Midnight temperature maximum (MTM) in Whole Atmosphere Model (WAM) simulations
Midnight temperature maximum (MTM) in Whole Atmosphere Model (WAM) simulations
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DOI：
10.1029/2009gl037759
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发表时间：
2009-04
影响因子：
5.2
通讯作者：
R. Akmaev;F. Wu;T. Fuller‐Rowell;Houjun Wang
中科院分区：
文献类型：
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作者：
R. Akmaev;F. Wu;T. Fuller‐Rowell;Houjun Wang
近40年前，卫星和地面仪器在热带上层热层定期观测到午夜最高温度（MTM），其典型震级为50-100 K。虽然已经提出了几种机制来解释这一现象，但以前用热层-电离层综合模型重现这一现象的尝试都是不成功的。首先，利用全大气模式（WAM）进行的长期模拟揭示了一个实际突出的MTM的存在，并重现了其日、季节和纬度变化的显著特征。初步分析表明，这一特征可以追溯到低层热层，主要表现为向上传播的昼夜潮汐波。它的频谱扩展到更高阶的纬向波数和频率，其相位推进到热层高层的午夜附近。产生这种波的可能机制可能涉及源自中低层大气的其他潮汐谐波之间的非线性相互作用。因此，我们的结果表明，MTM是由低层和高层大气以及电离层之间的动力联系驱动的另一种现象。
Discovered almost four decades ago, the midnight temperature maximum (MTM) with typical magnitudes of 50–100 K has been regularly observed by satellite and ground‐based instruments in the tropical upper thermosphere. Although several mechanisms have been suggested to explain the phenomenon, previous attempts to reproduce it with comprehensive thermosphere‐ionosphere models have been unsuccessful. First long‐term simulations with the Whole Atmosphere Model (WAM) reveal the presence of a realistically prominent MTM and reproduce the salient features of its daily, seasonal, and latitudinal variability. Preliminary analysis indicates that the feature may be traced down to the lower thermosphere, where it is manifested primarily in the form of an upward propagating terdiurnal tidal wave. Its spectrum expands to higher‐order zonal wavenumbers and frequencies and its phase advances to near midnight higher up in the thermosphere. Possible mechanisms generating this wave may involve nonlinear interactions between other tidal harmonics originating in the middle and lower atmosphere. Our results thus suggest that the MTM is yet another phenomenon driven by dynamical links between the lower and upper atmosphere and ionosphere.