of ENSO reveals that wind and thermocline thickness anomalies may be key factors controlling the zonal asymmetric evolution of SSTA.This study objectively classified different types of ENSO evolution， providing reference for climate dynamics and impacts of ENSO diversity.

As one of the most sensitive natural elements in response to climate change， snow cover has a significant effect on the Earth's surface radiation balance and water cycle.The global snow cover area is approximately 46×10⁶ km² and 98% of the snow cover distributed in the Northern Hemisphere.Due to its distinctive radiative properties （high surface albedo） and thermal characteristics （low thermal conductivity）， changes in snow cover play a crucial role in the energy balance and water cycle between land and the atmosphere.In the context of global warming， the snow cover in the Northern Hemisphere has been decreasing in recent decades， especially in the spring.Therefore， the capabilities of CMIP6 （Coupled Model Intercomparison Project Phase 6） data to simulate the snow cover area were evaluated based on observational data and the future changes in snow cover were also assessed using a multi-model average in this study.By using the snow cover products from the National Oceanic and Atmospheric Administration/National Climatic Data Center （NOAA/NCDC） as reference data， the Taylor skill scoring， relative deviation， and other methods were applied to evaluate the spring snow cover （SCF） data in the Northern Hemisphere from the International Coupled Model Comparison Project Phase 6 （CMIP6） during 1982 -2014.The ensemble average of the top three models was further selected to predict the spatiotemporal variation characteristics of SCF under different emission scenarios from 2015 to 2099， providing insights into the modeling capabilities of CMIP6 and future changes in SCF.During the historical period （1982 -2014）， SCF was characterized by high coverage at high latitudes and low coverage at low latitudes， with high-altitude regions such as Tibetan Plateau and eastern Asia having higher snow coverage than those at the same latitudes.Overall， 68.37% of the regions in the Northern Hemisphere showed a decreasing trend in SCF， while 31.63% of the regions showed an increasing trend in SCF.Most CMIP6 models overestimated SCF in the Tibetan Plateau region compared to the reference data.In addition， most models simulated larger areas with a decreasing trend in SCF than those evaluated by the reference data and underestimated SCF in March， April， and May.Various models exhibited differing abilities to simulate SCF， with NorESM2-MM， CESM2， BBC-CSM2-MR， NorESM2-LM， and CESM2-WACCM demonstrating superior capabilities.The Multi-Model Ensemble Mean （MME） consistently outperformed individual models， closely aligning with observational data.There were significant differences in the ability of the CMIP6 models to simulate the spatial distribution， inter-annual variation trends， and intra-annual variations of SCF in the Northern Hemisphere.At the end of the 21st-century （2067 -2099）， SCF in the Northern Hemisphere exhibited a decreasing trend in most areas， which intensifies with increasing emission intensity.The changes in SCF were relatively consistent under different emission scenarios before 2040.SCF maintains a steady state under the SSP1-2.6 scenario， showed a slight decreasing trend under the SSP2-4.5 scenario， and showed a significant decreasing trend under the SSP5-8.5 scenario after 2040.

