In this chapter, we present recent achievements made by Chinese scientists on the TP meteorology. It is seen that the formation and evolution of the Asian Monsoon, East Asian subtropical westerly jet, South Asian High and the continental stratus cloud over eastern China are closely linked to the thermal and mechanical forcing of the TP. The elevated heat source of TP can more effectively heat up the atmosphere aloft. The intensity, distribution and seasonal variation of the atmospheric heat source/sink over TP are presented in section 2. It is seen that the TP atmosphere acts as a heat source from April to September, and as a cold source in the other months. The sensible heat of the surface increases remarkably over the southwest of the TP, causing the obvious increase of <Qi> there in February and March, which makes a center of the atmospheric heat source appear over the north slope of the Himalayas. Afterwards, this center continues to intensify and experiences noticeable migration westwards twice, separately occurring in April and June. In summer, the latent heat of condensation becomes a heating factor as important as the sensible heat and is also a main factor that makes the atmospheric heat source over the east part of the TP continue growing. On the interdecadal time scale, <Q1> of the TP shows an abrupt change in 1977 and a remarkable increase after 1977.

The plateau sensible heat is an important part of <Q1> and plays a significant role in regulating general circulation. Wu et al (1997) put forward the concept of sensible heat driven air-pump (SHAP) and investigated its effects on the monsoon circulation and the seasonal transition of general circulation. It is found that SHAP gives an impact on general circulation mainly through two mechanisms: firstly, the closure of SHAP induces a convergence at upper troposphere and descending motion over the TP which in turn results in divergence at low troposphere and precipitation anomaly in its vicinities; secondly, the closure of SHAP induces a sharp cooling of low tropospheric atmosphere which will induce a positive upper tropospheric vorticity anomaly due to the direct proportional relationship between the local variation of vorticity and variation of heating rate with height. Thus, the upper tropospheric vorticity increases significantly and affects the global climate by virtue of the frequency dispersion of Rossby wave. In addition, the seasonal variation of general circulation near the TP is also closely linked to the TP SHAP. The numerical experiments show that without the SHAP, the simulated monsoon period is shortened and the most persistent longitude of the monsoon period also shifts from the Plateau region in the CON run to about 120°E in the NSH run. To explore the effect of the TP in East Asian monsoon, a series of numerical simulations have been carried out with various land-sea distributions and orography. The result shows the occurrence of East Asian subtropical monsoon is dependent on the existence of longitudinal large-scale land-sea distribution. However, the inclusion of the TP markedly strengthens the intensity of East Asian monsoon and extents the monsoon region northward.

The plateau sensible heat is influenced by snow to a large extent. Section 4 shows that snow anomalies over the TP change the soil moisture and the surface temperature through the snowmelt process at first, and subsequently alter heat, moisture and radiation fluxes from the surface to the atmosphere. SVD analysis shows that the snow depth anomaly, especially in winter, is one of the factors influencing precipitation in China; however, it is perhaps not the only one, and even not the most important one. Nevertheless, it is proved that the winter snow anomaly over the TP is relatively more important than that in spring for the regional precipitation in China. Results of numerical simulations show that the snow anomaly over the plateau has evident effects on China's summer monsoon climate. The increase of both snow cover and snow depth can delay the onset and weaken the intensity of the summer monsoon obviously, resulting in a decrease in precipitation in southern China and an increase in the Yangtze and Huaihe River basins. The influence of the winter snow depth is more substantial than that of both the winter snow cover and the spring snow depth. The mechanism of how the plateau snow anomaly influences the regional monsoon climate shows that abnormal circulation conditions induced by changes of surface fluxes may affect the underlying surface properties in turn. Such a long-term interaction between the wetland and the atmosphere is the key process resulting in later climatic changes.

The South Asian High (SAH), the strongest, largest, and most stable an-ticy clonic circulation system at 100hPa in the Northern Hemisphere, also results from the heating effect of TP (Mason and Anderson, 1958; Flohn, 1960). The SAH has two seasonal steady modes, one of which is the conti nental high in summer and the other the ocean high in winter. The continental high can be divided into two patterns as well, that is the Tibetan high and the Iranian high. The diagnosis based on the thermodynamic equation reveals that the TH is closely related to the diabatic heating of the TP, whereas the IH is more associated with the adiabatic heating in the free atmosphere, as well as the diabatic heating near the surface. It is found that the interannual variations of the SAH and precipitation are closely correlated to each other, especially the correlation between the longitudes of the SAH in June and precipitation in summer. Furthermore, the composites of the 100hPa flow fields in June for more and less precipitation in North China show that the SAH center shifts more westward and northward in years with more precipitation, whereas the opposite situation is found in years with less precipitation.

Analysis on the location of the westerly jet core at upper troposphere in June and July by using the NCEP/NCAR reanalysis data shows that the location of the westerly jet core shifts rapidly from 140°E to 90°E during 35th-39th pentads, which corresponds to the plum rain period over East Asia. The meridional temperature contrast in the troposphere is associated with the rapid location change of the jet core. The diabatic heating changes are the primary factor determining the seasonal evolution of the westerly jet core over East Asia. In the boreal midsummer the major westerly jet centers occur frequently at two positions, which correspond to the TP to the east from 85°E to 100°E and the Iranian Plateau to the west from 45°E to 60°E. Thus, the bimodality feature of the jet core is found over East Asia, similar to that of the SAH. Clearly this bimodality of the jet core is related to the elevated topography i.e. the TP and the Iranian plateau. Corresponding to the bimodality of the westerly jet core in midsummer, there exist obvious differences in geopotential height fields, air temperatures and circulations, as a result, the related climate anomalies are possibly apparent. The composites of surface air temperature and precipitation at 518 stations in China show that most regions in China experience negative temperature anomaly except the South China in TJM, and the opposite situation occurs in IJM. This implies that TJM corresponds to a lower surface air temperature and the situation is opposite in IJM. As to the rainfall anomaly distribution, a positive anomaly area is located at the south of the TP and the lower reaches of the Yangtze River valley while the South China and the North China are the less precipitation areas, and the distribution in IJM is opposite.

The formation of continental status cloud located on the leeside of the TP is linked to the mechanical forcing of the TP. This largest cloud optical depth is produced by persistent deep stratus clouds (primarily the nimbostratus and altostratus) during winter and spring. These deep stratus clouds are generated and maintained by the fictional and blocking effects of the TP. The plateau slows down the overflow, inducing downstream midlevel divergence; meanwhile it forces the low-level flows to converge downstream, generating sustained large-scale lifting and stable stratification that maintain the thick stratus clouds. These stratus clouds produce extremely strong cloud radiative forcing at the top of the atmosphere, which fundamentally influences the local energy balance and climate change. Analysis of the long-term meteorological station observations reveals that the monthly mean anomalous cloudiness and surface temperature vary in tandem. In addition, the surface warming leads to destabilization and desaturation in the boundary layer. This evidence suggests a positive feedback between the continental stratus clouds and surface temperature through changing lower-tropospheric relative humidity and stratification. It is shown that the positive feedback mechanism is more robust during the period of the surface cooling than during the surface warming. It is suggested that the positive climate feedback of the continental stratus cloud may be instrumental in understanding the long-term climatic trend and variations over East Asia.

Numerical models have been an important tool for climate research and operational prediction after extensive model developments and verifications. Whereas, the significant deviations of simulation from the observation still exist, especially in East Asia. One important reason is the existence of the TP. Since the East Asian weather and climate is closely related to the effects of the TP, it is worth to pay more attention to how to develop the suitable parameterization for Asian climate modeling with well considering the aforementioned dynamical and thermodynamic effects of TP in future studies.

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