梅雨期間中尺度對流系統之動能收支分析

Kinetic Energy Budgets of a Mesoscale Convective System Occurring in the Mei-Yu Season

林松錦(Song-Chin Lin) ； 蔡欽明(Chin-Ming Tsai)

《大氣科學》 17卷3期 (1989/09) Pp. 187-209

摘要

本文利用尺度分離之動能收支方程以及旋轉與輻散動能收支方程，針對梅雨期間華南地區之中尺度對流系統的演化過程進行動能收支診斷分析。動能收支計算結果顯示大尺度環流並未直接提供系統生成的動能，而是透過中、大尺度流場的交互作用達成。大尺度環流的地轉風偏差則是系統發展最主要的貢獻，當這些有利於中尺度對流系統發展的條件消失時，系統亦逐漸消散。風場輻散分量的動能雖然只佔總動能的十分之一左右，但在動能收支過程中的貢獻卻與風場的旋轉分量相當，對中尺度對流系統演化過程的影響甚至更為重要。分析中尺度對流系統東南方生成的850 hpa西南噴流發現，西南噴流的變動主要是由中尺度風場的變動而來。中尺度風場與大尺度環境風場風向的一致性是低層噴流生成最主要的因素。跨越等壓線的地轉風偏差是中尺度強風速帶生成與維持最主要的貢獻。

關鍵字

動能收支 ； 中尺度對流系統

並列摘要

This study utilizes the scale-separated and rotational/divergent kinetic energy budget equations to diagnose the evolution of a mesoscale convective system occurring in the southern China area during Mei-Yu season.Computational results reveal that, instead of the large-scale flow, the scale-interaction accounts for most of the generation of kinetic energy. The large-scale ageostrophic wind plays an important role in the development of mesoscale convective system, the system starts to decay as the wind becomes geostrophic. Although the divergent wind has only about 1/10 of contribution to the total kinetic energy, its contributions to the kinetic energy budget terms are comparable with the rotational counterparts. Analysis results also depict that the low-level jet at the south-eastern flank of the mesoscale convective system is a result due to the consistency of large-scale and mesoscal wind directions, and is maintained by the cross isobaric ageostrophic flow.

並列關鍵字

kinetic energy budget ； mesoscal convective system