HR: 09:45h
AN: A41F-07    [Abstracts]
TI: Precipitation from African Easterly Waves in a Coupled Model of the Tropical Atlantic Ocean
AU: * Seo, H
EM: hyseo@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Dr. Dept 0224, La Jolla, CA 92093, United States
AU: Jochum, M
EM: markus@ucar.edu
AF: National Center for Atmospheric Research, Oceanography Section; Room 4151850 Table Mesa Drive, La JollaBoulder, CO 80305, United States
AU: Murtugudde, R
EM: ragu@essic.umd.edu
AF: ESSIC/DAOS University of Maryland, 2207 CSS Bldg/ESSIC University of Maryland, College Park, MD 20742, United States
AU: Miller, A
EM: ajmiller@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Dr. Dept 0224, La Jolla, CA 92093, United States
AU: Roads, J
EM: jroads@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Dr. Dept 0224, La Jolla, CA 92093, United States
AB: A regional coupled climate model is configured for the tropical Atlantic to explore the role of synoptic-scale (2-6 day) African Easterly Waves (AEWs) on the simulation of mean precipitation in the marine Inter-Tropical Convergence Zone (ITCZ). Sensitivity tests with varying atmospheric resolution in the coupled model show that these easterly waves are well represented on both fine and coarse grids of the atmospheric model, with the mean variance of the waves on finer grid being roughly 20% larger. The resultant wind shear associated with the strong phase of the AEWs for both atmospheric grids is comparable. Significant differences in the model simulations are found in the precipitation fields, where extreme rainfall events occur in the strong shear of the easterly waves only on the higher resolution grid. This is indicative of the strong coupling between the easterly waves and rainfall. This is because the low-level convergence due to the waves is much larger and more realistic in the fine-resolution simulation, which enables strong precipitation events. The variability in rainfall on these time scales accounts for a significant fraction of the total variability. As a result, the simulation of mean rainfall in the ITCZ and its seasonal migration become more realistic in the higher-resolution case. This suggests that capturing these transient waves and the resultant low-level convergence is a key to improving the simulation of precipitation in global coupled climate models, with obvious implications for regional climate prediction.
DE: 1854 Precipitation (3354)
DE: 4504 Air/sea interactions (0312, 3339)
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly