Extreme wind events （EWEs） not only are a kind of meteorological disaster， but also serve as an important natural resource.The Qinghai-Xizang Plateau （QXP）， well known as the "roof of the world"， is vulnerable to global and regional climate change.However， the characteristics and mechanism of variability of extreme wind events over this region and associated mechanisms remain elusive.Under the background of global change， Chinese Sichuan-Tibetan Railway construction， the exploration on changes in the EWEs could deepen our scientific understanding the regional climate.In order to explore the spatial-temporal distribution characteristics of regional extreme wind events （REWs） over the central and eastern QXP for the period of 1982 -2021， daily data of maximum wind speed are utilized to define REWs.Further， with the aid of thermal - thermodynamic diagnosis and the multiple statistical methods， such as trend analysis， EOF and composite analysis， we explore the potential causes leading to the decreased frequency of RWEs.The results show that： （1） The REWs over the QXP significantly decreased since 1980， varied consistently throughout the QXP and occurred mostly in the northeastern QXP.The REWs as defined in the 95^th and 99^th percentiles decline with the rate of 44d/10a and 11.6d/10a.（2） During periods of REWs， the circulation pattern is "high in the west and low in the east" in the middle and high latitudes and "low in the west and high in the east" in the low latitudes.The main characteristics are as follows： the abnormal positive geopotopic in Mongolia-Siberia， the abnormal cyclonic circulation in Mongolia， the abnormal westerly wind in the northeast of the plateau， and the abnormal negative surface temperature in Mongolia.（3） In the context of global change， the weakening of the Siberian high in spring and the strengthening of the East Asian trough in winter leads to decreasing pressure gradient between the north and south sides of the QXP， the weakening of the westerly jet stream leads to decreasing momentum downdraft， and the rise of non-uniform surface temperature in Asia leads to the decreasing temperature gradient between the north and south sides of the QXP.At the same time， the abnormal cyclonic circulation weakened in Mongolia.It may be resulted from the co-influence of these large-scale circulation and local thermal factors that reduce the frequency of regional extreme wind events in the central and eastern parts of the QXP.

In the context of global warming， the Qinghai-Xizang Plateau is altering atmospheric circulation through sensible heat absorption and latent heat release.This not only impacts the water and energy balance of the plateau's ecosystem but also plays a crucial role in regulating Asian and global climates.In order to explore the change characteristics and influencing factors of evapotranspiration in different regions of alpine grassland ecosystem on the Qinghai-Xizang Plateau， and deepen understanding of plateau climate change and hydrological-ecological processes， based on the observed eddy and meteorological data in 2022， the variation characteristics and environmental influencing factors of actual evapotranspiration of alpine grassland ecosystems at the same altitude in Sijinlacuo （seasonal permafrost） and Tuotuo River （permafrost） on the Qinghai-Xizang Plateau were compared and analyzed.The results show that： （1） Significant differences existed between environmental factors at these two sites， particularly in wind speed， air temperature， and precipitation.The wind speed at Tuotuo River station greatly exceeded that at Shijinlasuo station； annual average air temperature and precipitation were lower at Tuotuo River station.（2） The average hourly evapotranspiration of Sijinlacuo Station at night was higher than those recorded at Tuotuo River Station， however， this trend reverses during daytime hours.The variation characteristics of daily evapotranspiration at the two stations had a similar trend.The date of sharp increase and maximum of evapotranspiration at Sijinlacuo Station were earlier than those at Tuotuo River Station.The monthly evapotranspiration of the two stations were unimodal， with the maximum value appeared in July in summer and the smaller value appeared in December， January and February in winter.（3） Wind speed and ground radiation showed differing correlations with evaporation across both stations.Wind speed had a stronger correlation with evaporation at Tuotuo River Station due to higher wind speeds compared to weaker correlations observed for Sijinlasuo Station where winds were less intense.Conversely， ground radiation showed opposite correlations with evaporation between both locations.Air temperature， water vapor pressure， and atmospheric longwave radiation demonstrated strong correlations with evaporation across both locations while air humidity， saturated water vapor pressure difference， and precipitation displayed weaker associations.Precipitation exhibited the weakest correlation.（4） Although precipitation served as the primary source of evaporated water content， sources such as glacier melt water and thawing permafrost played significant roles as well on the Qinghai-Xizang Plateau， resulting in subdued influence of precipitation on the evaporative process at both locations.These results contribute valuable insights into understanding regional variations in high-altitude grassland ecosystems' response to changing climatic conditions on the Qinghai-Xizang Plateau.

