In order to investigate the influence of soil moisture heterogeneity on the convective initiation stage of a mesoscale convective system over the Qinghai-Xizang Plateau， an typical case of mesoscale convective system， developed from an isolated convective initiation process over the Qinghai-Xizang Plateau on 10 August 2022， is studied by observational analysis and numerical experiments using satellite remote sensing data， cloud-to-ground lightning observations and reanalysis data.The results are as follows： （1） Under weak synoptic-scale forcing， the convective initiation stage of the mesoscale convective system occurred at 06:00 （UTC， the same as after）.The convective cloud then moved northeastward and intensified through merging clouds， accompanied by lightning activity during the development of the mesoscale convective system.（2） Based on the mesoscale numerical model WRF， we simulated the surface convergence in the southwestern dry zone formed by surface thermal forcing， as well as the development and intensification process of the updrafts caused by the surface convergence until the formation of the convective initiation with a moving direction along the soil moisture gradient.At convective initiation time， the low-level atmosphere over the convective initiation location was in a dry adiabatic state with a CAPE（CIN） of 946.5 J·kg^-1 （0 J·kg^-1）.2 m air temperature reached the convective temperature 1h before the occurrence of convective initiation， when the height of the planetary boundary layer was higher than the level of free convection.The convection then strengthened rapidly.（3） The results of the sensitivity experiments show that the removal of the soil moisture inhomogeneity weakened the intensity of the convection and shifted the position of the convective initiation westward， which is related to the fact that the soil moisture inhomogeneity changed the atmospheric dynamical， thermal and moisture conditions before the occurrence of the convective initiation.The soil moisture inhomogeneity indirectly increased the sensible heat flux of the dry zone located to the southwest of the convective initiation location by increasing the surface temperature， thus increasing the upward motion at surface before the occurrence of the convective initiation.Meanwhile， the direction of the wind field near the convective initiation location was also changed and thus increasing the convergence of the surface wind field and water vapor at the convective initiation time， which led to an increase in the intensity of the convection.（4） Under the condition of homogeneous soil moisture distribution， increasing soil moisture led to more abundant surface water vapour and stronger convergence of the surface wind field， which in turn led to an increase in the intensity of water vapour convergence and enhanced the development of convection.In addition， higher soil moisture inhibited the intensity of pre-convective initiation updraft development by decreasing surface temperature and sensible heat fluxes， which slowed the development of convection and led to a later convective initiation time.

The Three-River regions， as a crucial water source conservation area in China， plays a crucial role in maintaining the regional hydrological and climatic stability through its extensive highland wetlands.Considering the competitive interaction between soil moisture anomalies and precipitation feedback mechanisms under different environmental conditions， this study conducted control and sensitivity experiments based on the WRF meteorological model， combined with the CTP-HI_low framework and CAPE index， to assess the precipitation response under soil moisture anomaly conditions.The study preliminarily analyzes the impact characteristics and feedback mechanisms of soil moisture anomalies on regional weather， particularly precipitation processes.Specifically， based on transient simplified evaporation experiments and inversion methods， the WRF simulation incorporated hydrological measurement data from multiple soil samples collected within the study area.The results show that the hydraulic properties of wetland soils significantly influence surface thermal properties and energy distribution.The soil hydraulic parameters obtained using the simplified evaporation method significantly improved the model’s simulation of latent heat flux， sensible heat flux， surface temperature， 2-meter air temperature， and 2-meter specific humidity.Soil moisture anomalies have a significant impact on short-term precipitation processes.Under conditions of soil moisture anomalies， both CAPE and CTP values significantly increase， while HI_low values decrease， accompanied by an increase in atmospheric instability and water vapor content， leading to a clear positive feedback response in precipitation.In contrast， under dry anomaly conditions， CAPE and CTP values slightly decrease， while HI_low values increase， accompanied by reduced atmospheric instability and decreased water vapor content， with precipitation showing no clear feedback to soil moisture.The hydraulic characteristics of wetland soils， through regulating surface energy distribution and water vapor flux， significantly affect precipitation processes at both local and regional scales.Especially under soil moisture anomaly conditions， the hydrological regulation effect of wetland soils plays a crucial role in precipitation feedback mechanisms， further highlighting their key position in maintaining regional hydrological and climatic stability.

Stratospheric airships， due to their excellent performance， exhibit great potential in flight missions within the aerospace field.However， the complexity of the stratospheric environment presents significant challenges to flight safety.Therefore， conducting environmental forecasts in advance to mitigate flight risks is crucial for the successful completion of airship missions.Although existing thermodynamic models have provided a theoretical foundation for airship design， their analysis remains insufficient.In this paper， two key parameters， cloud top height and cloud top temperature， are introduced to deeply analyze their effects on the airship's thermal balance.Cloud top height determines the relative position between the cloud layer and the airship， while cloud top temperature directly reflects the thermodynamic state of the cloud layer.Both parameters influence the radiative exchange and thermal balance of the airship.Based on this analysis， the importance and urgency of incorporating these factors into thermodynamic models are emphasized， offering new insights for the optimization of future airship thermodynamic models and revealing the significance of studying cloud layer distribution characteristics.Additionally， the unique advantages of the Qinghai-Xizang （Tibet） Plateau as a natural laboratory are highlighted， and specific data analysis is conducted.This paper analyzes historical meteorological cloud observation data from 2015 to 2020 in the Qinghai-Xizang （Tibet） Plateau region using the CLARA-A3 dataset， focusing on the spatial distribution characteristics， daily mean and extreme values， cloud area proportions， and the correlation analysis between cloud top height and cloud top temperature.The results show that cloud top height exhibits a spatial distribution pattern of lower in the northwest and higher in the southeast， while cloud top temperature shows a trend of higher in the west and lower in the east.During the period from July to September， cloud top height reaches its highest annual value， and cloud top temperature reaches its lowest.The annual variation pattern of the cloud top parameters is also confirmed.Further analysis indicates the presence of extreme meteorological phenomena， such as ultra-high clouds and extremely low temperatures， with daily cloud top heights exceeding 18 km and cloud top temperatures below -83 ℃， which mostly occur between July and September.A Spearman correlation coefficient analysis reveals a moderate negative correlation between the two variables， with a strong negative correlation during the July-September period.This provides important data support for further quantifying the influence of cloud layers on airship performance.The study shows that the potential threat of cloud layers to airships cannot be ignored， particularly during the July-September period， when the deployment preparation for stratospheric airships should focus on the changes in local meteorological cloud parameters.Acquiring cloud observation data in advance and implementing meteorological forecasting preparation are key factors in ensuring the safe flight of airships.This research is the first to apply real meteorological data analysis to airship flight environment assessment， verifying the feasibility of data analysis techniques， and emphasizing the critical role of observational data in model validation， providing a new research perspective for improving the thermodynamic models of stratospheric airships.In the future， with the continuous optimization of dynamic prediction models， the safety of airships in complex meteorological environments is expected to be significantly improved.

