Frozen Soil Advances the Effect of Spring Snow Cover Anomalies on Subsequent Precipitation over the Tibetan Plateau

Frozen soil distributed over alpine cold regions causes obvious changes in the soil hydrothermal regime and influences the water-heat exchanges between land and atmosphere. In this study, by comparing the effects of snow cover anomalies and frozen soil thawing anomalies on the soil hydrothermal regime, the impact of the frozen soil thawing anomalies in spring on precipitation in early summer over the Tibetan Plateau (TP) was investigated via diagnostic analysis and model simulations. The results show that a delay (advance) in the anomalies of frozen soil thawing in spring can induce distinct cold (warm) anomalies in the soil temperature in the eastern TP. These soil tem-perature cold (warm) anomalies further weaken (enhance) the surface diabatic heating over the mideastern TP; mean-while, the anomalies in the western TP are inconspicuous. Compared to the albedo effect of snow cover anomalies, impacts of frozen soil thawing anomalies on soil hydrothermal regime and surface diabatic heating can persist longer from April to June. Corresponding to the anomalous delay (advance) of frozen soil thawing, the monsoon cell is weak-ened (enhanced) over the southern and northern TP, resulting in less (more) water vapor advection over the eastern TP and more (less) water vapor advection over the southwestern TP. This difference in water vapor advection induces a west-east reversed pattern of precipitation anomalies in June over the TP. The results have potential for improving our understanding of the interactions between the cryosphere and climate in cold regions.

Automated summary

By comparing the effects of snow cover anomalies and frozen soil thawing anomalies, this study investigates the impact of the frozen soil thawing anomalies on precipitation in early summer over the Tibetan Plateau. The results show that delayed (advanced) frozen soil thawing induces distinct cold (warm) anomalies in soil temperature, weakening (enhancing) surface diabatic heating over the mideastern Tibetan Plateau. Compared to the albedo effect of snow cover anomalies, the impacts of frozen soil thawing anomalies on soil hydrothermal regime and surface diabatic heating can persist longer.