Abstract Author: Kirsten L. Findell and Thomas L. Delworth
Abstract Title: Large-scale impact of common SST anomalies on drought and pluvial frequency and occurrence
Abstract: Simulations from five global climate models (GCMs) run as part of the U.S. Clivar Drought Working Group were analyzed to assess the impact of common sea surface temperature (SST) anomalies on drought and pluvial frequency, intensity, and duration worldwide. The suite of experiments used GCMs run with interactive atmosphere and land coupled to an ocean with prescribed SSTs. The control run SSTs were climatological, while the primary experimental runs added cold and/or warm SST anomalies from the Pacific and/or the North Atlantic to this climatology. Drought and pluvial thresholds were regionally determined relative to each modelís control simulation. The bulk of analysis centered on changes in frequency of months surpassing these threshold values. Analysis of individual drought factors (e.g., precipitation) reveal a strong sensitivity to SST conditions in the regions closest to the SST perturbation (e.g., the Americas and land areas adjacent to the Pacific warm pool), with little sensitivity in much of the rest of the world. Drought indicies, on the other hand, capture information about the time history of more than one controlling variable, and show much greater sensitivity to the prescribed SST anomalies, thereby revealing much more about the likely causes of droughts and pluvials throughout the world. Results are focused on regions of greatest agreement (e.g., the continental United States, Central America, Indonesia) and disagreement (e.g., India, Central Africa) between the participating models.