Numerical models have risen to prominence as indispensable tools for the in-depth study of the water cycle and these extreme hydrological phenomena， gaining widespread application across the globe.To delve into the spatiotemporal evolution patterns of global terrestrial water circulation against the backdrop of climate change and to decipher the intricate feedback mechanisms among atmospheric， land， and hydrological systems， the exploration of coupled atmospheric-land-hydrological models has emerged as a pivotal area of focus in the international research landscape dedicated to atmospheric and hydrological studies.This paper embarks on its journey by meticulously reviewing and delineating the evolution of coupled models， shedding light on the distinct advantages of the Weather Research and Forecasting Model Hydrological （WRF-Hydro） modeling system.It methodically dissects the primary sensitivity parameters of the WRF-Hydro model， while extensively covering its applications in analyzing surface runoff， soil moisture， the energy-water cycle， and the intertwined atmospheric and hydrological processes.The discourse culminates in a forward-looking exploration of the future directions in the development of the WRF-Hydro coupled model.Emphasizing strategic advancements， the paper advocates for a concerted effort towards the creation of robust scale conversion schemes， the refinement of parameterization methods， and the execution of high-resolution simulations.These simulations are crucial for accurately mapping the spatial and temporal dynamics of atmospheric and hydrological variables within basins， thereby significantly enhancing the model's capacity to intricately depict the interactions among atmospheric conditions， land surface phenomena， and hydrological processes.This comprehensive approach underlines the imperative to deepen our understanding and improve our modeling capabilities， aiming at a more effective prediction and management of the impacts arising from climate change and extreme hydrometeorological events.

The Three River Headwaters （TRH） region， known as the “Water Tower of China”， is a crucial freshwater source and an ecological barrier in China.Changes in precipitation concentration， seasonal precipitation amount， frequency， and intensity is a key process of water cycle in the context of global warming， holding significant implications for vegetation growth and water resource management in the TRH region.In this study， utilizing the CN05.1 daily precipitation gridded dataset from 1961 to 2020 prepared by the China Meteorological Administration， the Precipitation Concentration Index （PCI） were calculated， and the evolving patterns of precipitation concentration and intra-annual distribution in the TRH region were clarified.The climatology， relative interannual variability， long-term trends， and anomalies of annual and seasonal precipitation amount， frequency， and intensity were investigated.The results find that： （1） Precipitation in the TRH region exhibits a certain degree of concentration with PCI of 17.5.PCI increased from southeast to northwest， suggesting an increased precipitation concentration.Over the past 60 years， PCI has declined at a rate of -1.71% per decade， indicating a trend towards more evenly distributed monthly precipitation throughout the year.It’s noteworthy that the reduction in the proportion of precipitation during the growing season may have ramifications for agricultural production and ecosystem maintenance in the TRH region.（2） Over the past six decades， there has been a significant overall increase in precipitation amount and intensity during different seasons.However， precipitation frequency decreased during summer while increasing in other seasons.Enhanced precipitation intensity has predominantly contributed to the rise in precipitation amount during spring， summer， and autumn， while increased precipitation frequency has played a dominant role in elevating precipitation amount during winter.The increase rate in humidity during winter and spring was higher than that during summer and autumn.In spring， precipitation amount and intensity increased by 8.09% and 6.94% per decade respectively， while winter saw snowfall amount and frequency grow by 7.27% and 4.4% per decade.Also noteworthy is the distribution of droughts and floods in parts of the Yangtze River source area tends towards extreme， exacerbating the ecosystem vulnerability.（3） The regional average precipitation amount， frequency， and intensity in the TRH region have shown an increase of 1.36 mm， 0.024%， and 0.0056 mm·d^-1 per year over the past 60 years.The cumulative anomalies of precipitation amount， frequency， and intensity in the last 60 years were negative， with abrupt changes occurring in 2003， 1989， and 2003， respectively.There has been a significant decrease in precipitation frequency during the rainy season， coupled with a substantial increase in precipitation intensity.In contrast， both precipitation frequency and intensity during the dry season have experienced significant increases.These changes have been particularly pronounced in the past decade.This study can serve as a valuable reference for research concerning soil erosion， agricultural production， water resource management， and climate change in the TRH region.

Based on the meteorological observational data over Qinghai-Xizang （Tibetan） Plateau and atmospheric reanalysis dataset during 1961 to 2020， the snowfall variation characteristics over the Qinghai-Xizang （Tibetan） Plateau and its related corresponding circulation system were analyzed in this paper.Main conclusions are drawn as following： the spatial distribution of snowfall shows a uniformity with less in the northwest and more in the southeast.The characteristics of interannual and interdecadal variability are very evident.The interannual variability of the snowfall over Qinghai-Xizang Plateau was strong.The first mode of Qinghai-Xizang （Tibetan） Plateau snowfall anomalies is regional uniformity.In terms of the key circulation systems that affect Qinghai-Xizang （Tibetan） Plateau snowfall， when the snowfall over Qinghai-Xizang （Tibetan） Tibetan Plateau is more， the upper troposphere corresponds to the positive phase of the southern Eurasian （SEA） teleconnection， characterized as positive anomalies over the southwestern Europe， the Arabian Sea， and the northeast Asia， and negative anomalies over the Middle East and the Qinghai-Xizang （Tibetan） Plateau， while the Middle East jet is stronger； the positive （negative） phase of North Atlantic Oscillation （NAO） is conducive to more （less） snowfall over Tibetan Plateau， via modulating the SEA teleconnection and key circulation systems such as the Middle East jet stream.

