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

The increasing frequency of heavy rainfall on the eastern Fanjing Mountain due to the 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 of Tongren regional automatic weather station and ERA5 reanalysis data during 2014-2023.The results are as follows. (1) RF occurs about 15 times a year when an easterly airflow prevails at 925 hPa especially, and it is concentrated from May to September of the year with the most appearance occurring in June and August, followed by July. The number of RF events from June to August accounts for 65.3% of all RF events. (2) The precipitation of RF is affected by topography significantly with heterogeneous distributions. The maximum of precipitation amount, frequency, and intensity is 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 frequency and intensity above downpour. (3) Nighttime RF is more obvious than daytime RF, which contributes to the increased nighttime precipitation amount, frequency, and intensity. And the diurnal variation of precipitation amount is mainly contributed by the precipitation intensity, because the main peak value of precipitation amount around 08:00 is influenced by the precipitation intensity in May and June, while the secondary (third) peak value of precipitation amount occurs at 22:00 (15:00) is affected by the precipitation intensity in August (May and July). Furthermore, it is obvious to see that the characteristics of large precipitation and strong 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.