As a globally significant ecological security barrier and climate-sensitive region， the Qinghai-Xizang Plateau （QXP） plays a crucial role in regional and global carbon cycles. In recent years， climate warming and ecosystem changes have led to a complex pattern of concurrent strengthening and weakening in the plateau’s carbon sink capacity. To accurately assess the spatiotemporal patterns and mechanisms of carbon dioxide （CO₂） fluxes over QXP terrestrial ecosystems， researchers have established a flux observation network centered on eddy covariance techniques since the 1980s. This network now covers various surface types including grasslands， shrublands， wetlands， and lakes. The integration of satellite remote sensing and machine learning has further facilitated the upscaling from point-based measurements to regional estimates. Studies indicate that alpine meadows serve as stable and strong carbon sinks， with mean annual net ecosystem exchange （NEE） generally below -100 g·C·m⁻²·y⁻¹. In contrast， alpine steppes exhibit weaker sink strength， largely regulated by precipitation. Wetland and marsh ecosystems show high spatiotemporal heterogeneity in CO₂ fluxes， with hydrological dynamics and seasonal freeze-thaw processes driving their shifts between carbon sink and source states. Lakes on the plateau also act as carbon sinks， though the magnitude of CO₂ exchange varies significantly across lakes， reflecting integrated effects of climate， hydrology， and riparian vegetation. At the regional scale， grassland carbon sink strength is notably higher in the eastern and northeastern parts of the plateau compared to the arid west， indicating control by climatic and ecological factors such as temperature， precipitation， and vegetation productivity. High spatiotemporal resolution remote sensing products reveal an overall strengthening trend in the grassland carbon sink over the past several decades， primarily attributed to extended growing seasons and increased vegetation cover under a warming and wetting climate. However， several uncertainties remain， including sparse distribution of flux stations in western and high-altitude regions， large parameter discrepancies among flux models， inadequate representation of carbon emissions in permafrost zones， and a lack of systematic assessment of land use change impacts on CO₂ fluxes. Moreover， interannual variability in ecosystem productivity and soil respiration introduces additional complexity in quantifying the long-term carbon balance of the plateau. Future studies urgently need to integrate multi-source observation technologies-such unmanned aerial vehicles， satellite remote sensing， and subsurface monitoring-to enhance long-term monitoring of land-atmosphere feedbacks and ecological processes， and develop mechanism-based models that couple human activities with ecological responses. These advances will provide a scientific foundation for improving the accuracy of carbon sink estimates on the plateau， understanding its dynamics， and supporting China’s “Dual Carbon” strategy.

This study evaluates ERA5 and MERRA2 reanalysis datasets against OMI and MLS observations to assess their performance in representing the spatial distribution， vertical structure， and temporal evolution of ozone over the Qinghai-Xizang Plateau during 2005 -2023， with an emphasis on dynamic transport within the summer ozone valley core. Both datasets capture the seasonal ozone valley， with minima in summer and maxima in winter. ERA5 generally outperforms MERRA2 in reproducing total column ozone， with biases within ±1 DU， whereas MERRA2 exhibits systematic winter underestimation exceeding -5 DU. Vertically， ERA5 better reproduces the 100~50 hPa core， while differences at the 30 hPa secondary minimum are minor， mainly reflecting variations in formation mechanisms and assimilation strategies. In terms of temporal evolution， ERA5 more accurately reproduces total column ozone trends， whereas MERRA2 better captures concentration trends within the 100~50 hPa core， especially during spring and summer. Zonal transport reduces ozone and strengthens the valley， whereas meridional transport partially compensates； MERRA2 overestimates transport intensity， particularly zonal transport， resulting in lower core concentrations. Divergence analysis reveals decreasing zonal and increasing meridional contributions， producing an overall rise in total transport. This pattern aligns with MLS observations and confirms the dominant role of dynamic processes in maintaining UTLS ozone minima. Overall， both datasets reproduce the ozone field effectively， though they differ in representing core intensity and temporal trends. Mid-to-upper layer biases are influenced by vertical resolution and assimilation coverage， with MERRA2 more sensitive to satellite gaps. Differences also arise from chemical and dynamical coupling that ERA5 better reproduces climatological averages， while MERRA2 more accurately captures local temporal variations. ERA5 is thus preferred for studies of climatological ozone characteristics， whereas MERRA2 is more suitable for analyzing temporal evolution.

