西太平洋赤道域でのTOGA-COARE IOP期間中の乱流フラックスの直接測定と熱収支解析

Abstract

Turbulent flux measurements were carried out on board the R/V Hakuhomaru during TOGA-COARE IOP in Nov., 1992. She stayed at the station of 156°E on the equator, north of the Intensive Flux Array (IFA) of COARE region for more than 2 weeks (Asai, 1993). Turbulent fluxes were evaluated by the eddy correlation method, including ship motion corrections for wind velocity fluctuations. The weather situation was relatively calm for most of the period. Convective activity developed in the latter half of the period with occasional showers. It was found that heat fluxes from the sea surface were about 14Wm-2 and 88Wm-2 for sensible and latent heat fluxes, respectively, as mean values of the period when Brook's correction was accepted. However they increased to almost double when a gust front developed from the precipitating cumulus as a downdraft.Bulk transfer coefficients were estimated from eddy fluxes and bulk meteorological values. The average values of CH=1.32×10-3 and CE=1.16×10-3 were evaluated. The wind speed dependencies of the coefficients were investigated and increases in the low wind speed region were observed, which supports the previous prediction. The surface energy budget was investigated based on radiation and turbulent flux measurements. The net heat flux into the water was estimated to be about 68Wm-2 in this period.The present data of eddy correlation measurements are considered to be one of the sea truth standards, as well as the ones from the R/V Moana Wave, Franklin and Natsushima.