The Influence of Mechanical and Thermal Forcing by the Tibetan Plateau on the Spring Temperature Dipole in the Middle and High Latitudes

The analysis of the Tibetan Plateau (TP) by seasonal classification using EOF reveals the existence of a north-south temperature dipole phenomenon in spring, autumn and winter, with spring being the most evident. The spring temperature EOF indicates that there is a thermal dipole between the TP and its high-latitude regions, as confirmed by the correlation analysis curve. This finding suggests the presence of an inverse correlation of temperature between the surface of the TP and its mid and high latitude regions. In this study, we used the ERA5 reanalysis data to preliminary understand the thermodynamic forces of the TP impact the spring temperature dipole at middle and high latitudes. When the Arctic Oscillation index (AOI) is negative, the pressure in the Arctic is high. After the enhanced cold air is transported to the mid-latitude region, it is deposited around 60°N due to the topographic blocking effect of the Tibetan Plateau, and the mid-latitude region is cooled. The decrease of temperature gradient between the northern and mid-latitudes leads to the weakening of Ferrel cell and the weakening of cold air transport to the plateau, warming the plateau. The results will help us to play the role of "climate indicator" on the Tibetan Plateau, and provide certain reference for climate prediction, water resources management, ecological protection, disaster warning and other aspects.