LARGE-SCALE AIR-SEA INTERACTION IN THE NORTHERN-HEMISPHERE FROM A VIEW POINT OF VARIATIONS OF SURFACE HEAT-FLUX BY SVD ANALYSIS

Large scale relationships between surface heat flux (defined as the su m of sensible and latent heat fluxes at sea surface) and the atmospher ic circulation in the Northern Hemisphere during the northern winter h ave been examined, using the singular value decomposition (SVD) analys is. The dominant heat flux anomaly pattern in the North Pacific has la rge amplitude in the western and the central part of the subtropical. gyre, and the one in the North Atlantic exhibits a north-south seesaw in the western Atlantic. These patterns are closely related to the dom inant atmospheric circulation anomaly patterns known as the teleconnec tion patterns, i.e., the dominant surface heat flux pattern in the Nor th Pacific is related to the Pacific/North American (PNA) teleconnecti on pattern and the one in the North Atlantic is tied to the Western At lantic (WA) pattern (Wallace and Gutzler, 1981). Variations with a tim e scale of a few years are dominant in time coefficients of the leadin g SVD modes for both oceans. Decadal scale or trend-like variation is also seen in those for the North Pacific but is not apparent for the N orth Atlantic. We also investigated the relation between the surface h eat flux and the time rate of change of sea surface temperature (SST t endency). Local correlation coefficients between them are generally hi gh but not close to unity. This suggests that the SST tendency is dete rmined not only by the surface heat flux but also by other processes s uch as horizontal temperature advection and vertical mixing in the upp er ocean. The spatial patterns of the first SVD mode for the surface h eat flux and the SST tendency in each ocean are quite similar. They al so resemble the heat flux patterns of the first SVD mode paired with a tmospheric variables such as 500 hPa height in each ocean. This indica tes that the dominant pattern of the SST tendency in each ocean is org anized by the dominant large scale atmospheric circulation pattern suc h as the PNA teleconnection pattern.