To evaluate the applicability of air temperature data from three reanalysis datasets （ERA5， JRA-55， and MERRA-2） in the northern part of the Eastern Kunlun Mountains and its different subregions， this study used daily mean temperature observations from 28 national meteorological stations in the northern part of the East Kunlun Mountains during 1980 -2023. The air temperature data from the reanalysis datasets were corrected using a lapse-rate correction method. Four evaluation indicators， namely the correlation coefficient （CC）， mean bias （MB）， root mean square error （RMSE）， and mean absolute error （MAE）， together with the climatic tendency rate， were used to assess the applicability of annual and seasonal air temperature from the three reanalysis datasets at regional and station scales. The results show that： （1） Bilinear interpolation outperformed nearest-neighbor interpolation. After lapse-rate correction， the mean absolute value of MB of the three reanalysis datasets decreased by 0. 92~1. 81 ℃， and the RMSE decreased by 0. 69~1. 34 ℃. （2） After lapse-rate correction， all three reanalysis datasets reproduced the spatial distribution characteristics of mean air temperature in the study area， namely higher values in the east and lower values in the west， with the lowest values in the northeast， although overestimation occurred in some areas. （3） At the regional scale， ERA5 showed the best applicability. JRA-55 ranked second， while MERRA-2 showed the poorest applicability. Only the spring climatic tendency rate of ERA5 was higher than that of the observations； the remaining values were lower than the observed values. All three datasets showed a warming pattern characterized by stronger warming in summer and weaker warming in winter. （4） At the station scale， JRA-55 showed the best applicability. ERA5 ranked second， while MERRA-2 showed the poorest applicability. The annual and seasonal climatic tendency rates of the observations， ERA5， and JRA-55 were mostly concentrated within 0. 30~0. 60 ℃·（10a）^-1， whereas those of MERRA-2 were mainly concentrated within 0. 15~0. 30 ℃·（10a）^-1. Overall， the climatic tendency rates of the three reanalysis datasets were generally lower than those of the observations， and all exhibited a warming pattern of stronger warming in summer and weaker warming in winter. （5） The applicability of the three reanalysis datasets varied among different subregions. ERA5， JRA-55， and MERRA-2 performed best in the eastern agricultural region， the area around Qinghai Lake， and the Qaidam Basin， respectively. All three datasets captured the subregional warming pattern of stronger warming in summer and weaker warming in winter. The observations showed that the warming trend was ranked as follows： eastern agricultural region， where strong warming occurred at Tongde and Datong and the annual and seasonal climatic tendency rates at Tongde were ≥0. 97 ℃·（10a）^-1， followed by the Qaidam Basin， where strong warming occurred at Mangya， and then the area around Qinghai Lake. ERA5 showed warming trends closer to the observations in the area around Qinghai Lake and the eastern agricultural region and thus performed the best， followed by JRA-55， while MERRA-2 showed the poorest applicability. （6） For the northern part of the Eastern Kunlun Mountains， ERA5 should be prioritized for regional climate analysis， whereas JRA-55 should be prioritized for refined studies at the station scale.

This study investigates the spatiotemporal changes in temperature and relative humidity in the Northwest Region of China under future climate change scenarios， and estimates the frequency and duration of heatwave events in the area.The study employs the Weather Research and Forecasting model （WRF） to perform dynamical downscaling simulations using the National Centers for Environmental Prediction （National Centers for Environmental Prediction - Department of Energy Atmospheric Model Intercomparison Project II Reanalysis， NCEP-DOE Reanalysis 2） data during the baseline period.For the future period， dynamical downscaling is applied to the bias-corrected data from the Coupled Model Intercomparison Project Phase 6 （CMIP6） under the Shared Socioeconomic Pathway 5-8.5 （SSP5-8.5）.By analyzing temperature and relative humidity changes in the northwest region of China during the baseline period （2012 -2020） and under the SSP5-8.5 scenario for the future （2046 - 2055）， the study further explores the occurrence of heatwave events.The results indicate that： （1） The baseline simulation adequately captures the temperature and relative humidity patterns in the northwest region， with an overall cold bias in temperature and a dry bias in relative humidity.（2） Compared to the baseline period， the multi-year average temperature in the future period rises by 3.3±0.7 ℃， while the average relative humidity decreases by 7.8%±1.3 %， indicating a shift towards a "warm-dry" climate under high-emission scenarios.（3） Heatwaves are projected to intensify during the future simulation period， with an expanded affected area.Significant occurrences are expected in Xinjiang， western Inner Mongolia， western Shaanxi， Gansu， Ningxia， and central Qinghai， with an average increase of approximately 5 heatwave events per year and an average duration increase of about 60 days per year in these regions.Xinjiang's Turpan remains the most severely affected area by heatwaves in northwest China.

Under the background of global climate warming， compound drought and heatwave events （Compound Drought and Heatwave， CDHW） are having a profound impact various regions worldwide with increasing frequency， intensity， and duration.Based on the daily temperature and precipitation data from 1961 to 2021 in Inner Mongolia， we employed a daily-scale standardized index to identify different CDHW events in the study area.Subsequently，we analyzed the temporal and spatial evolution characteristics and influencing factors of various CDHW events using climate tendency rate， partial correlation analysis and geographic detectors.The results show that： the duration， frequency，drought intensity and heatwave intensity of the four types of CDHW events in Inner Mongolia from 1961 to 2021 increased gradually from the southwest to the northeast； The characteristic indicators of the four types of CDHW events exhibited an upward trend，with significant increases observed in the intersection type （d-and-h） and the heatwave conditioned on droughttype （h-cond-d） events； The correlation between precipitation and the changes in the four types of CDHW events was found to be high， with over 97% of the significance tests indicating a significant relationship； Soil type and downward shortwave radiation at the surface were identified as the main driving factors for the duration and frequency of different types of CDHW events.Moreover， the interaction between various driving factors showed an enhanced explanatory power for duration and frequency， with a greater impact observed on duration.

