Document Type : Original Article
Author
Assistant Professor, Department of Geography, Faculty of Letters and Humanities, Ferdowsi University of Mashhad, Mashhad, Iran
Abstract
Grasping the intricacies of drought dynamics particularly as global warming accelerates atmospheric evaporative demand remains paramount for effective water resource risk management. To achieve this, we developed a multi-model ensemble (CMIP6-MME) aeveraging outputs from the Coupled Model Intercomparison Project Phase 6. Initially, the methodological framework evaluated the performance of the CMIP6-MME in reproducing the 12-month Standardized Precipitation Evapotranspiration Index (SPEI-12) across nine synoptic stations over a historical (1990–2014). Statistical assessments revealed an interesting caveat: while Nash-Sutcliffe Efficiency values fell below zero (NSE<0) due to inherent temporal phase mismatches typical of General Circulation Models, Willmott’s Index of Agreement firmly validated the ensemble’s robust capacity to simulate regional climate behavior. These projections were driven by three distinct Shared Socioeconomic Pathways: SSP1-2.6, SSP3-7.0, and SSP5-8.5. The resulting simulations point toward the emergence of a starkly bipolar climate in Iran’s future. In the southern territories and lower latitudes, projections under the SSP5-8.5 indicate that drought intensity will deteriorate to severely critical thresholds (SPEI≤-2). Governed by the Clausius-Clapeyron thermodynamic relationship and a subsequent surge in precipitable water, these northern expanses will likely witness a mitigation in severe drought intensity. Paradoxically, the actual frequency of dry spells in these areas is projected to surge by up to 34%. Ultimately, this spatial migration of the nation’s drought epicenter underscores an urgent reality: mitigating the multifaceted impacts of climate change will demand highly localized and entirely distinct adaptation strategies across different geographic zones.
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