The impact of high-frequency weather systems on SST and surface mixed layer in the Central Arabian Sea

The role of high-frequency (sub-daily time scales) weather systems in modulating the sea surface temperature (SST) and the mixed layer (ML) depth in the central Arabian Sea is investigated using one-dimensional mixed-layer models for different monsoon seasons. Simulations forced by sub-hourly sampled meteorological variables, including surface wind, air temperature, humidity and cloud, are compared to simulations forced by daily-averaged meteorological variables. It is found that including high-frequency signals in the meteorological variables lowers the daily-mean SST (by 0.8°C on average) and damps its variability (the standard deviation decreases by 1.0°C), but has little systematic effect on the SST diurnal variability. There is a small but consistent deepening of the ML depth associated with the slightly intensified wind stress and heat loss due to high-frequency weather systems at this site. The cooling effect on the daily-mean SST is found to be closely related to the ML depth on daily-to-seasonal time scales. The impact of high-frequency weather systems is primarily driven by the high-frequency wind via the turbulent heat and momentum fluxes.