Midnight temperature maximum (MTM) in Whole Atmosphere Model (WAM) simulations
Article first published online: 14 APR 2009
Copyright 2009 by the American Geophysical Union.
Geophysical Research Letters
Volume 36, Issue 7, 16 April 2009
How to Cite
2009), Midnight temperature maximum (MTM) in Whole Atmosphere Model (WAM) simulations, Geophys. Res. Lett., 36, L07108, doi:10.1029/2009GL037759., , , and (
- Issue published online: 14 APR 2009
- Article first published online: 14 APR 2009
- Manuscript Accepted: 18 MAR 2009
- Manuscript Received: 13 FEB 2009
- midnight temperature maximum
 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.