Based on daily surface sensible heat flux （SH） data from 73 meteorological stations across the central-eastern Qinghai-Xizang Plateau， daily precipitation data from 402 stations in southern China， and ERA5 reanalysis data， this study investigates the springtime enhancement characteristics of SH over the central-eastern Qinghai-Xizang Plateau， its influence on spring rainfall in southern China， and the associated physical mechanisms.The results indicate that： （1） The springtime surface sensible heat peak time （T） and enhancement intensity （Q） over the central-eastern Qinghai-Xizang Plateau exhibit significant interannual and decadal variability， with a strong positive correlation between them.Specifically， a later occurrence of the peak sensible heat in spring is associated with a stronger enhancement intensity.（2） Both T and Q exhibit significant positive correlations with spring rainfall in southern China.To evaluate their combined effects， a composite index termed the Surface Sensible Heat Enhancement Index （I_SH ） is introduced.This index demonstrates a strong positive correlation with spring rainfall in southern China （correlation coefficient = 0.60， p<0.01）.Moreover， its influence is largely independent of external factors， such as sea surface temperatures in the central-eastern Pacific and the tropical Indian Ocean.（3） In years with a high （low） I_SH index， the springtime subtropical westerly jet is anomalously southward （stronger）， and the westerly winds south of the Qinghai-Xizang Plateau are anomalously strong （weak）.The average geopotential height at 500 hPa and 850 hPa over the Chinese mainland is anomalously lower （higher）， and the lower troposphere in southern regions is dominated by an anomalously low （high） pressure system.In eastern coastal areas， the low-altitude southwest （northeast） wind is anomalously stronger， leading to water vapor convergence （divergence）.Combined with warm （cold） advection and strong ascending （descending） motion， this creates conditions that are conducive （not conducive） to precipitation formation.Consequently， spring rainfall in southern China becomes anomalously abundant （scarce）.This study provides new insights into the factors contributing to spring rainfall variability in southern China， improves the predictability of regional spring weather and climate， and provides a robust scientific foundation for mitigating disaster risks associated with abnormal spring rainfall patterns.

The Three-River Source region （TRSR）， located on the Qinghai-Xizang Plateau （QXP）， are the source regions of Yangtze， Yellow and Lancang River， plays a critical role in water conservation and is renowned as the “Water Tower of China”.Under the background of global climate change， this region exhibits characteristics of rising temperatures and increased precipitation.Sufficient moisture supply is a prerequisite for precipitation， and the transport pathways and the characteristics of moisture sources have profound impacts on precipitation mechanisms， water resource regulation， and ecosystem stability in the TRSR.Current research predominantly employs traditional Eulerian methods for moisture transport analysis， which makes it difficult to accurately quantify the relative contributions of different source regions.Studies using Lagrangian trajectory models often focus on extreme precipitation， lacking long-term analysis.This study used CFSR reanalysis data to drive the Lagrangian model FLEXPART， conducting long-term forward simulations of 5 million air parcels from 1980 to 2017.Combined with the Water Sip moisture source diagnostic method， the research focused on the rainy season （May-September） in the TRSR， systematically identifying and analyzing the main moisture transport pathways， contribution proportions from various source regions， and further exploring their spatiotemporal variation characteristics and relationships with major large-scale circulation systems.Results indicate that the main moisture transport channels affecting precipitation in the TRSR during rainy season can be summarized as two types： one enters from the west or north along the mid-latitude Westerly， characterized by numerous air parcels at higher altitudes but with relatively lower moisture content； the other enters from the south or east along the Asian monsoon， although the quantity is relatively small， the routes pass through marine areas with low altitudes and rich moisture content.Moisture sources diagnostics using the Water Sip method reveal that the rainy season moisture sources for the TRSR exhibit a distribution pattern radiating outward from the QXP， with the most prominent expansion towards the South Asian monsoon region.The internal moisture cycle of the QXP plays a dominant role in precipitation in the TRSR during the rainy season， contributing 66.3% of the moisture.The South Asian monsoon region ranks second， contributing 18.87% of moisture， while the Westerly region and East Asian monsoon region contribute relatively less， at 7.00% and 3.08% respectively.From a spatiotemporal perspective， moisture sources during the rainy season in the TRSR showed an overall increasing trend from 1980 to 2017， with the most significant increases from the QXP and the southern of the Himalayas， exceeding 4 mm·（10a）^-1.This trend is closely related to the strengthening of the South Asian monsoon and plateau monsoon， which enhanced moisture transport capacity from the South Asian monsoon region， the interior and surrounding areas of the QXP.The moisture contribution from the western QXP to Central Asia showed a declining trend， mainly affected by the southward shift and weakening intensity of the Central Asian Westerly.Meanwhile， the trend in the intensity and position of the East Asian monsoon were not significant， resulting in a relatively weak effect on moisture transport to the TRSR during the rainy season.