Summer precipitation in the East Asian monsoon region is significantly affected by monsoon variations.Different monsoon configurations form distinct precipitation patterns in the East Asian monsoon region by affecting regional water vapor transport.Further， the phase changes in precipitation patterns are prone to the occurrence of abnormal precipitation events， which in turn induce droughts and floods.Based on the EOF analysis， the GPCC precipitation， NCEP/NCAR reanalysis data and different monsoon indices were used to study the spatial and temporal distribution of summer precipitation in the East Asian monsoon region.The effects of four different configurations of summer monsoon on summer precipitation patterns in the East Asian monsoon region were further investigated by combining correlation analysis and water vapor flux analysis.The results show that： （1） Precipitation in the East Asian monsoon region experienced a decrease followed by an increase from 1951 to 2020.The increase in precipitation anomalies after 2010， as well as the rapid fluctuations in precipitation series， indicate a decline in regional climate stability.The EOF successfully presents the distribution of summer precipitation over the East Asian monsoon region.It mainly exhibits as the three-pole structure of north-south "-， +， -"， followed by the dipolar-type structure with north-south reversed-phase variations.Precipitation anomalies occur in the phase transition of precipitation structure， mainly tripolar type followed by dipole type.（2） The combined influence of the East Asian， South Asian， West Pacific， and westerly circulation monsoon systems results in the summer precipitation anomaly in the East Asian monsoon region.The monsoon configurations leading to anomalous increase and decrease in precipitation are Configuration 1 （WNPMI strong， EASMI and AZCI weak） and Configuration 2 （AZCI strong， EASMI and SASMI weak） respectively.（3） At Configuration 1， the subtropical high is located in the southwest， the westerly trough appears at 40°N， and the southern monsoon is strong.These combine to form precipitation in the central part of the monsoon region through shear lines as well as uplift， leading to an increase in anomalous precipitation.In Configuration 2， the westerlies are strong and the southern water vapor dynamics are too weak to penetrate deep into the continent， resulting in an anomalous decrease in precipitation.The results of this study provide a theoretical framework for investigating the mechanisms behind precipitation anomalies in the East Asian monsoon region in the context of climate change.They also provide critical scientific references for managing the region's extreme precipitation occurrences， as well as preventing and controlling floods and droughts.

The Qinghai-Xizang Railway （QXR）， especially the 550-kilometer segment from Xidatan to Anduo， traverses a region characterized by complex terrain， diverse landforms， and a permafrost environment.In recent years， climate warming and permafrost degradation have significantly increased maintenance demands for the QXR， which is constructed atop permafrost.To understand the impacts of the intricate terrain and landforms along the QXR on local climate changes and to provide theoretical support for its operation and maintenance， this study utilizes station observation data along the railway and employs the Weather Research and Forecasting （WRF） model driven by ERA5 data to conduct high-resolution simulations with a grid resolution of 10 km×10 km.The results indicate that the six stations along the Qinghai-Xizang Railway exhibit a general warming trend from 1998 to 2020， with the lowest temperature increase rate at 0.27 ℃·（10a）^-1 and the highest at 0.56 ℃·（10a）^-1 years.The WRF model's simulation results show some discrepancies with observed annual mean temperature data.The simulation results are more accurate in summer and autumn， with correlation coefficients above 0.95 in summer and above 0.80 in autumn， but less accurate in spring and winter.Regarding precipitation simulation， the Nudging method effectively reduces the wet bias in summer precipitation on the Qinghai-Xizang Plateau.Precipitation gradually increases from the northern to the southern section of the railway， peaking in the central section.However， the WRF model still exhibits cold and wet biases in temperature and precipitation simulations on the Qinghai-Xizang Plateau.Exploring new methods or utilizing higher-quality driving data may further enhance the downscaled simulation results for this region.

This study uses the Weather Research Forecast Model （WRF） numerical forecast system and the Three-Dimensional Variational Data Assimilation （WRF-DA） system to investigate the impact of assimilating data from the Micro-Wave Humidity Sounder 2 （MWHS-2） onboard FY-3C and the Microwave Humidity Sounder （MHS） from NOAA-19 （National Oceanic and Atmospheric Administration-19） on the simulation and prediction of heavy rainfall events in the Yarlung Zangbo Grand Canyon.Three assimilation schemes are compared： the control （Con） scheme， the NOAA-19 scheme （MHS） and the FY-3C scheme （MWHS-2）.The results indicate that assimilation of MHS and MWHS-2 microwave radiance data using WRF-3DVAR （Three-Dimensional Variation） improves the simulation performance compared to the Con experiment.It improves the accuracy of the precipitation location， although the MWHS-2 experiment shows a northern bias in the precipitation area.Satellite data assimilation significantly improves the moisture field， but its effect on heavy rain intensity is less pronounced than its effect on precipitation area improvement.Data assimilation enhances the 700 hPa meridional wind component， leading to increased moisture transport within the study area.With respect to temperature， the assimilation of satellite microwave moisture data has a moderately positive effect， which forming an unstable vertical temperature structure in the 700~400 hPa layer， conducive to the generation and development of precipitation.Overall， the simulation results of the MHS experiment outperform those of MWHS-2， especially in the wind field， temperature and humidity fields.In addition， the root mean square error changes in the 24-hour forecast of the MWHS-2 experiment are relatively stable， indicating that MWHS-2 satellite data are more advantageous for medium to long-term simulation studies.