A persistent heavy rainfall event occurred in the Sichuan Basin from July 11 to 13， 2023， with the maximum cumulative precipitation reaching 656.5 mm， matching the historical record， while the second-highest cumulative precipitation reached 650.4 mm， breaking the station's observational record.The torrential rain triggered secondary disasters such as flash floods， landslides， and debris flows， resulting in significant losses.This study utilizes dense surface automatic precipitation observation data， Wenjiang sounding data， ERA5 reanalysis data， and FY-4A satellite Brightness Blackbody Temperature （TBB） data to analyze the atmospheric circulation background and physical mechanisms of this persistent heavy rainfall event.The results indicate that the South Asian High dominated over Sichuan， while the Western Pacific Subtropical High （WPSH） remained stable on the periphery of Sichuan and upper-level trough moved eastward.Continuous moisture transported from the South China Sea and the Bay of Bengal into Sichuan Basin， which provided ample water vapor for the heavy rainfall.Significant low-level warming and moistening in the western Sichuan Basin enhanced atmospheric instability.The large-scale circulation background created favorable conditions for the occurrence of the persistent heavy rainfall.On the evening of July 10， airflow inertial oscillation generated a low-level jet over the eastern Yunnan-Guizhou Plateau， which enhanced wind speed and moisture advection into the basin.The southeasterly flow， obstructed by the western mountains， induced frontogenesis and moisture convergence ahead of the foothills， leading to convective instability.The airflow ascended along the mountain slopes， forming a vertical circulation cell over the basin.Orographic lifting and this vertical circulation jointly triggered convection.The persistent southeasterly flow， mechanically blocked by the terrain， generated northerly winds in front of mountain， which converged with the southeasterly winds and formed a shear line， promoting organized convective development.The trumpet-shaped terrain and canyon topography enhanced precipitation.From July 11 to 12， the intensification of WPSH blocked the eastward movement of the southern branch flow and the trough from the plateau.This process， superimposed with the jet stream transport from the eastern Yunnan-Guizhou Plateau， resulted in enhanced convergence over the southern basin， triggering the development of Southwest Vortex.Latent heat release provided thermal condition for the development of the Southwest Vortex， while divergence and vertical transport supplied the dynamic conditions.Guided by the WPSH’s peripheral flow and influenced by latent heating， the southwest vortex moved westward， triggering vigorous convective activity.In the early hours of July 13， an eastward-moving upper-level trough guided cold air to move southward along the western basin.The convergence of cold and warm air produced intense frontogenesis， triggering precipitation in the pre-frontal warm sector.The intensification of cold air enhanced the development of the cold front and prolonged the lifespan of the Southwest Vortex， resulting in increased rainfall intensity and a significant eastward expansion of the heavy rainfall area.

To evaluate the performance of numerical weather prediction （NWP） models over complex terrain and improve warm-season （May-October） precipitation forecasting over the Western Sichuan Plateau， this study assesses four models—ECMWF， CMA-GFS， CMA-MESO， and SWC-WARR—using 116 heavy rainfall events during 2022 -2024. Based on REOF regionalization and dominant circulation classification， the models are evaluated with traditional categorical scores， Fractions Skill Score （FSS）， and Method for Object-Based Diagnostic Evaluation （MODE）. Results show that the global model ECMWF has the highest overall TS and FSS scores and the lowest false alarm rate in northwestern Sichuan， but significantly underestimates extreme rainfall intensity. CMA-GFS performs well in intensity forecasts for plateau vortex-type events and accurately locates rainfall for plateau trough-type and plateau shear-line-type events. Among regional models， CMA-MESO has a higher hit rate， while SWC-WARR shows the best spatial pattern matching. Both perform better in the complex terrain of southwestern Sichuan for mesoscale processes such as high-pressure influence-type and dual-high shear-type events. However， they present obvious systematic biases， including overestimated rainfall areas， significant wet biases， and earlier predicted precipitation onset， leading to higher false alarm rates and lower TS scores. The diurnal peak of FSS appears at 11:00 -14:00 （Beijing Time）， caused by the overlap of early regional model forecasts and late global model forecasts with observed afternoon convection. Cross-section analyses indicate that wet biases result from overestimated mid-low-level humidity， excessive orographic lifting， displaced moisture convergence centers， and positional errors of key weather systems. Premature low-level convergence during the convective initiation stage is the main cause of early forecast onset. For operational applications， large-scale processes should refer to ECMWF/CMA-GFS to determine rainfall ranges， while mesoscale convective centers should rely on CMA-MESO/SWC-WARR. It is recommended to shrink the rainfall areas and delay the predicted onset time of regional models by 2~4 hours to fit the observed afternoon convective characteristics over the Western Sichuan Plateau.

