Studying the impact of precipitation on PM_2.5 mass concentration in different regions can provide an important scientific support for the air quality assessment and forecast as well as pollution prevention in this region. Based on the hourly precipitation observation data and PM_2.5 mass concentration monitoring data in five typical cities (Chengdu, Leshan, Yibin, Mianyang and Dazhou) of Sichuan Basin from 2016 to 2021, the scavenging effect of precipitation processes on PM_2.5 was analyzed in different cities from some aspects including the occurrence time, duration, intensity of precipitation and the initial mass concentration of PM_2.5. The results show that the proportion of positive scavenging processes of precipitation on PM_2.5 increases with the increase of precipitation intensity or initial mass concentration of PM_2.5 in Sichuan Basin, and the scavenging rate rises. Under the condition of air pollution, the scavenging effect of precipitation with intensity exceeding 1 mm·h^-1 on PM_2.5 improves obviously in Sichuan Basin, and the scavenging rate reaches 35.0%. The scavenging effect is positively correlated with the duration of precipitation processes, and the scavenging rate of precipitation processes with the duration more than 3 hours is 9.0%-18.0% higher than that of precipitation processes with the duration less than or equal to 3 hours. The probability of positive scavenging processes is higher in the early morning and afternoon in Sichuan Basin, and the precipitation processes in the early morning have better scavenging effect on PM_2.5. In comparison, the proportion of positive scavenging processes is higher in Leshan and Yibin after the precipitation, and under different initial mass concentrations of PM_2.5, the scavenging rate is significantly higher than that in other cities with the increase of precipitation duration.

This paper addresses the spatial and temporal variation of cloud cover at different heights over southern China and its relationship with precipitation, which is useful for understanding the role of clouds in precipitation and feedback mechanisms as well as provides a basis and foundation for the development of cloud water resources. Based on 12 years (1998-2009) data from the D dataset of International Satellite Cloud Climatology Project (ISCCP), the temporal and spatial distribution characteristics of total cloud cover, low cloud cover, medium cloud cover and high cloud cover were analyzed over Southern China. And based on the CMORPH-AWS merged gridded precipitation product which combined National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center (CPC) morphing technique (CMORPH) with precipitation observations from automatic weather stations, the relationships between the cloud cover and precipitation intensity, precipitation frequency were analyzed over southern China. The results are as follows: (1) The spatial distribution of total cloud cover and medium cloud cover over southern China was similar. The high-value center was located over the junction of Sichuan Basin, Guizhou and Chongqing, while the low-value center was located in Yunnan. High clouds were distributed in the western part of southern China, and decreased from west to east. Low clouds were mainly distributed over the southeastern part of southern China. Overall, low cloud cover decreased from coastal area to inland area. (2) The seasonal variation of total cloud cover and high cloud cover was similar, with cloud cover more in summer and less in winter. Moreover, the high value center of total cloud cover shifted with the seasons. The high cloud cover changed seasonally. The moderate cloud cover and low cloud cover were more in winter and less in summer, with small seasonal changes. (3) With the increase of total cloud cover and high cloud cover, the precipitation intensity increased but the monthly precipitation frequency decreased. With the increase of medium cloud cover, the frequency of monthly precipitation increased, while effect on precipitation intensity varied little. (4) With the increase of cloud cover of stratocumulus and stratus clouds, precipitation intensity and monthly precipitation frequency decreased. With the increase of cloud cover of altocumulus, altostratus and deep convection clouds, precipitation intensity increased while monthly precipitation frequency decreased. In general, cloud cover and precipitation were closely related over southern China, especially total cloud cover and high cloud cover had a greater influence on precipitation intensity and precipitation frequency, while medium cloud cover only had a greater impact on precipitation frequency. The cloud cover of stratocumulus, stratus, altocumulus, altostratus, deep convection clouds had a greater influence on precipitation intensity and precipitation frequency, while cloud cover of cirrus and cirrostratus only had a greater impact on precipitation intensity.