Based on 109 hourly rain-gauge stations from June to August during 2005 -2020， the spatial and temporal distribution of annual rainfall amount， occurrence， rainfall intensity， and duration of summer hourly extreme rainfall events in the region of Southeastern Xizang Plateau-Western Sichuan Basin （28°N -33°N， 90°E - 105°E） are analyzed.Additionally， the diurnal variation of rainfall amount， rainfall intensity， and rainfall frequency during hourly extreme rainfall events in the region of Southeastern Xizang Plateau-Western Sichuan Basin are also explored.Results show that the hourly extreme the rainfall threshold， the annual rainfall amount， the rainfall intensity， and the duration of summer hourly extreme rainfall events in the region of Southeastern Xizang Plateau are lower than those in the region of Western Sichuan Basin， with the occurrence showing the opposite pattern.The annual rainfall amount and occurrence， and duration of summer hourly extreme rainfall events in the region of Southeastern Xizang Plateau increase over time.The annual rainfall amount and occurrence of hourly extreme rainfall events in the region of Western Sichuan Basin also increase， while the duration of hourly extreme rainfall events in the region of Western Sichuan Basin change insignificant.The rainfall amount’， the rainfall intensity’ and the rainfall frequency’ peak time of the summer hourly extreme rainfall events in the region of Southeastern Xizang Plateau -Western Sichuan Basin exhibit the eastward delayed features， and their peak time in the region of Western Sichuan Basin are 3 h， 4 h and 2 h later than those in the region of Southeastern Xizang Plateau， respectively.The most evident delayed feature exists in the rainfall intensity in June， with the peak time in the region of Western Sichuan Basin being 11 hours later than that in the region of Southeastern Xizang Plateau.However， both the Southeastern Xizang Plateau and Western Sichuan Basin regions exhibit insignificant interannual variation in the peak time of the rainfall amount， the rainfall intensity， and the rainfall frequency during summer hourly extreme rainfall events.

The Qinghai-Xizang Plateau， distinguished by its vast array of lakes， exhibits marked seasonal lake ice coverage， which is highly responsive to climatic shifts.This ice coverage plays a crucial role in the dynamic interchange of fluxes between the lake surfaces and the atmosphere.Despite the significance of these ice phenomena， the limited availability of extensive， long-term observational data on plateau lake ice has led to a reliance on reanalyzed ice datasets， particularly ERA5-Land.This study aims to rigorously evaluate the effectiveness and potential enhancements of ERA5-Land's lake ice data in the distinct environment of the Qinghai-Xizang Plateau.Focusing on data collected from 2010 to 2022 for Qinghai Lake and Ngoring Lake， this research meticulously examines the ERA5-Land reanalysis data's ability to accurately capture the intrinsic characteristics of plateau lake ice.The study uncovered that ERA5-Land tends to overestimate the ice thickness by about 0.54~0.62 m and erroneously prolongs the freezing period by roughly 68 days per year for these lakes.This notable discrepancy necessitated an in-depth error analysis， which synthesized ERA5-Land data with direct observational data from Ngoring Lake， revealing that inaccuracies primarily originated from the FLake one-dimensional lake model within the ERA5-Land system.In an effort to address these inaccuracies， the study employed the MCD43A3 surface albedo product for both Qinghai Lake and Ngoring Lake over the same period.This innovative approach significantly refined the FLake model by incorporating both a multi-year average albedo and a dynamic daily average albedo.These methodological improvements led to a substantial reduction in the average bias of ice thickness， by 85% and 90% respectively， and narrowed the deviation in the modeled freezing period by about 6 and 8 days per year.The enhancements were particularly notable in lakes with longer periods of snow cover， where the dynamic albedo adjustment proved to be highly effective.This research has successfully identified the albedo parameter within the FLake model as a key source of error in ERA5-Land's lake ice characterizations and has implemented practical adjustments to rectify this.These enhancements have markedly increased the model's precision in simulating lake ice， thereby significantly improving the accuracy of ERA5-Land reanalyzed lake ice data.This advancement is particularly pertinent for the unique climatic and geographical conditions of Qinghai Lake and Ngoring Lake on the Qinghai-Xizang Plateau and offers invaluable insights for future research and practical applications in this domain.The findings of this study contribute profoundly to our understanding and modeling of lake ice phenomena in high-altitude regions and have broader implications for climatological research and environmental monitoring on the Qinghai-Xizang Plateau.

In order to evaluate the predictive simulation ability of the CMA-CPSv3 climate prediction model （hereafter CMA-CPSv3 model） on two high-pressure systems， the South Asian High and the Western Pacific Subtropical High， that affect summer precipitation in China， the return simulated data by the CMA-CPSv3 model starting in March and May from 2001 to 2020 and ERA5 reanalysis data were used to firstly evaluate the model’s predictive ability on the characteristic indices of the two high-pressure systems， and then analyze the predictive ability of the differences in predicting the summer circulation system and water vapor characteristics between two high-pressure systems in the same good year and the same bad year， as well as their impact on summer precipitation in China， were compared.The possible reasons for the stronger prediction of the two high-pressure systems were explored.The main conclusions were as follows： （1） The CMA-CPSv3 model has the best prediction effect on the average ridge position of the West Pacific subtropical high and the South Asian high， with the predicted results of the intensity index and area index being significantly stronger or larger； Compared with the forecast starting in March， the forecast results starting in May have a certain improvement in the prediction of the West Pacific subtropical high.（2） The CMA-CPSv3 model has well predicted the circulation situation at 100 hPa and 500 hPa， with good predictions for temperature and wind fields.However， the predicted range of the South Asian High and the West Pacific Subtropical High is generally stronger.（3） The predicted positions of the ridge line of the two high-pressure systems in the same good year and the same poor year are relatively good， and the predicted areas and intensities are significantly stronger.The prediction deviation for the same good year is relatively small.It can better predict the spatial distribution of water vapor flux in East Asia and the distribution pattern of summer precipitation in China.（4） The upward motion of the predicted two high pressure systems in the longitude region is weaker than the ERA5 result， which may be one of the reasons for the larger range and stronger intensity of the predicted South Asian High and West Pacific Subtropical High.

