Upper vertical thermal contrast over the western Tibetan Plateau and its impact on convection over the Mediterranean region during ENSO events

Previous studies have shown that the vertical variations of upper-tropospheric temperature over the Mediterranean region significantly influence the convection over the western Tibetan Plateau (WTP) via modulating dynamics and thermodynamics over the WTP. Here we explore the possible connection the other way round, i.e., the impact of the Tibetan Plateau on the Mediterranean region. Results reveal that there exists an increase/decrease in upper-tropospheric temperature at the 100 hPa/250 hPa over the WTP during El Niño years. The upper-tropospheric temperature at 100 hPa/250 hPa is attributed to an anti-cyclonic/cyclonic circulation in the wind shear. The vertical thermal contrast (VTC) formed between the pressure levels (i.e., between 100 and 250 hPa) over the WTP induces a cyclonic circulation in the wind shear around 250 hPa over the Mediterranean region and thereby impacting the convection over the Mediterranean region. To substantiate, we explored the possible pathway for this teleconnection. An analysis of 200 hPa zonal winds (a proxy for the subtropical jet) regressed onto the WTP VTC exhibits westerly winds over the southern part of the Mediterranean region and easterly winds over the northern part implying a cyclonic circulation in support of convection over the Mediterranean region. Thus, ascertaining the role of the subtropical jet in facilitating the teleconnection between the WTP and the Mediterranean region. A dominant causality further corroborated the findings.