The saturation of gravity waves in the middle atmosphere. Part II: Development of Doppler-spread theory

Journal Article · Sat Jun 01 04:00:00 EDT 1991 · Journal of the Atmospheric Sciences; (United States)

DOI:https://doi.org/10.1175/1520-0469(1991)048<1361:TSOGWI>2.0.CO;2· OSTI ID:5418975

Hines, C O ^[1]

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1. Arecibo Observatory (Puerto Rico)

The irregular winds of the middle atmosphere are commonly attributed to an upwardly propagating system of atmospheric gravity waves. Their one-dimensional power spectrum has been reported to exhibit a nearly universal behavior in its tail region of large m: both the form ([approximately]m[sup [minus]3]) and the intensity of the tail are approximately invariant with meteorological conditions. This universality is often described as resulting from saturation of the system, with the physical cause of saturation being left for separate identification and analysis. Here the cause is attributed to nonlinear interaction between the waves of the full spectrum, most specifically to the advective nonlinearity of the Eulerian fluid-dynamic equations. This nonlinearity has the effect of Doppler shifting local intrinsic frequency of any given wave in the wind field imposed by all waves. Only an approximation to its effects is sought here, the wind field of the full spectrum being taken to be horizontal, horizontally stratified and constant in time, but otherwise that field is taken to have the statistical characteristics that would be expected of a wave-induced spectrum, including a propensity for growth with height. It is found that waves with relatively large vertical wavenumber m exceeding a characteristic value m[sub c] are substantially Doppler spread in vertical wavenumber, most particularly into a large-m tail. At sufficiently large m, waves are taken to be obliterated by dissipative processes. The net effect is to leave a tail that will be universal and can be identified readily with the observed tail. If the tail extends to a sufficiently large m -- a well defined value m[sub Minst] -- the spectrum as a whole renders itself unstable. The length of the tail is taken to be limited by the instability, any m values observed beyond M[sub Minst] being attributed to turbulence. 32 refs., 4 figs.

• OSTI ID: 5418975
• Journal Information: Journal of the Atmospheric Sciences; (United States), Journal Name: Journal of the Atmospheric Sciences; (United States) Vol. 48:11; ISSN 0022-4928; ISSN JAHSAK
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540110*
ATMOSPHERIC CIRCULATION
EARTH ATMOSPHERE
FLUID MECHANICS
GRAVITY WAVES
INSTABILITY
MECHANICS
METEOROLOGY
ONE-DIMENSIONAL CALCULATIONS
WAVE PROPAGATION