The Qinghai-Xizang Plateau Vortex is a mesoscale low-pressure vortex system generated within the boundary layer of the Qinghai-Xizang plateau in summer， which not only has an important influence on the weather patterns and precipitation dynamics across the plateau， but also profoundly impacts the surrounding regions.In this study， the database of the plateau vortex obtained from an objective analysis method， along with ERA5-land reanalysis data， was utilized to conduct a comprehensive statistical and analytical investigation of the vortex's activity from 1950 to 2021.Various analytical methods， including correlation analysis， regression analysis， Bayesian time series analysis algorithm， and probability statistics were used.Furthermore， the intensity and path of the plateau vortex during the years 1950 and 2021 were specifically examined to identify the areas most sensitive to its activity during this time span.Results reveal a noteworthy increasing trend （at a 95% confidence level） in both the annual number and duration of the plateau vortex， with climate tendency rates of 0.16·a^-1 and 1.25 h·a^-1， respectively.However， the growing trend for the total number and duration of the plateau vortex during the active period （May to August） is not statistically significant.The sensitive areas that affect the activity of the plateau vortex are located on the north side of the northern Qinghai-Xizang Plateau and near the Hoh Xil Mountains， corresponding to the main mountains in the central and western Qinghai-Xizang Plateau.Furthermore， the study investigates the relationship between land surface parameters and the vortex's characteristics， showing positive correlations between latent heat， surface longwave radiation， and surface soil moisture （0~7 cm） with the number and duration of the plateau vortex.Conversely， sensible heat exhibits a negative correlation， it is further found that the plateau vortex is relatively consistent with precipitation when the time scale of the study is inter-annual， while on the daily scale， the sensible heat is positively correlated with the number， duration， and intensity of the plateau vortex mainly in the sensitive areas and to the east of the sensitive areas， with the most significant correlation being in the months of May and June.In conclusion， the results derived from this study provide a solid theoretical foundation for further exploration of the land-atmosphere interaction mechanism in the identified sensitive area.Moreover， these findings lay a critical foundation for enhancing numerical simulations and data assimilation studies of the Qinghai-Xizang Plateau Vortex.

The Qinghai-Xizang Plateau has complex terrain and climate， which is a great challenge to the airdrop parachute landing and aviation safety.This research focuses on Qinghai-Xizang Plateau wind field simulation in boundary layer based on numerical calculation method.Firstly， the study built a WRF-LES system and scaled down to 40 m horizontal resolution based on the large eddy simulation （LES） scheme of WRF （Weather Research and Forecasting） model， and undertook the application study of large eddy simulation on the Qinghai-Xizang Plateau.Based on a strong wind case over the Qinghai-Xizang Plateau， the impacts of LES scheme and terrain elevation data on wind field simulation were evaluated through sensitivity tests.Then， the parameters in the standard sub-grid turbulent stress models of LES scheme were analyzed， and the optimal schemes for wind field simulation on the Qinghai-Xizang Plateau was obtained.Finally， a batch test was conducted to verify the applicability of the optimal schemes to the Qinghai-Xizang Plateau wind field simulation.The test results show that the WRF-LES system with a resolution of 40 m can simulate more precise and accurate wind field information， and the MAE （Mean Absolute Error） of simulated wind speed is reduced by 1.4 m·s^-1 and the RMSE （Root Mean Square Error） is reduced by 1.81 m·s^-1 compared with the ACM2 scheme； The high-precision ASTER terrain data can also improve the effect of wind field simulation， and the error is approximately deduced by 0.2 m·s^-1； The LES scheme that use 1.5-order turbulent flow energy scheme and set parameter coefficient 0.1 has the best simulation result， and the MAE is 1.56 m·s^-1 and RMSE is 2.06 m·s^-1； The batch test verifies that the large eddy simulation scheme is fit for the wind simulation on the Qinghai-Xizang Plateau， and the wind field simulation results in the 40 m resolution is significantly better than in the mesoscale resolution.The result shows that WRF-LES system can provide accurate wind field information for the parachute landing on the plateau.

