SPI-based Drought Variations in Xinjiang, China

Daily precipitation data at 53 stations during 1957—2009 in Xinjiang are analyzed based on Standardized Precipitation Index (SPI) technique with the aim to investigate the spatial-temporal patterns of drought events. The Mann-Kendall trend test is used to detect the trends of monthly SPI values, drought intensity and drought duration. Pre-whitening technique is applied before the Mann-Kendall trend test to eliminate the autocorrelation within the precipitation series.According to the results, the frequency of mild drought in North Xinjiang is less than the theoretical frequency, while frequencies of moderate, severe and extreme droughts are higher than the theoretical ones. The statistical condition of drought events in South Xinjiang is to the opposite. Although the drought disaster in Xinjiang is abating in general, the trend varies in different areas. The decreasing of drought in North Xinjiang mainly happens in winter. However, in spring, summer and autumn, the decreasing is insignificant and has obvious influences on agriculture. As the agricultural water demand is increasing tremendously recently, this insignificant decreasing of drought hardly compensate the shortage of water demand. As a result, this change may be not beneficial to agriculture. The abating of drought in South Xinjiang mostly occurs in summer, while the drought in the south part of South Xinjiang is aggravating. The drought in East Xinjiang slightly aggravates. In North Xinjiang, both the intensity and duration of drought have decreasing trends. The intensity and duration of drought in South Xinjiang are both slightly increasing. In the middle part of East Xinjiang, the intensity and duration of drought are both significantly increasing. These results provide theoretical and practical merits for better understanding of variations of drought, monitoring of drought, and mitigating the losses of drought disaster.