Lakes widely distribute in the Qinghai-Xizang Plateau， and most of them are seasonally frozen lakes.Under the background of global warming， lake ice thickness and phenology are changing significantly， which has a profound impact on regional climate evolution.However， the evolution characteristics of ice thickness and phenology on the climatological scale are not well understood at present.Therefore， in this paper， the lake ice thickness and phenological evolution characteristics of Qinghai Lake during 1979 -2017 were studied by using the field lake ice observation data from Qinghai Lake Xiashe Hydrology Station， MODIS Lake ice coverage dataset， meteorological observation data from Gangcha Meteorological Station and CMFD， combined with a quasi-steady state model of lake ice.The results show that the simulated average ice thickness is 0.31 m， which is close to the measured value of Xiashe Hydrology Station.The error in modelling breaking-up end is only 0.07 days， and the errors of the freezing-up start and the ice duration are 5.60 days and 5.67 days， respectively.The simulated maximum ice thickness decreases from 1979 to 2017 is in good agreement with the observed trend， that is， the ice thickness decreases by 0.003 m per year.In the freezing periods from 1979 to 2017， the freezing-up start of Qinghai Lake is delayed （0.23 d·a^-1）， the breaking-up end is advanced （0.32 d·a^-1）， and the length of the ice duration is shortened （1.02 d·a^-1）， especially in the 1980s （2.2 d·a^-1）.During the freezing periods of Qinghai Lake from 1979 to 2017 （from December to April of the following year）， the downward longwave radiation and air temperature （both of which showed an increasing trend） have a significant negative correlation with the average ice thickness and the maximum ice thickness， while the downward shortwave radiation （which showed a decreasing trend） has a significant positive correlation with the maximum ice thickness and the average ice thickness.The detrending sensitivity test shows that： downward longwave radiation， air temperature， downward shortwave radiation and specific humidity are the main driving factors of mean ice thickness and maximum ice thickness variability in Qinghai Lake from 1979 to 2017， contributing 42.08%， 40.93%， -36.99% and 17.45% to mean ice thickness variability， and 44.48%， 44.68%， -34.77% and 19.92% to maximum ice thickness variability， respectively.All the meteorological driving factors contribute 83.40% and 87.01% to the two factors.It can be seen that the maximum ice thickness variability of Qinghai Lake is more susceptible to the influence of meteorological conditions than the average ice thickness variability.The results of this study provide an understanding of the long-term evolution trend of lake ice in the cryosphere， and provide a reference for the study of other lakes in the Tibetan Plateau in the cold season.

The Qinghai-Xizang Plateau （QXP） is an important herbage producing area， ecological barrier and water conservation area， the vegetation ecological process on which can directly affect the changes of China and even East Asia.With global warming， the phenological period of vegetation on the QXP is constantly changing， affecting climate and ecosystem through carbon cycle and hydrothermal cycle， etc.The study of phenological change and its influencing factors has become a key issue， and the construction of models that can realize future phenological prediction is of great scientific significance.In this paper， based on the Normalized Difference Vegetation Index acquired by satellites during 2000 -2020 （MODIS NDVI）， the dynamic threshold method was used to extract the start of growing season （SOS） on the QXP， and its spatiotemporal variation was analyzed in combination with vegetation types， so as to construct multiple phenological models of SOS， air temperature and soil moisture， exploring the hydrothermal conditions required for different regions and types of vegetation to start growing.The results showed that： （1） From 2000 to 2020， the overall SOS advance trend of the QXP was most significant in the eastern part of the region， where the SOS advance rate exceeded 10 d·（10a）^-1.Coniferous forests， scrub， meadows， and alpine vegetation cover areas had a high percentage of SOS advance， and grasslands had about 50 % of slightly delayed areas.（2） The eastern and northern regions of the QXP showed an obvious warming and humidification trend.The average annual temperature rise rate was about 0.36 ℃·（10a）^-1， and the average annual soil moisture increase rate was about 3.8×10^-4 m³·m^-3 （p<0.01）.（3） The parameters of the four phenological models showed that the vegetation growth in the eastern and southern QXP required higher hydrothermal conditions.The main controlling factor for vegetation SOS in the south was air temperature， while in the north it was soil moisture.The temperature and soil moisture thresholds and main controlling factor of different vegetation types were also closely related to their spatial distribution locations.（4） The cumulative temperature and cumulative soil moisture threshold model established in this paper has the best simulation effect for the main vegetation types （grassland， meadow and alpine vegetation） on the QXP， and the root-mean-square error is only about 8 days， which has reference significance for the future SOS prediction and the interaction mechanism between phenology and climate on the QXP.

