Journal of Oceanography, Vol. 62 (No. 6), pp. 825-838, 2006
Yoshimi Kawai1*, Hiroshi Kawamura1, Sumio Tanba2, Kentaro Ando3, Kunio Yoneyama3 and Norio Nagahama4
1Center for Atmospheric and Oceanic Studies, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
2Faculty of Science and Technology, Hirosaki University, Hirosaki 036-8561, Japan
3Institute of Observational Research for Global Change, Japan Agency of Marine-Earth Science and Technology, Yokosuka 237-0061, Japan
4Global Ocean Development Inc., Yokohama 233-0002, Japan
(Received 20 March 2006; in revised form 8 June 2006; accepted 7 July 2006)
Abstract: In order to investigate the validity of buoy-observed sea surface temperature (SST), we installed special instruments to measure near-surface ocean temperature on the TRITON buoy moored at 2.07°N, 138.06°E from 2 to 13 March 2004, in addition to a standard buoy sensor for the regular SST measurement at 1.5-m depth. Large diurnal SST variations were observed during this period, and the variations of the temperatures at about 0.3-m depth could be approximately simulated by a one-dimensional numerical model. However, there was a notable discrepancy between the buoy-observed 1.5-m-depth SST (SST1.5m) and the corresponding model-simulated temperature only during the daytime when the diurnal rise was large. The evaluation of the heat balance in the sea surface layer showed that the diurnal rise of the SST1.5m in these cases could not be accounted for by solar heating alone. We examined the depth of the SST1.5m sensor and the near-surface temperature observed from a ship near the buoy, and came to the conclusion that the solar heating of the buoy hull and/or a disturbance in the temperature field around the buoy hull would contribute to the excessive diurnal rise of the SST1.5m observed with the TRITON buoy. However, the temperature around the hull was not sufficiently homogenized, as suggested in a previous paper. For the diurnal rise of the SST1.5m exceeding 0.5 K, the daytime buoy data became doubtful, through dynamics that remain to be clarified. A simple formula is proposed to correct the unexpected diurnal amplitude of the buoy SST1.5m.