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

Abstract Mesoscale convective systems (MCSs) are important air water sources to the Three‐river‐source (TRS) region known as the “Chinese water tower.” Using hourly equivalent blackbody temperature (TBB) data from geostationary satellites of Chinese Fengyun‐2 series during the warm season (May–August) in 2005–2020 and an objective algorithm, MCSs in the TRS are divided into meso‐α (MαCS), meso‐β (MβCS), and meso‐γ (MγCS), and MαCS and MβCS are subdivided into larger meso‐α (LMαCS), smaller meso‐α (SMαCS), larger meso‐β (LMβCS), and smaller meso‐β (SMβCS). Results show that a high‐frequency zone of MCSs in the TRS distributes along the source of the rivers. Most MCSs, except LMαCS, develop and dissipate in situ. The interannual variation in MCS frequency exhibits a decreasing trend, especially after 2013, mainly due to the decrease in MCSs in the source region of the Yellow–Lancang River. The occurrence of MCSs peaks in August, but MCSs are most likely to produce precipitation in July and usually generate between 1600–2200 h LST (UTC + 8). The precipitation caused by MCSs to the total precipitation (precipitation ratio, PR) accounts for about 40%; MCS PR is closely related to, and increases with, the horizontal scale of the MCS, with MαCS PR being the highest, exceeding 67%. The contribution of MCSs to precipitation is mainly reflected in weak precipitation, smaller than 10.0 mm/h. Most of the maximum precipitation of MCSs appears after MCSs reach their prime, with the maximum lag by MαCS up to 2 h.

Using conventional high-altitude detection， automatic weather station observations， radar detection and ERA-Interim Reanalysis， and the numerical simulation model on May 4， 2020， in the northeast of Yunnan-Guizhou plateau rare large hailstones （70 mm diameter， the breakthrough at present since the record of Guizhou can query the hail history） process is analyzed and simulated.The analysis shows that this rare hail weather occurred in the background of favorable environmental conditions， such as high CAPE and appropriate wet-bulb temperature 0 ℃ layer height， the warm zone before an upper trough.The synoptic system is a meso-γ isolated convective system called supercell storm.The storm is a classic supercell storm on the Doppler weather radar， and the vertical accumulated liquid water content （VIL） up to 105 kg·m-2 is an important reason for the formation of this rare large hail.The convergence line excitation and the development of small vortices are the trigger causes of supercell storm formation.The near surface cold pool is the main factor to promote the development and enhancement of supercell.The results of numerical simulation show that the supercell quickly strengthen when it reach Yangqiao， vertical rising movement of more than 15 m·s-1.Deep vorticity pairs appear in the cloud， and the positive vorticity band corresponds to the rising movement.The hailstone growth layer has a large content， which plays a key role in the development of supercell storms and the growth of hail.

Abstract Cloud vertical structure (CVS) has important influence on cloud radiative effect and atmospheric circulation, especially for the third pole of the world–the Tibetan Plateau (TP). However, the characteristics and formation mechanism of the CVS over the TP are not well understood. This study revealed the characteristics and formation mechanism of the CVS over the southeastern Tibetan Plateau (SETP) in summer using the radiosonde datasets and the ERA5 data sets during June–August from 2015 to 2021. Results show that SETP is cloudy for 71% of the summertime with 73% of the clouds single–layered and 27% multi–layered. Multi–layer cloud occurs more frequently over the eastern SETP. With the number of cloud layers increases, the vertical range of cloud increases but the layer thickness and the inter–layer distance decrease. Water vapor, ascent, circulation and vertical wind shear are important factors for CVS formation. Single–layer cloud tends to form when the strengthening of the water vapor and the ascent is most significant at 400 hPa. In comparison, a stronger South Asian High (SAH) brings more water vapor and stronger ascent to the upper level, helping form the upper cloud and favoring the two–layer cloud structure. Three–layer cloud is likely to form when the upper–level vertical wind shear strengthens and the ascent between the middle and low cloud layer weakens. This study deepens the scientific understanding of the characteristics and formation mechanism of the CVS over the TP, and provides scientific reference for modeling the cloud–climate feedback process over the plateau.

Recent years have witnessed contrasting trends in summer total rainfall (STR) over the Tibetan Plateau (TP), with an increase in the northern and a decrease in the southern TP. This study identifies four significant centers of rainfall trends: eastern TP (“region A”), Qiangtang Plateau (“B”), Qaidam Basin (“C”), and the northern foothills of the Himalayas (“D”). Heavy rainfall dominates STR trends in regions A and D, accounting for 55.6% and 52.0%, respectively. In region B, moderate and light rainfall contribute almost equally, accounting for 37.3% and 44.8% of the STR trend, respectively. Region C is primarily influenced by light rainfall, explaining 71.2% of the STR trend. Notably, the contributions of different rainfall intensities to STR in each region vary annually, with region A experiencing more heavy rainfall, region B having moderate dominance but less light rainfall, and region C and D showing reduced and increased light rainfall contributions, respectively. Mechanistically, the strengthening of the upper-level westerly jet and the South Asian High, coupled with changes in moisture transport and convective available potential energy, collectively cause variations in rainfall intensity, characterizing the spatial heterogeneity in STR in the TP.