Under the influence of global warming， the surface temperature of lakes on the Qinghai-Xizang Plateau， along with the total duration and mean intensity of lake heatwaves， has exhibited significant increases.These trends amplify the susceptibility of lake surface temperatures to heating during thermal stratification periods， accelerating summer warming rates and potentially inducing surface hypoxia.Previous studies analyzing lake heatwave characteristics have predominantly focused on spatially averaged metrics across broad regions， leaving the specific heatwave dynamics of Qinghai Lake poorly characterized.To address this knowledge gap， this study integrates in-situ observations of Qinghai Lake's water temperature and surface temperature， meteorological data from Gangcha Station， MODIS land surface temperature products， the Third Pole high-resolution near-surface meteorological forcing dataset （TPMFD）， and simulations from the one-dimensional Freshwater Lake Model （FLake） to investigate long-term changes in surface temperature and heatwave characteristics of Qinghai Lake from 1980 to 2022.Through correlation analysis and detrended decomposition methods， the driving mechanisms underlying these changes were systematically elucidated.The research shows that： （1） The air temperature， specific humidity and wind speed of TPMFD reanalysis data are highly correlated with those observed by Gangcha meteorological station， and the biases （BIAS） and root mean square errors （RMSE） are small.The correlation coefficients of the two data are 0.96， 0.84 and 0.74， respectively， and the BIAS is 0.55 ℃， 0.00068 g·g^-1 and -0.31 m·s^-1， respectively.The RMSE is 0.59 ℃， 0.00069 g·g^-1 and 0.38 m·s^-1， respectively.The change rate of the air temperature in TPMFD ［0.48 ℃·（10a）^-1］ is close to that of the observed air temperature ［0.44 ℃·（10a）^-1］.The variation rate of the specific humidity in TPMFD ［0.0001 g·g^-1·（10a）^-1］ is consistent with the observed variation rate.The variation rate of the wind speed in TPMFD ［ -0.1 m·s^-1·（10a）^-1］ is slightly smaller than that of the observation ［ -0.25 m·s^-1·（10a）^-1］.Moreover， the change rates of the air temperature， specific humidity， and wind speed in both TPMFD and the Gangcha Meteorological Station have passed the significance test at the 95% confidence level.The simulated water temperature and lake surface temperature of Qinghai Lake have a very good correlation with the in-situ observed water temperature and lake surface temperature of Qinghai Lake， and the biases and root mean square errors are relatively small.The long-term sequential simulated lake surface temperature also has a good correlation with the MODIS surface temperature， and both the BIAS and RMSE are within a reasonable range.The correlation coefficients between the simulation results and the three kinds of observations are 0.99， 0.96， and 0.98 respectively， the BIAS are 0.25 ℃， -0.1 ℃， and 0.87 ℃ respectively， and the RMSE are 0.58 ℃， 2.65 ℃， and 2.20 ℃ respectively.（2） From 1980 to 2022， both the characteristics of the lake surface temperature and lake heatwaves in Qinghai Lake showed a significant increasing trend （p<0.05）.The frequency of lake heatwaves fluctuated between 0 and 6 times.The total number of days with lake heatwaves each year increased significantly.The total number of days in 2022 reached 150 days.The mean lake heatwave duration in most years exceeded 10 days per occurrence.The maximum lake heatwave duration in 2022 even reached 76 days， and the mean lake heatwave intensity increased significantly.The intensity levels of heatwaves in Qinghai Lake in 2016 and 2022 were in a "severe" state， which is two orders of magnitude stronger than the multi-year average intensity level （"moderate" level）.（3） Air temperature， specific humidity， downward long-wave radiation， downward short-wave radiation， and air pressure are positively correlated with the simulated lake surface temperature.Moreover， they are positively correlated with the total days of lake heatwaves and the mean intensity.However wind speed is negatively correlated with in the simulated lake surface temperature， the total days of lake heatwaves and the mean intensity.The meteorological factors that positively contribute to the increase in lake surface temperature， from largest to smallest， are air temperature （23.83%）， specific humidity （20.52%）， wind speed （16.05%）， downward long-wave radiation （14.79%）， and downward short-wave radiation （10.68%）.The meteorological factors that positively contribute to the increase in the total days of lake heatwaves are air temperature （37.54%）， wind speed （35.86%）， specific humidity （30.03%）， downward long-wave radiation （28.27%）， and downward short-wave radiation （27.72%）.The meteorological factors that positively contribute to the enhancement of lake heatwave intensity are air temperature （13.25%）， wind speed （13.07%）， specific humidity （12.35%）， downward long-wave radiation （11.05%）， and downward short-wave radiation （10.98%）.Air pressure has an inhibitory effect on the increase in lake surface temperature， the total days of lake heatwaves， and the mean intensity.

The Yarlung Zangbo Grand Canyon region （YZGC） is an important water vapor transport channel on the Qinghai-Xizang Plateau， and the water vapor transport of the YZGC has an important impact on the weather and climate of the plateau.Based on the ERA5 reanalysis data and CN05.1 precipitation data from 1986-2021， this paper analyzes the water vapor transport characteristics of the YZGC during the summer monsoon and winter monsoon periods and studies its relationship with precipitation in Three-River Source Region （TRSR） during the plateau summer monsoon period.The results showed that： （1） The precipitation in the YZGC was more in the southeast and less in the northwest and showed an increasing trend in time， and the increase in the summer monsoon period was greater than that of the annual average and the winter monsoon period.The water vapor flux of the YZGC mainly comes from the southwest water vapor transport from the Indian Ocean to the Bay of Bengal， followed by the westerly water vapor transport from the southern branch of the mid-latitudes.（2） The south and west boundaries of the YZGC are the water vapor input boundaries throughout the year， and the east and north boundaries are the water vapor output boundaries， and the water vapor transport flux during the summer monsoon is stronger than that during the winter monsoon period.The YZGC is a positive area of net water vapor flux， and the net water vapor income shows a significant decreasing trend.（3） The low-level 1000~600 hPa originates from the Indian Ocean to the Bay of Bengal and the western Pacific Ocean， and the water vapor transport enters the plateau from the southern boundary of the YZGC， and the southern boundary is the main boundary of water vapor input.The upper layer is 600~300 hPa， and the middle and high latitudes are significant westerly water vapor transport， and the water vapor is mainly imported from the western boundary and exported from the eastern boundary.（4） There is a significant positive correlation between the water vapor flux of the YZGC and the precipitation in the central and eastern parts of the TRSR during the summer monsoon.Anomalous southeast water vapor transport from the Bay of Bengal， as well as anomalous southwest water vapor transport from the northern Bay of Bengal and the southwestern side of the plateau， enters through the western and southern boundaries of the YZGC， providing ample moisture to the central and eastern parts of the TRSR.The upward motion of this water vapor in the central and eastern TRSR leads to increased precipitation.

