Simulating Multi-Season Past Droughts
Abstract

Abstract Author: Sang-ik Shin, Robert S. Webb, and Prashant D. Sardeshmukh

Abstract Title: The impacts of tropical SSTs on the Regional Hydroclimate

Abstract: Changes in modern tropical sea surface temperatures (SSTs) are known to impact the regional hydroclimates. However, the areas of the tropical oceans that are most critical in controlling the regional hydroclimate still remain uncertain.

We addressed these issues by diagnosing the available observations and model simulations performed as part of the AMIP and CMIP3 projects, specifically 20th century climate simulations. We combined the near-surface air temperature and precipitation changes into a single hydroclimatic drought parameter - the Palmer Drought Severity Index (PDSI) - as distinct from a mere precipitation deficit or surplus. Then the constructed PDSI from the simulations and observations were correlated and regressed on to the tropical SSTs. Our results largely confirms the previous studies that suggested dominant influence of the tropical SSTs on the regional hydroclimate. We further identified the SST patterns with the greatest influence on the regional PDSI by using the atmospheric general circulation model simulations with prescribed tropical SST anomalies. The PDSI responses were determined for an array of 43 localized SST anomaly patches over the Indian, Pacific, and Atlantic Oceans. The identified “optimal SST patterns” for regional PDSI stress the importance of the tropical SST patterns in regional hydroclimate.