Abstract A 62‐day “extremely violent Meiyu” occurred in the Yangtze River basin from June to July in 2020, and its abnormal precipitation caused serious losses to the social economy. In this paper, the characteristics of newly formed mesoscale convective systems (MCSs) and the environmental conditions affecting the MCS formation during this abnormal precipitation event are investigated based on hourly datasets, including the temperature of brightness blackbody (TBB) data derived from the FY‐2F geostationary meteorological satellite, and the three‐source merged precipitation products from China Meteorological Administration. The results show that there were 31,778 times of short‐duration heavy precipitation (hourly precipitation exceeding 20 mm) occurred in the Yangtze River basin from June to July in 2020. The 69.3% of short‐duration heavy precipitation (hourly precipitation exceeding 20 mm) are closely related to the MCSs. The increase of newly formed MCSs leaded to more short‐duration heavy precipitation. The abnormal precipitation in the Yangtze River basin from June to July is mainly caused by elongated MCSs with an average lifetime of 6 h. The number of the newly formed MCSs presents obvious diurnal variations, with the most frequent at 20:00 (Beijing Time, the same below). The newly formed MCSs are prone to appear near the Yangtze–Huaihe shear line, and the magnitude of southerly wind at 500 hPa determines the distance between the MCSs and the shear line. The enhancement of vorticity advection at 500 hPa and water vapor convergence are conducive to the MCS formation. The weakening of low‐level jet corresponds to the increase of newborn MCS.

Based on conventional observation data,NCEP/NCAR reanalysis data,wind profiler radar and other intensive observation data,the evolution and structural characteristics of dry and cold air during Meiyu period in 2020 and its role in heavy rain are analyzed. The following conclusions are obtained. 1) The rainfall in Meiyu period begins to strengthen under the "single resistance" circulation pattern,and reaches its maximum under the "double resistance" circulation pattern. After the collapse of the "double resistance" situation,it gradually comes to an end. The weakening of the polar vortex,the accumulation of cold air in the south of 80°N,and the southward invasion with the disturbance of middle and high latitudes are the favorable conditions for the enhancement of precipitation. 2) During the Meiyu flood season,the activity of dry cold air in the middle troposphere is more obvious than that in the lower troposphere. The period of strengthening northerly wind at 500hPa corresponds well to the precipitation process. 3) The superposition of positive and negative circulation on both sides of the Meiyu front and the ascending branch of the secondary circulation,the divergence of the north-south wind in the upper troposphere and the convergence area in the middle and low-level jointly strengthen the dynamic uplift over the Meiyu front. 4) The wind profile radar observation and the mixed evolution of dry and wet air masses show that the invasion of dry and cold air in the middle and upper levels and the development of warm and wet air flow in the middle and low layers form a "wet dry wet" humidity stratification over the rain area,which enhances the convective instability stratification. After the invasion of dry and cold air,the dry and cold downdraft and the warm and wet updraft cause the convergence and rotation to rise,which is conducive to the formation of cyclones and the enhancement of precipitation.

The Tibetan Plateau shear line (TPSL) is an important precipitation-inducing synoptic system over the Tibetan Plateau and its downstream areas, and also a significant part of Tibetan Plateau meteorology. This paper reviews the research advances of TPSL in the last decade, including the spatiotemporal distribution of the TPSL and its relationship with heavy rainfall, the TPSL's structure characteristics and evolution mechanism, the interaction between the TPSL and the Tibetan Plateau vortex, etc. On this basis, the main aspects of TPSL research in the future are prospected in order to deepen the understanding of TPSL and provide reference for scientific research as well as forecasting and warning of disastrous weather over the Tibetan Plateau and its downstream areas.

The characteristics of diurnal variation of the surface sensible heat flux (SH) over the Tibetan Plateau (TP) are comprehensively investigated by using the long-term dataset of integrated land–atmosphere interaction observations (2006–2016) on the TP. Results show that the diurnal variation of SH shows obvious seasonal variabilities in terms of amplitude, duration, and peak time. At the Muztagh Ata Westerly Observation and Research Station (MAWORS), the Ngari Desert Observation and Research Station (NADORS), and the Qomolangma Atmospheric and Environmental Observation and Research Station (QOMS), the SH diurnal amplitude is consistently the largest in spring, followed by summer and autumn, and the smallest in winter, with a peak at 15:00. However, for the Southeast Tibet Observation and Research Station (SETORS), the amplitude in winter is rather violent with the peak at 12:00. We find that positive SH at most stations has the longest duration from May to August. Moreover, the peak time fluctuates from month to month, even showing a shift at the QOMS before and after 2015, and the double-peak phenomenon of SH mainly occurs in spring and autumn. Additionally, magnitudes of calculated SH with the conventional heat transfer coefficient (CDH) of 0.004 are about 64–100% larger than those of directly observed SH at the QOMS and the Nam Co Monitoring and Research Station (NAMORS). We here additionally recommend a new CDH values of about 2.24 × 10−3 in spring and 2.78 × 10−3 in summer, respectively, to more accurately calculate the TP SH.

