Simulating Multi-Season Past Droughts
Abstract

Abstract Author: Kristopher B. Karnauskas, Antonio J. Busalacchi

Abstract Title: Low-frequency tropical Pacific forcing of multi-year North American drought in CMIP3 models

Abstract: U.S. CLIVAR has initiated a Drought in Coupled Models Project (DRICOMP) to facilitate diagnostic research into the representation of drought in coupled models. An important yet poorly understood phenomenon with implications for understanding and predicting long-term North American drought is the occurrence of persistent cool episodes (PCEs) in the equatorial Pacific Ocean (i.e., lower frequency than model ENSO). We examine the representation of PCEs in several U.S. and international coupled models archived by the WCRP CMIP3 Multi-Model Database, including their relationship with multi-year North American drought variability. Drought variability is defined in terms of the Palmer Drought Severity Index (PDSI), so that the remote forcing of both precipitation and surface air temperature- and therefore evaporation may be considered. The representation of PCEs, and relationship between PCEs and long-term North American drought varies widely among models, and less so between pre-industrial and greenhouse warming experiments. The model large-scale mechanisms linking the low-frequency Pacific SST variability and long-term North American hydroclimate are discussed.