Based on the monthly cloud dataset of ISCCP D2 from January 1994 to October 2009, the temporal and spatial distribution characteristics of total cloud amount, cloud water path and cloud optical depth over five regions of China were analyzed in detail. The results are as follows: (1) The most liquid-phase cloud distributed over Sichuan Basin to southeast coast of China, while the most ice-phase cloud distributed over northern China and Tibet Plateau. The coverage of cirrus was the widest, and its cloud amount was the biggest over China, followed by cirrostratus, liquid-phase altostratus, liquid-phase cumulus, and the low cloud with ice-phase was the smallest. (2) The total cloud amount, cloud water path and cloud optical depth of stratocumulus, nimbostratus with liquid-phase and deep convective cloud were bigger, which indicated that the cloud water contents were rich, their contributions were bigger to precipitation over Sichuan Basin to southeast coast. (3) The seasonal variations of total cloud amount with different types were obvious over China, and their performances were different over five regions of China. The total cloud amount of most liquid-phase clouds especially nimbostratus was more in summer and less in winter over northern China and Tibet Plateau, while it was less in summer and more in winter over southwestern China and southeastern China. However, the regional difference of cloud amount with ice-phase was little, and the cloud amount of ice-phase altocumulus and altostratus was more in winter and less in summer over most regions, while that of ice-phase cirrostratus and deep convective cloud was more in summer and less in winter, which indicated that the temperature declining and convection weakenning were benificial to gather of ice-phase clouds and development to medium and low layers in winter, while the temperature increasing and convection strengthening were benificial to gather of liquid-phase clouds and development to high layer in summer. (4) The cloud water path of liquid-phase stratus and nimbostratus had obvious seasonal variations over China, and the regional characteristics were obvious, especially the monthly distribution appearred double peaks pattern over southeastern China, the peaks were in February and November. However, the peak of cloud water path of ice-phase clouds occurred in summer over northern China and winter in southern China.

The European Space Agency Climate Change Initiative soil moisture (ESA CCI_SM) product can provide soil volumetric water content data with high spatiotemporal coverage and a long time series. It can be used for drought monitoring on a regional scale. Gansu Province was selected as the study site for ESA CCI_SM testing. Soil volumetric water content data at the 0-10 cm depth from automatic station was used to evaluate the ESA CCI_SM product by analyzing the spatiotemporal variation characteristics of soil moisture in a long time series and construction of a soil moisture condition index (SMCI) for use in drought monitoring. The ESA CCI_SM product showed the best correlation (R=0.71) with observed values in the east of Gansu Province, followed by the middle, the south and Min county of Gansu Province. Overall, the 92% correlation coefficients of the sites were significant and passed 0.01 significant level. ESA CCI_SM indicated that it was more arid in the northwestern regions while it was more humid in the southeastern regions. Soil volumetric water content showed significant seasonal variation, which was relatively more humid in antumn, followed by summer, while in winter and spring it was drier. The SMCI constructed using the ESA CCI_SM product effectively exhibited the summer-autumn drought development from July to October 2002 and the spring-summer drought development from April to June 2009. This product had good drought monitoring capability in rain-fed agricultural areas in the middle and the east of Gansu Province.

the ground － based GPS data of JICA program，the characteristics of precipitable water in Western Sichuan Plateau
were analyzed in his paper． Comparison the estimates of precipitable water from GPS measurements with sonde observations shows that
the mean error is 0． 17 mm，that is，the precision of the estimates of precipitable water from GPS measurements can fill the requirements
of meteorological application． It is found that annual precipitable water in north part of Western Sichuan Plateau is 3 289． 6 mm，
while in south part that is 8 164． 4 mm． The precipitable water in the nighttime is a bit higher than that in the daytime． Precipitable
water contributes most in summer，secondarily in autumn，least in winter，which shows that there are distinctive dry and wet seasons in
Western Sichuan Plateau． Meanwhile，precipitable water varies with month obviously，as well as its monthly variation trend in the
nighttime is almost the same as that in the daytime．

