Local intraseasonal air–sea relationship over the North Indian Ocean and western North Pacific during the spring-to-summer transition

Abstract

This study investigates the local air–sea relationship associated with the two dominant intraseasonal oscillation (ISO) components during the spring-to-summer transition and compares their properties using multiple air–sea variables in the period 1998–2013. The amplitude of percentage variance in SST in periods of 10–20 and 30–60 days are comparable, but the locations of the maxima differ. A strong percentage variance in the 10–20-day SST is evident in the equatorial western Pacific, whereas for the 30–60-day SST the strongest ratio occurs in the North Indian Ocean (NIO), South China Sea (SCS), and North Pacific. Over the NIO, SCS, and Philippine Sea, there are significant correlations between SST and precipitation for both 10–20-day and 30–60-day ISOs. In contrast, the correlations between SST and surface heat fluxes cover a broader region and have larger coefficients. Thus, the atmospheric variables and surface heat fluxes show larger variations within the higher frequency band. However, the amplitude of the correlation coefficients between SST and surface heat fluxes, and SST and rainfall, is greater in the lower frequency band. The corresponding time lags for the different variables reveal that a strong local air–sea interaction is indicated over the NIO, SCS, and western North Pacific, from April to June in both timescales; however, the strength of the air–sea relationship depends on the region and variable.

Keywords

• Air–sea relationship
• intraseasonal oscillation
• spring-to-summer transition
• North Indian Ocean
• western North Pacific