HR: 16:00h
AN: OS44A-01 INVITED    [Abstracts]
TI: The Andes, the SPCZ and the eastern Pacific ITCZ
AU: * Takahashi, K
EM: ken.takahashi@noaa.gov
AF: Department of Atmospheric Sciences, University of Washington, Box 351640, Seattle, WA 98195-1640, United States
AU: Battisti, D S
EM: david@atmos.washington.edu
AF: Department of Atmospheric Sciences, University of Washington, Box 351640, Seattle, WA 98195-1640, United States
AB: Idealized coupled ocean-atmosphere model experiments indicate that the mechanical effect of the Andes mountains on the atmospheric flow and local air-sea interactions are enough to modify a zonally and equatorially symmetric distribution of tropical sea surface temperature (SST) and rainfall to become qualitatively similar to the observed in the Pacific. The main mechanism responsible is the advection by the southeasterly trade winds of low moist static energy air masses brought in contact with the surface of the southeast Pacific by subsidence induced by the presence of the Andes, which results in reduced SST (through surface evaporation) and precipitation in a region extending equatorward and westward from the southeast Pacific, leading to a precipitation distribution featuring a northward displaced intertropical convergence zone (ITCZ) and a south Pacific convergence zone (SPCZ) oriented in a southeast-northwest direction. Positive air-sea feedback processes are important for the magnitude of the response, particularly the interaction between low cloud albedo and SST in the southeast Pacific. The spatial extent of the dry and cool region is a function of the speed of advection by the trade winds, the entrainment rate into the atmospheric boundary layer and the surface drag coefficient, while its southeast- northwest orientation results mainly from the direction of the southeasterly trades. The latter promotes the formation of the SPCZ, which is organized further by local air-sea feedback.
DE: 3310 Clouds and cloud feedbacks
DE: 3319 General circulation (1223)
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
DE: 3374 Tropical meteorology
DE: 4572 Upper ocean and mixed layer processes
SC: Ocean Sciences [OS]
MN: 2007 Fall Meeting