The Seasonal Evolution of the Tibetan Plateau Snow Cover Related Moisture During Spring‐to‐Summer

Abstract

AbstractThe current work investigated the seasonal evolution of the Tibetan Plateau (TP) snow cover (TPSC) induced atmospheric moisture anomalies from May to August, by analyzing TP snow‐diabatic and TP snow‐hydrological processes during the 1979–2020 period using both observational data and a baroclinic atmospheric model. The results show that the TPSC and its related atmospheric moisture are featured by a westward retreat from the eastern TP in May to the western TP in August. The TPSC variation related atmospheric apparent heat source shows that excessive TPSC can cause local diabatic cooling to the above atmosphere and can be attributed to a local cyclonic pattern in the upper troposphere. This cyclonic pattern also moves westward along with the seasonal evolution of the TP snow during this period. Anomalous TP snow can impact atmospheric moisture through snow melt and snow evaporating process. Associated with the changes in TP snow, its related anomalous atmospheric moisture and circulations, significant moisture divergence appears over the mid‐eastern Himalaya during May and June (MJ) and the water vapor is mainly transported from the Himalaya to southeastern TP regions including Bhutan, Myanmar, Bengal and eastern India. Differently, during July and August (JA), significant atmospheric moisture divergence is located over the mid‐western Himalaya, and the water vapor is mostly transported from the Himalaya to southwestern TP areas including Nepal and western India. Further analysis shows that the TPSC anomaly induced anomalous atmospheric moisture accounts for 22%–45% of the climatological moisture for the mid‐eastern Himalaya during MJ, whereas it accounts for 65%–78% of the climatological moisture for the mid‐western Himalaya during JA.