Xin’an River Basin is a typical water-abundant area. Characteristics exploration of the drought events and study on the response of hydrological drought to meteorological drought in Xin’an River Basin largely benefits the scientific reference for basin water management. This study calculated the Standardized Precipitation Index (SPI) and Standardized Runoff Index (SRI) with the monthly data of inflow runoff and precipitation from 1960 to 2022 in Xin’an River Basin. Based on SPI and SRI, the evolution of meteorological and hydrological droughts under different time scales and the seasonal response of hydrological drought to meteorological drought were analyzed. The results are as follows: (1) From 1960 to 2022, meteorological and hydrological droughts in the Xin’an River Basin mainly occurred in the 1960s, late 1970s to mid-1980s and early 2000s. Meteorological and hydrological droughts have rarely occurred since the 21st century; dry and wet alternated frequently over the remaining periods of time. (2) Mann-Kendall trend test results show a wetting trend during the past 63 years, and the effects of drought have mitigated. While in winter and summer, it showed drought decreasing trend in the basin. The hydrological trend of becoming wet was more obvious than that of meteorological. (3) The correlation between hydrological drought and meteorological drought in Xin’an River is high. Also, the hydrological drought lags behind the meteorological drought for 1-3 months. The seasonal response of hydrological drought to meteorological drought in flood season shows higher correlation and faster speed than that in dry season. Because of the quick response of hydrological drought to meteorological drought in flood season, more focus and targeted steps should be taken on the drought state of the basin in the flood season.

Based on thunderstorm gales data in recent 40 years and the conventional and new monitoring data in recent 18 years in Shanxi Province, the spatial and temporal distribution of thunderstorm gales in Shanxi Province are analyzed firstly, and then the weather types, characteristic physical quantity thresholds and conceptual models of thunderstorm gales are studied by using the methods of cluster analysis and mesoscale weather analysis. The results show that the average number of thunderstorm gale days in Shanxi had the regional distribution characteristics with more in the north and less in the south, more in mountainous areas and less in plain, and more in western mountainous areas and less in eastern mountainous areas. The extreme thunderstorm gales mainly occurred in the north of Shanxi and Lüliang mountainous regions. The annual thunderstorm gales days in the western mountainous area showed an increasing trend, while there were no changes or decreasing trends in other areas. The thunderstorm gales mainly occurred from May to August, accounting for 75% of the total days of thunderstorm gales in the whole year, and thunderstorm gales occurred most frequently at 16:00 and 21:00 (Beijing Time) in a day. The flow patterns of thunderstorm gales in Shanxi are mainly divided into six types, which are forward-tilting trough, backward-tilting trough, transverse trough, subtropical high and low-level warm shear line, subtropical high and low-level cold shear line, and northwest air flow. The K index threshold of all patterns from April to May was significantly lower than that from June to September, while the temperature difference between 850 hPa and 500 hPa was obviously higher than that from June to September. When each pattern meets the characteristic physical quantity thresholds of each month, it can trigger the strong thunderstorm gale weather in Shanxi, while the flow pattern configuration of forward-tilting trough has the highest percentage of triggering extreme thunderstorm gales. Over the same period, the K indices of the patterns of backward-tilting trough, subtropical high and low-level warm shear line, subtropical high and low-level cold shear line are significantly higher than those of the patterns of forward-tilting trough and northwest air flow, while the Si index of the forward-tilting trough is obviously higher than that of other patterns, which indicated that the dynamic instability condition of the forward-tilting trough triggering thunderstorm gale is better than the thermal instability condition. The CAPE and 0 ℃ layer height thresholds of the patterns of subtropical high and low-level warm and cold shear lines are significantly higher and the thresholds of T-T_d and cloud top black body temperature in the lower layer are significantly lower than those of the other four patterns. Whether hail is accompanied by thunderstorm gale process can be accurately judged by 0 ℃ layer height threshold of each month.

A forest fire occurred in Qinyuan County, Shanxi Province on June 5, 2020. Based on the analysis of weather situation, radar echo, lightning location and other multi-source meteorological data, and European Centre for Medium-Range Weather Forecasts （ECMWF） fifth-generation global atmospheric reanalysis （ERA5）,the evolution characteristics of meteorological elements including temperature and precipitation were analyzed in the early stage and during the forest fire, and combined with the field investigation, the cause of the forest fire were given. The results show that the forest fire was caused by a positive lightning, the lightning point was at the edge of convective cloud and the lightning occurred at 15：39 BST on June 5, with the current intensity of 42.2 kA.There was no precipitation in the areas around fire site for 2 consecutive days in the early stage, the 2 m temperature in the areas around fire site increased significantly on the day of the forest fire, with the air temperature of 30-33 ℃, and the precipitation was less than 0.1 mm and it was breezy.

