Data tabulations and analysis of diurnal sea surface temperature variability observed at LOTUS

Abstract

Air/sea measurements from the Long-Term Upper Ocean Study (LOTUS) buoy in the Sargasso Sea are analyzed to learn how the diurnal response of sea surface temperature, ΔTs, is related to the surface heating, H, and the wind stress, S. Data are taken from the LOTUS-3 and LOTUS-5 records which span the summers of 1982 and 1983. The basic data are shown in monthly plots, and the analyzed daily values of ΔTs, H, and S are given in tables and in figures. Analyzed data show a clear trend of ΔTs increasing with H and decreasing with S. A best-fit, three-parameter, empirical function can account for 90 percent of the variance in a screened subset of the LOTUS data (172 days) and 81 percent of the variance of the full data set (361 days). The analyzed data are also compared with a theoretical model function now used for ocean predictions in the Diurnal Ocean Surface Layer model (DOSL) of Fleet Numerical Oceanography Center. The DOSL model function was derived from the assumption that wind-mixing occurs by a mechanism of shear flow instability. It is fully predictive and shows a parameter dependence consistent with the LOTUS data over a wide range of H and S. The DOSL model function can account for almost as much variance as the best-fit empirical function.