Extensive research has been conducted on daily scale precipitation the Hengduan Mountain.The hourly scale data， which provides additional insights such as diurnal patterns， remains largely unexplored.Therefore， a fundamental study of the characteristics of extreme precipitation at the hourly scale is essential in the Hengduan Mountain.In this study， we analyzed the spatial and temporal distribution characteristics of hourly extreme precipitation （95th percentile， R95） and very extreme precipitation （99th percentile， R99） using Multi-Satellite Retrievals for Global Precipitation Measurement （IMERG） half-hourly satellite precipitation data from 2001 to 2020.Furthermore， we explored further the contribution to the whole year of rainy and non-rainy seasons periods.The results showed that the distribution pattern of hourly extreme precipitation and hourly very extreme precipitation thresholds， amount， intensity， and duration were decreasing from southeast to northwest in the Hengduan Mountain， and the number was high in the east and west but less in the center.Hourly extreme precipitation and hourly very extreme precipitation amounts occupied 29.58% and 10.15% of the annual total amount， respectively.In the analysis of interannual variability， an increasing trend in the amount， number and intensity were found for hourly extreme precipitation and hourly very extreme precipitation， while the duration is generally showed a decreasing trend， with an increase in the amount of 4.93 and 2.83 mm annually， respectively.The amount experienced a significant increase in the northeastern part of the Hengduan Mountain.In terms of diurnal variations， the hourly extreme precipitation and hourly very extreme precipitation amount and number were concentrated at nighttime， with two peaks during 17:00 （Beijing Time， same as after） -21:00 and 00:00 -02:00.A discrepancy in the distribution of the maximum occurrence time were found in the northern and southern regions in the Hengduan Mountain.The increasing trend in the hourly extreme precipitation amount was primarily associated with an increase in number， which was more pronounced in the hourly very extreme precipitation.During the rainy season， the amount and frequency of hourly extreme precipitation and hourly very extreme precipitation accounted for over 90% and significantly influenced the annual pattern of characteristics.In contrast， during the non-rainy season， the maximum occurrence time of amount and number were delayed by 1 hour in the main region compared to the annual pattern.

By using conventional meteorological observations， ground densified automatic stations， ERA5 （0.25°×0.25°） hourly reanalysis and global topographic data， the differences between the characteristics and causes in snow depth of two extreme heavy snowfall events under the return flow pattern in southeastern Inner Mongolia on November 18 -19， 2020 （Process 1） and November 7 -8， 2021 （Process 2） were compared and analyzed， which can provide the certain references for improving the forecasting ability of heavy snowfall and its impacts in Inner Mongolia.The results show that： （1） The two processes occurred in the same season， with similar areas of heavy snowfall and 24-hour cumulative precipitation.Process 1 had a wider influence range， stronger snow intensity and rare freezing rain weather， while Process 2 lasted longer and had deeper snow accumulation， with 11 stations snow depth breaked the historical records.（2） Both Process 1 and Process 2 were caused under the effect of 500 hPa upper-level trough （vortex）， 700 hPa southwest jet stream， and 925 hPa northeast jet stream.Warm and humid air climbed along the cold air mass at the lower level， producing significant frontogenesis， and the combination of the mid-level front area and the low-level northeast reflux results in the extra large snowfall weather.（3） The intensity of the cold air at the lower level in Process 1 was weaker， the duration was shorter， while the intensity and thickness of the southwest airflow at the mid-level were stronger， resulting in a warmer and more humid mid-level atmosphere and deeper warm layer.The content of liquid water in the clouds at the mid and lower levels was significantly higher than that in Process 2， which conducived to the establishment of a melting layer.Snowflakes or ice crystals melt in the melting layer.In the early stage， it is freezing rain， and in the later stage， it falls to the ground in the form of wet snow.In Process 2， affected by the cold vortex， the system configuration was deeper， the lower-level atmosphere was relatively colder， the cold air mass was stronger and more persistent， which has no melting layer.The temperature conditions are suitable for the formation of flaky snowflakes in the air.After landing， it is mainly dry snow， which is more conducive to the formation of a larger snow depth.（4） At the initial stage of the snowfall， the near-surface temperature in Process 1 was above -1 ℃， and the surface temperature was around 0 ℃.Wet snow could not quickly freeze when it fell to the ground， and it was easy to form freezing rain with the near-surface temperature decreased.In Process 2， the near-surface temperature was -9 ℃ and the surface temperature was -3 ℃.The near-surface wind speed was weaker， which was conducive to the formation of snow accumulation when relatively dry large snowflakes fell to the ground.

