Annual and Semiannual Cycles of Diurnal Warming of Sea Surface Temperature in the South China Sea

Abstract

Based on the SeaFlux data set, an empirical parameterization, and a one-dimensional ocean mixed-layer model, the annual and semiannual cycles of diurnal warming of sea surface temperature (dSST) in the South China Sea (SCS) are examined. The amplitude of the annual cycle is greater than 0.1 °C, and the annual cycle reaches its maxima in April/May/June in most areas of the SCS, while the amplitude of the semiannual cycle of dSST increases from north to south with the month of its maxima changing from February to March along a northwest-southeast axis. Relative to the amplitude of the annual cycle of dSST, the semiannual cycle is of much smaller amplitude north of 17°N, but of comparable or larger amplitude south of 17°N. The annual (semiannual) cycle of wind speed is the most important factor for the annual (semiannual) cycle of dSST. The annual (semiannual) cycle of wind speed drives the annual (semiannual) cycle of dSST primarily by influencing oceanic vertical turbulent mixing. Aside from these basin-scale features, the dSST annual and semiannual cycles demonstrate robust mesoscale features in the lees of hills/islands as a result of sheltering from the monsoon.