Compound high-temperature and drought events is one of the complex extreme climate events with high incidence in the Shiyang River Basin, which has more serious impact on industrial and agricultural production and ecological environment than a single extreme climate event. Based on the average temperature, maximum temperature and precipitation data of five meteorological stations in the Shiyang River Basin from 1961 to 2023, the compound high-temperature and drought events were identified and determined using percentile threshold method and Ped meteorological drought index, and spatial and temporal evolution characteristics of compound high-temperature and drought events were analyzed with linear trend method. The results show that the spatial difference of annual average frequency of compound high-temperature and drought events was small in the Shiyang River Basin, however, the spatial difference of compound high-temperature and drought events frequency was obvious in each decade and increased decade by decade. Annual frequency of compound high-temperature and drought events decreased first and then increased in the Shiyang River Basin, it decreased before 1996 and then increased in the whole basin. Compound high-temperature and drought events mainly occurred from June to August, and the most occurred in July. The frequency of compound high-temperature and drought events with different grades changed greatly, with the increase of drought grade, the frequency of drought increased first and then decreased, the frequency of medium drought was the highest, and the frequency of extreme drought was the least.

In order to improve correction ability and forecasting level of intelligent grid. Based on the slice data of Gansu Province of objective guidance product from Central Meteorological Observatory of China and daily grid temperature data from Chinese Land Data Assimilation System Version 2.0 (CLDAS-V2.0) of CMA, the maximum and minimum temperature of 0.05°×0.05° grid points in the eastern Hexi Corridor (101.0°E-104.5°E, 36.0°N-40.0°N) were corrected, tested and evaluated by using Kalman filtering method and sliding training correction method. The results are as follows: (1) For seasonal comparison, the mean absolute errors of maximum and minimum temperature of Kalman filter and sliding training correction products were both smaller than objective guidance product at all seasons, and all values were less than 2.00 ℃. The forecast accuracy of maximum and minimum temperature of Kalman filter and sliding training correction products were greater than 70% at all seasons. which the maximum temperature was 6%-13% higher and the minimum temperature was 8%-24% higher. (2) For spatial comparison, the mean absolute errors of the maximum and minimum temperature of Kalman filter and sliding training correction products were 1.00-2.00 ℃, but greater than 2.00 ℃ in a few areas. The forecast accuracy of maximum (minimum) temperature of Kalman filter and sliding training correction products were greater than 70% (60%-70%) in most areas, and greater than 80%(70%) in a few areas. (3) As a whole, the correction skills of maximum and minimum temperature of Kalman filter and sliding training correction products were basically positive, and were greater than 0.300 in a few seasons and a few areas. It showed that the two correction methods have good prediction and correction ability, which can provide certain technical support for the future temperature forecasting operations.

Based on daily precipitation data from 44 national meteorological stations in the southern Xinjiang and the NCEP/NCAR reanalysis data from May to September (warm season) during 1961-2020, the spatial and temporal variation characteristics of rainstorm and large-scale circulation anomalies under different decades and climatic background (warm-dry period and warm-wet period) in the southern Xinjiang were analyzed. The results show that the cumulative rainstorm days, rainstorm stations and rainstorm rainfall in the warm season of the southern Xinjiang has been increasing since 1961, but the variation trend of rainstorm intensity and the proportion of rainstorm rainfall in total precipitation was not obvious. The cumulative rainstorm days, rainstorm stations and rainstorm rainfall in the warm-wet period in the southern Xinjiang were significantly more than those in the warm-dry period, and the rainstorm intensity and the proportion of rainstorm rainfall in the total precipitation had little difference in the warm-wet period and the warm-dry period. After entering the warm-wet period, the rainstorm days and rainstorm rainfall amount increased in most stations in the southern Xinjiang (the most obvious increase was at southwest stations), but the increase extent in mountain area was smaller than that in plain. The central Asian trough, central Asian vortex and Tarim easterly low level jet were the main influencing systems for the heavy rain in the warm season in the southern Xinjiang. The heavy rain in the warm season in the southern Xinjiang was dominated by low vortex type in the warm-dry periods, and low trough type in the warm-wet periods. The easterly flow 850 hPa extended westward more obviously in the low vortex rainstorm than in the low trough rainstorm. In the circulation difference field between the warm-wet periods and the warm-dry period, the circulation anomaly in the high latitude area of the low trough rainstorm and the low vortex rainstorm showed reverse change characteristics.

