Drought variability in Inner Mongolia of northern China during 1960–2013 based on standardized precipitation evapotranspiration index

Abstract

The standardized precipitation evapotranspiration index (SPEI) was widely used in climatology and hydrology studies, because its combination the sensitivity of the PDSI to the changes in ET (caused by air temperature fluctuations and trends) with the simplicity of calculation, but also has the robustness of the multitemporal nature of the SPI. In this article, the temporal and spatial pattern of drought based on SPEI was explored in the Inner Mongolia during 1960–2013. The results showed that SPEI can effectively reveal the multiscalar feature of drought, and the effect of air temperature rising on drought severity and cumulative effect of drought itself. SPEI is suitable for those longer time scales such as 6-month or longer, and better in semi-humid and semi-arid areas than in arid area, due to much zero values or extreme maximum values at shorter time scale or in arid area. Generally, there is a drying trend in the whole Inner Mongolia, and a very severe drought was revealed at multi-time scales during the 2000s. Annual SPEI change at 6-month scale from APR to SEP indicated that drought in plant-growth season is very frequent and increasingly serious, and it should be given more attention. The severities of drought vary in different sub-regions. A significant abrupt change point of drought change trend in the whole Inner Mongolia at 12-month time scale was diagnosed in late 1990s, while this abrupt point in the middle-west subarea is a little earlier than those in the northeast subarea and the southeast subarea. This lasting severe drought should be the result of joint action of increasing air temperature and obviously decreasing precipitation since 2000s. At the same time, the most severe and frequent drought mainly occurred along the Sino-Mongolia border and the Horqin Sandy Land, while the continuous belt along the Da Hinggan Ling Mountains, the Yinshan Mountains, the Hetao Plain and the Mu Us Sandy Land is the area with relative slight drying trend during the last decades. Drought spatial pattern indicated by SPEI was supported by spatial distribution of temperature vegetation drought index based on remote sensing.