Covariation of Finite-Amplitude Wave Activity and the Zonal-Mean Flow in the Midlatitude Troposphere. Part II: Eddy Forcing Spectra and the Periodic Behavior in the Southern Hemisphere Summer
Covariation of Finite-Amplitude Wave Activity and the Zonal-Mean Flow in the Midlatitude Troposphere. Part II: Eddy Forcing Spectra and the Periodic Behavior in the Southern Hemisphere Summer
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中纬度对流层有限振幅波活动与纬向平均流的协变。
DOI：
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
N. Nakamura
中科院分区：
文献类型：
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作者：
Lei Wang;N. Nakamura
AbstractPreviously，在本研究的第一部分中，作者使用垂直积分有限振幅波活动（FAWA）的纬度-纬度预算来描述纬向平均状态和涡动振幅的协变。在40° ~ 55 ° S的南半球夏季，FAWA表现出明显的20-30天的周期性，主要由低层涡动热通量驱动，这与最近发现的斜压环状模（BAM）相一致。ERA-Interim产品的分析表明，原始FAWA和涡动热通量的20-30天周期性在温暖的季节特别强劲。一个干的GCM被示出再现定性BAM样的涡动热通量谱，如果纬向平均状态类似于南半球夏季，如果表面热阻尼是足够强的。夏季观测到的涡动热通量同谱中，各分量都含有少数几个主频率。
AbstractPreviously, in Part I of this study, the authors used latitude-by-latitude budgets of the vertically integrated finite-amplitude wave activity (FAWA) to describe the covariation of the zonal-mean state and eddy amplitude. In the austral summer within 40°–55°S, FAWA exhibits a marked 20–30-day periodicity driven mainly by the low-level meridional eddy heat flux, consistent with the recently identified baroclinic annular mode (BAM).The present article examines the spectra of eddy heat flux that produce the periodic behavior in the Southern Hemisphere storm track. Analysis of the ERA-Interim product reveals that the 20–30-day periodicity in raw FAWA and eddy heat flux is particularly robust during the warm season. A dry GCM is shown to reproduce qualitatively BAM-like eddy heat flux spectra if the zonal-mean state resembles that of the austral summer and if the surface thermal damping is sufficiently strong. The observed eddy heat flux cospectra in summer contain a few dominant frequencies for each o...