Based on the ageostrophic dry Q vector （ {\mathit{Q}}^{\mathrm{D}}） partitioning method， combining with the ERA5 reanalysis data and the China Meteorological Administration （CMA） tropical cyclone best track data， the causes of offshore northward tropical cyclone （TC） gales in the coastal areas of Shanghai from 1981 to 2022 are diagnosed and analyzed.The results show that： （1） the stronger the wind force， the stronger the vertical upward motion， the lower the height of the strong updraft center and the thicker the vertical upward motion layer， which means the TC wind is closely related to the vertical motion within its circulation； （2） the range and intensity of the {\mathit{Q}}^{\mathrm{D}} vector divergence convergence area are correspond to the vertical upward motion zone during the gale process.The vertical upward motion center coincides with the {\mathit{Q}}^{\mathrm{D}} vector divergence convergence center.The stronger the vertical updraft is， the stronger the convergence intensity of the {\mathit{Q}}^{\mathrm{D}} vector divergence， which indicates that there is a good correspondence between the vertical upward motion in the area affected by the TC gales and the convergence zone of the {\mathit{Q}}^{\mathrm{D}} vector divergence； （3） the results of the {\mathit{Q}}^{\mathrm{D}} vector partitioning method show that during the period of TC gale， the convergence intensity of {\mathit{Q}}_s^{\mathrm{D}} and {\mathit{Q}}_n^{\mathrm{D}} vector divergence increases with the wind scale.For the same wind level， the convergence intensity of the {\mathit{Q}}_n^{\mathrm{D}}vector divergence is stronger than that of the {\mathit{Q}}_s^{\mathrm{D}} vector divergence.Furthermore， the higher the wind scale is， the more distinct the difference between the convergence intensity of the {\mathit{Q}}_n^{\mathrm{D}}and {\mathit{Q}}_s^{\mathrm{D}} vector divergence.In details， the different convergence intensity in the scale 10 wind region can be larger than the scale 7 wind region by two orders of magnitude， suggesting that the forcing of the mesoscale weather system is the main cause of the TC gales.The results of this study provide valuable guidance and have significant practical application value for the forecasting of TC gales.

Based on the observed precipitation data from 2010 to 2019 in the complex terrain region of southeastern Liaoning， this study identified 44 torrential rain events （TRECT）.By employing composite analysis methods and decomposing the lower-level wind field using flow-over and flow-around equations， the circulation precursors， common characteristics of circulation fields， and the dynamic impact mechanism·s of topography on regional torrential rain were systematically investigated.The results indicate that： Six days prior to the occurrence of TRECT events， the mid-troposphere over the Eurasian continent exhibited a blocking high pattern， followed by the eastward movement and development of a shallow trough near Lake Baikal.On the day of the event， the subtropical high moved northward and intensified， forming a slanting trough over the western part of the key area， with a closed cyclonic circulation appearing in the lower troposphere.The North China low-pressure system developed and moved eastward， positioning the key area at the top of the inverted trough， providing a favorable circulation background for widespread precipitation.During the peak period of the event， the flow over and around the terrain in the key area showed stronger southern and weaker northern characteristics， with high-value areas concentrated in the trumpet-shaped terrain region of the Changbai Mountain's foothills.Areas with flow-over speeds exceeding 4 m \cdots^-1 were located on the southern slopes of the low-altitude hills in the trumpet-shaped area， while flow-around was observed around the high-altitude mountains， with meridional branches of both flows playing a dominant role.The flow-over and flow-around entered the trumpet-shaped area by crossing and bypassing the mountains， respectively， primarily from two air stream·s originating from the Yellow Sea and the Korean Peninsula.In the trumpet-shaped area， the upward motion contributed by the flow-over accounted for more than 80% of the total system's upward motion， serving as the main dynamic source for precipitation enhancement.The flow-around， under the influence of topography， formed local positive vorticity， further enhancing the dynamic conditions for precipitation.This study systematically investigates the evolutionary characteristics of precursor large-scale circulation system·s associated with torrential rain events in the complex topography of the Changbai Mountain foothills， exploring atmospheric circulation precursors preceding extreme precipitation.Through mesoscale topographic dynamic forcing mechanism·s， it specifically elucidates the orographic lifting-convergence effect and flow-around vorticity development within the trumpet-shaped terrain of southeastern Liaoning Province.It provides a theoretical basis for improving the accuracy of regional mountain type rainstorm forecast.

This paper is mainly about the typical stable， low-motion， long-life warm southwest vortex rainstorm process on July 26-27， 2023.Based on the analytical field data of the Southwest Regional Model （SWC） and the precipitation data of weather stations， the paper studies the evolution of the horizontal and vertical structure of the southwest vortex at different stages of its life cycle and its relationship， in terms of space as well as time， with heavy precipitation.The research results are the following.First of all， there are five distinct stages within the life circle of the Southwest vortex causing the rainstorm on July 26， 2023： initial， development， peak， maintenance and decay.Secondly， the horizontal and vertical structures of the southwest vortex show asymmetric characteristics， and the dynamic and thermal structure of the low vortex differ in different evolution stages， thus affecting differently.In the initial phrase， the release of latent heat of condensation in the convergence uplift enhances the low vortex， and relies more on the transformation of the total potential energy to the kinetic energy， causing the low vortex to escalate.Since the strong dry cold air moving south weakens the transport of southerly warm humid wind and vapor， the atmospheric Stratified stability increases， and the low vortex attenuates accordingly.Finally， the synergistic effect of thermodynamic and dynamic forces is the main cause of the warm vortex rainstorm.The precipitation at the early stage of vortex development occurs in the warm and wet area around the vortex center， while that at the strong stage occurs on the side of the strong warm and wet airflow channel， with the intensity of precipitation corresponding well with that of vortex.Pseudoequivalent potential temperature and convergence are the key parameters indicating the precipitation area and intensity of the southwest vortex.

