A prediction theory of record-breaking PDSI of China

Abstract

The Palmer Drought Severity Index (PDSI) was calculated by using monthly air temperature and precipitation data in China during the period 1960 to 2007 Based on the monthly PDSI of 614 stations in China from 1960 to 2007, we theoretically study the statistics of record-breaking monthly PDSI (RBMP) in recent 48 years. According to the theory of record-breaking event, we have developed the universal mathematical formula to evaluate the record-breaking events. Based on the existing Gaussian distribution of monthly PDSI and the RBMP as the initial conditions, we compute the universal mean of the RBMP. Compared with the results of iterative calculations using the theoretical value, the values computed using the former method are closer to the real values. Then the next possible RBMP in the future are evaluated and predicted by the former method. The results show that the changes of extreme drought differ much in different regions of China and have obvious regional features. The drought trend in North China will continue, and the degree of extreme drought event of these regions are rising fast, extreme drought events more likely happen again in nearly two decades in the future. On the other hand, in South area, it is very improbable for more serious occurrence of extreme drought events in recent decades. The polarization trend in China will be further enhanced.