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Rich structures of air-sea interaction revealed by satellite
Shang-Ping Xie, University of Hawaii, Honolulu, HI; and M. Nonaka, Y. Tanimoto, H. Xu, and W. S. Kessler
Vast oceans are poorly observed by traditional measurements. New satellite observations are revealing interesting structures of oceans and the overlying atmosphere in detail never possible before. With a few recent examples, this paper illustrates the great potential satellite data offer for studying air-sea interaction and climate.
Lack of understanding how extratropical oceans affect the atmosphere is a stumbling block in recent efforts to study non-El Nino climate variability. Climatic datasets typically have resolutions of several 100 to 1,000 km and of a month to a season, poorly representing ocean fronts near major currents like the Kuroshio and Gulf Stream. It is on these narrow oceanic fronts, however, that ocean dynamics become important and cause large SST variations.
Satellite observations reveal a ubiquitous pattern of SST, winds and clouds near major ocean fronts/currents in various parts of the world ocean. This pattern is characterized by a positive SST-wind speed correlation indicative of ocean-to-atmosphere feedback, in contrast to the negative correlation that dominates on the basin scale and is now attributed to atmospheric forcing of the ocean mixed layer. This positive SST-wind speed correlation is consistent with the vertical mixing mechanismthe near-surface atmosphere is unstably stratified on the warmer flank of SST fronts, enhancing mixing that accelerates surface winds by bringing faster winds from aloft. Recent observational and modeling studies further suggest that ocean front��s effect is not limited to the planetary boundary layer but extends over the whole troposphere through the modulation of baroclinic waves and storm track.
Another important class of air-sea interaction that satellite begins to reveal is that triggered by land orography. Intense gap wind jets off Central America and the Costa Rica Dome in the ocean are an example. New satellite observations show that these wind jets have a delayed effect on atmospheric convection two seasons later in summer through the ocean memory in the thermocline dome.
.Session 1, In situ and satellite measurements of the air-sea interface
Monday, 9 August 2004, 9:00 AM-12:00 PM, New Hampshire Room
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