1961-2024年中国西北地区连续极端降水的时空特征

Spatiotemporal Characteristics of Consecutive Extreme Precipitation Events in Northwest China from 1961 to 2024

摘要:

短时极端降水可能引发小范围洪水，而连续多天的极端降水则可能导致土壤饱和、山洪暴发及农业减产等长期影响。基于1961—2024年中国西北地区374个站点的逐日降水数据，结合该地区干旱和半干旱气候特征，设定第90百分位日降水量和20 mm的绝对阈值为极端降水事件的判定标准，分析了连续极端降水事件的时空分布特征。结果表明，连续2 d极端降水事件主要集中在新疆西部、青海中东部和甘肃西南部，事件发生次数普遍超过60 次；连续3 d和4 d事件频次逐渐减少，集中在天山和巴颜喀拉山等高海拔区域，频次分别达到15 次和 6次以上，而宁夏和陕西等地区较少发生。事件主要集中在5—9月，7—8月为高峰，连续2 d事件夏季总数超过40 次，连续3 d和4 d事件分别减少至20 次和10 次以下。1961—1983年连续2 d事件频率显著增加，均值为29.73 次，1983—1997年事件频率下降至27.27 次，1997—2024年回升至31.28 次，但增速放缓。长时间尺度事件频次始终较低，主要集中在特定山地区域。研究结果揭示了西北地区连续极端降水频率上升的趋势，并为防灾减灾研究与政策制定提供了科学依据。

Abstract:

Short-term extreme precipitation can trigger localized flooding, while multi-day extreme events may lead to soil saturation, flash floods, and significant agricultural losses. Using daily precipitation data from 374 stations in Northwest China (1961—2024), and considering the region's arid and semi-arid climate, extreme precipitation events were defined using the 90th percentile daily precipitation and a 20 mm absolute threshold. The analysis revealed that 2-day extreme events were concentrated in western Xinjiang, central-eastern Qinghai, and southwestern Gansu, with over 60 occurrences. Longer events (3-4 days) were less frequent, mainly occurring in high-altitude areas like the Tianshan and Bayan Har mountains. Events peaked from May to September, with a summer maximum in July-August. While the frequency of 2-day events increased significantly from 1961—1983, it declined in 1983—1997 before rising again in 1997—2024, though at a slower rate. Longer events remained relatively rare, primarily in specific mountainous regions. These findings highlight a rising trend in extreme precipitation frequency, providing a basis for disaster prevention and policy formulation.