Influence of the Pacific Decadal Oscillation on Winter Temperatures and Precipitation Over the Southern Tibetan Plateau

We used observational data and a long-term piControl simulation from the Community Earth System Model Version 2 to investigate the influence of the Pacific Decadal Oscillation (PDO) on the winter climate over the Tibetan Plateau. The results showed that changes in the phase of the PDO have a significant effect on winter temperatures and precipitation over the southern Tibetan Plateau. Changes in the sea surface temperature (SST) during the positive PDO can weaken the Walker circulation and increase the SST in the Indian Ocean. Our analyses of the moist static energy showed that warming of the tropical troposphere over the Indian Ocean caused by the increased SST has resulted in the horizontal advection of anomalous moist enthalpy by the climatological zonal winds, which was responsible for anomalous ascending motion over the Tibetan Plateau. The additional moisture budget suggests that enhanced vertical motion contributes to the increase in winter precipitation and related total cloud cover over the Tibetan Plateau, leading to the increase of snow depth. The increased total cloud cover and snow depth, in turn, reduces net surface shortwave radiation. The surface air temperature of the Tibetan Plateau is then decreased as a result of the reduction in the net surface shortwave radiation. The PDO therefore has an important modulating role in the interdecadal variability of the winter climate over the Tibetan Plateau. We therefore need to focus on changes in the PDO in research related to the decadal prediction of the climate over the Tibetan Plateau. Under the background of global change, the climate of the Tibetan Plateau has undergone significant changes, and it has an important impact on the regional and global climate. Therefore, it is very important to find out the mechanisms of climate variabilities on the Tibetan Plateau. In this study, we aim to investigate the influences of the Pacific Decadal Oscillation (PDO) on the winter climate of the Tibetan Plateau and the related physical mechanisms by using observational data and a long-term piControl simulation from the Community Earth System Model Version 2. Results suggest that the PDO has an important modulating role in the interdecadal variability of the winter climate over the Tibetan Plateau. The positive PDO phase can increase winter precipitation and decrease the surface air temperature of the Tibetan Plateau. The related mechanisms are also investigated in this study. The positive Pacific Decadal Oscillation (PDO) can increase the precipitation and thereby decreasing the temperature in winter over the southern Tibetan Plateau The horizontal advection of anomalous moist enthalpy is responsible for anomalous ascending motion and increased precipitation The anomalous advection of zonal warm air is caused by warming of the tropical troposphere over the Indian Ocean due to the positive PDO