Mesosphere-thermosphere tidal coupling during the September 21-25, 1987, LTCS 1 campaign

Journal Article · Fri Feb 01 04:00:00 EST 1991 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/90JA01768· OSTI ID:5316180

Forbes, J M ^[1]; Salah, J E ^[2]

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1. National Center for Atmospheric Research, Boulder, CO (USA)
2. Massachusetts Inst. of Tech., Westford (USA)

The thermosphere ({ge} 90 km) is dynamically coupled to the mesophere and lower atmospheric regions by gravity waves, tides, and planetary waves which propagate upward from below and often undergo dissipation in the 80 to 150-km region. This paper focuses on the mesosphere-thermosphere coupling due to the solar semidiurnal atmospheric tide during the first Lower Thermosphere Coupling Study (LTCS) campaign interval of September 21-25, 1987. During this period, determinations of semidiurnal eastward (u) and northward (v) velocity components and temperature ({delta}T) are available within the 80 to 150-km region from a total of 13 incoherent scatter, meteor, and spaced antenna radars. A new method is developed and reported here for assimilating such data sets into a self-consistent global empirical description of the tidal dynamics between 80 and 150 km. Using a set of numerically generated Hough mode extension (HME) functions for u, v, and {delta}T corresponding to the (2,2), (2,3), (2,4), and (2,5) semidiurnal tidal modes, a least squares fit to the radar data is performed. The fit results in a single (complex) normalizing factor for each HME from which globally continuous and internally consistent semidiurnal oscillations in u, v, and {delta}T (as well as vertical velocity and density) can be derived. The quality of fit to these data from various height regions including both northern and southern hemispheres establishes the internal consistency between these measurements as well as the applicability of the method to future data sets. The resulting empirical model reproduces the data significantly better than recent theoretical models, suggesting use of the method for deriving tidal boundary conditions for thermospheric general circulation models.

• OSTI ID: 5316180
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 96:A2; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640200* -- Atmospheric Physics
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BOUNDARY CONDITIONS
DATA ANALYSIS
DIMENSIONS
DYNAMICS
E REGION
EARTH ATMOSPHERE
EARTH PLANET
GENERAL CIRCULATION MODELS
GRAVITY WAVES
HEIGHT
INTERACTIONS
IONOSPHERE
LEAST SQUARE FIT
MATHEMATICAL MODELS
MAXIMUM-LIKELIHOOD FIT
MEASURING INSTRUMENTS
MECHANICS
MESOSPHERE
NORTHERN HEMISPHERE
NUMERICAL SOLUTION
PLANETARY IONOSPHERES
PLANETS
RADAR
RANGE FINDERS
SOUTHERN HEMISPHERE
THERMOSPHERE
TIDE
WAVE PROPAGATION
WIND