Improvements of K Drought Index in Southern China

Drought indices are commonly used for detecting and quantifying drought spells. However, a index with multiple time scale and applicability in different regions is scarce. In this study, K drought index on daily time scale is devised based on a existing monthly K index according to accumulative and attenuation effect of disaster-inducing factor. The daily K index is presented on two forms: one is based on linear attenuation effect (K_l) and the other based on exponential damping (K_e). Monitoring effects of these two forms of daily K index are compared in Southern China. The results show that: (1) For time series variation of drought on special observe station, K_l has smaller amplitude of variation than that of K_e when drought is developing while K_l indicates less reduction of drought level than that of K_e when light precipitation is appearing. (2) Statistical calculations of unreasonable jump points for both K index forms demonstrate that K_l is more suitable in middle-northern part of southern China though both K index forms are feasible in south part of southern China. In all, the research suggests K_l as a great daily drought index due to its excellent monitoring effects in southern China.