Based on the observation data of daily maximum temperature from 105 national meteorological stations in Xinjiang and the NCEP/NCAR reanalysis data from May to September during 1981-2019, the spatial and temporal characteristics and circulation types of regional high temperature weather processes in Xinjiang were analyzed. The results are as follows: (1) During 1981-2019, there were 100 regional high temperature weather processes in Xinjiang, concentrating in the Yili valley plain, the southern edge of Junggar basin in northern Xinjiang, Tarim basin in southern Xinjiang and the plain area in eastern Xinjiang, which mainly occurred from June to August, with the most in July, the second in August and the least in June. (2) Since the 21st century, the number of high temperature weather processes showed an increasing trend and the intensity of the processes obviously enhanced. The start time of the processes showed an advance trend, while the end time pushed. In addition, the duration days of the processes showed a phased trend of “increase, decrease, increase”. (3) The circulation situation at 500 hPa geopotential height field causing the regional high temperature weather processes in Xinjiang could be divided into four types, namely the eastward extension of Iranian subtropical high type (accounting for 54.0%), the superposition type (accounting for 32.0%), the Xinjiang high pressure ridge type (accounting for 12.0%), and the westward extension of western Pacific subtropical high type (accounting for 2.0%).

Based on the hourly precipitation data at 81 national meteorological observation stations of Gansu Province from 1981 to 2018 and NCEP reanalysis data, the climate and circulation characteristics of extreme rainstorms were emphatically analyzed in different falling areas of Gansu Province. The results are as follows: (1) The extreme rainstorm weathers occurred mainly in Longnan, Tianshui, Pingliang and Qingyang of eastern Gansu, and the heavy rainfall centers concentrated in Kangxian and Huixian of Longnan. The extreme rainstorms were classified into four types including eastern Gansu, southern Gansu, southeastern Gansu and dispersion patterns, according to the falling areas of rainstorms. (2) The extreme rainstorms were easily to occur in July and August in Gansu, especially in mid-August. The extreme rainstorms in southern Gansu were earlier than in eastern Gansu. The precipitation of extreme rainstorms at night was more than in the daytime as a whole, the night rain characteristic was remarkable in Gansu, especially in southern Gansu and southeastern Gansu. In additional, the convective characteristic was significant in Gansu. (3) There were 2.5, 5 and 10 years period of extreme rainstorms in Gansu during 1981-2018, and the 2.5-year periodic oscillation was obvious. (4) The extreme rainstorms in Gansu were correlated with the subtropical high, and the falling area of rainstorm was significantly related to the location of subtropical high. Moreover, the extreme rainstorms in eastern Gansu were also related to the easterly airflow at the bottom of northern high ridge, the extreme rainstorms with dispersion pattern were related to the tropical low pressure in South China Sea, while the extreme rainstorms in southern and southeastern Gansu depended on the intensity and location of short-wave trough in Tibet Plateau.

 Based on conventional meteorological observation data in Tianjin and the ECWMF ERAInterim reanalysis data (0.125°×0.125°), the transformation processes of raintosleet and then sleettosnow were analyzed from October to next April during 2000-2015 in Tianjin. The humidity and geopotential thickness during the transformation process of precipitation phases were analyzed, and 9 factors, namely temperature on 850 hPa, 925 hPa,1000 hPa and surface, thickness from 1000 to 850 hPa and from 850 to 700 hPa, 0 ℃ layer height, -4 ℃ layer height and 925 hPa relative humidity, were identified, which had close relationship with transformation process of precipitation phases. Further, their corresponding threshold indexes for different precipitation phases were given. And through the analysis of 3 weather cases, the usability of the indicators had been further verified. The discriminant equation for precipitation phases was established by using the 9 factors, it was found that the backtesting discriminant accuracy for rain and snow was higher than 80%.

