Internal gravity wave (IGW) parameters obtained by the radiometer method have been considered by many other researchers. The results of the processing of regular radiometeor measurements taken during 1979 to 1980 in Obninsk (55.1 deg N, 36.6 deg E) are presented

Gavrilov, N. M.

Kalov, E. D.

English

NASA Technical Reports Server

N 8 8 -  1 4 5 2 3  1 7 3  
A STATISTICAL STUDY OF VARIATIONS OF INTERNAL 
GRAVITY WAVE ENERGY CHARACTERISTICS IN METEOR ZONE 
N. M. Gavrilov and E. D. Kalov 
Leningrad State University 
Leningrad-Petrodvorets, USSR 
Internal gravity wave (IGW) parameters obtained by the radiometeor 
method have been considered by SPIZZICHINO, (1975); GAVRILOV et al., 
(1976); GAVRILOV and DELOV, (1976); KARIMOV and LUKYANOV. (1979); KAZANIKOV 
and PORTNYAGIN, (1981) and KALCHENKO et al., 1983. This paper presents the 
results of the processing of regular radiometeor measurements taken during 
1979-1980 in Obninsk (55.1°N, 36.6"E). 
The Obninsk meteor radar takes simultaneous measurements in four areas 
of the meteor zone which correspond to antenna directions northwards, 
westwards, southwards and eastwards. The instrumentation used is described 
in PORTNYAGIN and SHIRENGER (1978), and the method of statistical data 
processing - in GAVRILOV (1984). The meteor station determines for each of 
the four directions a number of wind velocity values at random time moments 
at the average height of the meteor zone z = 93 km. To analyze the IGW 
horizontal structure, the area observed is divided in the direction of the 
antenna beam into horizontal subareas of width x = 100 km with the centers 
x biased by Ax = 25 km. For every group of meteor echoes in each of the 
horizontal subareas, a high frequency filtration (averaging over 10 minute 
intervals) and a low frequency filtration are performed (GAVRILOV, 1984), 
after which amplitude and phase spectral analyses of data over sliding 
12-hour time intervals are carried out. The subsequent statistical 
analysis of the spectra obtained makes it possible to recognize the IGW 
spectrum from the background of noise (GAVRILOV, 1984), as well as to 
determine the values of projections of horizontal wave numbers k and phase 
velocities c of IGW to horizontal axes oriented along the antenna beams 
(see above). 
9. 9. 
h 
Radiometeor data obtained in Obninsk for 582 days during the period 
from February 1979 to November 1980, were processed by the above-mentioned 
method. 
Fig. 1 shows histograms of the distributions of IGW parameters for 
summer for all the sounded directions. They look alike and h+y ma-vma at 
the values of c - 50-75 mps, V - 4-5 mps and k - (1-2) 10 km . Of 
similar appearance are histograms of the distributions of IGW parameters 
for other seasons. Analysis of the IGW quantities propagating in various 
directions has revealed that IGW propagating southeastwards prevail in 
winter, whereas those propagating northwestwards prevail in summer. The 
same seasonal dependence of the prevailing directions of the IGW 
propagation was earlier found out from observations of night airglow wave 
variations (GAVRILOV, 1982). Causes for this regular feature can be 
seasonal variations in the location of IGW sources and those in the 
direction of the zonal flux in the stratosphere which influences the IGW 
propagation from tropospheric sources (GAVRILOV, 1982). 
h h 
https://ntrs.nasa.gov/search.jsp?R=19880005141 2020-03-20T09:11:45+00:00Z
174 
Fig. 1 Histograms of the distributions of the IGW parameters for all the 
IGW directions. Dotted lines correspond to the corrected values 
of "corr' 
175 
Fig. 2 shows the mean values of ch, V and k calculated separately for 
each month of the observation period and for tge four groups of the IGW 
directions considered. and kh have no pronounced 
seasonal variations. - 30-150 
mps and dqreays with the increase of T. The values of kh lie within (1.5 
- 2 . 5 )  10 km and are hardly dependent on T at all. The most pronounced 
variation is observed only in the amplitudes of the velocity V; for IGW 
propagating in all the directions and for all the frequency groups, the 
maximum of V - 7-8 mps is observed during the winter months (November to 
March), and the minimum of V 4 - 6  mps - in summer (Fig. 2). In Figs. 1 and 
2 the histograms and V are shown by dotted lines for the values 
corrected for the effec? of the finite number of registered meteors 
(GAVRILOV, 1984). The mean winter values increase up to V - 12-15 mps, 
and the mean summer ones - up to V 
It can be seen that c 
The phase velocity of ch changes within c h h 
c rr 
corr - 8-9 mps. corr 
The components of the wave fluxes of energy F heat FTi, momentum F i' ij and mass F are described by formulae of the type: mi 
F. = <P'v' > + Evio ; FTC - po Cp <T'vti>; Fij = <v'.v'.>; Fmi = <P'v'.>, 
i 1 J  ( 1 )  
where dashes denote the wave components and the subscript o the background 
components of pressure p, density p ,  temperature T, the wind velocity 
component v * c is the specific heat capacity at constant pressure; E is 
the wave energ& the sign < > denotes averaging over the wave period; i = 
x, y, z correspond to the x, y, z axes oriented eastwards, northwards and 
upwards. The value of p', p ' ,  T' and v' required for calculations 
according to (1) are found from the measuredZv' and V I  by making use of 
i' 
hydrodynamics equations. X Y 