Observed soil moisture and precipitation as well as GLDAS and CMFD reanalysis data are used to analyze the spatial and temporal distribution and variation trend in the Loess Plateau region.Regression analysis， Granger causality test and singular value decomposition （SVD） are used to study the relationship between soil moisture and precipitation， and to analyze the temporal scale and spatial range of the influence of initial soil moisture on subsequent precipitation.The results show that the explained variance of the regression analysis of soil moisture and subsequent 1~2 months precipitation on the Loess Plateau is relatively high， with larger values in the summer and fall seasons （July， August， September， and October）.That the correlation between soil moisture and the subsequent 21 days of precipitation in different regions of the Loess Plateau （zones I， II， and III） is more frequent and concentrated than that in the whole region.This indicates that soil moisture on the Loess Plateau is heterogeneous so that a larger lagged precipitation time scale is just suitable for analysis at larger spatial scales.The Granger causality test shows that the initial soil moisture in the fall （October and November） across the Loess Plateau has a significant effect on the precipitation in the following 1 or 2 months， and the soil moisture in August also has a significant effect on the precipitation in October in Area III， which is consistent with the results of the regression analysis.The result of the SVD decomposition shows that from 1979 to 2014， when soils in the central， northern， and eastern parts of the Loess Plateau are wetter in July， the precipitation in the western and northern margins of the plateau is accordingly more in August.A wetter soil in the eastern part of the plateau in September means more precipitation in the western part of the plateau， as well as some parts of the northern and southern parts of the plateau， in October.The significant correlation between soil moisture and precipitation has fewer overlapping regions， suggesting spatial and temporal asymmetry in the influence of soil moisture on precipitation on the Loess Plateau.

The short-time heavy rainfall in eastern Gansu Province is prone to disaster， and difficult to forecast and early warning.Using hourly precipitation data from encrypted meteorological stations and NCEP/NCAR reanalysis data in summer of 2010-2021， 50 regional short-time heavy precipitation events in eastern Gansu Province are Screening out.Based on the geopotential height anomaly field at 500 hPa， a combination of K-mean objective cluster analysis and subjective synoptic verification are used to classify the synoptic-scale circulation situation of these events， and construct different conceptual models of synoptic scale system configuration by analysis-by-synthesis.The results are as follows： （1） The synoptic scale circulation situation of 50 regional short-term heavy rainfall events in eastern Gansu Province can be divided into four types： plateau trough eastward moving type， southwest airflow at the edge of subtropical high type， shear between two high pressures type and northwest airflow type.（2） The southwest airflow at the edge of the subtropical high type causes the largest number of regional short-term heavy rainfall， the plateau trough eastward moving type and the shear between two high pressures type have the same frequency， and the northwest airflow type is least.（3） There are significant differences in weather system configuration， uplift conditions， water vapor conditions and unstable conditions of these four types.When the plateau trough eastward moving type， southwest airflow at the edge of subtropical high type， shear between two high pressures type occur， the position of the western Pacific subtropical high gradually advancing from west to north， and the water vapor conditions and unstable conditions are gradually improving， the baroclinic frontogenesis causes a large range of short-term heavy rainfall when the high trough leads the cold air move to southeast.The uplift condition of the plateau trough moving eastward type is the best， and the falling zone of short-time heavy rainfall is southerly.Under the situation of the shear between two high pressures type， the cold air is northward and mainly enters from the lower troposphere， and the falling zone of short-time heavy rainfall is northward too.The convergence of cold and warm air is the most intense， the baroclinic frontogenesis is the strongest， and the range and intensity of short-term heavy rainfall are also larger.The dynamic conditions and water vapor conditions of the northwest airflow type are the worst in the four types， however， the strong dry and cold advection in the middle and upper layers superimposed with the warm and wet airflow or warm temperature ridge in the lower layer formed the best unstable conditions， and short-term heavy rainfall falling zone is dispersed.

