On the interaction between Kelvin waves at different phase speeds and the background flow
On the interaction between Kelvin waves at different phase speeds and the background flow
复制标题
不同相速开尔文波与背景流的相互作用
DOI：
10.1002/qj.4412
复制
发表时间：
2023
影响因子：
8.9
通讯作者：
Roundy, Paul E.
中科院分区：
文献类型：
--
作者：
Shaaban, Ahmed A.;Roundy, Paul E.
理论上，开尔文波在临界层附近被吸收，在临界层处，相速度与背景流的速度相匹配。然而，通过观测，我们还不清楚开尔文波的结构在临界层附近是如何演变的，也不清楚开尔文波是如何响应有或没有临界层的垂直风切变的。一种新的变系数回归技术，已被用于研究整个季节周期的演变关系，用于捕捉具有特定相速度的小波滤波波如何出现在不同的背景风或垂直切变制度或两者的组合。结果表明，在多普勒频移速度较慢时，纬向风和位势高度异常之间的同相关系松弛，随后在多普勒频移速度进一步减小时出现吉尔模式，表明在这些条件下缺乏主导开尔文波信号。我们将“观察到的临界层”定义为与开尔文波一致的信号逐渐消失的层，而不管多普勒频移速度的值如何，多普勒频移速度在“理论临界层”处减少到零。结果表明，在纬向风垂直切变为西风时，层顶不存在与Kelvin波一致的波结构，而在纬向风垂直切变为东风时，层顶存在与Kelvin波一致的波结构。本文第二部分给出了在垂直风切变作用下开尔文波的频散方程。Kelvin波的相速度随着Richardson数成比例地增加（因此随着垂直风切变成比例地减小）。Richardson数随所用数据的垂直分辨率而变化，在垂直风切变存在的情况下，增加了波的计算相速度的不确定性。
Kelvin waves have been theorized to be absorbed near the critical layer, where the phase speed matches the speed of the background flow. Nevertheless, it is not clear through observations how the structure of the Kelvin waves evolves near the critical layer or in response to vertical wind shear with or without a critical layer. A novel varying‐coefficient regression technique that has been used to study evolving relationships across the seasonal cycle is used to capture how the wavelet‐filtered waves with a specific phase speed appear in different background winds or vertical shear regimes or a combination of both. Results show a relaxation of the in‐phase relationship between the zonal wind and geopotential height anomalies at slower Doppler‐shifted speeds, followed by the appearance of the Gill pattern at further reduction of the Doppler‐shifted speed, demonstrating a lack of dominant Kelvin wave signals in those conditions. We define the “observed critical layer” as the layer where the signals consistent with Kelvin waves fade away irrespective of the value of the Doppler‐shifted speed, which reduces to zero at the “theoretical critical layer.” Results show that wave structures consistent with Kelvin waves are not present at the top of layer with westerly vertical shear of the zonal wind, yet they exist during the easterly vertical shear of the zonal wind. The second part of the paper presents the dispersion equation of the Kelvin wave under vertical wind shear. The phase speed of the Kelvin wave proportionally increases with the Richardson number (and hence proportionally decreases with the vertical wind shear). The Richardson number varies with the vertical resolution of the data used, adding uncertainty to the calculated phase speed of the wave in the presence of vertical wind shear.
登录
查看更多内容
影响因子：
3.1
作者：
J. Molinari;Patrick Durán;David Vollaro
通讯作者：
J. Molinari;Patrick Durán;David Vollaro
季节变化回归斜率系数的诊断及其在 MJO 中的应用
DOI：
--
发表时间：
2017
期刊：
影响因子：
--
作者：
P. Roundy
通讯作者：
P. Roundy
影响因子：
8.9
作者：
P. Roundy
通讯作者：
P. Roundy
稳定纬向剪切流中的赤道波
DOI：
--
发表时间：
1982
期刊：
影响因子：
--
作者：
R. A. Plumb;R. C. Bell
通讯作者：
R. C. Bell
印度洋上空的向上和向下大气开尔文波
影响因子：
8.9
作者：
A. A. Shaaban;P. Roundy
通讯作者：
P. Roundy