Energetics Characteristics of the Asian Winter Monsoon in the Source Region

Energetics characteristics of the Asian winter monsoon were studied with twice-daily upper air data during a 2-yr period over its source region. The energetics features over Siberia, northeastern Asia, China, and the Sea of Japan 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 China, the East China Sea, and the Sea of Japan, and the kinetic energy is generated intensely in this portion of the flow. Most of the kinetic energy generated over China is exported. Over the Sea of Japan area where the series of cyclonic disturbances develops, a strong dissipation occurs. During the cold air outbreaks, which are recognized with the intrusion of a strong, cyclonic, upper level flow into China, the kinetic energy generation and dissipation are increased drastically in the general area of China, the East China Sea, and the Sea of Japan. 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 presented.