The Source Area of the Yellow River is located in the northeastern part of the Qinghai-Xizang Plateau， and the meteorological stations are sparsely distributed in this basin， the study of the applicability of various precipitation data products has an important values in promoting the hydrological modeling in the basin.Based on the China Meteorological Assimilation Datasets for SWAT model Version1.1 （CMADS V1.1）， the Tropical Rainfall Measurement Mission （TRMM） precipitation datasets （3B42 Version7） and the Soil and Water Assessment Tool （SWAT） driven by these precipitation data， respectively， and the SWAT-CUP （SWAT Calibration and Uncertainty Program） and SUFI-2 （Sequential Uncertainty Fitting2） algorithm 27 sensitivity parameters were rate in simulating the variation of multi-year monthly average runoff， the simulated results were compared with the observations to evaluate the accuracy of CMADS and TRMM 3B42 precipitation data products and the applicability of SWAT model were evaluated in the Source Area of the Yellow River source area.The results show that： （1） The distribution of all three precipitation datasets showed an increasing trend from the west to the east， and TRMM 3B42 was in better agreement with the measured precipitation than CMADS data set in terms of annual and monthly variation.（2） The sensitivity analysis of the parameters showed that the sensitivity degree of SCS （Soil Conservation Service） runoff curve number， groundwater lagging coefficient， and soil evaporation compensation coefficient were stronger than that of the others.（3） The simulated runoff by using the CMADS and TRMM 3B42 precipitation datasets had better results than that by using the measured precipitation data， with the correlation coefficients R ² of 0.93， 0.92 and 0.88 for the rate period at the three hydrological stations， respectively， while the results of the TRMM 3B42 simulation were the next best， with the coefficients of correlation （R） of the rate-period and validation-period of above 0.80， and the Nash-Sutcliffe efficiency coefficient （NSE） of the simulations is above 0.50.This research demonstrates the applicability of CMADS datasets and SWAT model for runoff simulation in high-altitude areas with complex landscape types and sensitive to climate change， and provides a replacement solution for improving the hydrological models in areas where there are sparely meteorological stations.

Reliable precipitation information is particularly important for understanding the water balance and water cycle processes in the Qinghai-Xizang Plateau.As a new generation of satellite precipitation data， IMERG （Integrated Multi-satellitE Retrievals for Global Precipitation Measurement） represents an advanced iteration in satellite precipitation data， characterized by expanded coverage and heightened spatiotemporal resolution.However， due to the complex terrain in the Qinghai-Xizang Plateau， IMERG still has great uncertainty in the plateau region.In view of this， this study performs bias correction of IMERG daily precipitation data based on the Quantile Delta Mapping （QDM） method.The transfer function is established seasonally using CMFD （China Meteorological Forcing Dataset） precipitation and IMERG daily precipitation data during 2001 -2010 to correct IMERG daily precipitation during 2011 -2014.The results show that： （1） The QDM method can effectively correct the frequency， value， and spatial distribution of IMERG precipitation products， and the corrections are more effective for extreme precipitation and large negative deviation regions.The probability distribution of corrected IMERG daily precipitation is closer to that of the observations， and the precipitation deviation is more in line with the normal distribution.Monthly precipitation and the spatial distribution characteristics of annual and seasonal precipitation are improved.（2） The root mean square error of the corrected daily precipitation is reduced from 1.49 mm·d^-1 to 1.26 mm·d^-1 with an improvement by 15.44%.The critical success index CSI， probability of detection POD， false alarm rate FAR， precision rate， and F_score of the corrected daily precipitation in different precipitation intensities are improved， and the Bias score of tiny and torrential precipitation is enhanced.（3） After correction， the extreme precipitation is significantly improved， and the mean values of the simple daily intensity index （SDII） and percentile-based threshold indices （R95p and R99p） are closer to the observed values.The spatial distribution of extreme precipitation is effectively displayed， and the bias of extreme precipitation is reduced from over 30% to within 5%.The root mean square error of SDII， R95p， and R99p is reduced from 1.59， 6.54， and 14.89 mm·d^-1 to 0.65， 3.01， and 8.99 mm·d^-1 with the accuracy improved by 59.12%， 53.98%， and 39.62%， respectively.This study verifies the applicability of the Quantile Delta Mapping method in the Tibetan Plateau， which is beneficial for obtaining more accurate precipitation data for meteorological and hydrological studies in the region.

