Covariations of SST and surface heat flux on 10–20 day and 30–60 day time scales over the South China Sea and western North Pacific

Abstract

AbstractThis study investigates the variability and relationship between intraseasonal sea surface temperature (SST) and surface net heat flux (NHF) variations in the South China Sea and western North Pacific regions. It is shown that the intraseasonal SST variations and their coherence with surface heat flux variations display large differences between winter and summer and between 10–20 day and 30–60 day time scales. The intraseasonal SST variability is comparable on 10–20 day and 30–60 day time scales but larger during summer than during winter. The NHF variability is much larger on the 10–20 day time scale and during winter. The coherence between intraseasonal SST and NHF variations is higher during summer than during winter due to the seasonal change in the mixed‐layer depth. During summer, coherent intraseasonal SST and NHF variations are identified in a southwest‐northeast tilted region from the South China Sea to the subtropics on the 10–20 day time scale but within a broad zonal band from the South China Sea to the Philippine Sea on the 30–60 day time scale. Such difference is not discernable during winter. The contribution of NHF to the SST tendency is larger on the 30–60 day time scale than on the 10–20 day time scale and during summer than during winter. Latent heat flux provides a much larger contribution than shortwave radiation to intraseasonal SST variations in most regions except for the South China Sea during summer on the 30–60 day time scale.