Based on NCEP/NCAR reanalysis data， the leading modes of the westerly jet over the Asian continent during July-August from 1960 to 2019 and the associated mid-to-high latitude circulations has been investigated in this study.The results show that the first leading mode is characterized by an out-of-phase variation in the south-north direction along the jet axis， resulting in a north-south movement of the jet.The second leading mode exhibits an out-of-phase variation in the east-west direction along the Qinghai-Xizang （Tibetan） Plateau， as a southwest （northwest） - northeast （southeast） tilt of the jet stream axis， which is different from most previous studies emphasizing the intensity variations in the second mode.For the first leading mode， associated with the northward movement of the jet streams， the South Asian High （SAH） moves northward as well as the western Pacific subtropical high （WPSH） northward narrows and vice versa.Furthermore， this first leading mode is associated with the tripolar precipitation pattern over East Asia.Particularly， as the jet stream shifts northward （southward）， the precipitation decreases （increases） in the Jianghuai River and increases （decreases） in South China and North China.As well， the associated temperature variations also show a tripolar pattern over the Eurasian continent， with the boundary of around 20°N and 45°N.It suggests that when the jet stream moves northward， warm （cold） conditions cover East Asia， particularly in the central and eastern regions of China， the Korean Peninsula and Japan， while cold （warm） conditions dominant Lake Baikal， the Indian Peninsula and Indochina Peninsula.As for the second leading mode， the geopotential height in the east （west） side of the SAH increases due to the southwest （northwest）-northeast （southeast） tilt of the jet axis.Additionally， the second mode is related to the precipitation anomalies in the high latitudes of West Asia， Central Asia， and the Indian Peninsula.This mode is particularly important for the double dipole temperature pattern over the Eurasian continent.When the jet stream axis presents a southwest （northwest）-northeast （southeast） tilt， significant positive （negative） temperature anomalies are observed in the middle latitudes of East Asia and specifically in the high latitudes of West Asia.

Basin Vortex is a type of Southwest Vortex， which refers to the vortex generated in the Sichuan Basin on the 700 hPa isobaric surface， with two consecutive low pressures with closed Contour line or cyclonic circulation in the wind direction of three stations.It is the main system that causes precipitation in the Sichuan Basin， and the "southwest type" Basin Vortex is the most frequent and strong type of Basin Vortex.This article utilizes ERA5 （0.25°×0.25°） hourly reanalysis data， GPM satellite precipitation data， and the Southwest Low Eddy Yearbook explored the characteristics and development mechanism of a typical “southwest type” Basin Vortex that occurred in the Sichuan Basin from June 26 to 28， 2020.The results indicate that the Basin Vortex was generated in the southwestern part of the Sichuan Basin， then moved towards the northeast direction， reached the northeastern part of Sichuan， turned eastward， and disappeared after entering Chongqing， with a total life history of 48 hours.The formation and development of the Basin Vortex are closely related to its divergence zone located on the northeast side of the 200 hPa South Asian High and on the right side of the entrance area of the high-altitude jet stream， as well as the low-level decompression caused by the positive vorticity advection in front of the 500 hPa short wave trough.The southwest part of the Sichuan Basin at 700 hPa is located to the left front of the low-level jet stream， which is conducive to the development of convergent upward motion and the formation of low eddies.The high value area of frontogenesis in the northeast direction of the 700 hPa Basin Vortex， the strengthening of the low-level jet and the guidance of the southwest airflow in front of the 500 hPa high altitude trough are the main factors for the movement of the Basin Vortex towards the northeast direction.As the center of the 200 hPa South Asian High moves eastward over the Yangtze-Huaihe River and the upper level jet weakens， the 500 hPa shortwave trough moves eastward， and the Basin Vortex is located in the negative vorticity advection zone behind the trough.The vertical direction turns into a sinking motion， with surface pressure increasing and the low vortex gradually weakening and disappearing.Analysis of the vorticity budget equation reveals that low-level convergence is the main contributor to the increase in the Basin Vortex intensity， and the increase in positive vorticity of the Basin Vortex caused by low-level convergence almost runs through the entire life cycle of the vortex.In addition， the existence of high-altitude orthonormal vortices and the release of condensation latent heat from the Basin Vortex precipitation also play an important role in the development and movement of the Basin Vortex.