The daily precipitation data of Kunming Station for nearly 30 years from 1991 to 2020 were used to calculate the beginning and ending periods of Kunming rainy season （May-October）， further determine the length of the rainy season in Kunming.Additionally， statistical yearbook data for Yunnan Province and Kunming City were used， including year-end total population， urban built-up area， urbanization rate， per capita GDP， and other urban development factors， to determine the urban development process in Kunming.This process divided Kunming's urban development into a slow period （1991 -2003） and a fast period （2004 -2020）.The characteristics and differences in the length of the rainy season in Kunming City during these two periods were then analyzed and compared.Various analytical methods， including statistical analysis， wavelet analysis， and Mann-Kendall （M-K） mutation test， were employed to systematically analyze the temporal changes in the length of the rainy season in Kunming City.Additionally， the grey correlation analysis method was used to assess the correlation between the length of the rainy season and urban development in Kunming City.The results indicate that from 1991 to 2020， the start date of Kunming City's rainy season gradually became later， while the end date gradually became earlier， resulting in an overall trend of the rainy season getting shorter.Wavelet coefficient analysis revealed that there was no obvious regularity in the variation of the rainy season's length on time scales below 8 years， but on a 17-year time scale， there was a noticeable cycle of short-long-short-long-short variations， The rainy seasons from 2003 to 2008 and from 2014 to 2017 were relatively long， while the rainy seasons from 1991 to 2002， 2009 to 2012， and 2018 to 2020 were relatively short.The unclosed contour lines from 2018 to 2020 indicate a further trend of shortening.The M-K test showed that the length of the rainy season in Kunming City experienced four abrupt changes between 1991 and 2020， Occurring in 2002， 2008， 2012 and 2017.Regarding the relationship between Kunming's urban development and the length of the rainy season， the variation trend of the rainy season length during the slow urban development period remained relatively stable.However， after 2004， during the rapid urban development period， there was a significant reduction in the length of the rainy season in Kunming City， Extreme volatility became more pronounced as the urban development process accelerated.The SPSS （Statistical Product and Service Solutions） was used to predict the duration of rainy season in the next 10 years in Kunming City， The results show that the rainy season will continue to be shorter in the next 10 years in Kunming.When the grey correlation resolution was set at 0.5， four factors representing the urban development process had varying degrees of influence on the length of the rainy season in Kunming City， with correlation coefficients all exceeding 0.70， the results show that there is a significant correlation between the urban development and the length of rainy season in Kunming.Among these factors， the most influential one was the year-end total population， while the least influential was per capita GDP， with grey correlation coefficients of 0.88 and 0.70， respectively， signifying a high and significant correlation.The order of correlation coefficients for the four factors is as follows： year-end total population > urbanization rate > urban built-up area > per capita GDP.

Based on multi-source observation data and ERA5 reanalysis data， the characteristics of accompanying Atmospheric Rivers （ARs） in the Guangxi warm-sector torrential rain cases during the summer of 2010-2022 （June-August） are statistically analyzed.And the typical warm-sector torrential rain process under the background of ARs in Guangxi occurred in 2 -4 June 2022 are analyzed from the perspectives of thermal and dynamic based on the diagnosis of wave activity flux， horizontal frontogenesis and adiabatic heating.The results showed that： （1） Most warm-sector torrential rain cases are accompanied by ARs.When the ARs pass through Guangxi and remain below 1000 kg·m^-1·s^-1， the increase of ARs intensity is conducive to the warm-sector torrential rain.In most cases， the ARs are in the direction of southwest to northeast， and the direction angle are between 15° and 65° when ARs pass Guangxi.（2） During the typical warm-sector torrential rain process， the East Siberian blocking and the Northeast cold vortex are extremely active， resulting in the suppression of the Western Pacific Subtropical High （WPSH） and its southerly position which keep the ARs maintain in the Bay of Bengal， South China Sea， South China and north tropical Pacific， providing sufficient water vapor for the occurrence and development of warm-sector torrential rain.The increase of the pressure gradient caused by the maintenance of the WPSH and the eastward movement of the vortex， the acceleration of the monsoon flow at night jointly strengthen the local ARs.（3） The enhancement of ARs at night promotes the local water vapor convergence and vertical transport， cause the wet layer thickened and atmospheric precipitable water increase continuously， which is conducive to the increase of precipitation efficiency.At the same time， the continuous warm and moist transport is conducive to the establishment and maintenance of unstable stratification in the lower level， and the convective unstable structure runs through the whole precipitation process.（4） The convergent uplift and lateral friction of mountain topography promote the upward movement and vertical vorticity development， which， on the one hand， is conducive to the uplift of the warm and moist air accumulated in the front of the mountain triggering convection.On the other hand， it is conducive to the maintenance of convective system and cause more water vapor to condense into rain.In addition， the continuous frontogenesis forcing caused by the accumulation of warm and moist air is also conducive to the maintenance and intensification of precipitation.（5） The strong upward movement under the influence of ARs causes a large amount of water vapor to condense continuously and release latent heat which in turn strengthens the upward movement.The convection continues to develop and strengthen under this positive feedback mechanism.