Based on theNCEP reanalysis data(2. 5°×2. 5°) from 1948 to 2007, this paper analyzed the long-term mean characteristics and the seasona,l annual and decadalvariations ofprecipitablewater in Sichuan in recent60 years. It is found thatannualprecipitablewater in Sichuan is 181. 30 kg·m-2, and the spatialdistribution ofprecipitablewater is obviously unequalwith high inWestSichuan Plateau and low in Sichuan Basin. The precipitable water varies with season obviously, which ismost (74. 33 kg·m-2) in summer and least in winter. Themonthly precipitablewater is least(5. 82 kg·m-2) in January andmost(25. 77 kg·m-2) in July,and it increases from Februarywhile decreases from August. In recent60 years, precipitablewaterwaves around the average levelwith a slightdownward tendency. Meanwhile, the precipitablewater in rainy years is 1. 15 times asmuch as that in dry years.

Based on summarization ofmany documents and regulations related to surface meteorologjcal observation including“standard of surface meteorological observation”, “standard ofmeteorological radiation observation”and all kinds of technical regulations issued by  ChinaMeteorologicalAdministration and Gansu ProvincialMeteorologicalBureau for both weather station and automatic weather station, a system was p rovided for quick consultation of operation regulation for surfacemeteorological observation. With the examp le demonstration in the system, operators can handle the managementmethods for all kinds of observation records in a short time, and the system can help operators imp rove study effect and quality in operation when used as operation training or studymaterial.

A severe convective storm process occured in the middle of Gansu province on May 30，2005 was analyzed by using CIN·RAD／CC Doppler weather radar data．It is found that the main meso—scale system causing this 8evere convective storm was the squall hne．The storln first appeared at 15：00，then moved to the southeast，and from 16：15 to 17：03 the multi—cell storm became more strongly and developed into the super—cel storm with the characteristics of vortex and zonal echoes．Th ere were two obvious outflow boundaries observed in south of the supercel lying to the southwest and southeast of the hook echo of the storm ，respectively．The shape of the low elevation reflectivity in the left front flank of the superceU was an inverted“V”，the maximum of echo intensity ap-poared in the bounded weak echo zone with the value over 70 dBZ．Th e corresponding radial velocity maps showed a strong mature me·so—cyclone feature．In this period the maximum vertical integrated liquid water(VIL)reached above 70 ks／m and the height of echo top(ET)was 17—18 km．Hence，this storm presented the typical features of superceU storms．

The change of the 0℃level height in summer over the northeast side of the Qilian Mountain was analyzed, and the relationshipbetween the 0 `C; level height and surface temperature, precipitation, water vapor content in atmosphere and stream flow of inland rivers were discussed. Results show ; (1) The 0℃level height was obviously higher than normal in the late 1950s and the 1960s, and lower in the 1980s. It presented downward irend from the late 1960s to 1970x, and upward trend in the 1980s and 1990x, and it downward again in the first 4 years of the 21 s2 century; ( 2 ) From May to September, the positive correlation was found between the 0℃level height and surface temperature, water vapor content in atmosphere, and it was negatively correlated with precipitation, and there was low correlation

Based on the data of aerological and surface meteorological observation for many years，the trend of water vapor content and its transport over Lanzhou city were analyzed deeply. Results are as follows：（1）The water vapor content and its transport are relatively more in summer than that in winter，and the water vapor content increases from Feb to Jul，decreases from Sep to Jan，and keeps invariable in Jul and Aug；nearly 97% water vapor content concentrates below the height of 400 hPa；（2）The trend of water vapor content distinctly corresponds to the change of precipitation，rainy days and temperature，but also there are some differences；（ 3 ）Over Lanzhou city，the large center of water vapor transport is near the height of 500 hPa，the maximum diurnal variation of water vapor is at the layer of 700 ～ 600 hPa in winter，and these are obviously different from those over the east of China.