HR: 1340h
AN: T23C-0571    [Abstracts]
TI: The Effect of Atmospheric Heating From Precipitation Over the Tropical Western Pacific Warm Pool and the Maritime Continent on the Walker Circulation and Paleoclimatic Implications
AU: * Dayem, K E
EM: dayem@colorado.edu
AF: Department of Geological Sciences and CIRES, University of Colorado, Campus Box 399, Boulder, CO 80309 United States
AU: Noone, D C
EM: dcn@colorado.edu
AF: Program in Atmospheric and Oceanic Sciences and CIRES, University of Colorado, Campus Box 311, Boulder, CO 80309 United States
AU: Molnar, P
EM: peter.molnar@colorado.edu
AF: Department of Geological Sciences and CIRES, University of Colorado, Campus Box 399, Boulder, CO 80309 United States
AB: The late Cenozoic closing of the Indonesian seaway and the emergence of the maritime continent above sea level have potential to influence the Walker circulation in two ways. First, the islands of the maritime continent block flow between the Pacific and Indian oceans and allow formation of the tropical western Pacific warm pool. Second, the islands are a source of sensible heat to the atmosphere. Both are associated with high precipitation rates and latent heating of the atmosphere, which can lead to ascent in the western branch of the Walker circulation. We use precipitation rates from the Tropical Rainfall Measurement Mission (TRMM) satellite to estimate atmospheric heating due to precipitation over the maritime continent and the warm pool. Although rainfall concentrates over and adjacent to islands of the maritime continent, condensation associated with precipitation over the warm pool provides about twice the amount of latent heating largely because the surface area of the warm pool is about 1.9 times larger than that of the maritime continent. High precipitation rates over the maritime continent correlate with La Niña conditions and enhanced Walker circulation (surface easterlies and high-level westerlies over the western Pacific) during boreal spring, summer, and autumn, but not winter. High precipitation rates over the warm pool, however, are associated with a weakened Walker circulation except in boreal winter. Thus, heating over the maritime continent correlates with the strength of the Walker circulation throughout most of the year, and heating over the warm pool correlates with the strength of the Walker circulation only when the maximum precipitation rates shift east of the maritime continent. The correlation of rainfall over Indonesia with the strength of the Walker Circulation suggests that the emergence of a maritime continent may have led to a strengthening of the Walker circulation, and be related to a change in tropical Pacific climate from a permanent El Niño-like state to the present day El Niño-Southern Oscillation (ENSO) state.
DE: 1631 Land/atmosphere interactions (1218, 1843, 3322)
DE: 1854 Precipitation (3354)
DE: 3305 Climate change and variability (1616, 1635, 3309, 4215, 4513)
DE: 4922 El Nino (4522)
DE: 8177 Tectonics and climatic interactions
SC: Tectonophysics [T]
MN: Fall Meeting 2005