Clouds play an important role in the Earth-atmosphere system.To deeply analyze the cloud characteristics in the Loess Plateau region （LP）， the macro and micro physical characteristics of clouds were analyzed by using the CloudSat-CALIPSO data from 2007 to 2016 in four regions of the Loess Plateau， namely， semi-humid， semi-arid， arid， and cold arid.The findings indicate that： （1） In the LP， the annual average frequency of clouds exceeds 55%， with the highest frequency in spring and summer， and relatively lower in autumn and winter.The frequency of clouds in semi-humid region is higher than that in other regions.However， the months with the highest frequency of cloud occurrence in the other three regions are earlier than those in the semi-humid region.（2） The frequency of single-layer clouds is the highest in all regions， accounting for over 60% of the total cloud amount， with double-layer clouds being the main type among multi-layer clouds， accounting for about 25% of the total cloud amount.The seasonal variation of cloud height in each region shows that it is greater in spring and summer than in autumn and winter， and that it is greater in semi-humid region than in other regions in all seasons.The seasonal variation of cloud geometric thickness is not significant in all regions， which is between 1 km and 4 km， with mainly thin clouds， and 78.13% of the cloud geometric thickness is less than 2 km.（3） The annual average value of cloud liquid water content in all regions reaches more than 220.5 mg·m^-3， about 6.5 times of the annual average ice water content.It is mainly distributed in the altitude below 8.5 km， and the liquid water content gradually increases as the altitude decreases， in which the cloud liquid water content in the semi-humid region is larger than that in other regions.The ice water content in each region is small throughout the year， mainly distributed in the altitude layer below 16.5 km.（4） The values of the effective radius of liquid droplets in each region are mainly concentrated in the range of 12~16 μm， with a maximum of about 24 μm in the spring in the semi-arid region； the maximum value of the effective radius of ice particles occurs in the summer in the semi-humid region.The values of droplet number concentration in all regions were concentrated at 60~80 cm³， which were smaller than the mean value of ice particle number concentration， with peaks occurring in the summer in all regions， and the peak of ice particle number concentration occurring in the spring in the semi-humid and semi-arid regions.The results of this study can help to understand the cloud characteristics of the Loess Plateau and provide a reference basis for the simulation of cloud characteristics in the Loess Plateau by regional climate models.

