Effect of the southeastern Tibetan Plateau heat forcing on the tropical easterly jet in boreal summer

As a strong upper-tropospheric easterly jet stream over the Afro-Australian monsoon region, the tropical easterly jet (TEJ) originates from the meridional thermal contrast between the Asian landmass, the Tibetan Plateau (TP) in particular, and the tropical Indian Ocean in boreal summer. Here, we find that the atmospheric heat source anomaly over the southeastern TP can induce an opposite response of the upper-tropospheric zonal wind over the western Pacific, where the TEJ usually inflows and manifests as the double easterly jets. Positive TP heating anomaly could accelerate the northern branch of double easterly jets and decelerate the southern one, and vice versa. Two pathways linking the TP heating and the TEJ are proposed. First, positive heat forcing over the southeastern TP can directly induce the easterly responses over the South Asia by the thermal wind which is mainly determined by the changed meridional temperature gradient. The associated easterly response significantly accelerates the northern part of the TEJ. The other pathway suggests that the TP heating will indirectly modulate the southern branch of double easterly jets by changing the thermal condition over the western North Pacific (WNP). The negative WNP heat anomaly exerts a pair of upper-level cyclones straddling the equator with anomalous westerly in between, primarily decelerating the south branch of the double easterly jets over the Maritime Continent. Our findings suggest the TP heating anomaly significantly influences the upper-tropospheric TEJ, especially the double jets in its inflow region, advancing understanding of the TEJ variability and the Asian summer monsoon dynamics.