- 期刊
中尺度對流複合體環境條件之個案診斷分析：1981年5月27～28日個案
A Diagnostic Case Study of the Environmental Conditions Associated with Mesoscale Convective Complexes: 27-28 May 1981 Case
摘要
本文利用傳統及衛星資料針對1981年5月27～28日發生於華南地區三個中尺度對流複合體（Mesoscale Convective Complex簡稱MCC）演變過程進行診斷分析研究。結果顯示，低對流層的低壓／鋒面輻合及暖平流，中對流層短波槽和高對流層之速度輻散／分流及大氣不穩定度均為MCC之形成、組織及持續的有利條件。不穩定大氣有利於MCC之生成、發展與維持，當它們移至深厚之不穩定區時則增強，但可在微弱之潛在穩定或不穩定區達最大強度或消散。此外，MCC對環境不穩定度的影響不明顯。低對流層之氣旋式渦度及水平幅合均有利於MCC之形成與發展，唯當MCC達成熟後，此種低對流層之條件則變得較不重要。500mb之正渦度平流有利於MCC形成與增強，但其渦度場本身在MCC演變過程中並不重要。高對流層幅散為MCC形成與增強的重要條件，而伴隨MCC之高層外流似可加強環境風場之幅散。MCC之生成期至加強期各層均為上升運動，達成熟後，各系統之垂直運動之結構不同，其中一個MCC個案顯示，其垂直運動分布與美國所觀測到的MCC相似，具有高層上升低層下沉之結構。
並列摘要
Three cases of MCCs over southern China during the period of May 27-28, 1981 were selected to study the environmental conditions for the evolution of MCCs, the effects of MCCs on the environment as well as the processes responsible for the evolution of MCCs. The conventional observations as well as satellite data were used. Grid spacing at 120 km intervals was used to compute the kinematic parameters (vorticity, divergence, vertical velocity) and thermal parameters (vertical gradient of equivalent potential temperature, instability indices).Results show that the frontal convergence, warm advection at low level, short wave at middle level (500 mb) coupled with the speed divergence/diffluence at 300-200 mb were the conditions favorable for the formation, organization and maintenance of the MCCs, Unstable environment was a necessary condition for the initiation, development and maintenance of MCCs, MCCs tended to intensify as they moved toward the area with deep layer of strong potential instability. They could either reach maximum intensity or dissipate in weak potentially stable or unstable environment. The effects of the MCCs on the stability condition of environment were not obvious in this analysis.Strong cyclonic vorticity and convergence in the lower troposphere seemed to be the favorable conditions for the formation and intensification of the MCCs. After the mature stage of MCC, the vorticity and divergence fields in the lower tropsphere appeared to be to the evolution of MCC. Positive vorticity advection at 500 mb seemed to be an important contributor to the formation and intensification of the MCCs, while the 500 mb vorticity itself appeared to be rather unimportant in the evolution of MCCs. At upper level, divergence seemed to be important to the formation and intensification of MCCs. In the meantime, upper level divergence can be intensified by the divergent outflow of MCCs. The vertical velocity field revealed that the MCCs were associated with the upward motions from the developing to intensifying stage. After the maturing stage, the vertical velocity structure of the three MCCs were different. One of the analyzed MCCs had the structure similar to that observed in the United States with upward motion above and downward motion below.