Permafrost have a critical impact on the infrastructure construction， hydrology and ecology in the cold region.Under the background of global warming， it is of great significance to explore soil freeze-thawing cycle over the Western China.Based on the natural geographical and permafrost characteristics， the western region of China is divided into four sub-regions as the study region of this investigation.The ERA-5 surface temperature， soil volumetric water content and monthly air temperature data from January 1981 to June 2020 are to be deployed in analyzing the spatio-temporal distribution of soil freeze-thawing status， the active layer thickness and maximum freezing depth over the western China in the past 40 years.the correlationship between variables of freeze-thawing cycles and air temperature and altitude are discussed.The results show that： the spatio-temporal distribution of the start date of freezing and thawing has the characteristics of delayed freezing and early thawing from high-altitude areas to low-altitude areas over the western region.The high-altitude northern Tibetan plateau freezes the earliest， thaws the last， and freezes the longest.The sporadic areas on the Kunlun Mountains can last for more than 300 days.The Tarim Basin in the west-northwest with low altitude and low soil moisture content freezes the latest， melts the earliest， and lasts the longest.The melting in the Taklimakan Desert can last for more than 280 days.The thickness of the permafrost active layer is basically more than 2.0 m， only the area near the Karakoram Mountains has a large area with a thickness of less than 2 meters.the seasonal frozen soil of the Qinghai-Tibet Plateau has the largest freezing depth， and the thickness can reach more than two meters， and the Tarim Basin shows a shallowest freezing depth， and the thickness is less than 0.6 m.The start date of freezing was delayed over the western region， and the start date of thawing was advanced.The date of start freezing and the date of completely frozen increased at a rate of 0.089 d·a-1and 0.061 d·a-1.The date of start thawing and the date of completely thawed decreased at a rate of 0.102 d·a-1 and 0.156 d·a-1.When the freezing trend is rising and the thawing trend is declining， the duration of completely thawed increased by about 12 days at a rate of 0.256 d·a-1， and the duration of completely frozen is shortened by about 11 days with a rate of 0.164 d·a-1， during the study period， the start date of completely thawed was mutated in 1996.The date of start freezing and the duration of completely thawed were abrupted changed in 1997.The overall change trend of the start date of the freezing and thawing is the same over the western region， but there are locally slight differences.The duration of start freezing and completely frozen of the Loess Plateau decreased the fastest at the rate of 0.166 d·a-1 and 0.405 d·a-1.The duration of start freezing and the duration of completely frozen were shortened by around 7 and 16 days.The trends in the duration of completely melt period in all four regions showed an upward trend.However， the duration of completely frozen rises rapidly at a rate of 0.435 d·a-1 over the Loess Plateau， and increase about 17 days during 1981 -2020.There is a significant correlation between the start dates of freezing and thawing and the annual average temperature and altitude.The correlation between the annual average temperature and all freeze-thaw times exceeded 0.79， and the negative correlation between the date of completely thawed and the annual average temperature was as high as 0.963.The start date of freezing was delayed by 2.03 days per 1.0 ℃ increase， the start date of complete freezing was delayed by 2.12 days， and the start dates of completely thawed and frozen were advanced by 5.10 and 5.17 days， respectively.The start dates of freezing and completely frozen are advanced by 6.1 days and 4.5 days per 1000 m rise in altitude， respectively， and the start dates of thawing and freezing are delayed by 14.4 days and 19.9 days， respectively.This research clarifies the situation of soil freezing and thawing and its variation in the past years over the western China， and provides a scientific supports for the ecological system and infrastructure construction over the western region.

The Tibetan Plateau Vortex （TPV） is an important kind of precipitation system over the Qinghai-Xizang （Tibetan） Plateau in summer， and TPVs can produce disastrous weather in the downstream area when they move off the Qinghai-Xizang （Tibetan） Plateau.Investigating the influence of early factors on the QXPVs in mid-summer can provide reference for the forecast of disastrous weather caused by QXPVs.Based on CERES radiation products， ERA-Interim reanalysis data， and QXPVs’ datasets， the relationship between the surface net cloud radiative effect in Spring and the QXPV in July during 2001 to 2017 was discussed by using correlation analysis， SVD analysis， composite analysis methods.The results show that when the cloud radiative heating effect in the central India in spring is stronger， and the cloud radiative cooling effect in eastern China and the West Pacific region is weaker （stronger） in the north （south）， the QXPVs in July （especially warm QXPVs） are more frequent， stronger， and easier to move out of the Qinghai-Xizang （Tibetan） Plateau.Cloud radiative heating effect in the central India in spring could increase the surface temperature and reduce the stability of the atmosphere， thereby increasing the mid- and low-level cyclonic circulation of the Indian Peninsula， which is conducive to the transportation of water vapor from the Bay of Bengal to the Qinghai-Xizang （Tibetan） Plateau and provides water vapor conditions for the QXPVs； At the same time， the high-level divergence is strengthened， which in turn causes the intensifying and eastward extension of South Asian High （SAH）， and cooperates with the low-level system to provide dynamic conditions for the QXPVs.The Cloud radiative cooling effect weaker （stronger） in the north （south） of the eastern China and West Pacific region could increase the temperature gradient to the north and south， enhances the low （high）-level convergence （divergence）， which is conducive to the intensifying and westward extension of the West Pacific Subtropical High （WPSH）， thereby increasing the transportation of water vapor from the West Pacific to the inland， and provides water vapor conditions for the QXPVs.According to the results of SVD analysis， three Cloud Radiative Effect Indexes （CREI） are defined， which have certain indicative significance for the characteristics of the QXPVs in July.The relationship between the different CREIs and the circulation field verifies that the CRE of the Indian （eastern China and the Western Pacific region） in spring mainly affects the water vapor transportation on the southern side of the Qinghai-Xizang （Tibetan） Plateau and the intensifying of the high-level SAH （WPSH） in July， which affects the favorable conditions for the generation and development of QXPVs in July.

利用NCEP-FNL再分析资料、FY-2G卫星相当黑体亮温TBB数据,通过WRF(V3.8.1)模式对2015年8月5—7日的一次高原低涡过程进行了4组模拟试验,研究了云辐射效应对高原低涡过程的影响.结果表明,云辐射效应主要通过改变云区的辐射分布影响大气稳定度,从而影响高原低涡的发展和结构.在低涡生成阶段,白天云辐射加热抑制低涡南侧的对流,从而有利于水汽和动量向低涡源地输送;夜间云顶长波冷却促进涡区的对流活动,有利于低涡的发展.低涡成熟阶段中,涡心及其周围区域夜间辐射冷却的水平和垂直分布利于涡心下沉、外围上升的垂直运动分布,并与云辐射效应构成正反馈过程,有利于涡眼结构的形成.在低涡快速东移阶段中,云辐射加热和冷却的昼夜变化调节着低涡的强度和东移速度,而当低涡东移出高原后,这种作用则变得不显著.