To further improve the forecast accuracy of strong gusts and mitigate the disaster risks they pose， this study utilizes 24 h forecast 10m wind field data from the European Centre for Medium-Range Weather Forecasts （ECMWF） deterministic model spanning January 2022 to December 2023， as well as concurrent hourly observations of maximum gust speed and direction from ground stations operated by the China Meteorological Administration （CMA）. Focused on 358 national observation stations in Sichuan and its surrounding regions， this study proposes a novel gust parameterization method based on mean wind components following a systematic analysis of the limitations of the traditional gust factor method. Widely adopted in operational forecasting due to its simplicity and strong practicality， the traditional gust factor method exhibits substantial underestimation of strong gusts in Sichuan and adjacent areas. This limitation stems primarily from inherent forecast errors in numerical models， unbalanced distribution of sample data， and failure to account for gust forecast discrepancies induced by variations in mean wind components. To address this underestimation issue， this study develops a gust parameterization method based on the numerical model's 10 m u and v wind forecasts for individual stations. Specifically， observed gust wind directions are first adjusted to align with model-predicted directions， eliminating the interference of directional mismatches on gust speed forecast accuracy. For different sign combinations of the model-predicted 10 m u and v components， gust factors at designatedquantiles are calculated separately for the squared u and v components of direction-adjusted observed gusts and the squared u and v components of model-predicted winds. This approach fully incorporates the influence of differences in 10 m u and v wind components on gust forecasts while reducing biases in strong gust fitting caused by unbalanced sample distribution. Independent sample testing is conducted using data from January to November 2024， with comparative analyses of multiple gust forecast methods. The results demonstrate that three key measures-calculating gust factors based on designated quantiles， constructing a parameterization model using mean wind components， and performing wind direction alignment-can all effectively reduce the underestimation of strong gusts. In the evaluation of metrics such as forecast error and accuracy， the proposed method outperforms other approaches in strong gust forecasting. Notably， the contributions of the first two measures to mitigating strong gust underestimation are greater than those of wind direction alignment. Case validation during a cold air-induced strong wind event in March 2024 further confirms the superiority of the proposed method over the traditional gust factor method. Additionally， a comparative analysis is performed against the 3 hour maximum gust forecast product from the ECMWF deterministic model， a commonly used tool in operational forecasting. The results show that for gusts ≥13. 9 m·s⁻¹， the proposed method achieves higher forecast accuracy than the ECMWF model product. However， the mean error and mean absolute error of the proposed method in this wind speed range are slightly higher than those of the ECMWF model. This is primarily because the 10 m wind field data used in this study are model forecasts at instantaneous time points， which fail to fully capture the hourly variability of wind fields driven by transient meteorological processes. In future research， hourly maximum wind speed and corresponding direction forecast data from mesoscale numerical models will be integrated with the proposed method to further improve the forecast accuracy of strong gusts.

To understand the complex wind patterns in Urumqi， which is a gorge city on the northern slope of the Tianshan Mountains， the study set up three Doppler wind lidars at different altitudes along the city's north-south direction. These instruments operated simultaneously throughout the winter season of 2023 to 2024. The reliability of wind lidar data was validated through comparison with synchronous radiosonde data. The vertical structural variations of wind fields in the southern， central， and northern parts of the city were then analyzed in conjunction with air pollution changes. The results revealed that wintertime PM_{2. 5} concentrations in Urumqi exhibited a distinct north-to-south decreasing gradient. The urban area experienced 50 days of lightly polluted or worse conditions， 7 of which were severe， highlighting the acute wintertime pollution challenge. The wind speed and direction data from the Doppler wind lidars exhibited strong correlation （R>0. 95） with the sounding data， with only minor deviations observed. This finding serves to substantiate the reliability of the scanning lidar-derived measurements. The airflow over Urumqi exhibits a distinct three‐layer structure： below 500 m， winds are predominantly northerly （valley breezes） or westerly； between 500 m and 2000 m， southeasterly foehn winds prevail； and above 2000 m， the flow is dominated by northwesterly winds. Shallow foehn winds occur throughout the city， but both the depth and wind speed of foehn airflow exhibited a marked south-to-north attenuation. Valley winds prevailed in Urumqi from 13:00 to 20:00 （Beijing Time， hereafter）. While the northern urban area exhibited the thickest valley airflow （up to 800 m）， both the duration and wind speed of these winds were significantly lower than those observed in the southern and central sectors of the city. During the winter months， the southern urban area exhibited ascending flows， in contrast to the subsiding motions observed in the central and northern sectors. However， all regions demonstrated weak vertical velocities. On days when air quality was optimal， northwesterly winds predominate， with an increase in wind speed with increasing altitude. As levels of pollution increase， the altitude of low-level weak winds （<2 m·s^-1） rises， leading to stagnant near-surface conditions； simultaneously， the valley wind layer weakens in both height and strength， while the foehn flow intensified markedly and its jet core descended. Examination of the low-level wind field showed that severe pollution events are characterized by a 70% occurrence frequency of low near-surface wind speeds. When combined with the intense foehn-driven inversion， this leads to localized pollutant accumulation and trapping.

Global warming has increased the frequency and intensity of drought and heatwave events， exerting profound impacts on socioeconomic development.Based on meteorological observation data and reanalysis data in the warm season （May to September） from 1961 to 2022 in the Yangtze River Basin， this study compares and analyzes the climatic evolution characteristics of heatwaves， droughts， and drought and heat wave compound events（CDHEs）.The possible causes and differences influencing the three types of events are preliminarily investigated， with the main conclusions as follows.In terms of spatial distribution， the frequency and duration of heatwaves are the highest in the Three-River Headwaters region （upper reaches） and the Yangtze River Delta （lower reaches）， exceeding 2 times·a⁻¹ and 13 d·a⁻¹， respectively.Droughts and compound drought-heatwave events occur more frequently and last longer in the Sichuan Basin and near the main stem of the Yangtze River.The duration of droughts is about nine times that of heatwaves， while the frequency of droughts is only 0.6~0.8 times that of heatwaves.The frequency and duration of compound events are relatively low in the southern middle and lower reaches， whereas both heatwaves and droughts occur frequently over the western Sichuan Plateau.From 1961 to 2022， heatwave events， drought events， and CDHEs in the Yangtze River Basin have generally shown an increasing trend， except for the duration of drought events.The most rapid increase occurred in the upper reaches， with a significant and enhanced trend in extremity since the beginning of the 21st century.The correlation coefficients between the intensity of the Western Pacific Subtropical High （WPSH） and the South Asia High （SAH） and heatwave events reach up to 0.472 and 0.484， respectively.A westward-shifted， larger， and stronger WPSH， as well as a stronger and northward-shifted SAH center， correspond to longer durations of heatwaves and compound events， especially in the upper reaches， whereas the correlations with droughts are weak.Higher sea surface temperatures （SST） in the Tropical Indian Ocean correspond to longer durations of drought and heatwave events in the Yangtze River Basin， with a more significant impact on heatwave events in the upper reaches， where the correlation coefficient exceeds 0.5.Lower SST in the equatorial Pacific is associated with shorter durations， except for droughts.In addition， drought heatwave compound events in the upper reaches were dominated by surface sensible heating before the 21st century， and by latent heat release afterward.In the middle and lower reaches， latent heat release from surface evaporation plays a leading role.The duration of heatwaves shows a stronger correlation with land surface processes.

