Spatiotemporal Drought Characterization Using Gravity Recovery and Climate Experiment (GRACE) in the Central Plateau Catchment of Iran

Abstract

Droughts that occurred in the central plateau catchment of Iran have been monitored by Terrestrial Water Storage Deficit Index (TSDI) and three recently modified indices, namely aSPI, aSPEI and eRDI. Terrestrial Water Storage Changes (TWSC) for this area during April 2002–2016 was calculated using the GRACE spherical harmonics. The leakage error and noise of TWSC were evaluated by inter-comparison of this time series with regional mascon solutions; furthermore, to better comprehend the effect of climate on drought, the studied area was divided into semi-arid, arid, and extra-arid zones by using the modified De Martonne method. Using the meteorological data of 105 synoptic stations, the selected indices were calculated within a time scale of 3, 6, 9 and 12 months, and were compared to TSDI. Accordingly, the study area experienced multiple droughts during the studied period. The spatial distribution map for 2008–2009 drought showed that all indices indicated good conformity. The coefficient correlations between TSDI and other indices were different in each zone, but generally, the similarity of TSDI pattern increased with increasing time scales and was the most consistent with 9 and 12-month indices. Based on the spatiotemporal analysis of droughts, the severity, duration, and frequency of drought in the semi-arid zone were more than the other zones while no significant drought occurred in the extra-arid zone. Overall, the result indicated that GRACE-derived TSDI could be implemented successfully to predict spatiotemporal characteristics of droughts in extensive basins.