Climatic Characteristics of Atmospheric Heat Source over the Tibetan Plateau and Its Possible Relationship with the Generation of the Tibetan Plateau Vortex in the Summer

The NCEP/NCAR reanalysis data and the Tibetan Plateau Vortex (TPV) statistical data from the same data base for the period of 1981 to 2010 have been exploited in this study to analyze the summertime climatic characteristics of atmospheric heat source and its relationship with the generation of TPV. The linear trend analysis, Morlet wavelet, EOF decomposition and composite analysis methods are used. The result shows that the summertime average strength of atmospheric heat source is 105 W m^-2 over the TP. Moreover, the strength demonstrates a weakening trend that has obvious decadal variations. In particular, a significant periodic oscillation with a cycle of approximate 3 years is detected. In the years of high frequency of TPV, the strength is obviously higher than the climatically averaged value. The main anomaly of heat source is horizontally distributed over the Tibetan Plateau. Analyses of the vorticity advection and the vertical cross section of secondary circulation indicate that a positive vorticity advection from the southeast to the northwest at 500 hPa provides positive vorticity for the TPV over the Tibetan Plateau. At the same time, the Tibetan Plateau behaves as an atmospheric heat source in the summer. It promotes updrafts over the plateau, which are favorable for low-level convergence, high-level divergence, and cyclonic and anticyclonic circulation development. As a result, the generation of the TPV is promoted. Note that positive vorticity is produced above the Tibetan Plateau. Finally, by applying the principle of thermal wind and atmospheric thermal adaptation theory, this study provides a physical explanation for the link of the Tibetan Plateau atmospheric heat sources and the statistical result of the frequency of TPV generation.