Under the background of global climate warming and rapid urbanization， extreme heat events have become a significant threat to human health and social sustainable development， particularly in Yangtze River Delta （YRD）， a densely populated and economically developed region.Based on meteorological observations from 1961 to 2020， this study systematically analyzes the trends of daily maximum temperature， daily mean temperature， and heat wave indices in the YRD.Additionally， sensitivity experiments using the WRF model are conducted to assess the impact of urban land use on extreme high temperature events.The results show that： （1） Both daily maximum temperature and daily mean temperature in the YRD have exhibited significant upward trends over the past few decades， with the increase in daily maximum temperature ［0.194 ℃·（10a）^-1］ being more pronounced than that in daily mean temperature ［0.187 ℃·（10a）^-1］.Pettitt test results indicate a significant change point in 1993， with temperatures showing a downward trend before the change point and shifting to an upward trend after the change point.（2） The frequency， duration， and intensity of heat waves have significantly increased at rates of 0.190 time·（10a）^-1， 0.475 d·（10a）^-1 and 0.772 ℃·time^-1·（10a）^-1， respectively， indicating that the frequency， duration and intensity of heat waves increased significantly.The change point for heat wave indices lags behind that of temperature change point and occurring in 2000.It showed an insignificant downward trend before the change point， and turning into a significant upward trend after the change.Intensity of heat wave increasing at a much higher rate than frequency and duration.（3） Urbanization has a significant impact on temperature and heat waves.The daily maximum temperature ［0.243 ℃·（10a）^-1］ and daily mean temperature ［0.261 ℃·（10a）^-1］ of urban stations being significantly higher than those of rural stations ［0.171 ℃·（10a）^-1、 0.167 ℃·（10a）^-1］， suggesting that urbanization has an amplifying effect on warming.The increasing trends of heat wave indices at urban stations are also significantly stronger than those at rural stations， indicating that urbanization may enhance the occurrence of heat waves.（4） The WRF model can effectively simulate the hourly variation of temperature， and urban land use significantly affect urban station temperatures， especially during hot days， with a more pronounced effect at night.Urban underlying surfaces enhance the surface energy changes of urban stations during hot days by changing the surface energy budget （such as sensible heat flux， latent heat flux and surface heat storage）， which intensifies the temperature during hot days， while rural stations are less affected by urbanization.This indicates that the urbanization process has a more obvious impact on extreme high temperature events in urban areas.The frequency， intensity and duration of heat waves in the Yangtze River Delta region have shown a significant upward trend in the past few decades， and urbanization has played an important amplifying role in this.With the further development of urbanization， the frequency and intensity of extreme high temperature events are likely to increase further， highlighting the necessity of developing effective adaptation strategies and mitigation measures.

Based on the topographic characteristics of the Yunnan-Guizhou Plateau， the objective standard index of the intensity of the Yunnan-Guizhou quasi-stationary front in winter is defined by using the FNL atmospheric reanalysis data of 24 years （2000-2023）， According to this index， the strong quasi-stationary front events are selected， the temperature， humidity and wind structure of the strong quasi-stationary front events were studied， and the characteristics of different types of strong quasi-stationary front events are compared and analyzed.The results show that： （1） the Yunnan-Guizhou Quasi-Stationary Front manifests as a dense band of isentropic lines （θ _se） in the mid-to-lower troposphere， with the frontal zone tilting eastward with increasing altitude and the gradient distributed in a north-south band.Strong quasi-stationary front events occur most frequently in January （39%） and February （33%）， and their occurrence frequency shows significant interannual variability.（2） Strong Quasi-Stationary Front is characterized by a dense band of isentropic lines （θ _se） at the junction of Yunnan and Guizhou.Within the frontal zone， the wind exhibits convergence between northeastern and southwestern winds， with high humidity areas located in the central and western parts of Guizhou to the east of the front.Below 700 hPa， there is a stark contrast between the notably warmer western region and the significantly cooler eastern region.Below 800 hPa， abnormal easterly winds appear in the eastern area and transition into upward motion around 750 hPa， leading to an enhanced upward transport of moisture.This， in turn， promotes an abnormal structure with upper-level moisture and lower-level dryness to the west of the front.（3） Based on the strength of the cold and warm air on either side of the stationary front， strong quasi-stationary front events are classified into two types： the Cold Anomaly in the East （CE， 75%） and the Warm Anomaly in the West （WW， 13%）.On the surface， the frontal position of WW-type events shifts slightly eastward compared to CE-type events.In CE-type events， the stronger cold anomaly extends westward to 104°E and upward to 750 hPa， while in WW-type events， the stronger warm anomaly extends eastward， with the cold anomaly limited to the east of 106°E and contracting downward below 850 hPa.Below 800 hPa， the abnormal easterly winds in CE-type events are stronger and extend higher than those in WW-type events， promoting more moisture to ascend along the terrain and be transported westward.As a result， the center of positive relative humidity anomalies in WW-type events is located further east compared to CE-type events.

The effects of initial soil temperature and moisture were explored by performing a series of 84-hour numerical simulations form 10 to 25 December 2023， using the WRF model with soil temperature and moisture initialized with CMA-GFS forecasts and the China Meteorological Administration Land Data Assimilation System （CLDAS） analysis respectively.It showed that the relative humidity （RH2m） and the temperature （T2m） at 2 m were poorly during the first 21-hour integration and getting better during the following time integration initialized with CLDAS than that with CMA-GFS， with a maximum root mean square error （RMSE） decrease of 8.3% and 10% respectively.Further diagonosis indicated that the first 21-hour integration usually a accompanied with more sensible and latent heat fluxes in case of the soil temperature and moisture initialized with CLDAS.It means that the model would take a longer spin-up time during which any satisfiable forecasted T2m and RH2m might not be gotten， due to the in consistanece in initial conditions which came from the different source datasets containing some more reliable variables although.Spatially， when the model was initialized with CLDAS， it represented much more favourable with smaller negative deviation of RH2m and positive deviation of the daily maximum T2m， which maximally decreased by 8% and 1.5 °C in Henan respectively， and unfavourable with larger positive deviation of the daily minimum T2m in the southern region of Shanxi and central Hebei.Whereas， it represented pretty well performance of daily maximum and minimum T2m and bad performance of RH2m with larger negative deviation in the northern region of northern Shanxi and northern Hebei.Among groups of initial soil conditions， the moister and colder initial soil group had the best forecasting performance of T2m which is tightly closed to the observation， and the moister and warmer initial soil group has the worst although the T2m difference between the simulations initialized with CLDAS and CMA-GFS is small.Compared with the initial soil temperature， the initial soil moisture has a greater impact on T2m.The drier initial soil would lead to a better forecasting performance of daily minimum T2m， accompanied with larger sensible heat flux and smaller latent heat flux in the integration.

