Detection of an Annual Westward Propagating Signal in the Meridional Wind Component along 8°N in the Pacific

Abstract

A westward propagating signal with the annual period is detected in anomalies of the zonally averaged meridional wind component along 8°N across the Pacific Ocean. The propagating signal in the “eddy” (defined as the departure from the zonally averaged) meridional wind has approximately the same propagation speed as the well-known propagating signal in the zonal wind component along the equator, and the former has larger amplitude than the latter. The eddy SST gradient between the equator and 10°N exhibits a similar westward propagation and is in phase with the eddy meridional wind; the northward eddy wind is accompanied by the warmer eddy SST to the north. The propagating features in both the eddy meridional wind and the SST gradient are quite regular from year to year, except for El Niño years. In the El Niño periods, the regular features are disturbed in the western Pacific, but the in-phase relationship between these two parameters still holds. These relationships indicate that the boundary-layer mechanism is most likely to be of primary importance in the response of the eddy meridional wind to the SST variations.