Phenological changes are of great significance to the study of climate response and ecological environment.Based on the MODIS V6 snow product and reflectivity product in the past 20 years， the snow and lake ice phenology in the Qinghai Lake Basin were obtained， and the spatial distribution characteristics of the two were analyzed.On this basis， Theil-Sen Median method and linear regression method were used to analyze the variation trend of snow phenology and lake ice phenology， as well as the correlation between them in low altitude areas.The results show that： （1） Freeze-up start， Break-up start and Exist Duration of lake ice in Qinghai Lake are in the range of 321~389 d， 425~464 d and 0~174 d， respectively.On the whole， Freeze-up start and Break-up start of lake ice were delayed， and the delay rates were 0.3 d·a^-1 and 0.2 d·a^-1， respectively.Exist Duration of lake ice showed a shortening trend， with a shortening rate of 0.6 d·a^-1.There is a significant correlation between lake ice phenology and longitude.From east to west， Freeze-up start is postponed， Break-up start is advanced， and Exist Duration of lake ice is shortened.（2） Start of snow cover days， End of snow cover days and Snow cover days in Qinghai Lake Basin are distributed in the range of 275~404 d， 353~484 d and 3~209 d， respectively.Among them， start of snow cover days and End of snow cover days showed an early trend and a delayed trend respectively， and the change rates were 0.8 d·a^-1 and 0.11 d·a^-1 respectively.Snow cover days showed an increasing trend， with a growth rate of 0.6 d·a^-1.Snow phenology is closely related to altitude.With the increase of altitude， start of snow cover days is advanced， End of snow cover days is delayed， and Snow cover days increases.（3） Air temperature and negative accumulated temperature in winter are important factors affecting lake ice phenology.With the increase of temperature and negative accumulated temperature in winter， Freeze-up start will be delayed， Break-up start will be advanced， and Exist Duration of lake ice will be shortened.For snow phenology， there is a significant negative correlation between Snow cover days and the temperature.The temperature decreases and Snow cover days increases.（4） There is a potential relationship between some snow cover and lake ice phenology parameters in low-altitude watersheds.There is a significant negative correlation between the beginning date of snow cover and the beginning date of lake ice freezing， and the correlation coefficient is -0.404.As the lake surface insulation layer， the increase of snow cover days will also greatly slow down the speed of lake ice melting， resulting in the delay of lake ice melting date.Therefore， there is a positive correlation between the two， and the correlation coefficient is 0.349.The change law of ecosystem in the basin revealed by this study is of positive significance to the local ecosystem， and can provide theoretical basis and technical support for the environmental monitoring of Qinghai Lake Basin.

Based on the conventional observation， the cloud top blackbody brightness temperature data of Fengyun satellite， and the European Centre for Medium-Range Weather Forecasts 0.25°×0.25° ERA5 reanalysis data from 2006 to 2021， we have conducted a statistical analysis on the heavy precipitation events caused by extratropical cyclones over northern and northeastern China during the cold season.The results show that： （1） Most of the extratropical cyclones occluded during the explosive development phase， but the development process is different， with the Shapiro-Keyser （SK-type） and the classical Norwegian （NW-type） cyclones each accounting for half.The SK-type cyclone has a deep trough at 500 hPa， strong baroclinicity， and steering airflow in the north-northeast-orientation， resulting in westerly cyclone path， and northward， widespread precipitation； the NW-type cyclone has a shallow trough at 500 hPa， with weak cold advection behind the trough， and the steering airflow in the east-northeast orientation， resulting in an easterly cyclone path， more to the south and more intense precipitation.（2） The atmospheric rivers of the NW-type cyclone are more intensethan those of the SK-type cyclone， and the corresponding heavy precipitation is extensive and more intense.With the development of the cyclones， the atmospheric rivers of the SK-type cyclone gradually turn to a north-south orientation， and there is a clear backward-turning feature on the north side of the atmospheric river， resulting in a warm front precipitation center of the SK-type cyclone located in the northwest quadrant of the cyclone， and the warm front precipitation center of the NW-type cyclone is close to the center of the cyclones.（3） The warm front frontogenesis in the northwest quadrant of the SK-type cyclone is significantly more intense than that of the NW-type cyclone， and the intense lifting forced by the front is conducive to heavy snowfall.（4） The SK-type cyclone has an intense potential vorticity structure in the shape of treble-clef at 300 hPa， while the NW-type cyclone has weaker potential vorticity in the upper levels.The stratospheric potential vorticity over the SK-type cyclone extends downwards， connecting with the low-level potential vorticity to form a potential vorticity tower， with a deep warm occluded structure nearby； while， the upper-level potential vorticity of the NW-type cyclone does not extend downward significantly， and there is no potential vorticity tower generated.The SK-type cyclone first develops in the middle troposphere， and then reachesthe surface， while the NW-type cyclone develops from the lower troposphere.

