The Structure, Dynamics, and Energetics of a Simulated Easterly Wave

模擬東風波之結構、動力平衡與能量收支

林民生(Ming-Sen Lin)

《大氣科學》 3卷1期 (1976/05) Pp. 106-119

摘要

本文應用準地轉風模式模擬東風波，研究其結構、動力平衡與能量收支；此項非絕熱效應代表凝結加熱，蒸發及輻射冷卻。模擬產生之波動在對流底層為冷心型糟線，並隨高度向東傾斜，上升氣流區位於900 mb槽線之東；在對流上層則轉為暖性反氣旋。渦流方程式中，渦旋的當地趨勢項為最大，此項由水平渦旋平流和輻散項所共同合成。假設模式中包含積雲渦旋傳送效應，最顯著之差異為擾動的流線型式減弱。至於熱力能量平衡方面，則以垂直方向之平流項和非絕熱項為最重要。從能量收支的觀點來探討，發現東方波可以維持其平衡，此為對流上層之位能轉換為動能，而動能則自高層經由壓力通量項輸送至中，低大氣層。

並列摘要

A theoretical study on the structure, dynamics and energetics of a forced easterly wave has been made. The wave is generated by using a quasi-geostrophic model which incorporates an external diabatic heating. This heating has been formulated to represent the effects of cumulus convective heating, evaporational, and radiational cooling. The generated wave is characterized by a cold-cored trough in the lower half of the atmosphere which tilts eastward with height. A region of organized upward motions occurs east of the 900-mb trough. In the upper atmosphere, there is a warm anticyclone which is located about 800 km to the east of the surface trough. Analysis of the vorticity budget of the wave shows that the largest term is the local tendency, it is primarily the combined effect of the horizontal advection and the divergence terms. If the effect of cumulus transport is incorporated in the vorticity equation, the amplitude of the streamline pattern is decreased. The thermodynamic energy budget shows tnat the two dominant terms are the vertical advection and the diabatic terms. The easterly wave as a whole can maintain its kinetic energy by converting available potential energy to kinetic energy in the upper troposphere. Kinetic energy in this region is exported to the middle and lower troposphere by the pressure flux term.