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A Simple Model of Convectively Coupled Equatorial Rossby Waves
Journal of Advances in Modeling Earth Systems ( IF 6.8 ) Pub Date : 2019-01-17 , DOI: 10.1029/2018ms001433
Željka Fuchs‐Stone 1, 2 , David J. Raymond 1, 2 , Stipo Sentić 2
Affiliation  

Intraseasonal oscillations affect the weather not just in the tropics but all around the globe. The convectively coupled equatorial Rossby wave is observed as the westward‐moving intraseasonal oscillation. The fundamental physics of its coupling is still unknown; thus, many questions remain unanswered. How is its phase speed altered by convection? What makes it unstable? Why is it an intraseasonal oscillation? Using the Fuchs and Raymond model with linearized governing equations on an equatorial beta plane, first baroclinic mode vertical structure, and moisture and wind‐induced surface heat exchange (WISHE) convective parametrizations, this paper seeks a fundamental analytical theory that can explain the basic features of the convectively coupled equatorial Rossby wave. The WISHE‐moisture theory leads to a large‐scale, unstable westward propagating mode in the n = 1 case, which we call the westward propagating WISHE‐moisture mode. We find that the westward propagating WISHE‐moisture mode is indeed the free equatorial Rossby wave in the absence of moisture closure and WISHE. It is propagating westward due to the beta effect, and it slows down when it is convectively coupled. Its phase speed decreases mainly due to WISHE and cloud‐radiation interactions. The xy structure of the pressure and horizontal winds is similar to the free and observed Rossby wave, with convergent net flow. The strongest easterlies are to the west of the precipitation maximum increasing the moisture in that area. The mode is unstable due to the interplay of surface fluxes and moisture, which increases as a function of zonal wavelength.

中文翻译:

对流耦合赤道Rossby波的简单模型

季节内的振荡不仅影响热带地区的天气,而且影响全球的天气。对流耦合的赤道罗斯比波被观测为向西移动的季节内振荡。其耦合的基本物理原理仍是未知的。因此,许多问题仍然没有答案。对流如何改变其相速度?是什么使它不稳定?为什么会出现季节内振荡?本文将Fuchs和Raymond模型与赤道beta平面上的线性控制方程,第一斜压模式垂直结构以及湿气和风致表面热交换(WISHE)对流参数一起使用,寻求一种可以解释基本特征的基本分析理论对流耦合的赤道罗斯比波。WISHE水分理论导致了大规模的,n = 1例,我们称其为向西传播的WISHE水分模式。我们发现,在没有水分封闭和WISHE的情况下,向西传播的WISHE水分模式的确是自由的赤道Rossby波。由于贝塔效应,它向西传播,对流耦合时它放慢了速度。它的相速度下降主要是由于WISHE和云辐射相互作用。该X - ÿ压力和水平风的结构是类似的自由,观察Rossby波,具有会聚的净流量。最强的东风在降水最大的西部,增加了该地区的湿度。由于表面通量和水分的相互作用,该模式是不稳定的,水分的相互作用随纬向波长的增加而增加。
更新日期:2019-01-17
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