Based on autumn precipitation data from 1961 to 2021 in Shanxi Province， NCEP/NCAR reanalysis data， and sea surface temperature data， the spatial-temporal variation characteristics and cause diagnosis of autumn precipitation in Shanxi Province were analyzed and discussed by using EOF analysis， correlation analysis and regression analysis.The results show that the autumn precipitation in Shanxi Province was relatively high before the mid-1970s， but decreased afterwards， and began to increase again in the mid-2000s.Further exploration of the causes of this interdecadal variation from the perspective of atmospheric circulation reveals that， during periods of excessive precipitation， the 200 hPa latitudinal wind field is located in the north of the East Asian westerly jet， which is beneficial for enhancing the upward movement in Shanxi； The 500 hPa geopotential height field exhibits a significant “+-+” anomaly distribution in the Europe and Asia region， which is conducive to the southward eruption of high latitude cold air； The 850 hPa wind field is conducive to the transport of low latitude water vapor to Shanxi， and under such high and low altitude circulation configuration， it is conducive to an increase in precipitation in Shanxi.At the same time， there is a close relationship between autumn precipitation and sea surface temperature anomaly in Shanxi.When the sea surface temperature in the central North Pacific is higher and in the tropical Middle East Pacific is lower from March to May， the autumn precipitation in the southern part of Shanxi is prone to behigher.

Based on nine C-band Doppler radar observations of Heilongjiang Province and conventional data from 2010 to 2021， combined with 1-h interval ERA5 reanalysis data of 0.25°×0.25° from the European Center for Medium-Range Weather Forecasts， the types and activity characteristics of mesoscale precipitation bands associated with extratropical cyclones in Heilongjiang Province are statistically analyzed， and the similarities and differences in the environment fields of two types of mesoscale precipitation bands are compared through typical cases.The main results are： （1） Mesoscale precipitation bands are primarily divided into single， multi， transitory， and nonbanded.Precipitation bands are mainly located in southern and northeastern Heilongjiang and the northwest and northeast quadrants of surface cyclones， within 900 km from the cyclone centers， and occur in the mature stage of cyclones.The main movement types of mesoscale precipitation bands are laterally translating and hybrid.（2） Vertical profiles of physical quantities can well reflect differences in precipitation intensity of different precipitation bands.Single-banded bands have the most excellent low-level specific humidity and frontogenesis， causing the heaviest precipitation.Non-banded bands have extensively weaker low-level frontogenesis than single-banded bands， with maximum specific humidity near 800 hPa， causing a wide range of precipitation and a weaker precipitation intensity than single-banded bands.（3） The analysis of cases shows that both single-banded and multi-banded bands are located on the north side of the intense 850-hPa warm advection， the northeast quadrant of the surface cyclone， in a small moist symmetric stable or moist symmetric unstable environment.The direction of the mesoscale precipitation band is parallel to the frontogenesis.The differences between them are as follows： for the single-banded band， deformation leads to strong frontogenesis and the upward movement concentrated on a small area， accompanying the development and movement of the low-level low and the surface cyclone， while for the multi-banded， weak deformation and shallow frontogenesis accompanying little movement and intensity change， intense upper-level divergence and low-level warm advection caused more extensive upward motion with multiple upward centers， corresponding to multi bands.

This paper employs statistical methods to analyze the relationship between vegetation and climatology variables.Additionally， it quantitatively assesses vegetation feedback over East Asia using the equilibrium feedback assessment （EFA） method.The study reveals a significant correlation between vegetation and climate variables， including temperature and precipitation.In middle and high latitudes， positive feedback is observed between vegetation and temperature， while negative feedback is identified between vegetation and precipitation.In middle and low latitudes， positive feedback is observed between vegetation and precipitation， while negative feedback is identified between vegetation and temperature.In high latitudes， the positive vegetation anomaly tends to reduce the albedo by shading effect， leading to increased energy absorption and warming air during winter and spring.The analysis highlights that in low latitudes， the correlation between leading vegetation and precipitation is highly sensitive.It is mainly because the high year-round temperature in this area leads to the vegetation being dominated by precipitation signals.The study also finds a positive correlation between leading vegetation and precipitation in low latitudes.The increased vegetation stimulates moisture convergence and enhances evapotranspiration， resulting in more precipitation.The vegetation feedback parameter for temperature is positive in regions around the Da Hinggan Mountains and Baikal Lake， predominantly covered by evergreen needle-leaf forests.The feedback parameter in this area is approximately 1 to 2 ℃ · {(\mathrm{0.1}\mathrm{F}\mathrm{P}\mathrm{A}\mathrm{R})}^{-\mathrm{1}}.The positive feedback parameter is identified in the southern part of China， ranging from 0.2 to 1 ℃ · {(\mathrm{0.1}\mathrm{F}\mathrm{P}\mathrm{A}\mathrm{R})}^{-\mathrm{1}}.Regarding precipitation， the feedback parameter exhibits significant noise， making it challenging to distinguish signals except for the positive signal around the North China Plain.In the North China Plain， the feedback parameter for precipitation is approximately 1.5 \mathrm{c} \mathrm{m} · \mathrm{m} \mathrm{o} {\mathrm{n}}^{-\mathrm{1}} · {(\mathrm{0.1}\mathrm{F}\mathrm{P}\mathrm{A}\mathrm{R})}^{-\mathrm{1}}.