To perform the calculations, apart from the zonal wave number k one 
must also know the meridional wave number k . Statistical analysis has 
revealed that in the meteor zone the "noise''Yof IGW coming from various 
incoherent sources is mainly observed, and that harmonics with identical 
periods are found in mutually perpendicular directions only occasionally. 
Therefore, it is impossible to calculate the values of (1) for individual 
harmonics. 
X '  
However, considering the problem of the influence of IGW on the 
thermal regime and circulation of the upper atmosphere, not individual but 
long term averages of wave flux are important. The measured probability 
densities of the distributions of k (Fig. 1) and statistically reliable 
measurements data make it possible 'to use the methods of statistically 
modelling (Monte-Carlo) to calculate the mean values of (1). On a 
computer, by transformation of data from a random number generator, the 
random value k is modelled which has a probability distribution equal to 
the experimenth. Wave fluxes (1) and their monthly mean values are 
calculated. To minimize the error, calculations are made for 10 different 
realizations of the random value k and the results are then averaged 
again. Y 
Fig. 3 shows seasonal variations of the mean values of wave fluxes, 
all of which have a pronoyced -~easonal variation. -3 Th-5 vertical energy 
flux FZ varies from 6 x 10 Wm in winter to 1x10 Wm in summer. The 
176 
19792 f9802 
Fig. 2 Mean values of ch, V and k 
the North (N), West (W), South ( S )  and East (E). 
for the groups of IGW propagating to h 
177 
Fig.  3 Seasonal variat ions of the mean values of wave f l u x e s .  
l i n e s  correspond to the corrected values Vcorr. 
Dashed 
178 
directions of F and F correlate fairly well with the signs of the 
background wind %omponenes V and V . The vertical mass flux F is 
always directed upwards and f g  maxim&' in winter. 
and F are in antiphase with the variations of FT and F . The velocig 
of th%'vertical wave transport of mass is cornparhe w i R  the background 
vertical velocity. The 
values and signs of the moment fluxes F and F in Fig. 3 correspqqd to 
wave accelerations in the zonal direct? n in wixfer of -(80-100) ms /day 
westwards, and in summer +(l_q-20) m s /day eastwards; in the meridional 
difection, to +(lo-50) m s /day in spring and autumn and -(lo-50) m 
s /day in winter and summer. This gives an experimental confirmation to 
the existing hypothesis that IGW in the upper atmosphere contribute to the 
drag of the zonal flux and the formation of meriodional circulation. 
However, the values of wave accelerations obtained are somewhat lower than 
those used in numerical modelling (HOLTON, 1983), particularly for summer. 
The variations o y F  
.The vertical wave flux is of the type of FTz = FZ. 
f"" 
The variations of the IGW energy E with T - 0.5-6 hrs in the course of 
a 48-day cycle from July 8 to August 24. 1979, were investigated. The 
results of the spectral analysis of E and the background wind for four 
sounded directions in the period mentioned show that the main harmonics of 
the background wind are two day and semi-diurnal, whereas that of the wave 
energy is diurnal. The energy spectra of the wave variations of the 
meriodional wind increase in the region T 2 2 days in contrast to the 
spectra of E for zonal directions. Since tides in the middle latitudes are 
mostly stable, the main mechanism of the formation of diurnal and 
semi-dirunal variations of E is the modulation of IGW propagating from 
below under the influence of the vertical profiles of temperature and wind 
produced by tides. The diurnal tide in the meteor zone has much smaller 
vertical wavelengths than the semi-diurnal tide and a quasi-two diurnal 
variation. Therefore, it produces the largest amplitude of modulation of 
E. 
The variations of E with 4 to 8 day periods can be accounted for by 
first possible modulation of the propagating IGW by planetary waves and 
second, meteorological processes in the troposphere with 4 to 8 day 
periodicity causing an enhanced generation of IGW propagating upward to the 
meteor zone. 
References 
1. Spizzichino A., 1975, in: Atmospheric Circulation, Moscow, MIR Publ., 
p. 120-174. 
2. Gavrilov N.M., Karimov K. A., Koksharov I.I., 1976, Trans. Kirghiz 
State Univ., Ser. Phys. Sci., iss. 7, p. 20-36. 
3 .  Gavrilov N.M., Delov I.A., 1976, Geomagn. Aeron. (USSR), 16, No. 2, p. 
293-297. 
4 .  Karimov K.A., Lukyanov, A.E., 1979, Izvestia Sov. Acad. Sci., Physics 
Atmos. Ocean, g, No. 8, p .  877-880. 
I 5. Kazanikov A.M., Portnyagin Yu. I., 1981, Geomagn. Aeron. (USSR), 21, 
NO. 2, p. 371-372. 
1 7 9  
6. Kalchenko B.V., Kashcheev B.L., Oleinikov A.N., 1983, Abstracts of 
papers presented to I USSR Symp. on Middle Atmospheric Studies 
Alma-Ata, Febr. 
7. Wind Measurement at Heights 90-100 km by Ground-Based Methods. Ed. 
Portnyagin Yu. I., Shirenger K.L., Leningrad Gidrometeoizdat Publ., p. 
344, 1978. 
8. Gavrilov N.M., 1984, in: Meteor Studies, Moscow, Soviet Geophys. 
Committee, No. 9, p .  106-123. 
9. Gavrilov N.M., 1982, Izvestia Sov. Acad. Sci., Physics Atmos. Ocean, 
- 18, No. 1, p. 8-17. 
10. Holton, J.R.. 1983, J. Atmos. Sci., 40, No. 10. p .  2497-2507. 


A statistical study of variations of internal gravity wave energy characteristics in meteor zone

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server