Rainfall-induced disasters in Xinjiang are extremely severe. A comprehensive understanding of the relationship between hourly extreme precipitation and heavy rainfall occurrence in Xinjiang is essential for improving the monitoring and early warning capabilities for extreme precipitation events. Based on station-based hourly precipitation observations， this study analyzed the spatiotemporal characteristics of hourly extreme precipitation， 12-hour heavy rainfall， and the contribution rate of hourly extreme precipitation to 12-hour heavy rainfall. Furthermore， in combination with terrain factors， the effect of altitude and slope on the contribution rate were investigated. The results indicate that the proportion of hourly extreme precipitation was the highest in June， accounting for 27. 61% of the total， while it was the lowest in September， accounting for only 9. 39%. The amount of hourly extreme precipitation during 08:00（Universal Time， the same as after） -19:00 was significantly greater than that during 20:00 -07:00 of the following day， with hourly extreme precipitation occurring predominantly between 10:00 and 12:00. During 08:00 -19:00， high-value areas of hourly extreme precipitation were mainly distributed in the southwestern Ili Kazakh Autonomous Prefecture， western Bortala Mongolian Autonomous Prefecture， western Urumqi City， and northern Altay Prefecture. During 20:00 -07:00 of the following day， although the overall precipitation amount decreased， relatively high precipitation amounts remained in western Urumqi City and northern Altay Prefecture， while the high-value area in Ili shifted eastward. The spatiotemporal distribution of 12-hour heavy rainfall was similar to that of hourly extreme precipitation， and the two exhibited evident synchronicity during the evolution of precipitation. The contribution rate of hourly extreme precipitation to 12-hour heavy rainfall was the highest in July， with a median value of 79. 35% and a mean value of 69. 69%. In contrast， the contribution rates in May and September were not only relatively low but also highly variable， indicating that 12-hour heavy rainfall during these months was more likely to be formed through the accumulation of moderate-intensity or persistent precipitation. High contribution-rate areas were mainly distributed in mountainous regions and their surrounding areas. Compared with the period from 20:00 to 07:00 of the following day， altitude and slope had a stronger influence on the contribution rate during 08:00 -19:00. During 08:00 -19:00， high contribution-rate areas were primarily concentrated in regions at mid-low altitudes （1000~1500 m） and gentle slopes （2°~5°）， whereas during 20:00 -07:00 of the following day， they were mainly concentrated in low-altitude regions （<1000 m） with gentle slopes （2°~5°）.

The Panxi Plateau serves as a critical transitional zone from the eastern margin of the Qinghai-Tibet Plateau to the Sichuan Basin， forms a "plateau-plain" step-transition belt with the Chengdu Plain.Due to its dramatic topographic relief and complex underlying surface properties， the plateau exhibits significant spatial heterogeneity in soil resistivity.It has become one of the most lightning-active areas with the highest disaster risks in southwestern China.Lightning activity in this region is modulated not only by large-scale circulation systems （the South Asian Summer Monsoon， Plateau Monsoon） but also closely linked to meso- and microscale convective processes induced by local topographic ascent and underlying surface inhomogeneities.Currently， research on the response regularities and driving mechanisms of lightning activity in this transition zone to key geographical factors such as altitude and soil resistivity remains inadequate， with a particular lack of quantitative modeling and regional comparative analysis based on long-term observational data-thus failing to meet the targeted needs of lightning disaster protection under complex topographic conditions.This study， based on ADTD Lightning Location System data， digital elevation data， and soil resistivity data in Sichuan Province from 2010 to 2020， adopts spatial overlay analysis and quadratic polynomial regression methods， takes the typical geographical unit of the Panxi Plateau and the Chengdu Plain as the research object， and conducts research on the response regularities of lightning activity to key geographical parameters （altitude， soil resistivity， terrain-circulation synergistic effect）.The study results reveal that： （1） Cloud-to-ground （CG） lightning activity exhibits a distinct parabolic relationship with altitude （R²>0.79）， with distinct regional heterogeneities in its response characteristics.In the Chengdu Plain， CG lightning frequency shows a monotonic decreasing trend with increasing altitude， primarily due to high lower-atmospheric humidity that suppresses convective development-resulting in more active lightning activity in low-altitude regions.In the Panxi Plateau， by contrast， under the synergistic effect of topographically forced ascent and local instability energy， a peak in CG lightning frequency occurs within the 1500-3000 m altitude range.This reflects the differential modulation of the unique thermodynamic and dynamic configuration of the plateau-basin transition zone on lightning occurrence processes.（2） Soil resistivity is a key factor governing the spatial differentiation of CG lightning activity.In the Chengdu Plain， the proportion of CG lightning in the medium-resistivity zone （250-500 Ω·m） reaches 87.9%， with a density of 2.67 flashes·km^-²·a^-1； in the Panxi Plateau， the proportion of CG lightning in the high-resistivity zone （>500 Ω·m） is 94.8%， with a density of 1.57 flashes·km^-²·a^-1.This finding indicates that limited charge diffusion in high-resistivity regions facilitates the formation of strong electric fields， enhancing the probability of CG lightning occurrence and exhibiting a distinct charge accumulation threshold effect.Further analysis demonstrates an additional distinct positive correlation between soil resistivity and CG lightning intensity-particularly in the Panxi Plateau， where the intensity of positive CG lightning is significantly enhanced under high-resistivity conditions.（3） The multi-factor coupling interaction of terrain-resistivity-circulation is distinct.The average density of total lightning in the Chengdu Plain is 1.16 times higher than that in the Panxi Plateau， yet lightning intensity exhibits regional variations： the peak currents of positive and negative CG lightning in the Panxi Plateau are higher， primarily driven by a synergistic mechanism involving strong charge accumulation （attributed to unique thermodynamic and dynamic conditions） and high resistivity that inhibits leader propagation （requiring greater breakdown energy）.This study not only advances understanding of lightning formation mechanisms under complex terrain， but more importantly， provides a critical theoretical basis for lightning disaster risk zoning and lightning protection design in Southwest China.