Soil moisture， as a key hydrological variable connecting the surface and atmospheric water and heat exchange， affects the land-air water and heat exchange and carbon cycle process.However， due to the difficulty in monitoring soil moisture in alpine mountain areas， there are some difficulties in related research.The study of time stability can reduce the difficulty of soil moisture acquisition by selecting representative points.In this study， the slope of Shangzhangfanggou grassland in Shiyang River basin of Qilian Mountain was selected to set up a high-density and high-time resolution soil moisture monitoring network to explore the temporal and spatial variation and temporal stability of soil moisture on the slope scale in alpine mountainous areas.The research results show that： （1） The surface soil moisture （10 cm， 15.90%） is significantly higher than that in the deep layer （50 cm， 11.78%）， and its temporal variability （Cv _T=19.46%） is also stronger than that in the deep layer （Cv _T=10.67%）， but its spatial variability （Cv_S =20.05%） is weaker than that in the deep layer （Cv_S =27.06%）.（2） The time stability Index of Temporal Stability （0.24） is stronger than that of the deep layer （0.34）， and the surface layer and the deep layer can represent the surface soil moisture of the slope through 3 or 5 soil moisture monitoring points respectively （R ²> 0.90）.（3） Slope position and soil hydrological properties have obvious influence on time stability， and the time stability point is more likely to appear at the position with larger bulk density and smaller shape parameter n under the slope.The research results are helpful to better understand the temporal and spatial variation law， temporal stability characteristics and control function of soil moisture on slope in alpine mountain areas.

The CMA-MESO/CUACE CW is an atmospheric chemistry coupled model independently developed by China.At present， the CMA-MESO/CUACE CW 3DVar system realized the assimilation of ground-based aerosol observations of PM_2.5 and PM₁₀.In order to enhance the assimilation capability of the coupled assimilation system for non-conventional observations， based on the CMA-MESO three-dimensional variational assimilation framework of atmospheric chemical weather coupled system， the aerosol extinction coefficient is obtained by using the look-up table method.And then the observation operator， the tangent linear operator and the adjoint operator are established using the relationship between aerosol optical depth （AOD） and aerosol components.The assimilation tests were carried out for a haze process in North China on December 18 -20， 2016.The results show that after assimilating the AOD observations from the Himawari-8 satellite， the heavily polluted area of the PM_2.5 is enlarged， and the analysis in southeastern Shanxi is closer to the actual situation， but the analysis of PM_2.5 in the majority of the Shandong region is overestimated.The simultaneous assimilation of Himawari-8 AOD observations and ground-based aerosol concentration observations test is the best for the analysis of PM_2.5， it has the highest correlation coefficients （ACCs） and the smallest mean bias， root-mean-square error and standard deviation.The PM_2.5 forecast results in the heavily polluted area showed that the positive contribution of the assimilated Himawari-8 AOD observations to the PM_2.5 forecasts for the >350 μg·m^-3 magnitude could be sustained up to 48 h.However， the simultaneous assimilation of the Himawari-8 AOD observations and the ground-based aerosol site observations had the best test scores of PM_2.5 forecasts for each magnitude.

Raindrop size distribution （RSD） is fundamental in understanding the precipitation microphysics and quantitative precipitation estimation， especially in complex terrain with complicated rainfall mechanism and high spatial and temporal variability.In this paper， the RSD characteristics of different rainfall rates and rain types in the mountainous and plain areas of the Ili River Valley during the summer of 2020 -2022 are investigated using Parsivel² disdrometer.The results show that the precipitation in the mountainous and plain areas is mainly composed of small raindrops， and medium raindrops are the largest contribution to the rainfall rate R.Precipitation in the mountainous and plain areas mainly occurs during the late afternoon and early evening， and the concentration of large and medium-sized raindrops is higher in the mountainous areas in all time periods.The spectral width and the concentration of drops with diameters increase with increasing rainfall rate.The number concentration of medium and large particles in the mountainous areas is obviously higher than that in the plain areas during light rain and heavy rain.For the same rainfall rate and rain type， precipitation in the mountainous areas has higher mass-weighted mean diameter （D_m ） and lower normalized intercept parameter （log₁₀ N_w ）.In addition， the convective rain spectrum in the mountainous and plain areas of the Ili River Valley tend to be “continental-like convective cluster”.It is found that there are also significant differences in the μ-Λ relationship and Z-R relationship of precipitation between the two areas， and the empirical relationship of Z =300R ^1.40 clearly overestimates precipitation.The results reveal the microphysical characteristics of precipitation under different terrain conditions in the Ili River Valley， and provide a reliable factual basis for the subsequent retrieval of precipitation using radar data.

