Responses of the tropical easterly jet to distinct patterns of tropical Pacific SST anomaly in boreal summer

The present study distinguishes the different effects of the eastern Pacific-type (EP-type) sea surface temperature anomaly (SSTA) and the central Pacific-type (CP-type) SSTA on the tropical easterly jet (TEJ) by dividing the TEJ into the entrance (over the tropical western Pacific), core (over the tropical Indian Ocean) and exit regions (over equatorial Africa and the Atlantic). It is found that the EP-type SSTA can exert an inverse influence on the intensity of the TEJ between its exit-core region and the entrance region, while the CP-type SSTA mainly affects the entrance of the TEJ. This discrepancy can be attributed to the different magnitude and spatial extension of the diabatic heating associated with the enhanced precipitation induced by the two SSTA patterns. The EP-type SSTA could induce a stronger and wider-spread positive precipitation anomaly over the tropical Pacific than the negative precipitation anomaly over the Maritime Continent, while the CP-type SSTA can induce an enhanced precipitation over the tropical Pacific that is roughly equivalent in amplitude and spatial extension to the suppressed precipitation over the Maritime Continent. Thus, the EP-type SSTA can affect the entire TEJ through the dominant diabatic heating in the tropical Pacific and its subsequent Gill-Matsuno response, accelerating the entrance region and slowing the exit-core region. In contrast, the CP-type SSTA could only produce a significant acceleration in the entrance of the TEJ as the remote effect of the diabatic heating in the tropical Pacific is nearly neutralized by the diabatic cooling in the Maritime Continent. A series of numerical experiments based on a linear baroclinic model confirms the above conclusions and distinguishes between the independent contributions of the diabatic heating in the tropical Pacific and the diabatic cooling in the Maritime Continents to the TEJ.