The extreme characteristics and formation mechanism of the sustained heavy rainfall process in the middle reaches of the Yellow River from July to August 2022 were analyzed in detail using precipitation observation data from national and provincial meteorological stations， ERA5 reanalysis data from the European Medium Range Weather Forecast Center， and terrain elevation data from the National Environmental Information Center of the United States.The results indicate that： （1） a total of 11 heavy precipitation processes occurred in the middle reaches of the Yellow River during the research period， characterized by long duration， large cumulative rainfall， short precipitation time intervals， and high overlap of heavy rainfall areas.The standardized anomaly of accumulated precipitation at 18 stations exceeds 2.5， the maximum hourly rainfall intensity exceeds 50 mm/h during multiple processes， exhibiting significant extreme characteristics， and the extreme of precipitation is stronger in August than that in July.The distribution of heavy rain bands is closely related to the topographic characteristics of the middle reaches of the Yellow River.（2） From July to August， the standardized anomaly near Lake Baikal in mid to high latitudes Asia reached -2.5 to -1.5 （Exceeding -3.5 in August）， and the low trough is abnormally strong compared to the same period in previous year.During processes of heavy precipitation， the western ridge of the subtropical high is in a westward moving state.The ridge line of the subtropical high and the north-south boundary of the northern boundary have a large swing in July.Each north-south oscillation of the subtropical high combines with cold air from Lake Baikal， triggering a series of heavy precipitation processes.The ridge line and northern boundary of the subtropical high slowly retreat to the south in August with a small amplitude， and persistent heavy precipitation occurred at the edge of the subtropical high.（3） The water vapor come from the Bay of Bengal， South China Sea， and East China Sea， with an integrated standardized anomaly of 2.5 for the entire layer of water vapor flux in August.PWAT maintains 40~60 mm， with its standardized anomaly ranging from 2.5 to 3.5 in the southern part of Inner Mongolia and the northern part of the Shaanxi region， locally exceeding 3.5.The water vapor conditions are significantly stronger in August than in July.（4） There is an unstable stratification above the middle reaches of the Yellow River， characterized by upper dry cold and lower warm wet.Frontogenesis is formed north of 36°N in the middle and lower layers， and the upward movement occurs throughout the northern layer.The vertical velocity standardization anomaly reaches -2.5 to -0.5， which is corresponding to strong precipitation area.（5） The analysis of frontogenesis function in August shows that there were frontogenesis before and during the occurrence of precipitation in the northern part of the middle reaches of the Yellow River.The increase and decrease in frontogenesis values are consistent with the trend of precipitation intensity variations.The deformation term contributes significantly to the total frontogenesis， while the tilt term contributes significantly to the total dissipation.The process with high precipitation intensity results in higher frontogenesis extension height， while the process with low intensity results in lower frontogenesis height and relatively smaller frontogenesis value.

Meiyu precipitation of Zhejiang province was abnormally less than usual in 2018.During the Meiyu period， mean feature of large-scale circulation in mid-high latitude on 500 hPa exhibited a “trough-ridge-trough” pattern， while in low latitude， western Pacific subtropical High （WPSH） marched eastward and northward.Moreover， the upper-layer westerly jet over East Asia located northward and low-level jet supply south of Zhejiang was not sufficient.All the factors above worked together to form weak Meiyu.Inadequate moisture transport in the first and second ten days of June， inferior convergence of north and south flows， southward-placed westerly jet over East Asia， stronger South China Sea summer monsoon （SCSSM）， and weaker Indian monsoon acted jointly to cause a late Zhejiang Meiyu.There were three rainfall processes （process I， process II， and process III） and a time with few precipitation during the entire Meiyu stage.The formation of process I and II could be attributed to meeting of northward and southward air flows， while the essence of process III was typhoon-induced convection.The spatiotemporal variation of large-scale circulation associated with different processes was investigated comprehensively， and the result indicated that compared to process I， precipitation intensity of process II was very limited because of the forceless cold air invasion， more powerful SCSSM， and feeble transport of southwest moisture.Furthermore， the impact of precursory oceanic， atmospheric， and land signals on Meiyu was analyzed， and found that the primary climate characteristics were positive Ni?o index and negative North Pacific sea surface temperature （SST） anomaly in winter and spring， warm SST over southwest Indian Ocean in winter， decreased sea ice for the Kara-Barents Sea in spring， and Southern Annular Mode and Arctic Oscillation in the positive and negative phases respectively during April-May.Based on the monitoring time-series of Zhejiang Meiyu， the stable or strengthened climatic factors from winter to spring were extracted with two indices of correlation coefficient and ratio of the same sign， and moreover， winter and spring Meiyu prediction model were constructed using three methods of multivariable linear regression， multi-factors composite assess， and combined diagnosis.Generally speaking， all the linear statistical models were able to predict Meiyu precipitation anomaly over Zhejiang province well， especially for the negative anomaly cases.

Based on the daily temperature data of 99 national meteorological stations in Beijing-Tianjin-Hebei region from March to May 1961 to 2020， the statistical methods such as Mann-Kendall trend test were used to analyze spatial and temporal distribution characteristics of late spring coldness from frequency， duration days and ratio of occurring stations to all stations， and the risk probability of different levels of late spring coldness was evaluated based on the information diffusion theory.The results indicated that： In the past 30 years， 2570 cases of late spring coldness occurred at 99 national meteorological stations， with the mildest and the least severe.In terms of frequency， the mild and moderate late spring coldness decreased from north to south， while severe late spring coldness decreased from northeast to southwest， the mild， moderate-severe and the total late spring coldness were most in April， the inter-annual occurrence frequency showed a downward trend， with a significant decrease from March to May and May.In terms of total duration days， mild and severe late spring coldness decreased from northeast to southwest， with moderate late spring coldness showing a pattern of high in north and south and low in middle.The average duration days of mild late spring coldness at each station was not significantly different， while the difference was significant in moderate and severe late spring coldness， the average duration days increased sharply with the increase of level.The annual mean duration days of late spring coldness was 6.9 d·a^-1， showing a downward trend， with a decrease rate of 1.5 d·（10a）^-1.The ratio of the stations showed an inter-annual downward trend in duration days was 88.9%， with 35 stations showing a significant decrease and the southern region experiencing a greater decrease than the northern region.The inter-annual downward trend in ratio of late spring coldness stations in March to May and May was significant， with the highest ratios of mild and moderate-severe late spring coldness in April， and the ratio of mild late spring coldness was much higher than that of moderate-severe late spring coldness in each month.The risk of late spring coldness decreased in a stepwise manner as the level increased， The stations with risk was mild and a return period of about 2 years or less was about 34.3% of all stations， mainly in Beijing， Shijiazhuang， Xingtai and Handan； The stations with risk was moderate and a return period of 5~10 years and 10 years or less was about 90% of all stations， and the former was concentrated at the north and south ends of Beijing-Tianjin-Hebei region， while the latter was mostly located in the central part of Beijing-Tianjin-Hebei region.The risk of severe late spring coldness in the research area was relatively low， with up to 97% of severe stations with a return period of about 25 years or less.

The construction of automatic meteorological observation stations in China has been continuously improved.Currently， more than 60， 000 automatic meteorological observation stations have been built， providing abundant information of surface meteorological variables for weather and climate research.However， the practical application of ground automatic station data has always been constrained by high uncertainty in the quality of observation data.Strict quality control is a prerequisite for the effective application of automatic station data， but the high spatiotemporal resolution characteristics of automatic station observations bring more difficulties to quality control researches.How to accurately distinguish local small-scale weather information and local variation caused by erroneous data in high-resolution automatic station data has always been a difficult point in the research of quality control methods for spatiotemporal resolution automatic station data.On the basis of analyzing the spatial correlation scale and error characteristics of surface temperature， this study established a quality control method for temperatures from surface automatic station based on EOF （Empirical Orthogonal Function） analysis method， which only relies on observation data.The study conducted quality control experiments using surface automatic station temperature observations from January to May 2022， and compared the differences in surface temperature between the automatic station observation data and the Chinese reanalysis data CRA40 （CMA's global atmospheric Re-Analysis） before and after quality control.The results indicate that the established autonomous quality control method for observation data can effectively identify erroneous observation data， relying solely on the observation data itself， effectively avoiding the impact of background errors on quality control effectiveness.The quality control sub regions determined on the basis of correlation scale analysis further enhance the quality control method's ability to identify small-scale temperature changes in observation data， effectively preserving the reject of temperature extremum data corresponding to extreme events in small areas， the number of quality control modes determined by actual data characteristics can well separate the principal and residual terms of the observed data， significantly improving the accuracy of erroneous extreme value recognition.Further introducing sliding detection methods and overlap rejection standards can also retain as much valuable observation data as possible in areas with steep terrain.The quality control results of 1 month data show that the new quality control method can obviously and stably improve the spatial correlation coefficient between the surface temperature of automatic station data and the corresponding variable of CRA40 （CMA's global atmospheric Reanalysis） reanalysis data， and the average deviation is also reduced.Although the average data rejection rate is only about 8%， the spatial correlation coefficient can reach a maximum increase of about 0.02， which fully proves that proposed quality control method can effectively eliminate erroneous data and improve the spatial continuity of automatic station data.

To improve the simulation of precipitation and the accuracy of rainfall forecast over the low-latitude highland in Southeast Asia （LLHSA）， a regional air-sea coupled model is developed with the Weather Research and Forecast （WRF） Model （version 4.2） and ocean general circulation model NEMO （version 3.4）， using the coupler OASIS3-MCT.This new regional air-sea coupled model WRF-OASIS-NEMO is herein referred as WON.Both the atmospheric and oceanic components were configured into the same Arakawa-C grid with a horizontal spatial resolution of 0.25° and a coupling frequency of 1 hour， which are suitable for facilitating the mesoscale coupling between the atmosphere and ocean models.The evaluation of the WON model is based on the heavy precipitation event from August 16 to 18， 2020， where the simulation of WON model is compared with the standalone WRF model.The WON and WRF models simulated large precipitation over the northeastern LLHSA， the central and western LLHSA with daily precipitation around 20 mm·d^-1， which is generally consistent with the observation.The WON model ameliorated the underestimation bias of precipitation over the southern LLHSA and the overestimation bias of precipitation over the northwestern LLHSA and the western LLHSA in the WRF model.The WON model improved the simulation of the dynamic conditions of precipitation， with enhanced cyclonic circulation over the central and southern LLHSA and enhanced anticyclonic circulation over the western LLHSA.Hence， the WON model ameliorated underestimation of precipitation over the southern LLHSA and overestimation of precipitation over the northwestern LLHSA.Both WRF and WON models could reproduce the development characteristics of vertical helicity， that is， positive vertical helicity in the lower-mid troposphere and negative vertical helicity in the upper troposphere.However， the simulated vertical helicity is too strong near 400 hPa layer over the western rain belt， but too weak at 600~700 hPa layer.Compared with the WRF model， the WON model shows improvements mainly in the central-western part of the rain belt.The water vapor sources of this heavy rainfall include the water vapor transport from the southwest of the Bay of Bengal and the water vapor transport from the South China Sea.Both WRF model and WON model reproduced the spatial characteristics of water vapor flux.In the WRF model， the water vapor convergence is too strong over the northern Bay of Bengal， but too weak over South China Sea.The improvement of WON model is mainly over South China Sea.The simulation improvement of the WON model is mainly because the surface heat flux exchange over the Bay of Bengal caused the mid-lower levels of troposphere to become cooler and drier.The atmospheric convection was weakened， associated with a low-level anticyclonic bias over the northern Bay of Bengal.This anticyclonic bias improved the simulation of atmospheric dynamics and water vapor conditions for this heavy precipitation event.

Southeast Asia's Low-Latitude Highland （LLH） is one of the hotspots of land-atmosphere coupling in the world， with its land-atmosphere interaction has significant impacts on climate， hydrology and environment.This study employs Uniform Design （UD） method to conduct 48 groups of simulation using different parameterization schemes of Weather Research and Forecasting （WRF） model.By optimizing the parameterization schemes， the variables related to land-atmosphere interaction in this area are simulated and evaluated.The findings are as follows： （1） The ensemble of 48 simulation groups demonstrates good performance for near-surface air temperature， near-surface specific humidity， surface downward longwave radiation， surface upward longwave radiation and surface soil temperature， with average Taylor Skill Score （TSS） values exceeding 0.8； for near-surface wind speed， precipitation， surface sensible heat flux， surface latent heat flux， surface downward shortwave radiation and surface upward shortwave radiation， the ensemble simulation can adequately capture the characteristics of these variables， with average TSS values ranging between 0.4 and 0.8； but for surface soil moisture， the ensemble simulation performance is poor， with average TSS values less than 0.4.The variability among different simulation groups is minimal for near-surface wind speed， precipitation， surface latent heat flux， surface downward shortwave radiation， surface upward shortwave radiation， surface soil temperature and surface soil moisture （TSS range < 0.2）； but for the surface sensible heat flux， the variability among different simulation groups is significant （TSS range > 0.3）.（2） The optimal parameterization schemes based on equal-weighted averaged TSS can enhance simulation accuracy for near-surface air temperature， near-surface specific humidity， surface downward longwave radiation， surface upward longwave radiation and surface soil temperature， with correlation coefficients exceeding 0.9 and minor deviations from reference values.However， this optimization could not significantly improve simulation performance for near-surface wind speed， precipitation， surface sensible heat flux， surface latent heat flux and surface soil moisture， where deviations remain substantial.（3） The optimal parameterization schemes can reasonably capture the spatial and temporal features of land-atmosphere coupling， showing strong coupling strength in northeast and southwest LLH， with temporal correlation coefficient greater than 0.9.Nonetheless， the simulated values of coupling strength is generally weaker than the reference values， primarily due to poor simulation performance of surface latent heat flux and surface downward shortwave radiation.

The influence of winter circumglobal teleconnection （CGT） on the interannual variability of winter precipitation in the Southeast Asian low-latitude highlands were statistically analyzed using ERA5 reanalysis data from the European Centre for Medium-Range Weather Forecasts （ECMWF）， monthly mean precipitation data from the Climate Hazards Group Infrared Precipitation with Station data （CHIRPS） developed by the United States Geological Survey and the University of California and the monthly mean precipitation data of the Global Precipitation Climatology Project （GPCP） provided by the Global Precipitation Climatology Center.Results of correlation analysis show that the CGT presents two main patterns with approximately the same variance contribution rate.On the vertical direction， the CGT shows an equivalent barotropic structure with four anomalous centers.During the CGT positive phase， the negative anomalous centers are located near the Mediterranean Sea and the Indian Peninsula， and the positive anomalous centers near the Arabian Peninsula and Southeast Asian low-latitude highlands.The first mode of CGT （CGT1） significantly correlates with winter precipitation over the Southeast Asian low-latitude highlands on the interannual time scale.When the CGT1 is in the positive phase in winter， the anomalous "anticyclone， cyclone， anticyclone， cyclone" control the Western Europe， the northwestern Arabian Peninsula， the Arabian Sea and Southeast Asian low-latitude highlands， respectively.The anomalous southwesterly wind on the east side of the anomalous cyclone will increase the water vapor from the Bay of Bengal and the South China Sea to the Southeast Asian low-latitude highlands.The more water vapor converged and condensed in Southeast Asian low-latitude highlands finally results in heavier winter precipitation over the Southeast Asian low-latitude highlands.On the contrary， when the CGT1 is in the negative phase in winter， the Western Europe， the northwestern Arabian Peninsula， the Arabian Sea and the Southeast Asian low-latitude highlands are controlled by the anomalous "cyclone， anticyclone， cyclone， anticyclone".The anomalous northeast wind on the east flank of the anomalous anticyclone will reduce the water vapor from the Bay of Bengal and the South China Sea to the Southeast Asian low-latitude highlands.The anomalous divergence and descending motion further lead to less precipitation in winter over the Southeast Asian low-latitude highlands.The significant positive correlation between CGT and precipitation over the Southeast Asian low-latitude highlands， sharing almost the same key physical process as winter， can be observed in December， January and February.Results of typical case further confirm the key physical process through which the CGT modulates the interannual variability of winter precipitation over the Southeast Asian low-latitude highlands.

This study examines the inter-annual variation of the difference in summer precipitation over the east and west side of the Ailao Mountain， as well as its relationship between the East Asia summer monsoon and the South Asia summer monsoon based on in situ observations， reanalysis products and model sensitivity experiments.As the result， climatological statistics show that there is more precipitation on the west side than on the east side of the Ailao Mountain.Compared to the total summer precipitation amount observed over five pairs of state-level weather stations， the difference is higher on the north part than on the south part， with negative correlations to some extent.The observed differences in precipitation are generally with a negative correlation between the East Asia summer monsoon index， and with a positive correlation between the South Asia summer monsoon index.The linear correlation coefficients with the index of monsoon interface， which stands for the relative strengths of the East Asia and South Asia monsoons， are higher than those with one single monsoon.With one positive and one negative year selected based on the index of monsoon interface， we design and conduct a set of model sensitivity experiments through changing the boundary condition of wind and water vapor fields respectively to quantify the impact on precipitation difference of monsoons.The result shows that the anomaly in the wind field is the major contributing factor of the difference in precipitation on the two sides of the Ailao Mountain.On the other hand， the anomaly in the water vapor field makes synchronized changes in precipitation on both sides of the mountain， while it contributes little to the precipitation difference.

Frequent biomass-burning activities occur in the Indo-China Peninsula in spring， and the aerosol generated will affect the atmospheric radiation budget of southwest China through the atmospheric circulation.Exploring its influence on the atmospheric heating rate can provide a basis for studying its influence on weather and climate.Based on the MERRA-2 reanalysis data of hourly aerosol and radiation flux under clear sky， their temporal and spatial characteristics were analyzed first.Secondly， using statistical methods such as EOF and synthetic analysis， the temporal and spatial evolution characteristics of aerosol optical thickness （AOD） and surface aerosol direct radiative forcing （ADRF） over the Indo-China Peninsula and their relationship with atmospheric shortwave heating rate were discussed.The results showed that： （1） During the biomass burning season from March to April， there was an extreme value of AOD in the Indo-China Peninsula and Yunnan Province.The time series trend also showed a high consistency.The central value of AOD in Laos and northern Vietnam was more than 1， and the AOD in Yunnan Province gradually increased from north to south due to its influence.（2） The high-value center of biomass combustion AOD in the Indo-China Peninsula from March to April was consistent with that of total AOD， indicating that it was mainly affected by biomass combustion aerosol at this time.The horizontal flux divergence of biomass burning aerosol is as high as 28 kg·m^-1·d^-1 in northern Laos， which can be transported northeast to China.（3） The spatial and temporal distribution of surface ADRF and AOD showed a high consistency.The high-value center of surface ADRF also existed in the northern part of Laos and Vietnam in March and April， and its value could reach -36 W·m^-2.In the spatial distribution of the first mode of surface ADRF in EOF， the northeast corner of India bordering in Tibet of China， Laos， Vietnam and Thailand are all positive phase regions， with maximum values appearing from March to April.The extreme values decreased in 2017 and 2018 and increased again in 2019.The temporal variation trend of surface ADRF in Yunnan Province is consistent with that in the Indo-China Peninsula.（4） The statistical relationship between the negative surface ADRF and the atmospheric shortwave heating rate is as follows： The more the net radiant flux of the surface decreases， the greater the heating caused by the absorption of shortwave radiation by the lower atmosphere， indicating that the more the shortwave radiation flux trapped by the aerosol in the atmosphere， especially at 700 hPa in March and April.

Based on the daily MCI （Meteorological Drought Composite Index） of 125 stations in Yunnan province from April to June 2020， and the monitoring standard of regional drought process， the spatial-temporal distribution characteristics are analyzed， and the circulation causes of meteorological drought are also investigated.The results demonstrate that： （1） Two meteorological drought processes occurred from April to June 2020， one is a severe drought in southwestern area of Yunnan from April 1 to 25， and another was from May 9 to June 30 which is a severe drought with a long duration in the whole province.（2） From April 1 to 25 in 2020， the distribution of Mid-high latitude 500 hPa height field are two troughs and one ridge， a trough of low pressure in the Ural Mountains and eastern East Asia， and a ridge of high pressure in the area from Lake Balkhash to Lake Baikal， forming a "negative-position-negative" wave train which is conducive the cold air to the southward and impact of Yunnan.The low latitudes are controlled by a zonal positive abnormal height field， and there is south wind anomaly of 700 hPa in Yunnan， so the cold air mainly affects eastern of Yunnan.The Arabian-Sea-Bay of Bengal-South China Sea of 500 hPa height field is positive anomaly， which is not conducive to the transport of southwest warm and humid air to Yunnan.70% of the water vapor transport tracks to Yunnan come from the westerlies， so the regional meteorological drought process occurs in western Yunnan with less precipitation and higher temperature.（3） From May 9 to June 30， the seasonal transition of South Asian High is later than normal， and the establishment of the regional monsoon circulation in the Bay of Bengal is late also.Before the establishment of monsoon， all of the water vapor transport tracks to Yunnan region come from the westerly belt， and the specific humidity is mainly negative anomaly.After the establishment of the monsoon， 97% of the water vapor transport tracks to Yunnan come from the Indian Ocean， and the specific humidity was mainly positive anomaly.However， the circulation distribution in the middle and high latitudes of 500 hPa is not conducive the cold air to the southward and impact Yunnan.Meanwhile， the distribution of low latitude 500 hPa is positive anomaly， and the subsidence movement is strengthening， the correspondence between water vapor transport and the convergence rising motion was not good， so a sever large-scale meteorological drought occurred in Yunnan province.

