Spatial-temporal characteristics of rainstorm on the eastern Fanjing Mountain under the influence of easterly airflow in recent ten years

The frequent heavy rainfall on the eastern Fanjing Mountain due to the combined influence of topography and easterly airflow at low-level have bad significant effects on the lives and property of local people. This paper focuses on revealing the spatial-temporal distribution characteristics of rainstorm on the eastern Fanjing Mountain under the influence of easterly airflow (RF) at low-level based on the precipitation observation data from the national and regional automatic weather stations in Tongren City,Guizhou Province, as well as ERA5 reanalysis data during 2014-2023.The results are as follows. (1) RF often occurs under the background of prevailing easterly airflow at 925hPa,with about 15 occurrences per year, and it is concentrated from May to September of the year with the most appearance occurring in June and August, followed by July. The RF events from June to August account for 65.3% of all RF events. (2) The RF is affected by topography significantly with regional characteristics. The maximum of precipitation amount, frequency, and intensity are located at the eastern foot of Fanjing Mountain where the altitude difference is the greatest, followed by the narrow trumpet-shaped topography facing northeastward at the northeastern Fanjing Mountain. Also, it is more likely to occur that widespread extreme rainstorm on the eastern Fanjing Mountain than that on the northeastern Fanjing Mountain according to the distribution of precipitation frequency and intensity above the downpour. (3) RF precipitation amount, intensity, and frequency all show a diurnal variation pattern of being low value during the daytime and high value at nighttime. And the diurnal variation of precipitation amount is mainly affected by the precipitation intensity, because the main peak value of precipitation amount around 08:00 is contributed by the precipitation intensity in May and June, meanwhile the secondary (third) peak value of precipitation amount around 22:00 (15:00) is contributed by the precipitation intensity in August (May and July). Furthermore, it is obvious to see that the characteristics of larger precipitation aomunt and stronger precipitation intensity from May to September around 22:00. (4) It is clear that the RF in June and July lasting 6~7 h is extreme, while RF lasting 4 h is prone to occur in August.