Response of the equatorial basin‐wide SST to non‐breaking surface wave‐induced mixing in a climate model: An amendment to tropical bias

Abstract

One of the common problems of the coupled atmosphere‐ocean general circulation models (AOGCMs) without flux correction is that the simulated sea surface temperature (SST) deviates noticeably from the observation especially in the tropics, such as the too cold tongue in the eastern Pacific and a reversed SST zonal gradient in the equatorial Atlantic. The coupled atmosphere‐wave‐ocean general circulation model, which incorporates the non‐breaking surface wave‐induced mixing into the CCSM3 through a coupler, can improve the simulation of the tropical SST. On the ocean‐basin scale, the wave‐induced vertical mixing can generate “West‐Positive and East‐Negative” pattern for the equatorial SST that much alleviates the tropical bias. The formation mechanism for this basin‐wide response to the wave‐induced mixing is analyzed through sensitive experiments of AOGCMs and stand‐alone ocean general circulation models (OGCMs). First, in each basin, the SST becomes colder under the direct effect of the wave‐induced mixing, and the SST in the eastern part of each basin is colder due to the shallower ocean mixed layer than that of the western part. The SST in the western basin (or central basin in the Pacific Ocean) increases due to the weakened eastward zonal current. Then, the pattern of warm SST in the west and cold SST in the east is amplified due to the Bjernkes feedback in a climate system. The net heat flux feedback plays a negative role in this kind of SST response.