The characteristics of wet and dry spells for the diverse climate in China

Using a large precipitation dataset from 692 gauge stations across China for the period of 1960-2013, this study analyzed the characteristics of wet/dry spells related to four types of climate including arid, semiarid, semiarid to subhumid, and humid climate. A wet/dry spell is defined as the consecutive days with precipitation amount greater/less than a threshold. The frequency of wet/dry spells, the contributions of wet/dry spells with different lengths to the total number of wet/dry days and total precipitation amount were analyzed for different climate types. The wet/dry spells with the greatest contributions to the total wet/dry days or total precipitation amount vary with climate. For drier climate, long-duration dry spells contribute more to the total number of dry days, while short-duration wet spells contribute more to the total number of wet days and the total precipitation amount. The characteristics of wet/dry spells are closely related to local climate. Good regression relationships were obtained for the number of dry/wet spell versus spell length, and precipitation amount versus wet spell length. Although the correlation between precipitation amount and wet spell length has rarely been considered in stochastic precipitation generation, the relationships identified in this study justify the necessity of taking it into account.