Study on Air-sea Interaction under High-tide and Construction of Meteorology-oceanography Coupled Model

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・Mechanisms of air sea interaction and their parameterizationTurbulence structure and momentum, heat and mass transfer mechanisms near the air sea interface were investigated by the direct numerical simulation, DNS. In the low to moderate wave age regime (c/u^*<10,c : wave speed, u^* : friction velocity), cat-eye vortex is created around the critical level and it attenuates momentum exchange between air and sea. The wave development rate ss is well approximated by Miles'quasi-laminar model, i.e., for c/u^*<6,ss is almost constant (ss=15〜20) and then decreases to ss=0 in c/u^*=10〜15. In high wave age regime the critical level is located far above the wave, and the momentum exchange is determined by the turbulence and pressure field near the interface and results in the negative ss value. Sensible heat and mass (water vapor) transfer also shows the similar wave age dependence and has similarity with momentum transfer.In addition, from laboratory experiment and DNS thermal convection deve … More loping beneath the interface was simulated and heat and mass exchange was shown to be enhanced by 1.5〜2.0 times, compared with that above the horizontal heated solid wall.Based on these results of momentum, heat and water vapor exchange, the so-called bulk coefficient and roughness parameter on the air side and heat and mass exchange on the liquid side (e.g., ocean uptake of green house gases like CO_2) were parameterized and then those formulations were incorporated in the ‘community-based meteorology and oceanography model'.・Construction of community-based meteorology and oceanography modelA community-based meteorology and oceanography model was developed by coupling a meteorology model, ocean model and ocean wave model with the air-sea interaction module as the interface. It was applied to simulations of regional to local scale meteorological and oceanographical disasters.Applying it to the typhoon 9918 which caused a great injury due to high tide at Matsuai facing to the Yatsusiro Sea, high performance of the model was revealed by comparing it with the observed tide height in Yatsushiro and Hiroshima observatory sites, except for Matsuai. Taking into account the wave breakdown and its energy transfer caused by the shallow sea bed, the performance of the model was confirmed to be improved remarkably.This modified version of the model was applied to the following simulations ; 1)outlaying surge in winter by coupling MM5 meteorological model including bogus low pressure and WWIII ocean wave model, 2)wind and precipitation caused by the typhoon 9918, 3)influence of the Black Stream on surface wind and precipitation and 4)high tide in the Bengal Bay caused by the tropical cyclone in 1991.This numerical model system was graded up for high speed parallel processing on personal computer cluster machine and devoted for local governmental use in forecasting surge and high tide as the community-based meteorology and oceanography model. Less