An analysis of the diabatic heating characteristic of atmosphere over the Tibetan Plateau in winter Ⅰ: Climatology

The atmospheric diabatic heating over the Tibetan Plateau (TP) during winter was analyzed using the 3 kinds of reanalysis data. The results indicate that the TP in winter is not the strongest center of the heat sink in Eurasia, in contrast to the characteristic in summer as a strong heat source. On the whole, the atmosphere over the TP acts as a weaker heat sink, and there exist a region of positive diabatic heating near the western and southeastern TP. This analysis is a revision to the previous notion that the TP is a heat sink during winter. The diagnoses of the various diabatic heating components explain that this heating characteristic over the TP in winter is mainly due to the weaker longwave radiative cooling than that over the surrounding land area and latent heating near the western and southeastern TP. To further confirm the above results derived from reanalysis data, the surface radiation budget (SRB) data，the precipitation rates and vertical velocity reanalysis data from the TRMM and PREC/L are also used for diagnosis, which approve that negative total heating over the TP is weaker as a result of reduced outgoing longwave radiation at the top of the atmosphere due to lower air temperature over the TP and intensified condensation latent heating associated with more precipitation and ascending motion over the western and southeastern TP. Finally, the results of numerical experiments with idealised TP support the above results, that is, the existence of the TP weakens the cooling effect of land, and the atmosphere over the TP is a weaker heat sink during winter.