Based on the rainfall station observations and the products of Multi-source Merged Precipitation Analysis System of China Meteorological Administration (CMPAS), eight kinds of satellite-based precipitation products (FY-4A, CMOPRH-RT, IMERG-Early, IMERG-Late, GSMaP-Now, GSMaP-Gauge, PERSIANN-Now, PERSIANN-CCS) are comprehensively evaluated during the record-breaking extremely heavy precipitation process in East Gansu on July 15, 2022 by using quantitative analysis, classification and structural similarity methods. The results show that eight kinds of satellite-based precipitation products basically reflect the spatial distribution characteristics of precipitation with more in the central and eastern regions and less in the northwest. Except for the GSMaP-Now product, the other seven satellite-based precipitation products all underestimate the precipitation at the center of the rainstorm. The eight kinds of satellite-based precipitation products have a good ability to describe the peak value of heavy precipitation, and both peak stages of the heavy precipitation process are reflected, but all of them seriously underestimate the magnitude of heavy rainfall and above. For precipitation of different magnitudes, the GSMaP-Gauge is the best for estimating precipitation of magnitude below torrential rain, while the CMOPRH-RT is the best for heavy rain and above, and all products cannot correctly hit the precipitation of torrential heavy rainfall. In terms of the structural similarity index, the CMOPRH-RT product can best represent the structural distribution of the precipitation process from three aspects of total precipitation, precipitation magnitude, and precipitation morphological distribution. In summary, for this precipitation event, the CMOPRH-RT precipitation product had the best performance in all aspects.

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.