Heat Budget of the Siberian High and the Winter Monsoon

Abstract

The heat budget of the Siberian high is investigated by using a compositing method. Ninteen cases of strong Siberian highs that moved over China from the northwest were selected from datasets covering five winters (December through February of 1980?1984). The apparent heat source (Q1)and the apparent moisture sink (Q2) were estimated via budget calculations. The diabatic heating terms were also calculated via direct use of physical parameterization schemes. The vertical transports of sensible and latent heat from subgrid-scale of motions were estimated as residuals from the thermodynamic energy equation. Over the region of the region of the Siberian high, strong radiative cooling and large-scale descending motion (with large-scale mass convergence over the upper and middle tropospheric and divergence over the lower troposphere) contributes to a rapid buildup of the Siberian high. Heating in the upper troposphere due to subgrid-scale sensible heat transfer is also an important factor in the maintenance of mass convergence in the upper troposphere through enhancement of the warm upper-tropospheric anticyclone lying over the Siberian high. The transformation of the Siberian high commences shortly after it moves away from its source region. As the high arrives at lower latitudes, the sensible heating due to condensation in the lower troposphere enhance the transformation process of the cold high. A comparison of the heat budgets of the Siberian high at low latitudes is carried out over the land and the warm oceanic area to the southeast. In section 7 of this paper we present some planetary-scale signatures associated with the motion of the Siberian high. This motion is shown to be accompanied by an eastward shift of the tropical planetary-scale divergent circulation. This aspect is very similar to a shift of divergent circulation centers that one finds between non-El Niñ and El Niñ years.