On the Significance of the Sensible Heat Supply from the Ocean in the Maintenance of the Mean Baroclinicity along Storm Tracks
On the Significance of the Sensible Heat Supply from the Ocean in the Maintenance of the Mean Baroclinicity along Storm Tracks
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DOI：
10.1175/2010jcli3910.1
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发表时间：
2011-07-01
影响因子：
4.9
通讯作者：
Nakamura, Hisashi
中科院分区：
文献类型：
--
作者：
Hotta, Daisuke;Nakamura, Hisashi
通过分析行星波模型对取自全球再分析数据集的纬向不对称热强迫各个分量的稳定线性响应，评估海洋显热供应和潜热供应之间的相对重要性，以维持主要风暴路径区域的近地表平均斜压性。分别针对北大西洋、北太平洋和南印度洋进行的模型实验表明，作为对近地表感热加热的响应，沿风暴路径观测到的近地表斜压的明显局部最大值可以得到最有效的强化。结果表明，跨海洋锋区的海洋差异感热供应对于有效恢复表面斜压性特别重要，斜压性对抗极地涡流热传输的弛豫效应，为瞬态涡流的反复发展创造了有利条件，以锚定风暴路径。与所建议的不同，作为对积云对流或大规模凝结导致的潜热的响应，沿着风暴路径的近地表斜压的相应强化被发现效率较低。众所周知，极地涡流热通量汇聚是地表西风带增强的主要贡献者，尤其是在风暴路径的核心。在其出口区域，对海洋显热供应的行星波响应也对强化产生了重大贡献。相比之下，作为对潜在加热的行星波响应的表面风加速度被发现对沿着任何主要风暴路径的表面西风带的维持产生负面影响。
The relative importance between the sensible heat supply from the ocean and latent heating is assessed for the maintenance of near-surface mean baroclinicity in the major storm-track regions, by analyzing steady linear responses of a planetary wave model to individual components of zonally asymmetric thermal forcing taken from a global reanalysis dataset. The model experiments carried out separately for the North Atlantic, North Pacific, and south Indian Oceans indicate that distinct local maxima of near-surface baroclinicity observed along the storm tracks can be reinforced most efficiently as a response to the near-surface sensible heating. The result suggests the particular importance of the differential sensible heat supply from the ocean across an oceanic frontal zone for the efficient restoration of surface baroclinicity, which acts against the relaxing effect by poleward eddy heat transport, setting up conditions favorable for the recurrent development of transient eddies to anchor a storm track. Unlike what has been suggested, the corresponding reinforcement of the near-surface baroclinicity along a storm track as the response to the latent heating due either to cumulus convection or large-scale condensation is found less efficient. As is well known, poleward eddy heat flux convergence acts as the primary contributor to the reinforcement of the surface westerlies, especially in the core of a storm track. In its exit region, a substantial contribution to the reinforcement arises also from a planetary wave response to the sensible heat supply from the ocean. In contrast, the surface wind acceleration as a planetary wave response to the latent heating is found to contribute negatively to the maintenance of the surface westerlies along any of the major storm tracks.