关键词: 甘肃河东, 短时强降水, 天气过程, 时空分布

Abstract:

Using hourly precipitation data collected from automatic weather stations (AWS) in eastern Gansu Province during the summer months from 2010 to 2021, a total of 50 regional heavy rain showers were identified. An analysis was then conducted to examine the spatiotemporal distribution and intensity of such events in eastern Gansu Province. The obtained results can be summarized as follows: (1) The intensity of the heavy rain showers primarily ranged between 20 and 30 mm·h^-1, which accounted for more than 60% of such events. Intensities exceeding 40 mm·h^-1 represented less than 10% of such events. Notably, short bouts of intense precipitation with intensities exceeding 50 mm·h^-1 occurred in 74% of the heavy rain showers in the studied region. (2) In the studied region, heavy rain showers mainly occur from mid-June to late August, peaking in the period from late July to mid-August. While such events occur throughout the year, the interannual variability in their occurrence is significant and closely associated with the position of the Western Pacific subtropical high, the transport of abnormally warm water vapor from the South China Sea or East China Sea, and significant baroclinic features resulting from the interaction of weather systems at mid- and low latitudes. (3) The area typically affected by heavy rain showers in eastern Gansu Province accounts for only 3.17% of its total area. However, there are notable regional variations in the spatial distribution of these events, with areas struck by high-intensity rainfall being primarily located in the Taizishan region, the western section of the Qinling Mountain, Liupan Mountain, and Ziwu Mountain. Additionally, areas affected by rainfall of extreme intensity, exceeding 40 mm·h^-1, are concentrated in these high-incidence centers. (4) There is a clear pattern in the distribution of stations recording heavy rain showers under different circulation patterns. Stations associated with the eastward-moving plateau trough type are dispersed and most abundant. Meanwhile, stations related to the subtropical high’s southwestern airflow type record the lowest median number of such events. Finally, stations experiencing shear between two high-pressure systems are concentrated, while those associated with the northwest airflow type are the least numerous. There was no significant difference in the distribution of the events with heavy rainfall intensity among these circulation types. However, rainfall intensities between 30 and 50 mm·h^-1 are more likely to occur in the two high-shear types.

Key words: eastern Gansu Province, short-time heavy rainfall, weather events, spatiotemporal distribution