Dynamical propagation and growth mechanisms for convectively coupled equatorial Kelvin waves over the Indian Ocean
Dynamical propagation and growth mechanisms for convectively coupled equatorial Kelvin waves over the Indian Ocean
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印度洋上空对流耦合赤道开尔文波的动力传播和增长机制
DOI：
10.1002/qj.4179
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发表时间：
2021
影响因子：
8.9
通讯作者：
Matthews A
中科院分区：
文献类型：
--
作者：
Matthews A
对流耦合的赤道开尔文波（CCKWs）是高影响的热带天气系统，可导致海洋大陆的严重洪水。本文利用再分析资料构建了印度洋CCKWs涡度预算，以确定其向东传播和增长的基本机制。预算相当封闭，残差/子网格规模项很小。在对流层下层，CCKWs表现得像经过强烈修正的理论赤道开尔文波。涡旋拉伸，由开尔文波的发散作用于行星涡度（术语），是唯一的机制，通过理论开尔文波的涡度结构向东传播。在对流层中下层，这一项也是cckw向东传播的关键机制，但由于其结构和相位的微妙性与模态结构的组合有关，它也有助于增长。与理论开尔文波不同，其他涡度源项也在cckw的传播和生长中发挥作用。特别是，相对涡度（项）的涡旋伸展是最大的源项，这通过背景和摄动涡度和散度之间的相互作用强烈地导致了增长。背景气流的水平涡度平流有助于传播，但也会阻碍CCKW的增长。在这种复杂涡度收支中，源项的总和导致了CCKWs向东传播和增长。对流层上层CCKWs的结构和涡度收支与开尔文波的结构和涡度收支非常不同，似乎是对对流层下层结构的强迫响应。讨论了数值天气预报和气候模拟的意义。
Convectively coupled equatorial Kelvin waves (CCKWs) are high‐impact tropical weather systems that can lead to severe flooding over the Maritime Continent. Here, a vorticity budget for CCKWs over the Indian Ocean is constructed using reanalysis data, to identify the basic mechanisms of eastward propagation and growth. The budget is reasonably well closed, with a small residual/subgrid‐scale term. In the lower troposphere, CCKWs behave like strongly modified theoretical equatorial Kelvin waves. Vortex stretching, from the divergence of the Kelvin wave acting on planetary vorticity (theterm), is the sole mechanism by which the vorticity structure of a theoretical Kelvin wave propagates eastward. In the lower and middle troposphere, this term is also the key mechanism for the eastward propagation of CCKWs but, due to subtleties in its structure and phasing linked to a combination of modal structures, it also contributes to growth. Unlike in the theoretical Kelvin wave, other vorticity source terms also play a role in the propagation and growth of CCKWs. In particular, vortex stretching from relative vorticity (theterm) is the largest source term, and this leads strongly to growth, through interactions between the background and perturbation vorticity and divergence. Horizontal vorticity advection by the background flow contributes to propagation, and also acts to retard the growth of the CCKW. The sum of the source terms in this complex vorticity budget leads to eastward propagation and growth of CCKWs. The structure and vorticity budget of CCKWs in the upper troposphere is quite unlike that of a Kelvin wave, and appears to arise as a forced response to the lower‐tropospheric structure. The implications for numerical weather prediction and climate simulations are discussed.
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影响因子：
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DOI：
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发表时间：
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