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.

 The SAL quantitative verification method was used to evaluate precipitation forecast  results of the Grapes-Meso model on the rainfall event occurring on 5 September 2018 in Sichuan Province firstly, in this process, the optimal precipitation threshold scheme was selected through combination of three threshold schemes to identify the precipitation body. On this basis, SAL verification was applied to precipitation forecast of three heavy rainfall events in 2018 and rainfall processes from July to September in 2018 in Sichuan Province, and the verification results were compared with test score (TS) to understand prediction effect of the Grapes-Meso model in flood season in Sichuan Province. The conclusions are as follows: (1) The selected threshold determining method could identify the precipitation body well and the “connected neighborhood method” provided a good support for automatic identification of precipitation individuals. (2) The value of L reflected prediction effect of the model on precipitation forecast to a certain extent. If the value of L and the absolute value of A were both small, the probability of better prediction effect was bigger. (3)The overall prediction effect of the Grapes-Meso model on rainfall processes in Sichuan Province showed that the forecasted rainfall intensity was stronger and rainfall range was larger than actual rainfall, or forecasted precipitation center was smaller than the actual, or both cases were existed at the same time.