SGER: Hydrodynamics of the Caribbean Low-Level Jet and Its Relationship to Drought

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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.The principal investigators will analyze output from coupled atmosphere/ocean global climate models and the National Center for Environmental Prediction's (NCEP's) North American regional reanalysis to try to improve our understanding of the hydrodynamics of the Caribbean low-level jet and its relationship to summer drought over North and Central America and to evaluate our ability to capture this relationship in models. Past studies suggest that drought over the central United States is associated with a decrease in the poleward transport of moisture from the Gulf of Mexico by the Great Plains low-level jet. The meridionally-oriented Great Plains jet is located just north of the zonally-oriented Caribbean low-level jet, and, in monthly mean climatologies, they often appear to be connected. The basic hydrodynamics of the Caribbean jet and how it varies during drought are, however, not well known. The principal investigators will conduct exploratory evaluations of the roles of the Caribbean low-level jet in supplying moisture to the central United States through interactions with the Great Plains jet and in supplying moisture directly to Central America, by contrasting the climatology with times of drought. Atmospheric and surface moisture budget analyses, as well as thermodynamic balances, will be diagnosed in the reanalysis and in the general circulation model (GCM) output from 20th Century Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4) integrations in five models. These analyses may lead to a better understanding of the dynamics of drought and an assessment of how well models capture drought mechanisms.A broader impact of the study is in its potential to reveal a new physical link to North American drought that could contribute to drought prediction.