Drought severity and change in Xinjiang, China, over 1961–2013

Monthly climatic data from 53 sites across Xinjiang, China, were used to compare drought severity from the widely accepted Standardized Precipitation Index (SPI) with the recently proposed Standardized Precipitation Evapotranspiration Index (SPEI), as well as trends in the data from 1961 to 2013. Monthly Thornthwaite based ( ET o.TW ) and Penman-Monteith based reference evapotranspiration ( ET o.PM ) were computed and subsequently used to estimate SPEI TW and SPEI PM , respectively. The indices9 sensitivity, spatiotemporal distributions and trends were analyzed. The results showed that the TW equation underestimated ET o , which affected the accuracy of the SPEI estimation. Greater consistency was found between SPI and SPEI PM than between SPI and SPEI TW at different timescales. SPI and SPEI PM were sensitive to precipitation, but SPEI TW and SPEI PM were insensitive to ET o . The scope of spatial SPEI PM was wider than that of SPI at the same timescale. Obvious differences in SPI, SPEI TW and SPEI PM existed between northern and southern Xinjiang. SPEI PM was a better indicator of global warming than SPI. Both SPI and SPEI PM had increasing trends, which contradict previously reported trends in global drought. In conclusion, the decrease in drought severity observed over the last 53 years may indicate some relief in the water utilization crisis in Xinjiang, China.