Based on conventional meteorological observations， ERA5 upper-air reanalysis data， FY-2G infrared cloud imagery， and FY-4A satellite cloud-top brightness temperature （TBB） data， this study employed the mesoscale WRF model to perform a numerical simulation and diagnostic analysis of a shear-type warm sector rainstorm that affected Fujian， Jiangxi， and adjacent regions during 13-14 June 2022.The results indicate that： （1） the low-level shear line was the primary mesoscale system responsible for the development of the rainstorm， and its eastward intensification played a key role in triggering the convective systems associated with the heavy rainfall； （2） a pronounced monsoon surge associated with the monsoon trough and its eastern flank supplied abundant moisture， enhancing the southwesterly warm-moist airflow， which converged with the northwesterly dry-cold airflow guided by the upper-level trough over the southeastern Wuyi Mountains， thereby initiating strong convection； （3） the rainstorm occurred under favorable stratification and vertical circulation conditions， where the continuous transport of low-level warm-moist air， together with pronounced upper-level divergence and low-level convergence， induced vigorous vertical ascent， sustained instability in the mid-lower troposphere， and continuously triggered new convective cells， maintaining persistent heavy rainfall； and （4） The WRF model adequately reproduces the spatial and temporal distribution characteristics of precipitation， with a TS score of 0.33 and a bias of 0.79 for 24-hour accumulated precipitation at the heavy rainfall level （≥50 mm）.Furthermore， potential vorticity effectively captured the dynamical and thermodynamical characteristics of the event， with high potential vorticity anomaly regions corresponding spatially to the rainstorm area， and the rainstorm center frequently located to the south of the high-value anomaly zones.

The observation data collected from four gradient stations during the warm and humid seasons （May to September） spanning from 2019 to 2022 in the scientific observation experiment on the southern slope of Daguan Mountain， Chongqing， are used to analyze the spatiotemporal characteristics of precipitation along the mountain gradient and its relationship with the terrain. The results are as follows： （1） the monthly variation of precipitation amount shows a single - peak pattern， which is consistent with the activities of the East Asian summer monsoon. Both the monthly and daily variations of precipitation amount and precipitation frequency are significantly positively correlated with altitude. （2） The daily variations of precipitation amount and precipitation frequency show a double-peak pattern in the early morning and evening， while the daily variation of precipitation intensity shows a single-peak pattern in the early morning. High （low） altitude stations have more （less） precipitation amount and higher （lower） precipitation frequency， but the strong precipitation centers are scattered （concentrated）. （3） The terrain thermal circulation （upslope and downslope winds） drives the diurnal changes in precipitation peaks. The upslope wind formed by the solar radiation in the morning leads to the primary precipitation peak. In the evening， radiation cooling turns upslope wind into downslope wind， causing convergence and uplift at the valley bottom and resulting in a secondary peak in precipitation. （4） The invasion of cold air prior to precipitation leads to a drop in temperature and an increase in pressure. The lower the altitude， the more obvious the temperature drop. （5） In the Daguan Mountain region， the rainfall regime is dominated by frequent short-duration events that occur most often around midnight. Long-duration events， however， contribute over 80% of the total rainfall amount. Furthermore， the frequency of short-duration events increases with altitude， but the cumulative rainfall from long-duration events exhibits a decreasing trend with elevation. This study provides a scientific basis for improving precipitation forecasting in complex terrain.

