Numerical Simulation Study Of The Tibetan Plateau Weather And Climate Effects

The Tibetan Plateau (TP) has great influences on global climate, particularly on the weather and climate of China and East Asia. Due to the complexity of the climate system, the understanding of the role of TP and the underlying physics is incomplete, and there are inconsistent hypotheses that require more thorough investigation. With a numerical model in this paper, the virtual TP is isolated from the complicated climate system and its special effects on weather and climate are simulated. Same as the Aqua-Planet experiment (APE), the TP is introduced into the aqua-planet based on the real TP area and specified topography. The dynamic, thermal and sensible heat atmospheric pumping (SHAP) effects of TP are analyzed through the comparison of different experiments. The dynamical and thermal characteristics of the subtropical TP are highlighted by comparing with experiments where the TP is placed in different latitudes. Though the isolated TP is different from the real TP in terms of its area coverage and height, the experimental results are in good agreement with observations. This implies that the experiments using the isolated TP have captured the actual physical processes. This paper can be summarized in the following aspects: 1. For the integrated effects, the raising of TP has little influence on the surface sensible heat flux, while it greatly affects condensation heating. The existence of TP can modify the diabatic distribution and can lead to the formation of the LOSECOD quadruplet heating pattern around the TP. When TP is in the tropics, effects of condensation heating is dominant. The atmospheric response is the Gill-type distribution and the TP can influence the mid-and high-latitudes through the two-stage thermal adaptation. When TP is in mid-latitudes, the thermal influence is reduced while the dynamical influence is increased. The atmospheric response is the Rossby-wave distribution. When TP is in the subtropics, both the dynamical and thermal effects are important. The sensible and condensation heating in different locations have different effects on the atmosphere. Therefore, the TP in the subtropics are more complex compared with TP in other latitudes. The integrated effects gives different precipitation distributions for different TP latitudes. 2. For the dynamical effects, the linear climbing effect is dominant with low topography, while the nonlinear deflection effects are dominant when the TP is higher. As a response to the linear effect, an anticyclone is located over the TP along with a cyclone in the downstream area. A dipole of cyclone and anticyclone is formed due to the nonlinear effect. The anomalous response tilts westward with height, and reaches maximum around the upper troposphere. The critical height which distinguishes the linear and nonlinear dynamical effects changes with different latitudes. It is lower in mid-latitude and higher in the tropics. In the subtropics, the climbing and deflection effects are comparable, which implies that the TP has special effects in the subtropics. 3. The TP sensible heating mainly affects the lower atmosphere, where the air converges to the land associated with the cyclonic circulation. An anticyclone exists aloft. Its height is related to the height of the TP. The TP condensation heating can affect the troposphere directly, with maximum heating in the mid-troposphere. Above (below) the level of maximum heating is an anticyclonic (cyclonic) circulation. Though the circulation induced by sensible and condensation heating is different, the vertical structures of both are related to the heating profile. 4. In the subtropics SHAP is the integrated representation of the TP dynamical, sensible and condensation heating effects. The surface sensible heating over the TP lateral boundaries and the central regions are different. Around the TP adjacent area, the influence of lateral boundary heating is almost the same as that of the whole TP heating, while the influence over the center is larger outside the TP. SHAP has great influences on the seasonal variation and the formation of the Asian monsoon. The variations of both wind and precipitation imply that SHAP directly affects the formation of the monsoon east and southeast of the TP, and has little effects to that southwest of the TP. Through the experiments of this paper, better understanding of the special effects of the TP is gained. Based on the results, researches on the interactions of TP with other climate components and the associated weather and climate effects can be undertaken.