Extreme precipitation events in arid areas often lead to huge casualties and economic losses, the study on its evolution characteristics and formation mechanism can provide an important support for improving the accuracy of weather forecast. A rainstorm process occurred on 13 August 2022 in Jinta County of Gansu Province, which was located in arid region of Northwest China. Both daily precipitation and hourly precipitation broke through the historical extreme value at national meteorological station Hexi Corridor, and their extreme and local characteristics were significant. European Centre for Medium-Range Weather Forecasts (ECMWF) fifth-generation global atmospheric reanalysis (ERA5) and observation data were used in this paper to analyze the causes of the rainstorm. The results show that the rainstorm occurred in the north side of the stable South Asia high, and the dynamic forcing in the upper and middle level of troposphere was weak. The baroclinic system, the lower level shear line and surface cold front in front of the 500 hPa short-wave trough, was mainly located in the lower level. The continuous transport of low-level water vapor around the thermal over the Qinghai-Tibet Plateau provided the extreme water vapor condition and the moderate intensity stratification instability for the rainstorm area. In front of the formation of surface cold front, the regional difference of low-level water vapor transport in central and eastern parts of Jiuquan City formed an obvious wet frontal and dryline. The meso-γ-scale convective system which caused extreme short-term heavy precipitation was triggered by the dryline, and developed into deep moist convection leading to extreme heavy rain at the intersection point of the cold front and the dryline. The local characteristics were significant during the development of the dryline convective cells to deep moist convection.

The convective weather and lightning disasters occurred frequently in the northeastern verge of Tibetan Plateau. In order to analyze the characteristics of cloud-to-ground (CG) lightning flashes, the CG location data and daily precipitation collected by the advanced toa and direction （ADTD） system of Gansu Provincial Meteorological Administration and CIMISS during 2017-2020 are used to investigate the spatial and temporal characteristics of the CG lightning frequency, current intensity and the CG flashes density in the northeastern verge of Tibetan Plateau, and the relationship between the CG flashes density and precipitation. The results show that the annual average number of the CG lightning in this region in recent four years was about 2.71×10⁴ times. The annual average negative CG and positive CG lightning accounted for 84.27% and 15.73% of the total CG lightning flashes, respectively. The monthly distribution of the CG lightning flashes presented a single-peak pattern. Specifically, the CG lighting flashes mainly occurred in summer, which accounted for 70.11% of the CG lightning in the whole year. In spring and autumn, the percentage of the CG lightning was less than that in summer, and in winter the number was least. The diurnal distribution of the CG lightning frequency also showed a single peak. The peak value of the total CG and negative CG lightning occurred mainly from 10:00 BST to 12:00 BST in a day. The occurring time of peak value for positive CG lightning lagged one hour than the negative CG lightning. Although the number of monthly-averaged positive CG lightning was much less than that of negative CG lightning from April to October, the ratio of average current intensity of positive CG lightning flashes to that of negative CG flash was 1.56. The CG lightning flashes density greater than 0.24 fl·km^-2·a^-1 concentrated in Yongdeng County of Lanzhou, Luqu County, Maqu County and Hezuo City in Gannan Tibetan Autonomous Prefecture, Zhangjiachuan County in Tianshui City, Huachi County, Huan County, Zhenyuan County and Qingcheng County in Qingyang City, Wen County and the south of Longnan City. And the high incidence areas of positive CG lightning mainly occurred in Maqu County, Luqu County, the junction of Dingxi City and Gannan Tibetan Autonomous, and the central and southern part of Qingyang City. Lighting protection measures should be strengthened in the above areas. By comparing the density of the CG lightning and precipitation, it is found that the spatial and temporal distributions of lightning activity was consistent with precipitation in the northeastern verge of Tibetan Plateau.

