In order to further understand the prediction ability of current numerical prediction models, this paper selects 47 heavy rainfall processes that occurred in the Sichuan Basin from 2018 to 2020 and classifies them, then based on merged precipitation products and ground observation data, the prediction ability of European Centre for Medium-Range Weather Forecasts (ECMWF), China Meteorological Administration Mesoscale Model (CMA_MESO) and Southwest Center WRF ADAS Real-time Modeling System (SWC_WARMS) models in the range, intensity, extreme value, time and displacement deviation of heavy rainfall processes is validated and assessed by using threat score, space-time sliding and other methods. The results show that the 08:00 (UTC+08:00) prediction of each model is better than the 20:00 (UTC+08:00) prediction, the ECMWF is better in moderate rain and heavy rain prediction, the SWC_WARMS has a higher score in the rainstorm prediction. The prediction range of moderate rain by various models is generally larger than the actual, and gradually turns to underestimate with the increase of magnitude, in which SWC_WARMS is closer to the actual. For rainfall intensity, the average precipitation and extreme value of ECMWF and CMA_MESO are generally smaller than the actual, and the prediction of SWC_WARMS is closer to the actual. The time deviation of predictions of three models is not obvious, only a few initial forecast times have a time deviation of -6 to 3 h, the displacement deviation of ECMWF products is the smallest, the prediction of ECMWF and SWC_WARMS are mainly northerly in latitudinal direction, while in meridional direction, the prediction of ECMWF is mainly to the west, and the predictions of CMA_MESO and SWC_WARMS are mainly to the east.

In order to implement the localized application of ECMWF (European Centre for Medium-Range Weather Forecasting) model well and improve the accuracy of precipitation forecast in Sichuan Province, the systematic deviation characteristics of forecast of precipitation with various magnitudes from ECMWF model were analyzed from July to September during 2020-2021. The result shows that the rain days forecasted by ECMWF model are more than the observations in Sichuan Province from July to September during 2020-2021, especially in Panxi region and western Sichuan Plateau. The heavy rain days forecasted by the model are more than the observations in southwestern Basin and Panxi region, while they are less than the observations in southern Basin. Then, the correction experiment about 24-hour cumulative precipitation forecast was carried out based on quantile mapping method, and it was applied to heavy rainfall forecast. After the correction using quantile mapping method, the TS (Threat Score) of forecast of rainstorm and above is improved by 7%-15%, and the TS of forecast of precipitation with various magnitudes is 2%-4% higher than the multi-model integrated objective forecast products. The POD (Probability of Detection) of forecast of heavy rain, rainstorm and above is improved by 10%-20%. The corrected location of rain belt in particular rainstorm areas is closer to the actual.

In order to deeply understand the water vapor characteristics and sources of persistent rainstorms in the Sichuan Basin and improve the rainstorm forecast capability in this region, the meteorological observation data from 4 955 national and regional automatic meteorological stations in Sichuan Province, the global data assimilation system (GDAS) data, the fifth-generation atmospheric reanalysis (ERA5) from the European Centre for Medium-Range Weather Forecasts (ECMWF) are used to analyze the water vapor transport characteristics of a continuous rainstorm process in August 2020 in the Sichuan Basin by using the Lagrangian method. The results show that the characteristics of water vapor transport at different initial height layers are different before and during the heavy precipitation process. In the middle and high level (from 5 500 to 10 000 m), the low latitude ocean is main source of air mass trajectory before the heavy precipitation occurring, while the southern coast of the Mediterranean is main source of air mass trajectory during the heavy precipitation process and dry and cold air in the middle and high latitude westerlies is brought to the basin. In the middle and lower level (from 1 500 to 5 500 m), during the heavy precipitation process, the source of water vapor trajectory adjusts from the southern coast of the Mediterranean to the low latitude ocean surface and warm and humid air on the low latitude ocean surface is brought to the basin. In the lower level (from ground to 1 500 m), the source of water vapor trajectory first adjusts to the low latitude ocean surface before the heavy precipitation occurring, and warmer and wetter air flow is delivered to the basin compared with the middle and lower level. Quantitative analysis of the water vapor contribution rates of different sources shows that the water vapor from the Bay of Bengal to the Gulf of Thailand is the dominant (66.6%), followed by the Arabian Sea (23.9%), and the South China Sea is the lowest (9.5%).

The climatic feature of precipitation over 10 mm in Ningxia region in recent 49 years were analyzed by using daily precipitation data of 20 meteorological stations from 1961 to 2009. The results show that weather events with precipitation over 10 mm increased gradually with the variety of terrain from north to south, and the amount of the events in the loess hilly region of the south was double more than that in the irrigated area. Moderate rain contributed greatly to rainfall and rainstorm increased gradually. By the statistics of rainfall intensity, the frequency of rainfall more than 1.0 mm/h but less than 2.0 mm/h was the most, and more than 4.0 mm/h was the least in Ningxia, both the frequency of rainfall more than 3.0 mm/h but less than 4.0 mm/h and that less than 1.0 mm/h were gradually increased since the 1980s. The years with extremely more weather events with precipitation over 10 mm in Ningxia are 1961,1964,1985 and 1990.