The Drought Variability Based on Continuous Days without Available Precipitation in Guizhou Province, Southwest China

Abstract

Detecting the characteristics and variability of droughts is of crucial importance. In this study, Guizhou Province in China is selected as the target area, and the dataset there covering daily precipitation and drought records from 1960 to 2016 is adopted. The spatial and temporal differences in yearly and seasonal Dnp (the drought indicator of continuous days without available precipitation) values and longest Dnp as well as their trends are examined. Then the Dnp values and droughts are classified into different categories, and the relationships between Dnp and droughts are revealed. There was a steep increasing trend in yearly Dnp with a rate of 6 d/10a, and the Mann–Kendall (MK) value was estimated to be 5.05 in the past 56 years. The seasonal Dnp values showed significant increasing trends. Yearly and seasonal Dnp varied significantly in the space domain. There were slight increases in yearly and four seasonal longest Dnp values in the time domain. Although the increases in the spring and summer were not significant, heavy droughts tended to occur at this time. As to the Dnp values corresponding to different levels of droughts, there was only a decrease in mild drought, while there were significant increases in mild, moderate, and heavy droughts. The mild droughts increased significantly in summer, and the moderate droughts increased significantly in spring. Different levels of Dnp also varied in the spatial domain. The elevation effect is not obvious in Guizhou province.