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					Spatial Characteristics of Total Ozone Annual Oscillation in the Tropics

Konstantin N. Visheratin
Institute of Experimental Meteorology, SPA "Typhoon", Obninsk, Russia

Abstract.      Spectral amplitudes of oscillations with the
periods from 10 to 14 months were calculated from
monthly mean TOMS total ozone data from 1979 to 2002.
The amplitudes obtained with a latitudinal-longitudinal
resolution of 1o by 1.25o were used to study spatial charac-
teristics of the total ozone annual harmonic and its side
lobes. The sharp topographic effects (land – sea contrasts)
were found over coastlines. The minimum of the annual
oscillation (AO) amplitude is shifted from the equator
southward to 4o-5oS with the least amplitudes at the region
between 110oE and 150oE. The amplitudes of sidelobes
with the periods of about 10.7-10.8; 11.25-11.3 and
12.7-12.8; 13.4-13.5 months near the region of AO mini-
mum are equal or exceed the amplitude of AO. It is as-
sumed that a mechanism of the appearance of these side-
lobes connected not only with the known Gibbs phenome-
non but with beating of the annual oscillation and oscilla-
tion induced by the Moon node revolution period.

Introduction
     In the tropical region the total ozone content (TО) has
the least values, the long-term linear trends oscillate about
zero, and TO variability is defined mainly by the quasi-
biennial oscillations [WMO, 2002]. Seasonal variations
which determine amplitude of an annual TO oscillation in
this region are minimal also. It allows to study spectral
structure of the TO oscillations practically at absence of the
most powerful annual harmonic that introduce distortions
to spectral intervals near to 12 month. As the amplitudes of
TO oscillations in equatorial area are small, it raises re-
quirements to accuracy of measurements. De facto the sa-
tellite (ТОМS/EPTOMS) measurements are now almost
                                                                   Figure 1. Global maps of total ozone mean values (a) and an-
the standard and agree well with the ground-based TO
                                                                   nual harmonics amplitude (b).
measurements. With this in mind, we used monthly TOMS
data from 1979 to 2002 to study the spatial characteristics
of total ozone annual oscillation in the tropics. To explore            More detailed map of an annual harmonic for the re-
TO spectral characteristics the modified Fourier transform         gion of AO minima (0oS -10oS) is shown in a Figure 2. As
was used (more in detail technique is described in [Vishe-         can be seen from Figure 2, the amplitude of an annual
ratin, 2004]).                                                     harmonics varies from 10 to 12 DU above Southern Amer-
                                                                   ica and from 0.5 to 1 DU near Borneo an Sulawesi Islands
Results and Discussion                                             at 110o to 120oE and westward New Guinea overBismark
                                                                   See at 145o to 155oЕ (the second interval is the region of
    Spatial distribution of the TO (averaged from 1979 to
                                                                   the absolute minimum of AO and simultaneously the region
2002 in each point of ТОМС grid 1o*1.25 o) and AO am-
                                                                   where the quasi-biennial oscillation with period 28.5 month
plitude distribution (hereinafter amplitudes are given in
                                                                   has over equator local maximum [Visheratin, 2004]). Thus
DU) are shown for globe in a Figure 1. Let's mark that on
                                                                   the AO minima are placed in region of deep convectional
these maps, especially on the map of averaged values (Fig-
                                                                   motions (see for example [Ardanuy and Krishnamurti,
ure 1a), coastal lines of continents and even of islands are
                                                                   1987]). For globe as a whole the minimum of AO is dis-
clearly visible. The reasons can be connected to real dis-
                                                                   placed from equator southward. Sectional view for the
tinction of ozone concentrations above ocean and land (for
                                                                   latitude 4.5oS, for which the values of AO are minimal is
the first time this fact was probably marked by [Guschin,
                                                                   shown in Figure 3 in comparison to the profile of an earth
1976]), with features of TOMS TO processing, and with
                                                                   surface. Above coastal lines of
arising of convectional cells above coastal lines.
                                                                     imately to 0.0045 month-1, that is close to the lunar tropical
                                                                     year or period of the Lunar nodes revolution 18.6 year.


                                                                     Figure 4.   The spectra of total ozone variation in region be-




Figure 2. Common view of spectral amplitude of the annual
harmonic in region between equator and 10oS. Arrow pointed to
region where AO amplitude has minimum.

                                                                     tween equator and 10.5oS at 120.625oE (a) and at 150.625oE (b).




Figure 3. Sectional view of AO amplitude at 4.5oS (upper curve)
and Earth core profile. Zero line for spectral amplitude coincides   The arrows indicate position of annual harmonic and sidelobes at
with the see level.                                                  latitude 4.5oS.

Africa and Southern America there are the sharp local mi-                Acknowledgments       Thanks are due to Dr. Jerry Ziemke for
nima. These minima are placed over earth close to cost and           attention to this work and helpful discussions. The work was
occupied significant territory. It confirms the assumption           partly supported by the Russian Foundation for Basic
that over coastal lines there are circulating cells with as-         Research (Grant 04-05-64702).
cending streams of air resulting in the lower ozone concen-
tration. It is curious to mark also the sharp decrease of AO         References
over Sumatra Island near Indian - Pacific Oceans boundary.           Ardanuy P. E., Krishnamurti T.N., Divergent circulations inferred
     The analysis of spectral structure of oscillations has            from Nimbus-7 ERB: application to the 1982-1983 ENSO
shown that in points where the AO has minimum the oscil-               event, J. Meteor. Soc. Jap., 65, 353 -371, 1987.
lations (sidelobes) with periods 10.7-10.8, 11.25-11.3 and           Guschin G.P., Main features in distribution of atmospheric total
                                                                       ozone over oceans aquatory, Proceedings of Main Geoph. Ob-
12.7-12.8, 13.4-13.5 months continue to exist. These oscil-            serv., Leningrad, 357, 83– 101, 1976.
lations are usually connected with Gibbs phenomenon ap-              WMO: "Scientific Assessment of Ozone Depletion: 2002". WMO,
peared at the Fourier analysis of finite time series. Howev-            Rep. No. 47., 498 pp., Geneva, Switzerland, 2003.
er in this case annual harmonics amplitude is less than              Visheratin K. N., Global Maps of Total Ozone QBO from TOMS
these sidelobes and methodical reasons (connected with                  Data Set, Thesis No 203, this Proceeding, 2004.
features the Fourier analysis) for occurrence of Gibbs si-
delobes are absent. Therefore it is necessary to assume that
there are other mechanisms of arising of these sidelobes.
One of possible mechanisms is connected with beating of
AO with a long-term oscillation. Frequency differences
between 5 peaks (4 sidelobes and AO) are equal approx-

				
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