Energetics Characteristics of the Asian Winter Monsoon in the Source Region

Abstract

Energetics characteristics of the Asian winter monsoon are studied with twice-daily upper air data during a 20-year period over its source region. It is found that the energetics features over Siberia, North-eastern Asia, China Main and the Japan Sea, are distinctly different reflecting the different roles and characteristic flow patterns of these regions in the system of the winter monsoon. Siberia, under the dominance of the anticyclonic flow, shows a general adiabatic destruction of kinetic energy through cross-isobaric motion. Northeastern Asia, under the influence of a major cyclonic system, is dominated by typical patterns of energy transformations as observed in most areas of transient synoptic disturbances. The strong westerlies dominate over the general area of the China Main, East China Sea and Japan Sea and the kinetic energy is intensely generated in this portion of the flow. Most of the kinetic energy generated over China Main is exported. Over the Japan Sea area where the series of cyclonic disturbances develops, a strong dissipation takes place. During the cold air outbreaks, which are recognized with the intrusion of a strong cyclonic upper level flow into China Main, the kinetic energy generation and dissipation are drastically increased in the general area of the China Main, East China Sea and Japan Sea. However, basic energetics features of different regions in the prevailing systems of the Asian winter monsoon remain unchanged. A case study of a cold air outbreak is also presented.