Contrast of 10–20-day and 30–60-day intraseasonal SST propagation during summer and winter over the South China Sea and western North Pacific

Abstract

This study documents the structure and propagation of intraseasonal sea surface temperature (SST) variations and relative contribution of surface latent heat flux and shortwave radiation to the SST propagation in the South China Sea (SCS) and western North Pacific (WNP) regions. The emphasis is on the contrast of intraseasonal SST propagation between summer and winter and between 10–20-day and 30–60-day time scales. The dominant SST pattern during summer displays a tilted southwest–northeast band from the SCS to the subtropical WNP on both time scales, but with a larger value in the subtropical WNP on the 10–20-day time scale and in the SCS on the 30–60-day time scale. The dominant SST pattern during winter resembles that during summer, but with a larger value in the SCS. In summer, the SST anomalies show obvious northwestward and northward propagations in the SCS–WNP region on the 10–20-day and 30–60-day time scales, respectively. The cloud–radiation effect is a dominant factor for the SST propagation on both time scales in the SCS–WNP region, with a supplementary effect from the wind–evaporation effect on the 10–20-day time scale. In winter, the SST anomalies show southward propagation on both time scales in the SCS, while the southward propagation in the WNP is weak and confined to the subtropics on the 10–20-day time scale. The wind–evaporation effect makes a larger contribution to the SST propagation than the cloud–radiation effect on both time scales in the SCS–WNP region.