Simulating Multi-Season Past Droughts
Abstract

Abstract Author: Kerry H. Cook and Edward K. Vizy

Abstract Title: Hydrodynamics of the Caribbean low-level jet and its relationship to drought

Abstract: Output from coupled GCMs and NCEP's North American regional reanalysis is analyzed to improve our basic understanding of the hydrodynamics of the Caribbean low-level jet (CLLJ) and its relationship to summer drought over North and Central America.

Past studies indicate that drought over the central U.S. is associated, at least in part, with a decrease in the northward transport of moisture from the Gulf of Mexico by nocturnal jets that form over the Great Plains in summer. The climatology shows a meridionally-oriented Great Plains low-level jet (GPLLJ) to the north of a zonally-oriented CLLJ, and the two flows appear to be connected. The degree to which these jets act in concert to tranport moisture from the tropics into middle latitudes on shorter time scales, and the relationship of the positioning and strength of both jets to the North Americal subtropical high (and its westward extension), is presented.

The role of the CLLJ in determining drought conditions in the central U.S. through interactions with the GPLLJ, and in supplying moisture directly to Central America, is investigated by contrasting the climatology with times of drought. Moisture budget and vertical stability analyses, as well as thermodynamics balances, are presented.