Characteristics of dry-wet changes in Xinjiang based on SPEI index

Based on the monthly observed temperature and precipitation data of 55 meteorological stations in Xinjiang from 1961 to 2015, using the standardized precipitation evapotranspiration index (SPEI) was adopted. The results show that: In recent 55 years, precipitation and temperature in Xinjiang have an increasing trend, with the change rates of 8.90mm/10a and 0.39℃/10a, respectively. The warming characteristics were obviously stronger than that of humidification, forming the spatial and temporal differences and complexity of dry and wet changes. From 1961 to 1987, it was in the alternate period of drought and drought alleviation, and 1987-1996 was in the drought relief period. Among them, 1997 and 2008 were the more serious drought years, and the proportion of drought stations was 82% and 78% respectively. EOF1 reflects that the overall dry and wet changes in the study area were weakening, and there was a drying trend; EOF2 was a reverse change in the northern and Southern Xinjiang; EOF3 shows that the East Tianshan had a drying trend, while the western part of Southern Xinjiang has the trend of drought alleviation. The spectra of wavelet coherence and cross wavelet transform showed that the SPEI values in Xinjiang have resonance periods of different time scales with the Atlantic multi-year intergenerational oscillation (AMO), El Nino Southern Oscillation (ENSO), North Atlantic Oscillation (NAO) and Pacific interdecadal oscillation (PDO), but in different time domain correlation has certain differences, illustrate the atmospheric circulation index was one of the factors influencing the region year SPEI.