Q向量在診斷分析上的應用

On The Application of Q-Vector in Diagnostic Analysis

林松錦(Song-Chin Lin) ； 胡志文(Jyh-Wen Fu)

《大氣科學》 14卷1期 (1986/09) Pp. 63-76

摘要

大氣運動的垂直速度和天氣的變化具有極密切的關係。對於垂直速度若能給予準確且迅速地估計，常能提高天氣預報的效率與準確度。鑒於傳統的準地轉ω方程式在定性討論上不容易，Hoskins等定義一Q向量並重導原有的準地轉ω方程式。在新的ω方程式中他們將原有的兩個強迫函數完全合併成一個以Q向量表示的簡單強迫函數。這個方法不論在定量上或定性上都較其它方法簡捷。Q向量不只在計算垂直速度上有它的優點，從等壓面上Q向量的分佈也可看出非地轉風的運動。在鋒面區附近由Q向量場和溫度場的分佈亦可決定垂直於鋒面方向上的垂直環流以及鋒生和鋒消的趨勢。本文將Q向量的理論應用於一個案分析。結果顯示，利用新ω方程及傳統準地轉ω方程計算所得的垂直運動場相當接近，而且Q向量對於鋒生的趨勢以及垂直次環流也有合理的預測。

並列摘要

The atmospheric vertical motions have close relations with the daily weather change. Convenient and accurate estimation of vertical velocity usually can improve the efficiency and accuracy in weather prediction. In order to overcome the difficulty of conventional quasi-geostrophic ω-equation in estimating vertical velocity directly from the weather map, Hoskins et al. defined a Q-vector and re-derived the quasi-geostrophic ω-equation. In their new ω-equation, the original two forcing functions were combined into one which is a function of the Q-vector only. This technique for the estimation of verticaI velocity has been proved to be advantageous in both qualtitative and quantitative respects. In addition to the convenience in estimation of vertical velocity, distribution of Q-vector on an isobaric surface can depict the ageostrophic motions. In the vicinity of the front, the cross-frontal circulation and the tendency of frontogenesis can also be determined from the Q-vector and temperature fields. In this study, Q-vector theory was applied in a case analysis. Results indicated that vertical motions computed from Hoskins' new ω-equation were comparable with those from the conventional ω-equation, distribution of Q-vector also had reasonable indication of the frontogenesis and secondarily vertical circulation.