广东省汛期分钟尺度极端降水的时空分布及持续性特征

Spatiotemporal Distribution and Duration Characteristics of Minute-Scale Extreme Precipitation during Flood Season in Guangdong Province

为提高华南季风区高频尺度极端降水发展规律的认识,基于2013~2021年自动气象站逐5分钟降水观测资料,分析广东汛期5分钟极端强降水的时空分布和降水事件持续性特征,并与小时尺度极端降水进行对比。结果表明,5分钟极端降水阈值(E5min)呈显著的经向差异并在珠江三角洲地区形成高值中心,受地形山脉的固有影响小,而1 h极端降水阈值(E1h)自沿海向陆地减小,高值区主要位于偏南风的地形迎风坡。前汛期E5min自西南向东北减小,后汛期分布相对均匀。与小时极端降水的日变化特征不同,前汛期各地E5min均有双峰结构(主峰在下午,次峰在早晨),后汛期仅毗邻珠江口的3个区具双峰分布,其余地区为单峰型。基于固定站点极端降水事件持续时间呈现显著的地域差异,阳江以东的南部沿海、龙门暴雨中心附近平均持续时间最长,阳江以西沿海地区和珠江三角洲核心城市群地区次之,西北部和东北部最短。进一步归纳具有时空关联的极端降水事件发现,白天极端事件较夜间的频数更高、移速更快、范围更广,而夜间事件的持续时间更长。对比而言,内陆地区降水系统的移速较沿海地区快,尤以广东西北部最快,导致该区5分钟降水效率高,但小时阈值较低。珠江三角洲中南部沿海地区极端降水事件的持续时间最长(夜间可达2.3~3.77小时),可能与该地区受城市群、海陆效应等综合影响有关。

To improve the understanding of extreme precipitation development at smaller time scales in the South China monsoon region,the spatial and temporal distributions of 5-minute extreme heavy rain and the persistent characteristics of extreme rainfall events in flood seasons were analyzed.The 5-minute precipitation observation data were obtained from automatic weather stations from 2013–2021 and compared with the characteristics of hourly extreme precipitation.The results show that the 5-minute extreme precipitation threshold(E5min)has a significant meridional difference,forming a high-value center in the Pearl River Delta region,with overall little inherent influence from mountainous terrain.However,the 1-hour extreme precipitation threshold(E1h)decreases from coast to inland areas.The high-value area is located on the windward slope of the southerly wind terrain.In the pre-flood season,E5min decreases from southwest to northeast and is distributed evenly in the post-flood season.In contrast to the diurnal variation characteristics of E1h,E5min values in the pre-flood season all have double peaks(the main peak in the afternoon,with the secondary peak in the morning).Only the three regions adjacent to the Pearl River estuary have double peaks in post-flood season;the rest are unimodal.The longer the average duration of extreme precipitation at each station,the more obvious the spatial differences.The longest durations are on the southern coast east of Yangjiang and the adjacent area of Longmen,followed by the coastal areas west of Yangjiang and the core agglomeration of the Pearl River Delta.The shortest durations are in the north.Further correlating extreme events with spatial and temporal data,it is found that daytime extreme events are more frequent,move faster,and have a wider range than nighttime events,while nighttime events last longer.The speed of inland precipitation systems is higher than that of coastal systems,especially in northwestern Guangdong,resulting in a high 5-minute precipitation efficiency but a low hourly threshold.The durations of extreme precipitation events in the central and southern coastal areas of the Pearl River Delta are the longest(up to 2.30–3.77 hours at night),which may be related to the comprehensive effects of urban agglomeration and sea–land interactions in this region.