With the rapid development of China's air transportation， the special meteorological conditions of plateau airports have increasingly highlighted the impact on flight safety.In particular， gales represent a critical meteorological factor that significantly impact both flight safety and operational efficiency in aviation systems.Utilizing ground observation data of Lijiang Airport from 2021 to 2023， along with ERA5 reanalysis data， we conducted an analysis on the temporal characteristics and formation mechanisms of surface gales at Lijiang Airport.The results show： （1） surface gales predominantly occur during the dry season， which spans from January to April each year.These gales tend to be concentrated between 05:00（UTC， the same as after） and 11:00 am on a daily basis.Notably， the peak period for strong winds occurs between 07:00 and 09:00 am， accounting for 54% of the total number of gales events.（2） The occurrence of gale events was usually accompanied by a significant change in wind direction， especially around 03:00 when the wind direction rapidly shifts from northerly to southerly， and the wind speed increases significantly thereafter.Therefore， airports should be prepared for runway switching before 03:00 am to avoid overshooting the tailwind due to sudden changes in wind direction， which would affect flight safety.During surface gales， even though the positive crosswind speed might not reach the threshold that restricts aircraft takeoff and landing， some extreme events， where the positive crosswind speed exceeds 10 m·s^-1， could still pose a threat to flight safety.（3） The analysis of physical quantity and circulation background fields revealed that the convergence of variable pressure winds， driven by the afternoon thermal lows， enhanced the vertical convective activity and destroyed the stable laminar knots in the lower atmosphere， and then induced the downward transmission of 500 hPa westerly jet momentum to form the surface gale through turbulent mixing.Furthermore， prior to the outbreak of the cold wave， the northern cold vortex accelerated the 500 hPa westerly airflow， further intensifying the surface gales.By analyzing the thermal and dynamic driving mechanisms of extreme surface gales， we had constructed a conceptual model of surface gales.This model provides a theoretical foundation for further enhancing the accuracy of wind warnings and improving flight safety assurance capabilities.（4） The wind shear characteristics exhibit distinct spatiotemporal patterns： during the phase of decreasing surface wind speed， wind shear weakens at 450~550 hPa while strengthening at 550~650 hPa.This variable feature provides an important reference for early warning of wind shear.

The WRF-Chem model （v4.4） was employed to simulate ozone （O₃） concentrations in the Haikou region of Hainan Province during the autumn of 2016 （September to November）， complemented by the FLEXPART-WRF model for backward trajectory analysis.The research aimed to quantify the contributions of physical and chemical processes to O₃ variations， examine the characteristics of regional transport， and identify potential source areas.Process analysis was applied to evaluate the influence of various mechanisms on O₃ concentration changes.Results indicated significant diurnal variation in the roles of chemical processes， vertical mixing and dry deposition.During the day， chemical reactions contributed an average of 11.5 μg·m^-3 to O₃ levels， with a peak of 17.8 μg·m^-3， while a net negative contribution was observed at night.Vertical mixing and dry deposition processes were major removal mechanisms during daylight hours but weakened considerably at night.Although advection transport had a relatively minor impact， its influence varied under different air mass origins.Cluster analysis of FLEXPART-WRF-simulated backward trajectories demonstrated that O₃ concentrations in Haikou were strongly affected by the direction of incoming air masses.Higher concentrations were associated with northern and northeastern air masses， while lower levels were linked to cleaner air masses from the southeast and south.Overall， chemical processes dominated the increase in O₃ concentrations， whereas vertical mixing and dry deposition processes served as the principal removal mechanisms.The contribution of advection transport to changes in O₃ concentration is relatively small.Potential source regions were further identified using the Potential Source Contribution Function （PSCF） and Concentration Weighted Trajectory （CWT） methods.Key source areas were located in the northeastern coastal regions and the southeastern part of Guangdong Province， contributing an average of 60~70 μg·m^-3 per month.These findings provide critical insight into the evolution of atmospheric composition in tropical coastal cities and offer a scientific basis for the development of regional air quality management strategies.

This study conducts a systematic comparative analysis of two extreme heavy rainfall events in Gansu Province， occurring in July 2022 （‘7·15’） and July 2024 （‘7·22’）， using multi-source observational data and reanalysis datasets combined with various diagnostic methods.The key findings are as follows： （1） The two events differed in 24-h cumulative precipitation， hourly rainfall intensity， and frequency of short-duration heavy rainfall.The ‘7·15’ event had greater cumulative rainfall and stronger instantaneous intensity， but its spatial extent of extreme rainfall （≥50 mm） and frequency of short-duration heavy precipitation were significantly lower than those of ‘7·22’.（2） Both events exhibited extreme characteristics.The ‘7·15’ event broke historical records for short-duration rainfall intensity at more stations than ‘7·22’， whereas the latter showed higher cumulative precipitation totals and more frequent short-duration heavy rainfall events.（3） Significant differences existed in short-duration precipitation metrics.The ‘7·15’ event had substantially higher proportions of moderate and heavy rainfall （44.55% and 10.68%， respectively）， with maximum 5-min and 1-h sliding precipitation reaching 30.9 mm and 93.6 mm.In contrast， ‘7·22’ was dominated by light rainfall （60.70%）， with only 8.68% heavy precipitation events and maximum 5-min/1-h accumulations of 15.3 mm and 83.6 mm.The ‘7·15’ event demonstrated more extreme precipitation characteristics and greater disaster potential.（4） The two events exhibited both similarities and differences in their dominant weather systems， moisture convergence， and thermodynamic/dynamic lifting conditions.Both were warm-sector convective heavy precipitation events triggered by the coupling of upper- and lower-level systems including the subtropical high， mid-to-low-level vortex shear， and surface convergence lines.While the ‘7·15’ event showed significantly weaker values than‘7·22’ in moisture convergence intensity， vertical convergence depth， moist layer thickness， frontogenesis， vertical updraft intensity， and CAPE， it demonstrated greater precipitable water throughout the atmospheric column at the rainfall core， stronger convective instability during intense precipitation， and higher vertical ascent heights during peak rainfall periods.

