颮線基本結構的數值模擬研究

A Numerical Simulation of Squall Lines

林李耀(Lee-Yaw Lin) ； 郭鴻基(Hung-Chi Kuo)

《大氣科學》 27卷4期 (1999/12) Pp. 319-340

摘要

本文利用RAMS模式模擬出颮線的基本結構特徵，並與觀測作校驗與比較。我們除了利用RAMS模式在處理雲微物理方面的優越性外，並建議水平大區域範圍（large domain）模擬的重要性，以避免非物理性的邊界干擾。經過模式計算輸出各物理場的診斷分析，我們驗證Weisman（1992）水平渦度平衡概念模式的合理性，並發現渦度主要貢獻來源為水平速度之垂直差異。另外我們也驗證颮線移速與低層風切之正相關性，並發現包含冰相之模擬實驗其移速較不含冰相實驗稍快。最後我們分析模式尾流低壓（wake low）結構並與觀測作比較。

關鍵字

颮線 ； 水平渦度平衡 ； 尾流低壓

並列摘要

The Regional Atmospheric Modeling System (RAMS), equipped with a full set of cloud microphysical parameterization, was used to simulate squall lines. In contrast to the previous studies, a large domain was used hence eliminated non-physical disturbance from boundaries. The general features of model storms have replicated the basic multi-cellular character and airflow, typical of squall lines. The intensity of physical fields developed by the model storms appeared to be reasonable. In addition, we examined the extended horizontal vorticity balance theory of Weisman (1992). Our results suggest that the primary contribution of horizontal vorticity owes its origin from the environmental vertical wind shear. While examining the relationship between the propagation speed of the squall lines and the environmental low-level wind shear, we found that squall lines move faster in the full-ice experiment than that without ice phase. The differences between the wake low produced by our model simulation and observations were also compared.

並列關鍵字

Squall line ； Horizontal vorticity balance ； Wake low