Future drought projection under CMIP6 SSP Scenarios in Urmia Lake basin, Iran

Document Type : Research Paper

Authors

1 Associate Professor, Department of Geography, Ferdowsi University of Mashhad, Mashhad.

2 Department of Geography, Ferdowsi University of Mashhad, Mashhad.

3 Department of Geography, Yazd University, Yazd

Abstract

The Urmia Lake basin is one of the most vulnerable areas to frequent and high-intensity droughts in Iran. The aim of this study is to project meteorological drought in the Urmia Lake basin through the 21st century. We investigated the standardized precipitation-evapotranspiration index (SPEI-1) by using the bias-corrected CMIP6 models under SSP1-2.6 and SSP5-8.5 scenarios during the period 2026-2100. We evaluated the performance of individual CMIP6 models and multi-model ensemble (MME) generated by the independent weighted mean (IWM) method with three statistics including NRMSE, MBE, and PCC. Overall, all individual CMIP6 models show good performance in the Lake Urmia basin, despite some overestimations of precipitation. However, the generated CMIP6-MME has increased the PCC values in all stations to 0.99. The CMIP6 MME show good performance of the SPEI-1 index in autumn, winter and spring against observation from ground stations in the historical period. The result indicates a significant increase in drought events mainly in the west and north of the Urmia Lake basin in the warm period of the year during 21st century. The severity and the percentage of below-normal years for the basin-averaged drought is more in the middle 21st century (2051-2075) than the far future (2076-2100), especially for the SSP5-8.5 scenario. These results can provide a basis for the development of drought adaptation plans in the Urmia Lake basin.

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