Interpretation of the vertical structure and seasonal variation of the diurnal migrating tide from the troposphere to the lower mesosphere
Interpretation of the vertical structure and seasonal variation of the diurnal migrating tide from the troposphere to the lower mesosphere
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DOI：
10.1016/j.jastp.2013.07.010
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发表时间：
2013-12
影响因子：
1.9
通讯作者：
T. Sakazaki;M. Fujiwara;Xiaolin Zhang
中科院分区：
文献类型：
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作者：
T. Sakazaki;M. Fujiwara;Xiaolin Zhang
利用MERRA （Modern Era Retrospective analysis for Research and Applications）的再分析资料和一个线性潮汐模型，研究了从对流层到中下层的日迁移潮（DW1）的纬向结构和季节变化。对于纬向垂直结构，观测到的特征由四种最低阶经典霍夫模很好地表示，每种霍夫模都有自己独特的垂直传播特征。热带地区DW1温度对流层廓线主要受第一对称传播霍夫模的控制。对流层的恒定相位是由于对流层的静态稳定性很小。从季节变化来看，从平流层到下层中间层的振幅在至日达到最大值。这是由反对称传播霍夫模式的主要贡献造成的。发现这种季节变化不能用非绝热加热的季节变化来解释。利用线性模型，我们发现背景纬向风对季节性有重要影响。此外，利用改进的模式耦合方法，我们解释了除了由绝热加热产生的一次潮外，由背景纬向动量的经向平流产生的次潮对DW1也有很大的贡献，造成了上述热带地区从平流层到中下层的季节性变化。这表明，激发和传播特性都可以用独立的经典霍夫模的叠加来解释。也就是说，每一种霍夫模态不仅主要受到绝热加热的激发，其次还受到机械强迫的激发，然后按照自己的垂直传播特性进行传播。
The latitudinal–vertical structure and the seasonal variation of the diurnal migrating tide (DW1) from the troposphere to the lower mesosphere are investigated, using reanalysis data from the Modern Era Retrospective analysis for Research and Applications (MERRA) and a linear tidal model. For the latitudinal-vertical structure, the observed feature is well represented by the four lowest-order classical Hough modes each of which shows its own unique vertical propagation characteristics. The tropospheric profile of DW1 temperature in the tropics is found to be mainly controlled by the first symmetric propagating Hough mode. The constant phase in the troposphere is due to the small static stability in the troposphere. For the seasonal variation, the amplitude from the stratosphere to the lower mesosphere maximizes at solstices. This is caused by a major contribution from the anti-symmetric propagating Hough mode. It is found that this seasonal variation is not explained by that of diabatic heating. Using a linear model, we found that background zonal wind is important for the seasonality. Also, using a modified mode-coupling approach, we interpret that in addition to primary tides generated by diabatic heating, secondary tides generated by meridional advection of background zonal momentum have a large contribution to the DW1, creating the above-mentioned seasonal variation from the stratosphere to the lower mesosphere in the tropics. It is suggested that both excitation and propagation characteristics can be physically interpreted in terms of the superposition of independent classical Hough modes. That is, each Hough mode is not only primarily excited by diabatic heating but also secondarily by mechanical forcing, and then propagates by following its own vertical propagation characteristics.