| The focus of this study is air-sea exchange processes of momentum, heat and fresh water from the diurnal to intraseasonal time scales in various regions including western Pacific, Kuroshio current, and S. China Sea. In particular, a systematic investigation on the effects of such air-sea exchanges on typhoon and intraseasonal oscillations (ISOs) at both regional and local scales is being performed. The regional-scale study concerns region-wide effects of surface winds, warm SSTs, air-sea exchanges, and upper-ocean thermal/dynamic structures on typhoons and ISOs. The local-scale study concerns air-sea exchange processes in general, and particularly in high wind speed (>35 ms-1) and ocean surface wave conditions. The research tasks basically consist of three steps. First, oceanic mixing processes in response to observed surface forcing will be carried out using mixed layer ocean models and 3-D ocean models. Second, the atmospheric response to the same observed surface forcing will be performed using an atmospheric model. Then the atmospheric model will be coupled with the ocean models for fully coupled study. In this meeting, I will report a preliminary analysis of observed surface fluxes based on ECMWF operational assimilation data and TRMM data for the summer of 2000 and 2001, and the upper-ocean response to the observed forcing. The latter is based on two 1D-ocean mixed layer models: a Kraus-Turner type mixed layer model and a Mellor-Yamada type model. For typhoons in the South China Sea and Western Pacific, the effect of shear-induced turbulent mixing and Ekman upwelling on the upper ocean is being evaluated carefully. For tropical intraseasonal oscillations, the relative role of heat fluxes to wind stresses in affecting upper ocean heat content is being analyzed. |
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