East‐west SST contrast over the tropical oceans and the post El Niño western North Pacific summer monsoon

Abstract

The circulation and SST anomalies during the post El Niño Asian summer monsoon season were examined through data analysis and linear equatorial β plane model calculations. Over the Philippine Sea, a negative precipitation anomaly and low‐level anti‐cyclonic anomaly were found. Over the western equatorial Pacific, a low‐level easterly anomaly prevailed. An east‐west SST anomaly contrast dominated over the tropical Indian and Pacific Oceans, with positive anomalies over the Indian and western Pacific Oceans and negative anomalies over the central to eastern Pacific. The β plane model demonstrated that the anti‐cyclonic anomaly over the Philippine Sea was a Rossby response to the negative precipitation anomaly found in this region. The easterly anomaly along the equator was part of a Kelvin response to the SST anomaly contrast. On the northern side of this anomalous easterly, a negative vorticity anomaly developed. This could induce the moist Rossby wave over the Philippine Sea.