Interdecadal change in the relationship between the tropical easterly jet and tropical sea surface temperature anomalies in boreal summer

Abstract

The interdecadal change in the relationship between the tropical easterly jet (TEJ) and the tropical sea surface temperature anomalies (SSTAs) in boreal summer is studied. It is found that TEJ’s relationship with the SSTAs reverses over the tropical eastern Atlantic (EA), while enhances obviously over the tropical eastern Pacific (EP) after 1981. During 1960–1980, an Atlantic Niño-like SSTA over the EA can weaken the TEJ through the upper westerly anomaly of the anomalous Walker circulation between EA and tropical Indian Ocean. In the meantime, a Pacific El Niño-like SSTA over the EP can also diminish the TEJ intensity via a Kelvin wave response east to the diabatic heating induced by enhanced precipitation in situ. Observations and model experiments show that the EA and EP SSTAs can contribute to the TEJ variability in a joint or independent manner. During 1981–2001, as the associated Pacific El Niño-like SSTA is enlarged in the magnitude and the spatial extension, it exerts a stronger impact on the TEJ variability. Different from the pre-1980 period, the SSTA over the EA featured by an Atlantic Niña-like instead of Niño-like pattern could weaken the TEJ, which doesn’t work without the co-existence of the EP SSTA. Such Atlantic Niña-like SSTA develops in the previous spring and strengthens the warm SSTA over the EP in summer, and then affects the TEJ indirectly. The interdecadal change of the TEJ-SST relationship is likely related to the changes of the variability and spatial configuration of the tropical SSTAs.