Moisture Sources of the Precipitation to the West of Tibetan Plateau in winter and its Associated Cloud Characteristics

Precipitation over the western Tibetan Plateau (TP) happens most in boreal winter. This study shows that the western TP is moisture sink in boreal winter, having a net moisture convergence of 1-3mm/day. The atmospheric water vapor transport for winter precipitation to the west of the TP during 1979-2016 DJF is examined using Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT). The climatological water vapor transport mainly comes from the westerly belt, originating from subtropical Atlantic oceans and Mediterranean Sea. The precipitation to the western TP also has strong interannual variation affected by the interaction of warm air from North Indian and cold air from North Atlantic. An anomalous anticyclone dominates over the Arabian Sea, which weakens the Indian winter monsoon and intensifies strong water vapor transport from Arabian Sea to the west of TP. Besides, an anomalous anticyclone persists over the north Atlantic in 200hPa and leads cold air to propagating southwards and downward to the west of TP. The relationship between precipitation to the western TP and cloud vertical microphysics is analyzed using CloudSat/CALIPSO and Tropical Rainfall Measuring Mission (TRMM) precipitation data.