Qinghai Lake is not only the largest lake in China but also an important part of the national ecological security strategy.Under the background of global warming， the water level of Qinghai Lake changes rapidly， which has great effects on the surrounding traffic facilities， residents' safety and the development of animal husbandry， etc.Therefore， it is necessary to study the water level evolution characteristics of Qinghai Lake and its water balance under climate change.Based on the hydrological data of Buha River hydrology station and Xiashe hydrology station， meteorological data of Gangcha meteorological station and CMFD， and water balance equation， this paper first analyzes the inter-annual and intra-year water level evolution characteristics of Qinghai Lake from 1956 to 2020， and the water balance components， such as runoff into the lake （ R_s）， precipitation （P） and evaporation （E）.The second reveals that the changes in water level values calculated in the same months are synchronized with the changes in R_s， P， and E.Finally， the ridge regression method is employed to quantitatively calculate the contribution rates of R_s， P， and E to the water level change of Qinghai Lake based on calculations made for December.The results show that the annual average water level declined at a rate of 0.8 m·（10a）^-1 from 1956 to 2004， of which the main reason for the decrease between 1979 and 2004 was that E exceeded the sum of P and R_s.However， from 2004 to 2020， the water level increased at a rate of 1.9 m·（10a）^-1， of which the main reason for the increase between 2004 and 2018 was the increase of P and R_s.Qinghai Lake exhibits evident intra-annual variations， with the water level starting to rise in May and reaching its peak in September， which aligns with the monthly variations of R_s， P， and E.Furthermore， the impact of the current year's P， R_s， and E changes on the annual water level change for the same months of September to December is greater than that of the previous year.Specifically， the contributions of the current year's P， R_s， and E changes to the water level change calculated based on December data are 10%， 70%， and 20%， respectively.

Using the observed precipitation data of 154 meteorological stations in East of Northwest China， NCEP/NCAR atmosphere reanalysis and Arctic sea ice data from 1961 to 2020， the possible impacts and mechanisms of the key area Arctic sea ice on the main distribution mode of precipitation in July during the main flood season in East of Northwest China was analyzed using SVD and other climatic statistic methods.The results show that there are two mainly sea ice modes influencing the distribution pattern of precipitation anomaly in July in East of Northwest China.One is that when the sea ice density in the Barents Sea and the Kuril Islands is relatively small （large）， and that in Davis Strait is relatively large （small）， wave trains propagating southeastward from the Davis Strait and southwestward from the Sea of Okhotsk are stimulated， resulting in the anomaly field of "high in the west and low in the east" （"low in the west and high in the east"） at the 500 hPa geopotential height anomaly field over the East of Northwest China， which leads to the regional precipitation anomaly exhibiting a "consistent less （more）" pattern.The other is that when the sea ice density in the eastern part of the Beaufort Sea is relatively small， the wave train from the Caspian Sea to the Okhotsk Sea is stimulated and matched with the positive geopotential height anomaly over South China， making the cold air path eastward and southward， as well as the subtropical high stronger， which together lead to the precipation characterized by "less in the north and more in the south"， on the contrary， the pattern of precipitation anomaly is reversed.The prediction model， which is established with sea ice in key areas as the prediction factors derived by “SVD projection method”， has certain prediction ability for grasping the precipitation anomaly trend and the spatial distribution pattern of the main flood season in July in East of Northwest China， especially for the "regional consistent less type" and "north more and south less type".

