Characteristics of spring consecutive dry days with different durations across China based on the objective zoning approach

The duration of dry periods is closely related to drought conditions and is used to evaluate the degree of drought. In this article, using the rotated empirical orthogonal function (REOF) and K-medoids clustering methods and considering the spatial continuity, 500 stations in China are divided into 10 clusters to analyze the variation characteristics of consecutive dry days (CDDs) with different durations in spring. In Clusters 1-5 over the middle and lower reaches of the Yangtze River, South China, North China, and eastern and western Southwest China, the contribution percentage of short-duration CDDs to total dry days decreases, while that of medium- and/or long-duration CDDs increases, which leads to an increase in the total dry days and the duration of CDDs. In Clusters 6-8, the total dry days decrease, which are mainly contributed by the decreases in medium-duration CDDs (for Cluster 6 over southern Northeast China) or long-duration CDDs (for Clusters 7-8 over northern Northeast China and southern Xinjiang). The total dry days change little in Clusters 9-10 over eastern Northwest China and northern Xinjiang, which is attributed to the offset among the changes in the three-type duration CDDs. In Clusters 6-10, the duration of CDDs shortens overall. The decadal changes of spring dry days in China exhibit remarkable regional differences. The total day days and three-type duration CDDs in some clusters (1, 4, and 8) all have significant decadal changes, but they have not in Cluster 7. And the decadal change times also exhibit regional differences. The investigation of different-duration CDDs in this study provides more information on droughts at different time scales in China.

Automated summary

This study analyzed the variation characteristics of consecutive dry days with different durations in spring in China using statistical methods. The results showed significant regional differences in the changes of dry days, with some regions exhibiting notable decadal changes in drought conditions. The investigation provides more information on droughts at different time scales in China.