What do climate projections say about future droughts in Alabama?

Abstract

Abstract. Droughts are one of the costliest natural disasters triggered by severe shortage of water. In recent years, the Southeast US has been hit by several severe droughts. The recurring nature of these droughts have called for a more pragmatic approach to mitigating their impacts. This study intends to study how droughts in Alabama will change in the future as a result of projected changes in the climate. Commonly used drought indices are being computed and analyzed to quantify changes in frequency, severity and spatial extent of future droughts. Historical and future droughts are being quantified by the means of Standardized Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI), Palmer’s Drought Severity Index (PDSI), and Self-calibrating Palmer’s Drought Severity Index (sc_PDSI). Regionally-downscaled precipitation, temperature, and soil water content data for the Southeast for high emission scenario (A2) from three General Circulation Models, the Hadley Centre Coupled Model Version 3 (HadCM3), the Geophysical Fluid Dynamics Laboratory (GFDL) and Community Climate System Model (CCSM), from the Third Coupled Model Inter-comparison Project (CMIP3) archive are being used for this purpose. Data from 1969 to 2000 are being used for historical simulation, while from 2039 to 2070 are being used for future projections. Preliminary principal component analysis of SPI from GFDL and HadCM3 models indicate that the frequency of drought is likely to increase in the future. Years similar to the severe drought years of Alabama during the 1980s can be seen occurring more often during the future period being considered. In addition to frequency, the severity of future droughts are also projected to increase. The study of spatial patterns of droughts indicated that future droughts are expected to be spread across larger areas as compared to the ones in the past. The comparison of these results to that from other drought indices is expected to bolster the validity of these results. The analysis of drought trends can be applied in a drought monitoring/early warning system and can be used to proactively mitigate the effects of droughts. If droughts can be projected/forecasted well ahead of time, their consequences can be tackled more appropriately. The results of this research are expected to help us understand expected changes in droughts in the Southeast US and would help us better prepare to mitigate the economic, social as well as environmental effects of droughts.