 Based on the hourly precipitation data of 10 national meteorological stations from 2012 to 2019, the diurnal variation characteristics of precipitation in different seasons in the Yili River Valley of Xinjiang were analyzed. The results are as follows: (1) The diurnal variation characteristics of cumulative hourly precipitation in the Yili River Valley showed a single peak in spring, summer and winter, and a double peak in autumn. The low value period of diurnal accumulated hourly precipitation in four seasons appeared in the afternoon (15:00-19:00), the high value period appeared in the morning (10:00-12:00) in spring, autumn and winter, and in the first half of the night in summer (22:00). (2) The diurnal variation characteristics of cumulative precipitation frequency and cumulative precipitation in the same season were similar. There were significant regional differences in spatial distribution of hourly average precipitation and peak precipitation frequency. (3) Shortduration precipitation events were the main events in four seasons in the Yili River Valley, with the highest proportion (89%) in summer and the lowest proportion (70%) in winter. Short duration precipitation events were the main contributors to total precipitation in summer, while long duration precipitation events were the main contributors to total precipitation in winter. (4) There was a close relationship between the daily circulation of precipitation and the persistence of precipitation in four seasons in the Yili River Valley. The precipitation events lasting for 2-8 hours and 1-4 hours were the main contributors to the diurnal variation of precipitation in spring and summer. Three types of precipitation events with different durations had roughly equal contributions to the diurnal variation peaks of precipitation in autumn and winter in the Yili River Valley.

Based on daily PM2.5 concentration data during 2014-2017, the annual and monthly variations of PM2.5 concentration were analyzed in Xi’an, and in heating and non-heating seasons its difference was obvious. Combined with daily meteorological elements observations from  meteorological stations, the correlation between meteorological elements and PM2.5 concentration in different seasons was analyzed. The hourly PM2.5 concentration data of 13 air-quality automatic monitoring stations in 2017 were used to analyze the spatial distribution and diurnal variation of PM2.5 concentration in Xi’an. The main conclusions are as follows: The PM2.5 concentration showed a U-shaped characteristic within a year, which was higher in winter but lower in summer. The difference of PM2.5 concentration in recent years was mainly in January, February, November and December，during this period, the wind speed, precipitation and cold air activity frequency had some influence on PM2.5 concentration. The days of PM2.5 exceeding standard in heating season and its ratio to PM2.5 exceeding standard days in the whole year increased but both of them declined in non-heating season. The difference of PM2.5 pollution in various regions was larger in winter but it was smaller in summer. The PM2.5 concentration presented obvious diurnal variation, and its fluctuation curve was M-shaped. The correlation between meteorological factors such as temperature, relative humidity, wind speed and precipitation and PM2.5  concentration was different in different seasons. High level PM2.5 pollution was more likely to occur on those days with low temperature, high humidity, low wind speed and less precipitation. The range of basic meteorological elements under different levels of PM2.5 pollution condition obtained by statistics had some indicative significance for the air quality forecast of PM2.5 pollution.

Based on the conventional weather charts，FY － 2D satellite images，surface meteorological data，physical quantity field and NCEP reanalysis data，a heavy rainfall process which occurred on August 6， 2013 in Wuwei of Gansu Province was systematically diagnosed． The results show that the heavy rainfall was caused by interaction of multiple factors under a certain large － scale circulation background． Dramatic change of surface meteorological factors was an energy release process of strong convection weather． Local high humidity and moisture convergence provided an abundant moisture source． High － level divergence，low － level convergence and strong rising motion were the dynamic conditions． Strong unstable energy and unstable stratification were the necessary conditions of enhancing the convection enhancement and rainfall intensity increase． Development and strengthening of convective cloud clusters resulted in heavy rainfall process．

Diagnostic analysis and numeric simulation were made on a heavy rain process in the southeast part of Gansu during 1 － 2 July
2005 using NCEP data of 1° × 1° with 6 h intervals and WRFV3． 1 meso － scale model． Based on the data of model output，the relation
between the helicity of this process and the rainfall intensity was analyzed． The results show that the short － wave trough from Plateau
and the moisture from South China Sea and Bengal were important causes of the heavy rain process． WRF model had the ability of
simulating this heavy rain’s precipitation; The spatial distribution of the helicity had certain indication about prediction of heavy rain in
eastern part of northwest China． The shape of maximum value center of positive helicity correlated with the shapes of short － wave trough
from Plateau and shear line on 700 hPa; The maximum value center of positive helicity which occurred under 400 hPa may be a great
cause for heavy rain in northwest part of China．