Based on the model sounding analysis field and forecast field of North China RMAPS (rapid-refresh multi-scale analysis and prediction system), the environmental parameter characteristics of four types of severe convection weathers were contrastively analyzed in Shanxi Province, and the classification indexes and criterion of severe convection weathers were summarized. And on this basis, the category forecasting scheme of severe convection weathers was designed in Shanxi Province, then the occurrence probability of severe convection weathers with four types on grid points was calculated, and the feasibility of classification forecast of severe convection weathers was further explored. The results are as follows: (1) The environmental parameters including convective available potential energy (CAPE), K index, temperature difference between the middle and lower level, temperature dew point deficit on low level, 600 hPa temperature and low-level vertical wind shear had a certain indicative significance for distinguishing types of severe convection weathers in Shanxi. (2) The low-level vertical wind shear and 600 hPa temperature between hail or thunderstorm-gale and short-term heavy precipitation or thunderstorm had significant difference. Using the 20.0 ℃ temperature difference between 700 hPa and 500 hPa as a threshold, the thunderstorm-gale could be distinguished from short-term heavy precipitation, hail and thunderstorm weathers. Taking the 4.0 ℃ temperature-dew point deficit on 700 hPa as a threshold, the short-term heavy precipitation could be distinguished from hail, thunderstorm-gale and thunderstorm weathers. The above results could be used as the basic criteria of recognition of severe convection in Shanxi Province. (3) The classification forecasting scheme had a certain forecasting ability to severe convections in Shanxi Province, and it could capture the possible falling areas of hail, thunderstorm-gale and short-term heavy precipitation to some extent during a large-range severe convection process. The short-term forecasting ability of classification scheme was slightly higher than that of average level of forecasters’ subjective forecast, and the threat score was improved by about 0.01-0.06.

Based on daily meteorological data of 10 national meteorological stations in mountainous area of central and southern Ningxia from 1981 to 2018, the calculation model of comprehensive suitability for potato in mountainous area of central and southern Ningxia was established by integrating the indexes such as temperature, sunshine and water suitability, and characteristics of temporal and spatial variation of temperature suitability （PT）, sunshine suitability （PS）, water suitability （PW）, comprehensive suitability （P） were analyzed emphatically. The results show that the thermal and sunshine resources were suitable in mountainous area of central and southern Ningxia, which could meet the needs of potato’s growth in different growth stages. Among them, water was the main limiting factor affecting the growth stages of potato, and the annual fluctuation of water suitability was the largest. The variation coefficient of the comprehensive suitability from the branching stage to the flowering stage was the largest, which was the most unstable period when the climatic conditions affected the growth and development of potato. From the perspective of spatial variation, the comprehensive suitability of the whole growth period of potato showed an increasing trend from northeast to southwest, and the most suitable areas were in Xiji county, most areas of Haiyuan county and Yuanzhou district, western of Pengyang county, the most areas of Longde county and Jingyuan county except the higher elevation ridge of the Liupan Mountain, which had the unique climatic advantages suitable for potato production.

Based on the surface observation and sounding data in Changchun city from 2005 to 2014, this study analyzed the influence of air temperature at different altitudes on precipitation types in winter half year. The results show that the surface air temperature had a great influence on precipitation phase change, which could be well predicted by using 1.7 ℃ as a critical index to distinguish rain from sleet, and -0.1 ℃ as a critical index to distinguish sleet from snow. The method of combining surface temperature of 2 m with upper air temperature of 925 hPa was more accurate in judging precipitation types. The faster the surface temperature increase or decrease near 0 ℃, the shorter the duration of sleet.

Based on the monthly precipitation observation data at 21 weather stations in North China, global reanalysis data from NCEP/NCAR and circulation indexes data from National Climate Center of China from 1955 to 2014, the variation tendency, mutation and periodic characteristics of cyclonic wind shear frequency in low level in North China were analyzed by using the trend analysis, Mann-Kendall test and wavelet analysis methods, and the influence factors of cyclonic wind shear were preliminary discussed. Results show that the frequency of low-level cyclonic wind shear in North China decreased significantly during 1955-2014, the mutation of cyclonic wind shear frequency appeared in 1967, and there was quasi-3-year period oscillation during 1955-1965 and 1992-2000, while the 4-year period oscillation was significant during 1980-1992. The mutation and periods characteristics of low level cyclonic wind shear frequency were basically coincide with the precipitation in the same periods in North China. The turning change of low-level cyclonic wind shear was obvious in North China, which was mainly caused by the more significant adjustment of atmospheric circulation in the previous year.