- 期刊
平流層瞬間增溫的數值模擬與折射指數平方
A Numerical Simulation of Stratospheric Sudden Warming and Refractive Index Square
摘要
本文主要是描述使用一個原始方式之中層大氣環流模式，模擬波數2之行星尺度羅士培在一正壓初始環境風場下，經由不斷低邊界之波動能量供應，得原本小振輻之擾動在近平流層頂處在垂直上傳行星波動與平均緯流風相互運作下快速增長，形成所謂平流層極區空瞬間增溫的現象。模擬結果顯示本模式可以成功地模擬出平流層瞬間主要增溫現象。在此模擬中，臨界層扮演了一個重要的角色，當垂直上傳行星波遇見臨界層時。此波動不再繼續上傳，此時在臨界層下端形成甚大波動動量輻合區，使的平均緯流風快速減速，溫度急促上升，最後終使得整個平流層極區環流轉向，溫度梯度逆轉。為了解平均緯流風在導引垂直上傳尺度波動的動力性質，本文同時亦利用一解析之平均緯流風模式計算準地轉位渦度及折射指數平方參數在空間上的分佈情形，並探討其在預測平流層瞬間增溫上的可能應用。
並列摘要
A three-dimensional, semi-spectral, numerical model based on the primitive equations in the spherical, log-pressure coordinate system is used to simulate the sudden stratospheric warming episode in the middle atmosphere. The role large-amplitude vertically-propagating planetary scale waves (wavenumber 2) association with the evolution of the zonal mean flow is studied. It is found that the appearance of a zero wind line is important in determining the propagation and the transfer processes of the planetary scale waves. No significant wave activities are observed above the zero wind line. Large amount of momentum and heat are transported poleward by large-amplitude planetary waves associated with the descending of the zero wind line. This effect reverses the direction of the direction of the horizontal temperature gradient and the mean zonal wind.In accompany with the simulation, a diagnosis of propagation property of the planetary waves in the upper atmosphere is also studied. It is found that the refractive index square Qm, suggested first by Mastsuno (1970) and is determined primarily by the curvature of the mean zonal wind, is helpful in analyzing the propagation characteristics of the planetary waves in the middle atmosphere.