High-precision precipitation data are crucial for watershed water resource management， ecological conservation， and hydrological modeling.However， existing satellite remote sensing precipitation products have relatively low spatial resolution in complex terrain regions， making it difficult to accurately capture the spatial heterogeneity of precipitation.Therefore， this study takes the Three-River Source Region as the research area and， based on the widespread applicability of Tropical Rainfall Measuring Mission （TRMM） products， first employs Geodetector to analyze the explanatory power of ten environmental factors on precipitation spatial distribution， including Normalized Difference Vegetation Index （NDVI）， Actual Evapotranspiration （AET）， Land Surface Temperature （LST）， Wind Speed （WS）， Total Cloud Cover （TCC）， Digital Elevation Model （DEM）， Slope， Aspect， longitude （Lon）， and latitude （Lat）.The study also explores the enhancing or weakening effects of factor interactions to provide scientific basis for data input in downscaling models.Subsequently， Geographically Weighted Regression （GWR） and Multiscale Geographically Weighted Regression （MGWR） models are constructed to enhance the spatial resolution of TRMM precipitation data from 0.25°×0.25° to 1 km×1 km， and the downscaling accuracy of the two models is compared.The research results indicate： 1） Based on Geodetector results at monthly， seasonal， and annual scales， seven environmental factors with strong influence on precipitation spatial distribution in the Three-River Source Region are selected as input variables for MGWR and GWR models， namely NDVI， WS， AET， Slope， TCC， LST， and DEM.2） Downscaling result evaluation based on data from 12 stations shows that TRMM precipitation products have high applicability in the Three-River Source Region.The MGWR model outperforms the GWR model in terms of R²， BIAS， and RMSE indicators， particularly showing higher downscaling accuracy in the comparison between dry and wet years.The MGWR model performs better than the GWR model across monthly， seasonal， and annual scales， reducing errors in TRMM precipitation products to some extent.Especially in high precipitation areas and topographically complex regions， the MGWR model can more precisely capture precipitation spatial details， and its bandwidth optimization strategy reveals the scale differences of various environmental factors.3） In different topographic and geomorphological regions （Lancang River Source， Yellow River Source， Yangtze River Source）， the overall goodness of fit of MGWR downscaling results exceeds 0.85 in all three source regions， demonstrating the applicability and accuracy of this method under diverse terrain conditions and different precipitation levels.The Geodetector-MGWR downscaling framework constructed in this study can effectively enhance precipitation spatial resolution in complex terrain regions.

Based on Southwest Vortex cases documented in the Southwest Vortex Yearbook from 1998 to 2021， this study analyzed the source region characteristics and precipitation patterns of eastward-moving Southwest Vortices using ERA5 reanalysis data and CHM_PRE daily precipitation datasets.The formation conditions of heavy precipitation associated with eastward-moving Southwest Vortices were investigated through dynamic composite analysis， examining both the circulation patterns and spatial structure of the vortex systems.The principal findings are as follows： （1） For eastward-moving Southwest Vortices， vortex genesis occurs predominantly over the Sichuan Basin， followed by the Jiulong and Xiaojin regions.The genesis regions of eastward-moving Southwest Vortices exhibit a relatively concentrated spatial distribution， with preferential development in the western and northern sectors of the basin， as well as the eastern portions of the Xiaojin and Jiulong areas.（2） Eastward-moving Southwest Vortices are characterized predominantly by extended lifespans， with precipitation zones tracking the vortex center trajectory and primarily affecting the Sichuan Basin， the middle and lower reaches of the Yangtze River， and regions to the south.Eastward-moving Southwest Vortices produce intense precipitation， with only 2 out of 35 cases classified as light to moderate rainfall， while the remainder reach heavy rain intensity or above.Among these vortices， 12 cases exhibited heavy precipitation centers located on both the northern and southern sides of the trajectory， classified as the north-south precipitation pattern； 20 cases showed heavy precipitation centers positioned on the southern side of the trajectory， classified as the southern precipitation pattern.（3） Composite analysis of the circulation patterns associated with both heavy precipitation types of Southwest Vortices reveals that in the middle troposphere， both patterns are influenced by northwesterly flow on the northern flank of the Tibetan Plateau and southwesterly flow ahead of the Bay of Bengal trough on the southern flank.These two airstreams converge east of the plateau to establish westerly steering flow that guides the eastward propagation of Southwest Vortices.The north-south precipitation pattern exhibits stronger low-level southwesterly flow and a more intense Bay of Bengal trough compared to the southern pattern， resulting in enhanced moisture transport toward the Sichuan Basin and Yangtze River valley.In the Southwest Vortex circulation associated with the north-south precipitation pattern， the robust upper-level South Asian High is positioned farther north， creating stronger divergence at the tropopause over the basin and enhanced upward motion through low-level convergence coupling， which facilitates precipitation extension northward of the vortex center， thereby establishing the north-south precipitation distribution.（4） Composite analysis of the spatial structure of eastward-moving Southwest Vortices indicates that the low-level vortex exhibits a quasi-circular horizontal distribution， with pronounced asymmetry between major and minor axes during the mature stage.The vortex displays a characteristic thermal structure with cold air in the lower levels and warm air aloft， while a strong upward motion center is located in the southeastern quadrant of the vortex.The key differences between the two vortex types are as follows： the north-south precipitation pattern features more abundant low-level moisture， stronger positive vorticity centers， and more pronounced coupling between low-level convergence and upper-level divergence.These enhanced dynamical and moisture conditions synergistically promote precipitation intensification and facilitate the northward extension of the precipitation zone beyond the northern periphery of the vortex.

