Upward and downward atmospheric Kelvin waves over the Indian Ocean,Quarterly Journal of the Royal Meteorological Society

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Upward and downward atmospheric Kelvin waves over the Indian Ocean
Quarterly Journal of the Royal Meteorological Society ( IF 3.0 ) Pub Date : 2021-07-08 , DOI: 10.1002/qj.4122
Ahmed A. Shaaban ₁ , Paul E. Roundy ₁

Affiliation

Stratospheric Kelvin waves are often understood as plane gravity waves, yet tropospheric Kelvin waves have been interpreted as a superposition between the baroclinic modes. Fourier filtering is used to decompose the ECMWF-Interim reanalysis dynamical fields into upward and downward propagating components. Then wavelet regression is used to isolate the propagating Kelvin waves over the Indian Ocean across different speeds at zonal wavenumber 4. Results for fast waves show dry upward-phase signal in the troposphere, while downward-phase Kelvin waves occupy most of the stratosphere. The presence of upward-phase tilted waves in the troposphere suggests that the tropospheric Kelvin wave is not a superposition of the upward and downward components, as one might expect in a normal mode. We found that propagating Kelvin waves in the troposphere obey gravity wave dynamics with geopotential height in phase with the zonal wind, the vertical velocity out of phase with the zonal wind, and the temperature in quadrature with the zonal wind. Both dry and moist tropospheric Kelvin waves show a westward vertical tilt, suggesting that tilt probably cannot be a superposition between baroclinic modes coupled to convective and stratiform heating. In the context of radiating gravity waves, results suggest that faster tropospheric Kelvin waves appear to be associated with higher Brunt–Väisälä frequencies, and waves maintain similar vertical tilt across a wide range of phase speeds.

中文翻译：

印度洋上空向上和向下的大气开尔文波

平流层开尔文波通常被理解为平面重力波，但对流层开尔文波被解释为斜压模式之间的叠加。傅里叶滤波用于将 ECMWF-Interim 再分析动力场分解为向上和向下传播的分量。然后使用小波回归来隔离在印度洋上以不同速度以 4 号纬向传播的开尔文波。快波的结果显示对流层中的向上相位信号干燥，而向下相位的开尔文波占据平流层的大部分。对流层中向上相位倾斜波的存在表明对流层开尔文波不是向上和向下分量的叠加，正如人们在正常模式下所期望的那样。我们发现在对流层中传播的开尔文波服从重力波动力学，位势高度与纬向风同相，垂直速度与纬向风异相，温度与纬向风正交。干燥和潮湿的对流层开尔文波都显示出向西的垂直倾斜，这表明倾斜可能不是斜压模式与对流和层状加热耦合的叠加。在辐射重力波的背景下，结果表明更快的对流层开尔文波似乎与更高的布伦特-维萨莱频率相关，并且波在很宽的相位速度范围内保持相似的垂直倾斜。以及与纬向风正交的温度。干燥和潮湿的对流层开尔文波都显示出向西的垂直倾斜，这表明倾斜可能不是斜压模式与对流和层状加热耦合的叠加。在辐射重力波的背景下，结果表明更快的对流层开尔文波似乎与更高的布伦特-维萨莱频率相关，并且波在很宽的相位速度范围内保持相似的垂直倾斜。以及与纬向风正交的温度。干燥和潮湿的对流层开尔文波都显示出向西的垂直倾斜，这表明倾斜可能不是斜压模式与对流和层状加热耦合的叠加。在辐射重力波的背景下，结果表明更快的对流层开尔文波似乎与更高的布伦特-维萨莱频率相关，并且波在很宽的相位速度范围内保持相似的垂直倾斜。

更新日期：2021-09-06

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