The Land surface of the Sichuan Basin is characterized by complexity and diversity， with frequent occurrences of heavy rainfall.This study utilizes global reanalysis data from the U.S.National Centers for Environmental Prediction and various categories of land use data， including default land use data from the WRF model， MODIS （Moderate Resolution Imaging Spectroradiometer）， and USGS （United States Geological Survey）.Additionally， the 2015 LUCC2015 （Land use datasets in China 2015） datasets and the 2015 GLASS （Global Land Surface Satellite） land use datasets are incorporated.The WRF（Weather Research and Forecasting）model is used to simulate a heavy rainfall event in Sichuan Province.The impact of changes in land surface classification and variations in terrain height on heavy rainfall is discussed through four sets of land use experiments and two sets of terrain sensitivity experiments.The results indicate that the experiments involving different land use types have a significant impact on regions experiencing heavy precipitation.In comparison to the MODIS experiment， the precipitation distribution from the USGS experiment is more concentrated， with a larger coverage area for intense precipitation centers； the LUCC2015 experiment results in a reduction in rainfall intensity in the northeastern part of the Sichuan Basin， accompanied by a more concentrated precipitation distribution； the GLASS experiment simulation， characterized by a relatively uniform land use， results in a reduction in the intensity of both intense precipitation centers.Additionally， the precipitation centers in the northeastern part of Sichuan shift southward.Various land use types also exert influence on near-surface meteorological parameter fields.Through a comprehensive analysis of the various land use experiments， it is evident that a reduction in urban built-up areas results in a decrease in 2 m temperature by 0.5 to 1 ℃； the reduction in vegetation coverage results in an increase in 2 m temperature and an enhancement of 10 m wind speed； the decrease in surface roughness leads to a significant enhancement in 10 m wind speed， with a magnitude of change ranging from 2 to 4 m·s^-1.Compared to the default land use types in WRF， the simulated results under the underlying surface types in the LUCC2015 experiment are better.The topography exerts a pronounced influence on heavy rainfall.Following the reduction in elevation of the western mountainous region in the basin， the absence of mountain barriers allows for a more abundant presence of lower-level water vapor and energy.Consequently， moisture and energy can be transported to more northern regions of Sichuan.With the reduction in elevation of the terrain， the low-level airflow intensifies convergence ahead of the mountains， triggering stronger upward motion of air and resulting in enhanced precipitation intensity.This phenomenon leads to a westward shift in the precipitation location and a more concentrated coverage of rainfall.Conversely， with the uplift of the terrain， the mountainous barrier impedes the entry of warm and moist airflow from the south.As a result， energy and moisture become more dispersed， causing a reduction in airflow convergence in the western and eastern parts of the basin.The weakening of low-level airflow ascent leads to a decrease in precipitation intensity and a more dispersed distribution of rainfall.

In order to scientifically and accurately calculate the water surface evaporation in the central Yunnan region， based on the monthly meteorological data from Yuxi Meteorological Station near the 'Three Lakes' basin in Central Yunnan from 2014 to 2021， the effectiveness of the FAO PPP-17 Penman formula in calculating water evaporation in this area and the error sources is analyzed through comparative analysis and correlation analysis.On this basis， aiming at the sources of calculation errors and the characteristics of seasonal changes， the water surface reflectance and the solar radiation parameters in the Penman formula are dynamically modified with the season changes using Morton empirical formula and other methods.Furthermore， based on the principle of heat balance， a new estimation model of water surface heat flux was derived by using error inverse derivation.The water surface heat flux term is added to the FAO PPP-17 Penman formula to correct the heat balance of the water surface.The results showed that： （1） The water evaporation calculated by the FAO PPP-17 Penman formula in the study area was generally overestimated， with a mean relative error of +15.2%.The error has seasonal characteristics of small in winter and large in summer， and periodic variation characteristics which is similar to a sine curve.The calculation error mainly stems from the inappropriate value of solar short-wave radiation parameters in the formula and the neglect of the influence of water surface heat flux， resulting in an imbalance in the heat budget.（2） After dynamically improving the parameters of the FAO PPP-17 Penman formula and adding the water surface heat flux to it， the calculation accuracy is significantly improved.Compared to the unrevised version， the accuracy with relative errors within ± 5%， ± 10%， and ± 20% increased by 40.6%， 42.7%， and 32.3%， respectively.The results of off-site tests show that the optimized Penman equation exhibits high fitting accuracy in the ‘Three Lakes’ basin of central Yunnan， and the model's accuracy with relative errors within ±10% is over 75%.（3） This study developed a nonlinear estimation model for water surface heat flux， which can reasonably simulate the nonlinear response of water storage heat to seasonal variations and water surface radiation intensity.Furthermore， the model has demonstrated satisfactory results in evaporation calculations within the "Three Lakes" region.

