Seasonality and time scale dependence of the relationship between turbulent surface heat flux and SST

Xiaoshan Sun,Renguang Wu

doi:10.1007/s00382-021-05631-0

Abstract

The present study examined the relationship between turbulent surface heat flux (SHF) and sea surface temperature (SST) variations using daily observational data. The SHF and SST relationship displays notable differences between winter and summer and prominent time-scale dependence in both seasons. In the mid-latitude SST frontal regions, SST has a larger role in driving SHF in winter than in summer. In the subtropical gyre regions, SHF plays a larger role in the SST change in summer than in winter. In winter, SHF has a larger effect on the SST change in the South China Sea than in the Arabian Sea and Bay of Bengal. In summer, the SST effect on SHF is dominant in the Arabian Sea, whereas the SHF impact on SST is dominant in the Philippine Sea. In the Gulf Stream, Kuroshio Extension and Agulhas Return Current, the SST effect extends up to 90-day time scales in winter, the SHF impact is limited to time scales below 20 days and the SST effect is dominant on time scales above 20 days in summer. In winter, the SHF effect extends up to 90-day time scales in the Bay of Bengal, South China Sea, and Philippine Sea, but is limited to time scales below 40 days in the Arabian Sea. In summer, the SST effect extends up to 90-day time scales in the Arabian Sea, whereas the SHF and SST effect is large on time scales shorter and longer than 40 days, respectively, in the Philippine Sea.

Highlights

Ocean and atmosphere interact in various manners
In the Arabian Sea, the atmospheric forcing is dominant in winter, but the oceanic forcing is dominant in summer
In the Bay of Bengal and the South China Sea, atmospheric forcing is dominant in winter and the oceanic forcing is accompanied by atmospheric feedback in summer

Summary

Introduction

Ocean and atmosphere interact in various manners. One of the ocean–atmosphere interaction processes is the exchange of turbulent heat fluxes. In small ocean mixedlayer depth regions, the contribution of SHF to the SST change tends to be large In such regions, the SHF and SST relationship likely belongs to the atmosphere-driven case, such as the central part of the mid-latitude North Pacific (Wu and Kinter 2010) and the tropical North Indian Ocean and western North Pacific in boreal summer (Duvel and Viallard 2007; Ye and Wu 2015; Wu et al 2015). In regions with large atmospheric perturbations, such as the tropical Indian Ocean in boreal winter where intraseasonal oscillations are strong, the amplitude of SHF anomalies may be Seasonality and time scale dependence of the relationship between turbulent surface heat flux.

Datasets and methods

Stochastic model simulations

Regional feature of the covariance

Seasonality of lead–lag correlation at different locations

Time scale dependence of lead–lag correlation at different locations

Summary and discussions