A synoptic view of the Western Tibetan Vortex

The Western Tibetan Vortex (WTV) is a large-scale atmospheric circulation pattern recognized from monthly data. It has a quasi-barotropic structure, with its center located over the western Tibetan Plateau (TP) and provides the leading mode of variability of the western TP atmospheric circulation. However, existing research on the WTV mainly focuses on its interannual and seasonal variability, lacking detailed examination of synoptic scale processes. We utilize the daily ERA-Interim reanalysis to assess the intrinsic timescale of WTV activity, and the lifecycle of WTV events, at the synoptic scale.

We find that the temporal evolution of the WTV at the synoptic scale can be interpreted as a red-noise (First-order Markov) process with an e-folding timescale ranging from 4.6 to 6.9 days, with a relatively longer duration in spring and summer and shorter duration during autumn and winter. The composite lifecycle of synoptic WTV events is characterized by a three-center wave train-like pattern across Eurasia (Scandinavia-West Siberia-western TP) during the developing and peak phases, while transitioning to a two-center dipole pattern (West Siberia-western TP) during the dissipating phase. During the developing and peak phases, intensity changes propagate eastward, accompanied by the eastward movement of nearly all three centers. In contrast, during the dissipating phase, the intensity of the two centers shows minimal propagation, with the West Siberia center shifting westward in position. Our results indicate that wave activity may differ between the developing-peak stages and the dissipation stage. This provides a foundation for further exploration on the dynamical characteristics of the WTV.