The research on the distribution of cloud water content and its evolution rules has important significance for the exploitation and utilization of regional cloud water resources. The paper analyzed the temporal variation characteristics of liquid water path (LWP) and integrated water vapor (IWV) in central Guanzhong Plain by using observation data of MWP967KV ground-based microwave radiometer at Jinghe station of Shaanxi Province from October 2017 to December 2020. Combined with ground precipitation and Doppler weather radar observation data, the development and evolution characteristics of water vapor and liquid water before precipitation in various cloud systems were compared by some cases study. The results indicate that the IWV exhibits obviously seasonal variations in central Guanzhong Plain, with the highest in summer, followed by autumn and spring, and the lowest in winter. Specifically, the peak appears in July, and the valley appears in December. The LWP is higher in autumn and summer, in winter it is the lowest. Notably, the peak is in September, and the valley is in December. The distribution of the IWV and LWP exhibits a single peak and single valley pattern over the course of a day, but the occurring time of their peak and valley is different. The diurnal maximum of the IWV occurs from 07:00 to 08:00 in summer and autumn, 23:00 in spring and 13:00 in winter, while the diurnal minimum of the IWV occurs at about 12:00 in spring, summer and autumn, 22:00 in winter. The diurnal maximum of the LWP occurs from 07:00 to 09:00 in spring, summer and autumn, while in winter it is slightly late (10:00). The diurnal minimum of the LWP appears at the nighttime in all seasons. The growth time of cloud water content before precipitation is different for different types of cloud systems. On average, the development time of stratiform cloud systems is 15.6 hours, and for other cumulus cloud systems it is 9.0 hours. In the initial stage, the IWV in both cloud systems varies prior to the LWP, and the fluctuation amplitude is increasingly violent as precipitation approaches. Additionally, the LWP in both cloud systems firstly exhibits a sudden violent increase before the rainfall being triggered, and the IWV and LWP in stratiform cloud system vary greatly in different seasons as precipitation is triggered. In the afternoon, the duration of strong convection developing is short, with an average time of 30 minutes. In the initial stage of development and before precipitation, the LWP varies and jumps sharply at the first.

In order to study the main geographical influencing factors of summer precipitation and the best interpolation method of precipitation in the complex Sichuan Basin, especially the mountainous area around the basin, Sichuan was divided into four regions by using cluster analysis based on 10 years (2010-2019) summer precipitation data of 157 automatic meteorological stations in Sichuan Province. The correlation analysis and the multiple regression analysis methods were used to screen out the geographical influencing factors of precipitation in each region. In addition to using the cooperative Kriging interpolation method, the traditional interpolation method is used to compare. The interpolation results are tested by cross-validation method. The results are as follows: (1) The geographic influencing factors that can be used to characterize the summer precipitation in Sichuan were mainly longitude, latitude, altitude, slope and normalized difference vegetation index. (2) Due to the diversity and complexity of the topography in Sichuan, the effect of precipitation interpolation after the division was better than that before the division.(3) When the number of precipitation influencing factors in the selected area was moderate, the coKriging interpolation method was better, and when the number of precipitation characterization factors in the selected area was single or too many, the radial Basis function interpolation method or empirical Bayesian Kriging interpolation method were more effective.

Based on topography and forecasted 3-hour wind fields, relative humidity fields initialed from 20:00 BST and 08:00 BST by using the SWCWARMS (southwest center WRF ADAS real-time modeling system), the precipitation correction equation was constructed by calculating the terrain precipitation estimates combined with precipitation fields forecasted by SWCWARMS. The daily precipitation, precipitation processes in Sichuan Basin and in western Sichuan Basin during flood season from June to August during 2018-2020 are corrected, and the precipitation in the steep terrain transition zone from the eastern slope of western Sichuan Plateau to the western Sichuan Basin was tested and evalcated only. The results are as follows: (1) The TS of the precipitation correction value with each magnitude was improved compared with TS of forecasted precipitation by the SWCWARMS. The correction effect of precipitation forecasted initialed from 20:00 BST was better than that initialed from 08:00, and the correction effect of the precipitation processes in western Sichuan Province was the best for heavy rain and above. Compared with the SWCWARMS, the relative improvement rates of TS of corrected value of precipitation with heavy rain, torrential rain and heavy downpour were 19%, 25% and 37%, respectively, the hit ratio was higher, the false alarm rate and miss rate were decreased significantly. (2) The correction equations of precipitation had a good correction effect on both torrential rain and general precipitation cases of precipitation processes in western Sichuan Province occurring in the steep terrain transition zone, even for cases of precipitation area predicted by the SWCWARMS was far from the actual situation.