Climatic Characteristic Analysis of Cloud Water over the Tibetan Plateau

Analyses of cloud liquid water path (LWP) and cloud ice water path (IWP) over the Tibetan Plateau are performed with MODIS monthly data, ERA-Interim reanalysis data and other datasets during the period of 2001-2016. The distribution features, trends and relationships with circulation and water vapor transport are examined. Results show that the annual means of LWP and IWP are of the similar distribution shapes with precipitation and precipitable water. The Nyingchi region has accumulated abundant LWP, IWP, precipitation, and precipitable water. LWP and IWP have obvious seasonal variations because of Indian Ocean Monsoon and they are the most abundant in summer and scarce in winter. Water vapor transport, dynamical effect, and thermodynamic effect of the Tibetan Plateau are the main influencing factors for the distributions of LWP and IWP in summer. In southern Tibetan Plateau, the relative humidity is high and the vapor rises strongly, which promotes the formation and accumulation of LWP and IWP. LWP and IWP show a similar variation patterns with elevation. And their general variation pattern in the interval of 3000 to 5500 m is agreed with the variation pattern of precipitation gradient. They quickly increased with elevation and then gradually become stable. Decreasing trends of annual mean and seasonal mean of LWP and IWP are found in the period of 2001-2016 and the similar trend is also found for cloud amount over the Tibetan Plateau. The increasing trend of the divergence of water vapor flux is the closely related with the decreasing trends of LWP and IWP.