Ozone data recorded by balloon-borne sondes released at various sites around the world revealed that frequently the vertical ozone distribution in the stratosphere is remarkably laminated. Recently, measurements of ozone profiles near the winter polar vortex have shown strong laminae close to the vortex boundary. Also, a statistical study published recently has shown that laminae are most commonly found between 12 and 18 km at high latitudes in winter and spring in both hemispheres but they are not found in the tropics and are rarely observed in the subtropics. Ozonesonde ascents performed in Athens (37.9 deg N, 23.8 deg E) during the winter 1991-1992 in the framework of the European Arctic Stratospheric Ozone Experiment (EASOE) have shown that the lamination phenomenon was very frequently present in our region which is in contradiction with previous measurements at our latitudes. The characteristic minimum of ozone at 15 km has been also detected. Finally, the correlation of the occurrence of these two phenomena in relation with the circulation of air masses showed that the laminated profiles are connected in the lower stratosphere while the appearance of the ozone minimum around 15 km is connected with the influence of the subtropical jet-stream

Chronopoulos, George

Kalabokas, Pavlos

Varotsos, Costas

English

NASA Technical Reports Server

N95-11107
ON THE LAMINATED STRUCTURE OF OZONE
IN THE SUB-TROPICAL ATMOSPHERE
Costas Varotsos, Pavlos Kalabokas and George Chronopoulos
Department of Applied Physics, University of Athens
33, Ippokratous Str., 106 80 Athens, Greece
ABSTRACT
Ozone data recorded by balloon-
borne sondes released at various sites
around the world revealed that
frequently the vertical ozone distribu-
tion in the stratosphere is remarkably
laminated. Recently, measurements of
ozone profiles near the winter polar
vortex have shown strong laminae close
to the vortex boundary. Also, a statis-
tical study published recently has
shown that laminae are most commonly
found between 12 and 18 km at high
latitudes in winter and spring in both
hemispheres but they are not found in
the tropics and are rarely observed in
the subtropics.
Ozonesonde ascents performed in
Athens (37.9°N, 23.8°E) during the win-
ter 1991-1992 in the framework of the
European Arctic Stratospheric Ozone
Experiment (EASOE) have shown that the
lamination phenomenon was very
frequently present in our region which
is in contradiction with previous
measurements at our latitudes. The
characteristic minimum of ozone at 15
km has been also detected. Finally, the
correlation of the occurence of these
two phenomena in relation with the cir-
culation of air masses showed that the
laminated profiles are connected with
the North-Northwest circulation in the
lower stratosphere while the appearance
of the ozone minimum around 15 km is
connected with the influence of the
subtropical jet-stream.
INTRODUCTION
The existence of a laminar struc-
ture (layers of enhanced and depleted
ozone) in ozone profiles has been first
reported about thirty years ago (Her-
ing, 1964; Hering and Borden, 1964)
based on ozonesoundings performed over
North America and Switzerland. Dobson
(1973) made a systematic analysis of
the laminar structure in ozone profiles
in the lower stratosphere over a wide
longitudinal and latitudinal range,
adopting ozone partial pressure change
> 30 nb as criteria for the detection
of laminae. For the statistical analy-
sis of the laminar structure he divided
the ozone profiles into three groups :
group 0 - profiles containing
almost no lamina
group I profiles exhibiting
moderate lamination
group II - profiles extensively
laminated
He found that the features of the
laminated structure vary with latitude.
Between January and April the lamina-
tio,_ phenomenon is most frequently
found. At latitudes below about 20°N in
the spring and below about 30°N in the
autumn, a laminated structure of the
ozone is very seldom found. About 35%
of all profiles were group-II at high
latitudes in spring, while group-I days
reached a peak frequency of 70% in
June. Group-II days were rarely
observed at any latitude during the
summer, while group I was found in
Polar regions throughout the year. Dob-
son (1973) could not find an explana-
tion for the incidence of these layers
at a preferred height of 15 km nor for
the constancy of the preferred height
with latitude. He showed though that
