SGER: Seasonal Cycle of Drought in Coupled Climate Models and its Implication for the Hydro-ecosystem

University Of Maryland, College Park, College Park MD

Investigators

Abstract

This is a grant under a Climate Variability and Predictability (CLIVAR) Program pilot project called DRICOMP, for the Drought in Coupled Models Project, which focuses on making initial explorations into the mechanisms of drought as they are represented in the output of global climate models and on attempting to assess the reliability of these models in simulating drought. This research explores implications of the hypothesis that the severity of drought is better understood if its seasonal cycle is revealed. For example, the impact of a drought is greater when it occurs during the dry season than during the wet season. The investigators will explore the seasonal cycles of precipitation changes in the newly available Coupled Model Intercomparison Project 3 (CMIP3) models, going beyond the typical analysis of total precipitation change. The 20th century control climate simulations will be analyzed and compared with observations, in an initial effort to assess the realism of their seasonal cycles as well as their annual means. In doing so, a region-dependent criterion will be developed that may be useful for evaluating predicted climate change. Then, precipitation changes from the 20th century to the future from all the archived models will be analyzed. Their seasonal cycles, especially the dry season behaviors, will be emphasized, and regions with more robust signals will be classified by seasons, providing initial insights into the likelihood and the mechanisms of future droughts. The focus will be on three regions: the Mississippi basin, the Sahel, and the Amazon, which represent three distinct climatic regimes and which have great economic and environmental significance. The projected future changes in precipitation, temperature, soil moisture and other relevant variables from representative CMIP3 models will be used to drive a coupled land-surface and dynamic vegetation model, VEGAS. The ecosystem and water cycle sensitivity to different characteristic changes in seasonal cycles will thus be assessed. The simulated soil moisture and vegetation state will be compared to traditional drought indices such as the precipitation anomaly, the Palmer Drought Severity Index (PDSI), and the Standardized Precipitation Index (SPI). These analyses may help answer the important question of how adequate are the traditional drought indices for the purposes of characterizing and predicting future changes in the hydro-ecosystem. Broader impacts of the studies are in its contribution to assessing the risk of drought in a warmer climate. The project will involve a graduate student and will provide her/him with one month of support.