Based on automatic weather station observations of precipitation， ERA5 reanalysis data and NCEP GDAS data， through methods such as water vapor budget analysis， HYSPLIT backward trajectory tracking and water vapor transport contribution rate， this paper analyzed the water vapor transport characteristics of a severe rainstorm event that occurred in the southeastern part of Gansu Province from July 22 to 24， 2024， and quantitatively discussed its water vapor source and contribution rate.The results showed that the rainstorm area was located in the exit zone of the upper-level jet stream， where the airflow divergence enhanced the vertical transport of low-level water vapor， causing the moist layer deeper.The continuous synergic influence of Typhoon " Prapiroon" and the subtropical high transported water vapor over the South China Sea and the Bay of Bengal to the rainstorm area， providing sufficient water vapor， and the rainstorm area maintained a significant near-surface wet area and high precipitable water.The results of water vapor budget and tracking analysis showed that the inflow of water vapor mainly occurred at the southern boundary of 800~500 hPa， with a maximum inflow of 1237 kg·m^-1·s^-1.Before the rainstorm， the water vapor mainly originated from the South China Sea and the Bay of Bengal， and the water vapor channels accounted for 48% and 42% of all tracks respectively， and the water vapor transport contribution rate was 51.45% and 43.31% respectively.When the rainstorm occurred， water vapor mainly originated from the South China Sea， its water vapor channels accounted for 53% of all the tracks， and the contribution rate of water vapor transport was 57.98%.In addition， the water vapor transport in the Western Pacific and Northwest Passage also contributed to the rainstorm.This would be conducive to understanding the formation mechanism of the extraordinary rainstorm in Northwest China， and provided certain references for the future forecast of extraordinary rainstorm in Gansu Province.

From July 22nd to 24th， 2024， Gansu Province was hit by an extremely rare torrential rain in history.A total of 12 stations accumulated rainfall exceeding 300 mm， with the maximum reaching 351.4 mm.The overall intensity was the strongest in the northwest region since 1961.Based on the Precipitation observation data from Automatic Weather Station （AWS）， this study evaluated the CMA Multi-source Precipitation Analysis system in China （CMPA）， Radar Quantitative Precipitation Estimation （Radar-QPE）， Fengyun 4B Quantitative Precipitation Estimation （FY4B-QPE） and the European Centre for Medium Range Weather Forecasts Reanalysis v5 （ERA5） monitoring capabilities of four precipitation products during this extremely heavy rainstorm.The results showed that： （1） CMPA had the best performance in spatial distribution， which could accurately capture the precipitation and extreme value in the core area of rainstorm， with the least spatial variability， ME was only 0.002 mm·h^-1.Radar-QPE could identify the location of the rainstorm area， but underestimate the precipitation in the core area， FY4B-QPE significantly overestimates the precipitation in the core area， while ERA5 underestimates the precipitation in the core area， ME was respectively -0.151， 0.192 and 0.08 mm·h^-1.（2） CMPA was the most accurate in capturing time evolution with the smallest error， CORR was up to 0.999.Radar-QPE underestimated precipitation during heavy precipitation hours， and the error increased significantly with the increase of precipitation intensity， the errors of FY4B-QPE and ERA5 increased significantly during heavy precipitation hours， especially FY4B-QPE had worse behavior in the core area， CORR was respectively 0.96， 0.24 and 0.22.（3） The diurnal variation characteristics of CMPA and AWS were the closest.There were deviations in the peak value and distribution of precipitation in Radar-QPE.The peak position of FY4B-QPE was located to the east and north， and the precipitation time was advanced.There was no significant peak of ERA5 in the meridian direction， but showed a negative deviation in the zonal direction that was slightly northward.（4） CMPA and AWS were highly consistent in precipitation probability distribution， showing the best spatio-temporal consistency.Radar-QPE and ERA5 overestimated the first precipitation peak and underestimated the precipitation above 5.0 mm/h.FY4B-QPE underestimated weak precipitation and overestimates heavy precipitation.These results provided a detailed comparison of the monitoring capabilities of different precipitation products in rainstorm precipitation events， and offered a reference for the dynamic monitoring， early warning and hydrological application of rainstorm event.

Heavy rainfall is the main catastrophic weather in Longnan city， Gansu Province.The disasters caused by heavy rainfall do great harm to social and economic development and people's life and property.In this paper， the processes of the two strongest rainstorms since 1961 in Longnan city， "7·22" in 2024 and "8·14" in 2020， are taken as examples.Based on meteorological， disaster situation and geographic information data， the disaster causing processes of the two rainstorms and heavy precipitation are analyzed and compared by using the theory of natural disaster system.The results show that： "7·22" and "8·14" rainstorm processes have strong precipitation intensity， large cumulative rainfall， long duration of heavy precipitation and obvious extremity， which overlap repeatedly with the previous rainstorm areas， and are the main causes of disaster caused by "7·22" and "8·14" rainstorm processes.The population and economic losses caused by "7·22" and "8·14" rainstorm and heavy rainfall accounted for 8.5%， 6.5%， 35.8% and 45.2% of the total population and GDP of Longnan city， respectively."8·14" rainstorm and heavy rainfall disaster was significantly more serious than "7·22".The two process rainstorm disaster levels of severe grade occurred in Wudu district and Wenxian county， which are economically strong and populous in Longnan city.In the 9 counties of Longnan city， Wudu district and Wenxian county have the most hidden geological disaster points， the average slope and river network density are large， and the risk of disaster caused by heavy precipitation is high.As a result， the precipitation of Wudu district and Wenxian county is not the largest during the two heavy rains of "7·22" and "8·14"， but the disaster is the heaviest.