Upper Vertical Thermal Contrast Over Western North Pacific and its Impact on the East Side of Tibetan Plateau During ENSO Years

ABSTRACT The present study reveals significantly out-of-phase changes at 100 and 250 hPa over the western North Pacific (WNP) during ENSO years. We found that the tropospheric temperature exhibits an increase and decrease in the 100 and 250 hPa respectively over the WNP during the La Niña episodes. The tropospheric temperature pattern over the 100 and 250 hPa during La Niña episodes are found to be described by an anti-cyclonic and cyclonic circulation in the wind shear respectively. Concomitant with the tropospheric temperature change an increase/decrease of convection over the WNP is observed during the La Niña/El Niño years. The further finding shows the robust dynamical changes in the subtropical jet over the WNP during ENSO episodes act as pathways leading to moisture transport towards the east side of the Tibetan Plateau and thereby affect the convection pattern over there. To affirm the findings, a novel causal inference technique is used to identify a dominant causality between the WNP vertical thermal contrast (VTC) and the longwave fluxes over the east side of the Tibetan plateau.