The Normalized Differential Vegetation Index （NDVI） is an essential index of vegetation growth status and an indicator of terrestrial ecological conditions.North China is China's political and cultural center， with complex and diverse land cover types， and is a critical agriculture production region in China.Meanwhile， the vegetation ecology in North China has become very fragile under the influence of climate warming and drying and intensified human activities.Based on satellite data NOAA/AVHRR NDVI and meteorological data information， this study explores the spatial and temporal variability characteristics of NDVI in North China and the effects of climate change and human activities on NDVI from 1982 to 2019 using trend analysis， partial correlation analysis， and residual trend analysis.The results showed that （1） The vegetation NDVI in spring， summer， fall， and growing seasons in North China from 1982 to 2019 exhibited a significant upward trend with strong spatial heterogeneity， among which the fastest growth rate of 0.024 （10a）^-1 was observed in the summer and growing seasons.The percentage of the area with significant increase was 57.35% and 58.10%， respectively.（2） NDVI in spring， summer， and growing seasons in North China displayed a significant positive correlation with precipitation， while NDVI in fall was mainly influenced by air temperature.NDVI in summer was positively affected by both air temperature， precipitation and relative humidity.（3） The effects of climate change and human activities on vegetation growth in North China have regional differences.In the vegetation increased areas， the relative role of climate change is 45.64%， and the relative role of human activities is 54.36%.In the vegetation decreased areas， the relative role of climate change is 32.66%， and the relative role of human activities is 67.34%.（4） Among different land use types， the vegetation growth of forest and farmland in North China is faster， and the vegetation improvement is mainly affected by human activities， the relative effect of human activities is 66.07% and 60.82%， respectively.The vegetation degradation of grassland is also mainly affected by human activities， the relative effect is 69.48%.Human activities have an essential influence on the vegetation NDVI in North China， which mainly stems from the construction of major human ecological projects such as the Three North Protective Forests and the influence of urban expansion and population surge in recent decades in China， and the research results also provide necessary theoretical support for the construction of ecological barriers as well as ecological， environmental protection in North China.

In order to understand the long-term evolution of meteorological drought in Chongqing， the localized revised meteorological drought comprehensive index （RMCI） of 34 national stations in Chongqing from 1960 to 2022 was used in conjunction with local standard for regional meteorological drought process evaluation to synchronously compare with the meteorological drought comprehensive index （MCI） process data from 1981 to 2020， then analysed the data structure and spatiotemporal distribution characteristics of the historical 63 a RMCI.The conclusion was as follows： （1） The cumulative frequency of the 40a RMCI single station process in Chongqing was 4.2% higher than that of MCI， and the frequency-intensity fitting of both showed a significant exponential distribution.The difference rate in the start time between RMCI and MCI single station processes was only 8.1%.The northeast of Chongqing was a consistently high incidence district of drought at all levels for RMCI and MCI single station processes， while the frequencies were relatively low in the central urban area， southwest， and middle districts.（2） The daily data of Chongqing's 63 a RMCI showed a normal distribution overall， with small（significant） differences in the distribution of mild， moderate， and severe drought（extreme drought） daily data across whole region and various districts.The daily data of RMCI severe and extreme drought in the central urban area was consistently relatively high and low compared to other districts， respectively.The frequency-intensity of RMCI single station process and regional process data were significantly inversely correlated， with the station-averaged frequency of mild， moderate， and extreme droughts for single station processes occurring in the western district of Chongqing being the highest， and the absolute range of extreme drought in regional process data was the highest， followed by moderate drought.（3） The intensity trends of RMCI single station and regional meteorological drought processes in Chongqing during the 63 a were not significant， but both showed a significant decreasing trend from 1962 to 2013.The overall weakening of both processes intensity in Chongqing after 2013 was related to the interdecadal decrease in high-temperature days since the 21st century.It could be considered that meteorological drought process events had complex interannual and interdecadal signals.The RMCI single station process events mainly exhibited periodic oscillations of 2~6 a and quasi-20 a， with the "drying out" of single station process events occurring in parts of Chongqing northeastern and southeastern districts being particularly significant.The RMCI regional process events exhibited periodic oscillations of 2~3 a， 4~6 a， and 8~12 a， with the highest frequency and strongest intensity of regional process events starting during the hot summer drought period and July， while the frequency and intensity of autumn drought period and December was relatively lowest and weakest， respectively.

Climate change has significant implications for the livability of cities.Analyzing climate change trends and developing corresponding adaptive strategies can enhance the livability of typical regions and mitigate the adverse effects of climate change.In this study， Shenzhen City in Guangdong Province was taken as an example to analyze the variation patterns of various climate factors including temperature， wind speed， Air Quality Index （AQI）， and relative humidity from 2018 to 2022.A livability index assessment model was established using the entropy weight method to analyze the variation patterns of the livability index.The main environmental constraints on the livability index were identified， and adaptive optimization strategies at the community scale were proposed based on these findings.The application effect of the adaptive strategies was subsequently validated.The results indicate that the livability index of Shenzhen City had been decreasing over the past 15 years， transitioning from highly livable to moderately livable.The main environmental factors contributing to the decline in livability index were identified as decreasing wind speed， increasing temperature， and enhanced UV radiation.The construction and renovation of adaptive residential buildings and greening of communities significantly improve the livability at the community scale.However， they are unable to reverse the trend of decreasing livability index caused by climate change.The findings of this study can provide valuable insights for urban planners， managers， and relevant stakeholders in urban planning and design.