Using FNL （Final Reanalysis Data）， ERA5 （ECMWF Reanalysis V5） reanalysis data， and GPM （Global Precipitation Measurement） global half-hourly precipitation data， a strong precipitation event in the southwestern plateau of China was selected to study the forecasting ability of two initial perturbation methods， Breeding Growth Mode （BGM） and Local Breeding Growth Mode （LBGM）， in convective-scale ensemble forecasting of complex terrain rainfall.The MODE （Method for Object-Based Diagnostic Evaluation） method based on object diagnostics was used to evaluate the model's ability to predict the location， structure， and intensity of precipitation objects， and compared with scoring methods such as Threat Score （TS） to comprehensively assess the model's forecasting performance.The results show that： （1） The ensemble forecast systems BGM-EPS and LBGM-EPS， generated using BGM and LBGM methods to produce initial perturbations， have better ensemble mean forecast scores for precipitation of all magnitude levels at 24 hours compared to the control forecast， and LBGM-EPS has a higher TS score for heavy rainfall compared to BGM-EPS， this indicates that the LBGM method has a certain improvement effect on ensemble forecasts for heavy precipitation.However， the underlying mechanisms behind the different initial perturbation methods are worthy of further investigation； （2） Overall， the WRF model can capture precipitation objects well， especially for rainfall forecasts in complex terrain of the plateau mountains， with a better overall similarity in precipitation targets for LBGM-EPS compared to BGM-EPS， highlighting the advantage of LBGM method in representing convective-scale ensemble forecasting of intense convection.The initial perturbation total energy of BGM and LBGM shows a developing trend with forecast time.In the same forecast time， LBGM has a larger perturbation total energy than BGM， which better represents the growth of forecast error.This can partially explain why the LBGM method outperforms the BGM method in terms of precipitation object matching in the MODE evaluation； （3） Compared with traditional TS scoring and other verification methods， the MODE method can better reflect the spatial position information of precipitation forecasts， and under the same convolution radius and precipitation threshold， the ensemble mean forecast based on LBGM method performs better in identifying precipitation objects.By flexibly setting the convolution radius and determining the precipitation threshold， the WRF model can capture precipitation objects in complex terrain areas during heavy precipitation events.However， the matching degree of precipitation targets in high-altitude areas is lower than that in low-lying areas.The LBGM-EPS method outperforms the BGM-EPS method in terms of the shape of precipitation objects and the matching of precipitation areas， resulting in better identification of precipitation objects.The quality of precipitation object matching using the MODE method is related to parameter settings such as precipitation threshold and convolution radius， rather than the complex terrain background related to terrain gradients.

Squall lines often produce extremely disastrous gales and play a crucial role in the safety of hytropower stations.This article explores a squall line event over the lower reaches of Jinsha River on June 4， 2016， which brought 13-level wind at the canyon of Baihetan Hytropower Station.This research detect the formation mechanism of this squall line from environmental conditions and medium-scale meteorology.The following conclusions are obtained： （1） Before the squall line arrived， the ground pressure dropped steadily by 9 hPa because of the low pressure， and the temperature of the canyon rises up above 14 ℃.As the squall line arrived， the pressure rises sharply with thunderstorm high pressure， and the temperature dropped more than 10 ℃.At the same time， the relative humidity reached as higher as 70%， accompanied by short-term precipitation.After the squall line left， the aforementioned meteorological elements restored to their original values.（2） Analysis on the synoptic scale circulation， we finds that Baihetan hytropower station located in the south of southwest vortex， which induced a wind convergence background at the low level.Meanwhile， the station lied in right side of the jet stream inlet at upper level， and strong vertical motion formed by the wind shear.As a result， the squall line to come into being.Furthermore， in the troposphere before the squall line， the atmospheric circulation displayed a dry-cold advection in the middle-upper level superimposed over a warm-wet advection and higher ground temperature in the lower levels， increasing the temperature lapse rate.t As a result， the strong static instability and convection accumulated， and the conditions were favorable for the squall line to live a long time.The analyses from vertical wind speed showed that the subsidence movement made the momentum spread down， and promoted the uplift in the front side of line， and a positive feedback effect developed， promoting a stable mechanism for the strong storm.（3） Radar of Zhaotong detection indicates that echo cell that greater than 30 dBZ aggregated costly into a band and embed with the strong echo cores of greater than 50 dBZ， as a cylindrical convective cloud of higher than 10 km.On the radical velocity field， the meso-scale convergence line coinciding with the banded strong echo， as well as MARC （Mid-Altitude Radial Convergence） characteristics of the mid-altitude radial convergence， were the trigger mechanism for the squall line.As the cloud structure of the storm， strong upward movement in front of the squall line leaded to the dome.As the squall line arrived， the echo core dropped rapidly， and the extreme gale of downburst formed， resulted the new convective monomers come in being along the canyon.