- 著者
- 鈴木 直弥 上田 陽平 高垣 直尚 植木 巌 池田 篤俊
- 出版者
- Advanced Marine Science and Technology Society
- 雑誌
- 海洋理工学会誌 (ISSN:13412752)
- 巻号頁・発行日
- vol.27, no.1, pp.73-79, 2022-07-30 (Released:2022-08-27)
- 参考文献数
- 23
Drag coefficient on the ocean surface is determined by various studies based on different mechanisms, such as turbulence and wave breaking, closely related to wind speed. The global ocean datasets of wind speed are distributed by various temporal resolutions based on reanalysis, assimilation, and satellite data. Recently, the wind speed data with higher temporal resolution have been provided. Using 6-hourly and hourly wind datasets, the air-sea momentum fluxes were estimated by several drag coefficient models proposed by Large & Yeager (2009), Andreas et al. (2012), Takagaki et al. (2012), & Hwang (2018). The globally averaged annual mean air-sea momentum fluxes were derived from the different drag coefficient models. The maximum difference of the annual mean values among the models reaches approximately 30% of annual mean values. The meridional structure of zonally averaged annual mean air-sea momentum flux has double peak at relatively higher latitudes from 40°S/N to 60°N/S. At those peaks maximum difference among the models reaches more than 30% of the zonally averaged annual mean. In terms of differences in temporal resolution on the wind speed datasets on each grid, the differences between hourly and 6-hourly wind data became larger with decreasing average period. The maximum difference of 66.7% was recognized on daily mean. The large difference was remarkable in higher wind speed regions, such as typhoon’s paths in the western Pacific. The effects of wind variability on different temporal resolution datasets are significant for estimating the air-sea momentum flux.
1 0 0 0 OA 表面張力および粘度変化による風波乱流場の制御と台風の弱体化計画
風波水槽に界面活性剤を微量に混和させた溶液を満たし,その水面上に風を吹かせることにより,水面波の測定実験を行った.その結果,界面活性剤の影響は低風速域において特に顕著で,風波の発生を完全に抑制すること,また,砕波が生じる高風速域において界面活性剤は砕波を促進することが確認された.さらに,直接数値計算法を用いることにより,表面張力の低下は風波の波高を増加させること,このため界面活性剤による風波の抑制作用は表面張力の低下によるものではないことを明らかにした.また,粘性の変化も確認できなかったため,このような抑制作用は,マランゴニ効果によって引き起こされていると考えられる.