Report describes method for estimating gravity-wave density variation from wind speed profile between 60 and 100 km. Single profile is inadequate for valid determination of mean or background values and ensemble averaging over several related profiles is recommended

Miller, E. B.

English

NASA Technical Reports Server

1972	 B72-10143 
NASA TECH BRIEF 
Marshall Space Flight Center 
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Atmospheric Density Variations Related to Internal Gravity Waves 
Atmospheric density variations may be associated 
with a number of physical phenomena which include 
turbulence, auroral activity, atmospheric chemistry, atmo-
spheric heating, and "gravity waves". Evidence of gravity 
waves, or waves resulting from the effects of compress-
ibility and bouyancy, has been shown from data obtained 
on wind-speed profiles between the altitudes of 60 and 
100 km. These. data are determined by a number of 
methods such as radar tracking of chaff, optical track-
ing of the chemilumine scent trails from rocket releases, 
acoustical techniques, and the radar tracking of the ioni-
zation trails of meteors. A report has been available that 
describes a method for estimating gravity-wave density 
variation from wind speed profile between 60 and 100 kin. 
The relation of the meteor-trail wind data to internal 
gravity waves is characterized by roughly horizontal winds 
which exhibit a strong variation over vertical distances 
of a few kilometers. A typical variation might depict a 
vertical scale of about 12 km, a horizontal scale exceed-
ing the vertical scale by a factor of 20 or more, and a 
period of about 200 minutes. The wind variations are 
generally seen to increase with height, and a background 
wind shear is frequently evident. 
From the analysis of the effects of background wind 
shear and mean temperature, under certain approxi-
mations, the background wind shear has no effect upon 
the magnitude of the gravity-wave density variations, 
although the mean temperature and its vertical gradient 
may be more significant in this respect. The report con-
siders the background or mean values that are deter-
mined from typical vertical profiles of either wind speed 
or temperature. In addition, wind shear and temperature 
gradients are introduced into the gravity wave problem, 
while the simple formulation of an analytical expression 
that relates density variations to wind speed variations 
for gravity waves is retained. It is concluded that a single
profile is inadequate for a valid determination of the 
mean or background values and that ensemble averaging 
over several related profiles is recommended. 
The report on the method for estimating gravity-wave 
density variation from wind speed profiles presents the 
basic gravity-wave theory. Special attention is given to 
the justification of the assumptions that are used in 
establishing and specializing the basic equations. The 
expression for estimating the variations in density asso-
ciated with velocity variations in the presence of wind 
shear and temperature gradients is developed and justified. 
Critical levels, temperature and wind profiles, and sta-
bility are also presented. The method also relates the 
physical significance of parameters and parametric regimes 
and includes a discussion on the problem of estimating 
the background wind speed and the mean temperature 
from available data. 
Note: 
Requests for further information concerning the report 
on atmospheric density vatiations related to internal 
gravity waves may be directed to: 
Technology Utilization Officer 
Code A & TS-TU 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: 1372-10143 
Patent Status: 
No patent action is contemplated by NASA. 
Source: E. B. Miller of

Northrop Corp.

under contract to

Marshall Space Flight Center

(MFS-2 1637) 
Category 03 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19720000143 2020-03-17T03:30:38+00:00Z


Atmospheric density variations related to internal gravity waves

Method for estimating gravity wave density variation from wind speed profiles between 60 km and 100 k

Atmospheric density variations related to internal gravity waves

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