Based on daily observation data and disaster data from automatic weather stations in Hedong region of Gansu Province from 2008 to 2017, the 75 hail cases were selected with some standards and divided into three types according to main weather influencing system of hail and mesoscale diagnostic method, including the northwestern airstream, the low trough and the low vortex types. Then statistical characteristics of radar products and radar echo feature under the three weather types of hail were compared, and the typical hail cases were chosen to verify the results. The results show that the maximum reflectivity (Z_max) and the height of maximum reflectivity ( H_{Z_{\mathrm{m}\mathrm{a}\mathrm{x}}}) had relatively little differences under the three weather types of hail, Z_max was above 50 dBZ and H_{Z_{\mathrm{m}\mathrm{a}\mathrm{x}}} was above 2.0 km. There were significant differences in echo top height (ET), core area thickness (H), center height of echo reflectivity above 45 dBZ (H_{45 dBZ}), the maximum height of storm body echo reflectivity equal to or more than 30 dBZ (TOP), vertically integrated liquid water content (VIL), and the density of vertically integrated liquid water content (VILD). The H, H_{45 dBZ}, TOP and VIL of the northwestern airstream type were significantly higher than those of other types, and ET of the low trough type and VILD of the low vortex type were lower. The frequencies of overhang echo for the three types of hail weather were all higher than 61.0%. The frequencies of three body scattering and side-lobe echo for the the low trough type were 35.5% and 48.4%, respectively, and the probability of bounded weak echo was 12.9%. The frequencies of bounded weak echo area for both of the northwestern airstream type and the low vortex type were higher than 38.5%. The indicators of three body scattering and side-lobe echo could predict the hail weather 18 to 30 minutes in advance, which had some significance in hail weather forecast.

 Based on cloud to ground (CG) lightning data from ADTD and VLF-3D lightning positioning system and lightning disaster records in Shanxi Province in 2017, the temporal and spatial distribution and current intensity of CG lightning detected by  two systems were comparatively analyzed. The results show that the detection efficiency of three-dimensional system to CG lightning was higher than that of ADTD system, and the number of detected lightning by three-dimensional system was twice as large as that of ADTD system. The positioning accuracy of three-dimensional system to lightning disasters was higher than that of ADTD system. The daily (except for the positive lightning) and monthly variation characteristics of monitored CG lightning by three-dimensional system and occurrence time of peak values were basically consistent with ADTD system. Compared with ADTD system, the high-value region of lightning density with 3.0 fl·km-2·a-1 and above from three-dimensional positioning system increased significantly, while the minimum values below 0.3 fl·km-2·a-1 reduced greatly.

Plant litter is an important part of ecosystem in Mu Us sandy land, and its stock volume and redistribution process play important roles in affecting nutrient cycling between surface soil and plant and soil erosion resistance. Based on the field survey and sampling data, the spatial distribution characteristics of litter of Salix psammophyla normal plant were studied in typical sand dunes of southeastern edge of Mu Us sandy land. The results show that the distribution patterns of Salix litter approximately appeared concentric circle, fan-shape and crescent-shape with the centre of Salix base under the long-term influence of the northwest wind, and the biomass of litter decreased significantly with the increase of the distance (30 cm, 60 cm and 90 cm) from the Salix base. Compared with the concentric circle pattern, the biomass of litter for crescent-shaped and fan-shaped patterns decreased in the northwest of base and increased in the southeast of base, especially for the crescent-shaped pattern the changes were significant. The northwest wind played an important role in migration and redistribution of leaves and fruits in Salix communities, so the northwest wind was main reason for the formation of three pattern of litter. These results might provide scientific basis for vegetation optimization layout and ecological reconstruction in wind-sandy area of northern China.

In order to strengthen the objective quantification of autumn rain monitoring and evaluation in West China and improve forecast method of autumn rain in Shaanxi, the climatic characteristics of autumn rain in Shaanxi and their relationship with atmospheric circulation and SST during 1961-2016 were analyzed by using correlation analysis and regression analysis based on the daily precipitation at 77 weather stations of Shaanxi, NCEP reanalysis data, NOAA sea surface temperature (SST), moving average SST index from the Climate Prediction Center in USA and SST index from the National Climate Center in China. The results show that the average onset date of autumn rain in Shaanxi was on September 10, the change trend of the onset date wasn’t obvious in Shaanxi from 1961 to 2016 as a whole, but there were obvious interdecadal variation characteristics. The average end date of autumn rain was on October 7, and it had an earlier tendency in the past 56 years. The intensity of autumn rain decreased in Shaanxi during 1961-2016, but the trend wasn’t significant, and the interdecadal variation was obvious. In the year of strong autumn rain in Shaanxi, the anomalous circulation on 500 hPa with ‘+, -, +’ appeared over Eurasian mid-high latitude, and the western Pacific subtropical high and the Indian-Burma trough were stronger. The intensity of autumn rain in Shaanxi was closely related with ENSO events. The development of cooling (warming) SST in equatorial central-eastern Pacific in spring and summer was beneficial to strong (weak) autumn rain in Shaanxi, and the previous SST anomaly in 

Niño3.4 area of tropical Pacific was interannual prediction signal to the intensity of autumn rain in Shaanxi, which had better indication to autumn rain intensity in Shaanxi.

t:The circulation andmoisture flux characteristics atmiddle and lower levels during a continuous autumn rain process from October24 toNovember6 of2008 in Yunnan Provincewere analyzed. Results show thatduring thisweather process the western Pacific SubtropicalHigh at500 hPawentwest and was stronger than average, and the southwest air currents in front of the trough and in the periphery  ofSubtropicalHighwere beneficial towatervapor transportation toYunnan. Its influence systemswere the southwestair current in front of the trough, the low-level jet and shear line atmiddle and lower levels. Therewere plentiful vaporduring the continuous rain process atmiddle and lower levels. During the previous stage of the process themainwatervapor source in lower levelof tropospherewas in South China Sea and Bay ofBenga,l and during the later stage itwas in South China Sea. Thewater vaporwas convergence overYunnan during thewhole process, and the heavy rain occurred in the area ofdivergence ofvapor flux less than -32×10-7g·hPa-1·s-1·cm-2.