there is a strong correlation between
the existence of a characteristic ozone
minimum at 15 km with the occurence of
a double tropopause especially in lati-
tudes around 40°N. He made also the
assumption that the laminated structure
and the ozone minima at 15 km are of
the same origin since the variations in
the frequency of their appearance with
both season and latitude are very simi-
lar.
854
https://ntrs.nasa.gov/search.jsp?R=19950004694 2020-06-16T11:29:30+00:00Z
Another statistical study of the
lamination phenomenon has been pub-
lished recently (Reid and Vaughan,
1991). In this study the laminar stuc-
tures found in the altitude range
9.5-21.5 km were only examined. Laminae
were categorized according to their
vertical extent (called depth) as well
as the change in ozone partial pressure
inside them (called magnitude). They
used also same criteria to separate
genuine laminar features from instru-
mental noise or large-scale features in
the ozone profile. The acceptable depth
for laminae was chosen to be beetween
200 m and 2.5 km while the minimum mag-
nitude 20 nbars. The above study showed
that laminae are most abundant bellow
18 km at high latitudes during winter
and spring which is in accordance with
the findings of the Dobson's study. But
Reid and Vaughan (1991) disagree with
Dobson (1973) as far as the origin of
laminae is concerned. Based on the
observation that their magnitude is
greatest and their depth least during
winter and spring they rule out the
suggestion of Dobson (1973) that they
all originate near the subtropical jet-
stream, although the possibility
remains that a small number of laminae
may be generated by stratosphere-
troposphere exchange around these fea-
tures (Begum 1989). Instead of that
they suggest that laminae may represent
evidence for a process which can cause
exchange of air in and out of the polar
vortex. This suggestion is supported by
recent polar ozone campaigns where
laminae particularly sharp and deep
near the winter polar vortex have been
detected. (Mc Kenna et al., 1989).
Given the ozone distruction which is
known to take place within the vortex,
the possibility that such exchange can
spread ozone depletion to lower lati-
tudes should be taken into consider-
ation.
RESULTS AND DISCUSSION
We have performed 29 ozonesoundings
in the period between December 1991 and
April 1992 (6 in December, 7 in Febru-
ary, 8 in March, 8 in April). The
ozonesondes which has been used for the
vertical soundings were the electro-
chemical concentration cells (ECC,
Scientific Pump) after Komhyr (1969).
For the measurement of temperature and
humidity as well as the data transmis-
sion we used RS-80 radiosondes (Vais-
ala). The interface card for the digi-
tization of signals and the receiving
system were also from Vaisala. The data
were taken during the ascent of the
balloon (TOTEX, 1200g). The ascent
velocity was about 5m/s. The ozone-
soundings were performed at 10 h G.M.T.
For the identification of laminar
structures the same criteria were used
as in the work of Reid and Vaughan
(laminar depths less than 2.5 km and
magnitudes higher than 20 nb). Features
having depths higher than 2.5 km are
regarded as ozone maxima and minima.
The first important finding of our
study is that the lamination phenomenon
has been very frequently observed over
our region. These laminar events were
significantly more frequent observed
than those in previous measurements at
our latitudes. This difference becomes
much more pronounced in February and
March where the lamination frequency
over Athens is about twice as that
observed over Cagliari, Italy (39.1°N)
(fig. i). We should mention here that
the data of Cagliari were taken in the
period between 1972-1975. This fact in
combination with the observation that
the laminar events are much more pro-
nounced at the edge of the polar vortex
leads to a possible explanation that
the polar vortex has been moved more
southwards during the last 20 years.
The on going discussions about ozone
depletion in the middle latitudes over
the last 15 years mention this possi-
bility (Stolarski et. al., 1991). It
is worth noting that the nearest ozone-
sounding station to Athens (in Hohen-
peissenberg Germany 47,5°N) is quite
far in order to more information about
the situation over our region.
If we examine the weather maps pro-
vided by the German Weather Service we
observe that there is a significant
