The Western Tibetan Vortex as an emergent feature of near-surface temperature variation?

<p>The Western Tibetan Vortex (WTV) was identified through research efforts to understand the causal mechanisms responsible for the &#8216;Karakoram Anomaly&#8217;. The WTV has been shown to be an important anomalous circulation system influencing near surface climate over the Tibetan Plateau (TP). Existing researches have characterised the dynamical characteristics and thermodynamic behaviours of the WTV in detail. Scientific consensus has not yet been established. However, regarding the physical mechanisms which produce the WTV itself, a recent argument has asserted that the WTV is the set of wind field anomalies resulting from changes in 2m near-surface air temperatures (T_2m) over the western TP. This argument can spur constructive discussion for improving our understanding on the WTV. This paper examines whether a putative thermal-generating machanism for the WTV can explain the established defining features of the WTV. In particular we evaluate if warmer (colder) T_2m over the western TP is sufficient to drive downward (upward) wind anomaly in the overlying air column. Detailed consideration is given to whether the supposedly thermally induced vortex does indeed have the expected baroclinic structure &#8211; i.e. cyclonic (anti-cyclonic) wind anomaly at the mid-lower (mid-higher) troposphere &#8211; rather than a quasi-barotropic structure &#8211; i.e. cyclonic or anti-cyclonic wind anomaly at both the mid-lower and mid-higher troposphere &#8211; &#160;as the research first identifying the WTV reported. This work thus seeks to determine the &#8216;direction of causality&#8217; of whether &#160;the WTV drives T_2m over the western TP or the thermal forcing of the western TP&#8217;s T_2m is the mechanism generating the WTV. This work utilises ERA5 meteorological reanalysis data to assess how the WTV may impact the western TP&#8217;s T_2m through modulating the cloud cover and hence net surface radiation. These analyses complement previously published evaluation of the prosoposed adiabatic heating mechimism through which the WTV impacts the mid-lower tropospheric and near surface air temperarure. It is important to note that further evaluations of the skill of the newly released ERA5 dataset in representing the atmospheric conditions accurately over the western TP are still needed.</p>