Plate 2.5 Extreme Regional Precipitation of Varying Duration and Return Period 1981–1993

Precipitation is an areal phenomenon, limited in extent and duration. Precipitation depths of a given duration in any defined area have a maximum and a minimum. Areal precipitation determined for increasingly large concentric areas around the maximum results in characteristical decreasing curves, known as depletion curves.降水属于面域性气象现象，其空间尺度与持续时长均存在局限。在任意划定的区域内，对应某一固定持续时长的降水深度，存在最大值与最小值。以降水最大值点为中心，逐步扩大的同心区域所计算得到的面降水量，将呈现出特征性的递减曲线，这类曲线被称为耗竭曲线（depletion curves）。