correlation between the appearance of
laminar events and the establishment of
a North-Northwest circulation in the
lower stratosphere over our site. In
this case we could also say that the
site is under the influence of the
polar vortex. The above observation is
in agreement with the findings men-
tioned above about the enhancement of
laminar phenomena at the vortex bound-
ary. One characteristic example we
observe in fig. 2. Eight days with the
above characteristic have been observed
in our data set.
We found also at least 4 days where
a distinct minimum at 15 km was
observed. By examining the weather maps
we find out that during these days our
site was influenced by the subtropical
jet-stream. One characteristic example
is observed in fig. 4. This is in
agreement with the observations made by
Dobson that the 15 km minimum is asso-
ciated with air coming from the sub-
tropical region. Finally in fig. 6 we
observe a case where our site was
855
influenced by both types of circulation
of air masses in the lower strato-
sphere. The distinct minimum around 15
km as well as laminar structures are
clearly shown.
REFERENCES
1. Hering, W. S. , 1964. "Ozone
observations over N.
America" Vol. i, A.F.C.R.F.
2. Begum, Dil Afroze, 1989.
"Studies of the total ozone
field around the sub-
tropical jet stream".
Ph.D. Thesis, University
of Wales.
3. Hering, W.S. and Borden, T.R.,
1964. "Ozone observations
over N. America. Vol. 2,
A.F.C.R.F.
4. Dobson, G.M.B., 1973. "The lami-
nated structure of
the ozone in the atmo-
sphere". Quart. J. R. Met.
Soc., 99, p.p. 599-607.
5. Reid, S.J. and Vaughan, G. ,
1991. "Lamination in
ozone profiles in the lower
stratosphere" . Quart. J.
R. Met. Soc., 117, p.p.
825-844 .
6. Mc Kenna, D.S., Jones, R.L.,
Austin, J. , Browell,
E.V., Mc Cormick, M.P. ,
Krueger, A.J. and Tuck,
A.F., 1989. "Diagnostic
studies of the Antarbtic
vortex during the 1987 Air-
borne Antarctic Ozone
Experimental:, Ozone mini-
holes" J. Geophys. Res. ,
94, p.p. 11641-11669.
7. Stolarski, R.S., Bloomfield, P.,
Mc Peters, R.D. and
Herman, J.R., 1991. "Total
ozone trends deduced from
Nimbus 7 TOMS data". J.
Res. Lett., 18, p.p.
1015-1018.
I 0 - -
_3b ;
Z
r_ 1,0 i -" " \,
+j .... \ I
O+O [ _ _ + ! : L •. ! t J i __ L
JAN I'EI] MAR APR 5lAY JLiN JUI, AI;C MI£P O<I NIW PEC 3,iN
Figure i. Monthly variation of the
average lamina frequency per profile
for Cagliari (dashed line) and Athens
(asterisks) .
Iq.]LATIVE rlI'.',lll)I'l'Y (,_.)
0 20 ,I () OD 8 () 1 oo
"q :'
\ ,'+ ] 11F"4L,. .,h
10 ,!£.._ "'C ' Y.. '" < ;;(}
\.
= i
g+
7--'-
<
h .
0 .1 1] I ;-' I (; <'0 %,
OZONI: ;L'J.tTL_.I, I'l.:l,:.'-+.'-'[_i.:[]_ rot;. Q
-_-_ + - - T • . T r - _ " , ..... r " ,
--80 -I0 0 I_)
Tt<hl[q"]l"..'kTlr]_}'i t,<r: dl
Figure 2. An example of an ozone
profile with laminar structure, over
Athens.
• _ - _ - ./ .... -q._ _ -
+= _. . -¢ +: . .._ . +_ , . : , _. _ _ .
• I, ': '. *; _.,_<--.++ -,'+?__ "- _-+" . " .+_ ,_ft'lu -( : '':""t ?+- ,,
+ ,_ + . ,- ,: ; ,_p,P,_',,.,, ?
.(=,(-.++ -}-+ :+ ., _ : - ,.+ •
+:, + :,,. ;,+" : -,,+
.... -+.,;7 -._(."? +l; ";+_-"+
'" ':' ---L ..... 7<""
, , <. .........
-," 7,:- . :. - ,:,[__ -£,
.. - .... ,k,,_cz
Figure 3. Weather map at 200 hPa of
the day when the profile of the figure
2 was taken.
O
856
RELATIVE HUMIDITY (_)
0, 20 40 60 80 100
bs5
l
3<
\.
<: 2
I
iL
fi
Ib
] "j'
gD
s i!'"g_
-1 8 2_:;
g¢
B
0
< t
_ _s _'" -
k_Ls
-.-:.
_7H[_:S-SFLEEC[
2u-3-1992
:30
"--: ,: _
I ] T : [ _ r r-r r r'T T r_,q,_,-,rT-T- 0
I) 4 [] 12 i 6 2 0 _ 4
OZONIC PAR'I'[A!. PRESS;U[{'( U ",
- 80 -,10 0 ,I 0
'YF:_/PE R,VI'U RE (£-'ad)
-25
:20
,.,..
10
Figure 4. An example of an ozone
profile with a distinct minimum at 15
km, over Athens.
,', , " 4," _ /:.::_x_::.:--: <- ,_-
: , " - ,- 7 ,,. .i-_-: ,!. -=4-!i" _l _ , ,
Figure 5. Weather map at 200 hPa of
the day when the profile of the figure
3 was taken.
I0
RELATIVE HUMIDITY (,_)
0 20 40 60 80 100
_--_ ...... :,?_L_'. ..... L____:
k _+ b35
r, k :/ ATHENS CR
_:_.. r _°
C-
-<
L
5_L =
g :
mlO ,-
L_
P>
-. i-
% - .
If0
"-,. .
_ \
0 4 8 12 16 20 24
OZONE PARTIAL PRESSURE(ITq)a)
- 80 -,t O 0 40
TI'i_I P ERA'I'U RE (grad)
Figure 6. A day with both laminated
ozone profile and the 15 km ozone mini-
mum.
Figure 7. Weather map at 200 hPa of
the day when the profile of the figure
6 was taken.
857


On the laminated structure of ozone in the sub-tropical atmosphere

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