Abstract:

In order to further understand the influence of Yuanbao Mountain on rainfall in northeast of Guangxi Zhuang Autonomous Region, the spatial and temporal distribution characteristics of precipitation in Yuanbao Mountain and its surrounding areas were analyzed based on the hourly observation data from 2021 to 2022 of the Guangxi Yuanbao Mountain gradient meteorological observation system, which consists of 21 regional automatic meteorological stations. The results indicate that the average annual precipitation in Yuanbao Mountain is nearly 2700 mm, which is comparable to that in the coastal areas of Guangxi. It is distributed from high in the east to low in the west, with large precipitation values concentrated on the windward slope. The annual precipitation on the windward and leeward slopes differs by nearly 900 mm. The number of precipitation days increases with altitude. Monthly precipitation has a single peak, with most precipitation occurring from May to July. In the southern regions, the maximum monthly precipitation occurs in June on windward and leeward slopes of Yuanbao Mountain, accounting for more than 28% of the annual precipitation, and the maximum monthly precipitation in the northern regions occurs in May. The peak daily rainfall mainly occurs at 04-05 am, with little rainfall activity during the daytime, reaching a minimum at 16-17 pm. In addition, the number of annual heavy rain days in Yuanbao Mountain ranges from 9.5 to 18.5 days, mainly occurring from May to July. The maximum number of heavy rain days occurs in June in all regions. The number of heavy rain days in high altitude regions is higher than that in low altitude regions. The intensity of heavy rain on the windward slope and southern slopes of the mountain is significantly greater than that in other regions. Moreover, the frequency of short-term heavy rain in Yuanbao Mountain is 10~32 times per year. There are significant differences in the starting and ending months and the duration of short-term heavy rain in different regions. Short-term heavy rain mainly occurs in the early morning, but it is slightly delayed with increasing altitude. Short-term heavy rain occurs most frequent on the windward slope, and the intensity of short-term heavy rain is similar in different regions.

Key words: Gradient observation, Topography, Hourly rain