A Further Assessment of the Association between Sea Surface Temperature Gradient and the Overlying Mid-Tropospheric Circulation

Abstract

The local association between ocean and atmosphere was examined statistically by correlating the anomalous sea surface temperature (SST) gradient and the anomalous geostrophic wind at the 700 mb level using 30 years (1949?78) of monthly data. Under the assumption that anomalous oceanic thermal gradients are transmitted to the lower troposphere via anomalous fluxes of latent and sensible heat, and by applying the thermal wind relationship, a significant positive correlation is expected. This analysis is an extension of earlier work by Harnack and Broccoli and includes results for both the Atlantic and Pacific, for both zonal and meridional components, for lags as well as contemporaneous associations, and includes an examination of spatial variability. The major findings are: 1) the expected association is found in both oceans and for both components, although it is somewhat stronger in the Pacific and when relating the zonal wind to the meridional SST gradient, 2) the best association is found in the zonal band of 35?45°N, although some seasonal variability is experienced in the Pacific, 3) the lag relationships are significant only at zero lag or with atmosphere leading ocean and 4) the effect of the association is enhanced by time averaging (over 3 months).