Spatiotemporal drought variability on the Mongolian Plateau from 1980-2014 based on the SPEI-PM, intensity analysis and Hurst exponent.

Knowledge about variations of drought can provide a scientific basis for water resource planning and drought mitigation. In this study, the variations and patterns of drought identified by the Standardized Precipitation Evapotranspiration Index (SPEI) were investigated on the Mongolian Plateau for the period 1980-2014, based on intensity analysis, linear regression, the Mann-Kendall test, wavelet analysis, and Hurst exponent. The results show that: 1) the annual SPEI decreased at a rate of -0.0133/yr over the past 35years, and a major abrupt change occurred in 1999; 2) drought on the Mongolian Plateau intensified from 1980 to 2014, and the drought in Mongolia has been more serious than in Inner Mongolia since the beginning of the 21st century; 3) the rate of drought/wet changes in 1980s-1990s and 1990s-2000s were faster than in 2000s-2010s. In 1980s-1990s, the different drought levels were transformed into various wet levels. In 1990s-2000s, the wet levels were transformed into drought, and in 2000s-2010s, the losses of drought levels were larger than the gains in wet levels; 4) the Hurst exponent is a reliable way to predict drought tendency, with a predictive accuracy as high as 91.7%; 5) the mean H value of the SPEI time series during 1980-2014 was 0.533, indicating that the future drought trend is generally consistent with the current state. In the future, the proportion of area with increasingly severe drought (72.2%) will be larger than that with increasingly wetter conditions (27.8%) on the Mongolian Plateau.