Net primary productivity（NPP） directly and truly reflected the dynamic changing process of terrestrial vegetation ecosystem.Understanding the driving mechanism of climate change and human activities on vegetation change was of great scientific significance to ecological protection and sustainable development.Based on MOD17A3/NPP product， using linear trend analysis， Mann-Kendall significance analysis， Hurst index and partial correlation analysis， the temporal and spatial distribution characteristics of vegetation NPP in Yunnan Province from 2001 to 2021， the future sustainability and the relationship between vegetation NPP and meteorological conditions were discussed.Residual analysis used to quantitatively assess the relative contributions and combined action of climate change and human activities to the vegetation NPP.The result as follow： （1）Spatially， the annual mean NPP value of Yunnan vegetation from 2001 to 2021 was high in the south and low in the north.The order of values from the high to low was woodland （1106.7 gC?m^-2）， shrub （964.4 gC?m^-2）， agricultural land （946.6 gC?m^-2） and grassland （878.8 gC?m^-2） in different vegetation types.The vegetation NPP increased and then decreased with increasing altitude.（2）During the study period the annual mean vegetation NPP was 1020.8 ± 30.7 gC?m^-2， with minimum and maximum values occurring in 2010 （950.0 gC?m^-2） and 2019 （1062.1 gC?m^-2）， respectively.The vegetation NPP showed a significant increase with an increase rate of 2.1 gC?m^-2?a^-1 （p<0.05）.The increasing and significantly increasing areas accounted for 70.0% and 26.3% of the total area of the study area， respectively.The vegetation NPP of different vegetation types showed a similar variation trend.The increasing rates showed grassland （4.1 gC?m^-2?a^-1）> farmland （3.5 gC?m^-2?a^-1）> shrub （2.8 gC?m^-2?a^-1）>forestland （1.3 gC?m^-2?a^-1）.The average value of the Hurst index was 0.60.The proportion of the area that would continue to increase and change from decrease to increase was 55.5% and 9.3%， respectively.This indicated that the vegetation NPP would continue to increase in most areas in the future.（3）The average temperature in Yunnan Province showed a significant increase from 2001 to 2021， while precipitation and solar radiation showed a fluctuating decrease.These climatic factors positively correlated with vegetation NPP in most areas， and the effect of temperature on vegetation NPP was greater than that of precipitation and solar radiation.（4） The relative contribution rates of climate change and human activities to vegetation NPP change in Yunnan were 27.1% and 72.9%， respectively， with positive contributions accounting for 59.4% and 64.6% of the total area of the study area， and relative contribution rate greater than 60% accounting for 12.7% and 73.4% of the area， respectively.The impact of human activities on vegetation NPP was greater than that of climate change in most areas.The vegetation improvement in Yunnan was mainly caused by the combined effect of climate change and human activities， while the degradation was mainly caused by the human activities and the combined effect.The ecological protection and restoration projects had a significant contribution to the improvement of vegetation NPP in Yunnan.

To reveal the response of flue-cured tobacco suitable planting regions in Yunnan Province to climate change， the distribution characteristics of flue-cured tobacco suitable planting regions in Yunnan Province under contemporary climate conditions were studied by using maximum entropy （MaxEnt） model， which was based on the measured distribution data of flue-cured tobacco in Yunnan Province and the relevant environmental variable data.Furthermore， the change of suitable planting areas for flue-cured tobacco in Yunnan under future climate change conditions was analyzed.The results showed： （1） According to order of contribution of environmental variables to Yunnan flue-cured tobacco cultivation， the dominant environmental variables affecting Yunnan order of contribution of environmental variables to Yunnan flue-cured tobacco cultivation cultivation were， in order， the average precipitation in May， the average temperature in the hottest season， the classification of soil texture， and the content of soil carbonate.The cumulative contribution rate of such four items reached 80.9%， and the overall impact of climate variables on planting flue-cured tobacco in Yunnan is higher than that of soil variables.（2） In the current conditions， the suitable planting regions of flue-cured tobacco in Yunnan Province are mainly in Qujing， Kunming， Chuxiong， Zhaotong， Dali， Baoshan， Linchang， eastern Yuxi， northcentral Honghe， northwest Wenshan， also scattered in southern Lijiang and central Pu’er.The total suitable area is 23.82×10⁶ hm²， accounting for 60.44% of the land area of Yunnan province.（3） Under the RCP4.5 and RCP8.5 emission scenarios， the area of suitable planting areas of flue-cured tobacco showed an increasing trend in different degrees， increasing to 28.28×10⁶ hm² and 26.09×10⁶ hm²， respectively， accounting for 71.76% and 66.19% of the total area of the province.The displacement of the center of mass （geometric center） of the total suitable planting area along the easterly-northerly direction， and this displacement was mainly caused by the migration of the centroids in the highly suitable planting regions.