Interdecadal variation of surface potential vorticity over the western Tibetan Plateau driven by local snow during boreal winter

The surface potential vorticity (PV) over the Tibetan Plateau (TP) plays a crucial role in weather and climate anomalies across eastern China. However, the drivers behind the surface PV variation have rarely been explored. Using observational, reanalysis, and model simulation data, this study examines the basic characteristics of the surface PV over the TP, then focuses on identifying the driver responsible for its interdecadal variation during boreal winter. Results indicate that both the intensity and variability of surface PV exhibit a distinct seasonal cycle, with a minimum in the warm season and a maximum in the cold season. During boreal winter, the interdecadal variation of surface PV is thermally driven by the surface static stability, which is closely linked to the surface diabatic heating rate. Further results reveal a significant interdecadal relationship between the surface PV over the TP and the amount of local snow. Analyses of radiation and heat fluxes demonstrate that increased snow depth enhances the upward reflection of incoming shortwave radiation, suppresses upward longwave radiation and sensible heat flux, and thereby intensifies surface diabatic cooling. This diabatic cooling strengthens atmospheric static stability, leading to enhanced surface PV. Conversely, decreased snow depth results in the opposite situations. The validity of the proposed mechanism—encompassing snow depth, diabatic heating anomalies, static stability, and surface PV—is corroborated by numerical simulations. Beyond the albedo and hydrological effects of snow, the relationship between snow and surface PV revealed in this study introduces a new perspective: a distinct PV effect of snow.