This paper analyzed the continuous detecting data ofLanzhou CINRAD /CC Radar abouta hailprocess occurred in Dingxi on July 18, 2008, summarized themain characteristics of the radarproducts during this hailprocess such as reflectivity, radial velocity,RCS vertical section, vertical integrated liquid content and so on. Then it discussed the detection methods for monitoring hail by DopplerRadar, found out the typical echo characteristic of supercell storms such as hook echo, bounded weak echo region(BWER),echowal,l suspended echo, obvious influx nick, existingmesocyclone etc., and summed up some informationwhich are good fornowcasting ofhai,l such as severe change ofVIL, corresponding relationship ofET and hailprocess, obvious three-body scatter characteristic and so on, these information will be of great value for us to detect severeweather events by radar.

Based on the basic observationaldata and automaticweather station data, a regionalheavy dust storm occurred onApril29,2009 inHexiCorridorwas analyzed from the causes of the synopticmeteorology, physics quantity fields and so on.The results show that itwas a duststorm thatcaused by the gale behind the cold front, and ithappened in the zone ofstrong pressure gradient. Groundmeteorological elements had a strong response to the outbreak of the dust storm, which can be used as a reference for forecast of dust storms. Therewas an obvious upwardmotion in the outbreak area ofduststorm with the lower level convergence and the high-leveldivergence. The frontogenesis function and helicity indicated the area of dust storm verywel.l

By analyzing the dopp ler radar data of the strong convective weather p rocesses occurred in Zhangye city in 2006, the intensity characteristics of belt - shaped and block echoes are summarized. Radar echo characteristics of mesoscale system of strong convective weather p rocesses, including low - jet,warm advection, cold advection, contrary wind area and vertical wind shear, are analyzed. The echo features are quantified objectively, and the stability index is introduced. The concise criterion for feasibility short - time forecast is obtained.

By using the conventional weather observation data during 1986-2004, the climate and atmospheric circulation characteristics and influence systems of hail weather in Liaocheng were analyzed, and the effect of terrain and geography on hail weather was also studied. Results show that the annual mean hail days in Liaocheng were 2.7 days, 8 days at most a year, and hail occurred mainly in April-September, especially in June. The main influence systems of hail weather presented five types of low vortex, trough, transversal trough, northwest current and southwest current at the edge of the subtropical high, and low vortex as well as northwest current in the middle-high level influenced hail weather most. There were three hail paths of west, northwest and north moving to Liaocheng. The geography and the terrain characteristics of the Liaocheng city have extraordinary effect on the formation of hail weather.

A sectional strong frost occurred continually in the east of Hexi corridor in the morning on 3 and 4 and 5 May 2004. This process engendered the most serious harm to farming and forestry in this city. Using real time MICAPS data and ground automation OhSPTVat10riS,  We analyze meteOTOlOglCal and  ChmatOlOglCa1 TeaSOriS  Of th1S  frnSt  Calalnlty  Weather pTOCPSS.  The  TPSLI1tS  S110W  that  Strong cold air explosion is directional reason of this frost calamity. Crop developing is brought forward because of air temperature anomaly high, air temperature and ground temperature below 0℃last for a long time, which aggravate extent of this frost calamity. We obtain a point of view for prediction frost on the basis upwards and put forward effective measures of defending frost.

Dronght is the most serious meteorological disaster in GanSll  1neSS  pltateall.  It considering meteorological factors comprehensivly because of the complexity Model of America and the  modified Pahner  Drought Severity  Model for of drought .On is difficult to develop a drought index the base of  the Palmer Drought Severity China,  we fLn-ther  modified the model in  stations CalClllatlOn Of pOtentlal eVapOtTanSplTatlOn and TLInOff,  etC.  AS a TPSlllt ,a TPV1Sed m0(lel Of dTOllght SPVPTlty haS been eStahhShed In paper which is expected to he applicable for drought research on this region.