In this research, the observation datasets from 106 gauge stations over the central and eastern areas of the Tibetan Plateau (TP) and the ERA (ECMWF Re-Analysis)-Interim reanalysis datasets in the summers of 1981–2016 are used to study the characteristics and synoptic patterns of extreme precipitation events over the TP. By using a modern statistical method, the abnormal circulation characteristics at high, middle, and low latitudes in the Northern Hemisphere during extreme precipitation events over the central-eastern Tibetan Plateau are discussed, and the physical mechanisms related to the extreme precipitation events are investigated. The results show that the largest amount of extreme precipitation is found in the southern and eastern areas of the TP, where the frequency of daily extreme rainfall events (exceeding 25 mm) and the frequency of all extreme precipitation events both show obvious quasi-biweekly oscillation. When the daily extreme precipitation event threshold over the TP is met and more than 5 stations show daily extreme precipitation at the same time, with at least three of them being adjacent to each other, this is determined as a regional extreme precipitation event. As such, 33 regional daily extreme precipitation events occur during the summer periods of 1981–2016. According to the influence system, the 33 regional extreme precipitation events can be divided into three types, namely the plateau trough type, the plateau shear line type, and the plateau vortex type. For the plateau trough type, the South Asian high is anomalously strong at 100 hPa. For the other two types, the South Asian high is slightly weaker than usual. For the plateau shear line type, the development of the dynamic disturbance is the strongest, reaching 200 hPa. In the plateau trough type and plateau vortex type, the water vapor is transported by the westerly belt and the southwesterly flow from the Bay of Bengal.

With the increasing integration of wind farms and electric vehicles (EVs) in power systems, voltage stability is becoming more and more serious. Based on vehicle-to-grid (V2G), an efficient power plant model of EVs (E-EPP) was developed to estimate EV charging load with available corresponding response capacity under different charging strategies. A preventive control strategy based on E-EPP was proposed to maintain the static voltage stability margin (VSM) of power system above a predefined security level. Two control modes were used including the disconnection of EV charging load (‘V1G’ mode) and the discharge of stored battery energy back to power grid (‘V2G’ mode). A modified IEEE 14-bus system with high penetration of wind power and EVs was used to verify the effectiveness of preventive control strategy. Simulation results showed that the proposed strategy can not only improve the static voltage stability of power system with considerable wind generation, but also guarantee the travelling comfort for EV owners.

Based on ERA-Interim data from June to July during 1981–2016 and daily meteorological dataset of China Surface Meteorological Stations (V3.0), 10 typical Yangtze-Huaihe cold shear lines (YCSL) over eastern China (28°~34° N, 110°~122° E) in summer are selected, and the structural characteristics of the YCSL during the evolution process are investigated by the composite analysis. The results indicate that the YCSL is horizontally in a northeast–southwest direction and vertically inclines northward from the lower layer to the upper layer. The vertical extension of the YCSL can reach 750 hPa, and its life time is about 54 h. The evolution process of the YCSL is affected by the comprehensive configuration of the high-level, medium-level, and low-level weather systems. The southward advancement, strengthening, and eastward movement of the north branch low-pressure trough over the Yangtze-Huaihe region at 850 hPa is a key factor for the evolution of the YCSL. Because the structural characteristics of the YCSL have obvious changes in the evolution process, the evolution process can be divided into the development stage, strong stage, and weakening stage. In terms of dynamic structures, the YCSL corresponds well with the axis of the positive vorticity belt, whose center is located at 850 hPa, and reaches the maximum in the strong stage. The YCSL is located in the non-divergence zone, and there are strong convergence centers located on its south side. The YCSL also locates in the ascending motion zone between two secondary circulations on the north and south sides, with the maximum ascending velocity in the strong stage, and its large-value area presents an upright structure. In the development stage, there is an ascending motion along the YCSL, but in the strong and weakening stages there are an ascending motion below 800 hPa and a descending motion above 800 hPa along the YCSL. In terms of thermal structures, the YCSL is located in the low temperature zone of the lower layer, and there is a high temperature zone around 500 hPa. Due to the dominant role of dry and cold airflow from the north, the YCSL locates in the dry and cold air during the development and strong stages, and then the warm and moist airflow from the south invades, resulting in the weakening of the YCSL. There is a convective unstable layer on the south side of the YCSL and a neutral layer on the north side. The water vapor gathers near the YCSL, and there are two water vapor convergence centers on the east and west sides of the YCSL, respectively. The water vapor convergence zone is mainly below 600 hPa in the low troposphere and the convergence center is located at around 900 hPa. The atmospheric baroclinicity is one of the reasons for the northward inclination of the YCSL.