An analysis of the diabatic heating characteristic of atmosphere over the Tibetan Plateau in winter Ⅱ： Interannual variation.

The climatological characteristic of diabatic heating over the Tibetan Plateau (TP) during winter was analyzed in Part Ⅰ. This paper is Part Ⅱ of the work, which discusses the interannual variation of the diabatic heating over the TP during winter and its relationship with atmospheric circulation anomalies in the Northern Hemisphere by means of data diagnoses and numerical simulations. The mode of the most prominent interannual variations of atmospheric diabatic heating over the TP during winter is mostly due to the abnormal latent heating over the western and southeastern side of the TP. Different from the interannual variation in summer, there appear consistent cyclonic (or anticyclonic) deflection circulations over the TP from the upper troposphere down to the lower troposphere when the columnintegrated diabatic heating over the TP is above (below) normal, showing an equivalentbarotropic structure. The results of numerical experiments show the heating abnormality over the TP during winter is closely related with the westerly wind variation on the southwest side of the TP. When the westerly there is stronger than normal, there appears a cyclonic circulation over the northwestern TP due to the topography blocking, and the detouring flow around the south side of the TP also becomes stronger, forming a remarkable cyclonic deviation circulation around the main part of the TP. These then lead to the increase of latent heating and total heating over the west part of the TP and its south side. It is further demonstrated that the abnormality of diabatic heating in winter over the TP is a consequence of the atmospheric circulation abnormality in the Northern Hemisphere and the mechanical forcing of the TP. The heating anomaly over the TP is closely related with the teleconnection wave ray emanating from northwest to southeast in the Northern Hemisphere. Therefore, it can be considered as a local response to the atmospheric circulation anomaly in the Northern Hemisphere.