Numerical models play an important role in clarifying seeding agent diffusion， rain enhancement mechanisms and effectiveness evaluation.By using a mesoscale model with AgI seeding process， sensitivity experiments of numerical simulation on rain enhancement by silver iodide （AgI） seeding for convective-embedded stratiform clouds on May 3， 2023 in Shangqiu， Henan Province are conducted.The AgI seeding agent diffusion， interactions with cloud microphysics and rain enhancement mechanisms， as well as sensitivity experiments with various seeding location and seeding amount are investigated.The results indicate that the supercooled water content distributes dispersedly in stratiform clouds with embedded convection， with higher content in the embedded convection region.When seeding AgI in a location with higher AgI nucleation rate in temperature and higher supercooled water content， there is an apparent reduction in supercooled water content and increase in cloud ice， resulting in increases in snow and graupel in clouds and the rainfall on the ground.Sensitivity experiments show that the temperature of seeding location， supercooled water content and seeding amount are all critical to the surface rain enhancement.The optimum seeding method for rain enhancement should be conducted in a location where the temperature meets the threshold for AgI nucleation with higher supercooled water content and appropriate agent amount is seeded.For convection-embedded stratification clouds， if seeding in embedded convection where the temperature cannot meet the AgI nucleation threshold， the seeding agent can be efficiently transported by updraft to the upper-level low-temperature region where nucleation can take place， enhancing the precipitation at the surface.

To reveal the activity patterns of mesoscale convective systems in the northwestern Sichuan Basin under the influence of typhoon peripheries and to improve meteorological support for airport aviation safety and low-altitude economic operations， this study analyzes a thunderstorm with heavy rainfall at Mianyang Airport on July 11， 2025， induced by the outer circulation of Typhoon "Danas". Using multi-source data-including automated observations from Mianyang Airport， FY4A satellite imagery， dual-polarization weather radar， and ERA5 reanalysis-and applying synoptic diagnostic analysis and short-term nowcasting techniques， this work systematically investigates the triggering and development mechanisms of the event， with the aim of supporting aviation safety and low-altitude meteorological services. The results indicate that： （1） the event was initiated by the combined influence of the outer circulation of Typhoon "Danas" （the 4th typhoon of the year） and local circulation patterns. Key factors included the northward and westward extension of the 500 hPa subtropical high， a trough over Xinjiang guiding cold air southward， enhanced easterly flow at 700 hPa supplying abundant moisture， and a surface convergence line that served as a crucial trigger for convection. （2） Pre-event sounding data from Wenjiang Station revealed strong convective potential， with a CAPE of 2547. 5 J·kg^-1， CIN of 0， a K-index of 44. 7 ℃， and significant vertical wind shear. Dynamically， the coupling of upper-level divergence and lower-level convergence promoted deep ascent. Thermally and in terms of moisture， high pseudo-equivalent potential temperatures at 700 hPa and 850 hPa， considerable whole-layer moisture flux， and relative humidity exceeding 90% at 500 hPa provided ample energy and moisture for convective development. Moist potential vorticity analysis showed a negative MPV1 center in the lower layers before the event， offering an indicator of convective initiation. （3） FY4A satellite imagery detected a mesoscale convective cloud cluster northeast of the airport one hour before the event. The cloud-top brightness temperature reached 215. 78 K prior to thunderstorm onset， corresponding to the active stage of severe convection. Variations in cloud cluster morphology and cloud-top brightness temperature helped identify the developmental phase of the convection. （4） Dual-polarization radar observed a bow echo with 60 dBZ reflectivity 20 km east of the airport before thunderstorm initiation. It moved westward at 20 km·h^-1 and eventually covered the airport， with an echo top reaching 7 km. Radial velocity patterns， including positive-negative velocity couples， adverse wind regions， and meso-β-scale convergent cyclones and divergence signatures， corresponded to different stages of the convective process. Based on these findings， a three-tiered forecasting system-covering medium-short-term， short-term， and nowcasting timeframes-was developed for severe convection at airports. By integrating multi-source data， the system allows accurate prediction and early warning issuance. It offers a scientific basis for forecasting and warning of airport severe convection induced by typhoon outer circulations， effectively reducing operational risks and enhancing both airport efficiency and low-altitude flight safety.

In order to verify the availability of wind profiler radar （WPR） data in in the Jiulong Area on the southeastern margin of the Qinghai-Xizang Plateau， improve the application value of WPR data in plateau area. This study systematically compares horizontal wind profiles from WPR and Southwest Vortex radiosonde observations with four times daily ［02:00 （Beijing Time，the same as after）， 08:00， 14:00， 20:00］ of the Jiulong Area from 2015 to 2022. Two temporal matching strategies （single-timepoint and multi-timepoint smoothed data） were employed to assess data consistency. The results reveal： （1） the WPR data acquisition rate exhibits a vertically non-monotonic pattern （decline-rise-sharp decrease）， with diurnally varying effective detection heights （valid data ratio： 0. 8）， peaking at 20:00 and reaching minimum at 08:00. （2） The WPR and radiosonde data showed strong correlation， which was further improved by temporally averaged WPR data. （3） Vertical stratification is evident， upper-level WPR-radiosonde correlations strengthen with altitude， whereas lower-level wind components show superior stability. Temporally averaged data significantly improve the quality of u and v components below 3000 m， but only marginally improve wind direction estimates. （4） The differences in the u， v components and wind direction between both WPR schemes and the radiosonde data approximately follow a normal distribution. Comparative analysis across different times indicated that the data quality of the u and v components was optimal at 08:00， whereas the largest errors in wind direction occurred at 14:00. （5） The frequency distributions of wind direction and speed from both WPR schemes were generally consistent with those from the radiosonde. The temporally averaged WPR data showed closer agreement with the radiosonde derived winds. However， both schemes slightly underestimated the frequency of southeasterly winds compared to the radiosonde， with this discrepancy being most pronounced at 14:00.