JOURNAL
OF GEOPHYSICAL
RESEARCH,
VOL. 103, NO. D7, PAGES 8477-8490, APRIL 20, 1998
Latitude dependenceof the quasi-biennial oscillation
and quasi-triennial oscillation characteristics
of total ozone measured by TOMS
R. P. Kane
and Y. Sahai
Instituto Nacional de PesquisasEspacias,Sao Josddos Campos,Sao Paulo, Brazil
C. Casiccia
Grupo de EstudiosAtmosfdricos,Universidadde Magallanes,Punta Arenas, Chile
Abstract. The 12-monthmovingaveragesof total ozonemappingspectrometer(TOMS)
total ozonedata for 14 years(1979-1992) were examinedfor quasi-biennialoscillation
(QBO) and quasi-triennial
oscillation(QTO) and comparedwith stratospheric
low-latitude
zonalwind and equatorialeasternPacificsea surfacetemperature(SST). The equatorial
ozone had a strongQBO with a period of --•30 months,and its maxima tallied with
westerlywind maxima.At other latitudesthe ozonemaximaspacingswere often different
from 30 months,more so in the northern hemisphere.A spectralanalysisshowedthat
both hemisphereshad one peak at --•20monthsand anotherpeak at --•30months,only up
to --•50ø latitude. At higherlatitudesthesepeaksshiftedto --•23and --•36months.For 0ø50ø the ---30-monthperiodicityin the northernhemisphereshowedabruptphasechanges,
while the southernlatitudesshoweda roughlygradualphaseshift. The northern
hemispherehad an additionalperiodicityat --•4years,roughlymatchingthe SST. Analysis
of the same data without 12-monthaveragingshowedthe abovecharacteristicsmore
clearlyand revealedadditionalpeaksat --•0.7years(8-9 months)and --•1.30years(16-17
months).All of thesepeaksshowedshifts(mostlyincreases)at higherlatitudes.
1.
Introduction
A quasi-biennialoscillation(QBO) in the equatorialstratasphericzonal windswas discoveredby Reedet al. [1961] and
Veryardand Ebdon [1961].Soon,it was alsodiscoveredin the
total column ozone near the equator by Funk and Garnham
[1962]and at middleandhighlatitudesbyAngellandKorshover
[1962]. Hasebe [1980, 1983], Tolson [1981], Hilsenrathand
Schlesinger
[1981],and OltmansandLondon [1982]studiedthe
latitudinal structure of the ozone QBO using Dobson and
Nimbus4 backscattered
ultraviolet(BUV) data and reported
hemisphericasymmetry,implyingthat the ozoneat the equator
was stronglyconnectedwith the ozone in the northern subtropics but not with the ozone in the southern subtropics.
Using9 years(1979-1987) of total ozonemeasurements
from
the total ozonemappingspectrometer(TOMS) on Nimbus7,
Bowman [1989] reexaminedtheseresultsand stated that the
equatorialQBO in ozonewasmuchmore symmetricthan was
reportedearlier and was generallyout of phasewith ozone in
the subtropics.Also, the extratropicalQBO ozone anomalies
were confinedto the winter and springseasonsand conceptually, were like a ---27-manthQBO period modulated by the
12-manth seasonalcycle,resultingin the sum and difference
componentsof---8.3 and 21 months,besidesthe QBO period.
Shiotani [1992] used TOMS data from 1979 to 1989 and reported annual, quasi-biennial,and ---4-yearperiodicitiesfor
equatorialtotal ozone. Earlier, Hasebe[1980] had noticed a
Copyright1998 by the American GeophysicalUnion.
Paper number 97JD03651.
0148-0227/98/97JD-03651 $09.00
4-yearperiodicityfrom ground-basednetworkozonedata of 15
years,whichwasconfirmedlater by Hasebe[1983],usingNimbus4 BUV dataalso.Hasebe[1983]reporteda polewardphase
propagationof the QBO in the northern and southernmidlatitudes and an equatorwardphasepropagationat northern
high latitudes.Zerefoset al. [1992] also reported a poleward
phasepropagation.However, the QBO pattern obtainedusing
a linear regressionmodel by Yang and Tung [1994] from
TOMS data showedlittle evidenceof a gradualphasepropagation. Yangand Tung [1995] reexaminedthe TOMS, BUV,
and Dobson data and reported that first, the QBO signalwas
strongestin the middle and high latitudes and was present
mainly in the winter-springseason.Second,the extratropical
ozoneQBO signalwasout of phasewith the equatorialozone
signal, the latter being in phase with the equatorial stratasphericzonal wind QBO signal.Third, there was no gradual
phasepropagation.Instead,there were three distinctregions,
namelytropical,midlatitudinal,and polar regions,in each of
which the ozone QBO signalhad a fairly constantphase,and
large phase shifts occurredin the in-betweentransition regions.Many other detailswere mentioned.
In mostof theseanalyses,monthlyvaluesare used,and the
QBO characteristicsshow considerableseasonaldependence
(strongin winter-springetc.). However,QBO characteristics
couldalsohave a season-independent
component.In this paper we proposeto isolatethis componentby calculating12month moving averages,which would eliminate (or at least
reduceconsiderably)the seasonaleffects,and to comparethe
characteristicsat different latitudes,usingTOMS data for 14
years(1979-1992).Also, an updateof the earlierTOMS analysesby Bowman[1989] and Shiotani[1992] is given.
8477
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KANE
ET AL.: LATITUDE
DEPENDENCE
OF QBO AND
TOMS TOTAL
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OZONE
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3-
MONTHLY
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(b) 4-SEASON
( I2-MONTH
340
32O
34O
320
- •
-
MOVING
_
AVERAGE
12-SEASON
•
OZONE(56)
2001-x----x•
x•X
oISUNSPO
T x"-•x
•x..__.•_...
x-- x'•
-
)
(C)(36_MONTH)
MOVING
AVERAGE
I0
0
-IO
]
(12-36)
(d)
OZONE
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Figure 1. A sampleplot of total ozonemappingspectrometer(TOMS) total ozoneat 35ø-45øNincluding
(a) 3-monthlyaverages,
(b) 4-season(12-month)movingaverages
(the dotsindicatemaxima),(c) 12-season
(36-month)movingaverages(the crosses
representsunspotnumbers),and (d) Parameter(12-36) representing the differencebetween4 seasonand 12 seasonaverages(Figurelb minusFigurelc).
2.
Data
The data used are the TOMS ozone data (Bowmanand
Krueger[1985],Herman et al. [1991], upgradedversion7.0),
averagedover 5ø latitudebelts,from which data for the 45øW
longitudeare selectedfor analysis.Figure 1 showsa sample
plot and illustratesthe processing
procedure.Figure la shows
the 3-month averagesof TOMS ozone data for the 35ø-45øN
latitudebelt. Even thoughonly 4 points/yrare plotted, a strong
seasonalvariationis seen,whichmasksother effects.Figure lb
showsthe 4-season(12-month)movingaverages,
designated
as
ozone(12), wherethe maximamarkedby dotsindicatepossible QBO. However,there is alsoa downwardtrend, including
a solarcycleeffect.This canbe estimatedby evaluatingfurther
12-season(36-month)movingaverages,designatedas ozone
(36), as shownin Figure lc. The crossesshowthe sunspot
numbers,whichseemto showa downwardtrend parallelto the
ozone changesduring 1980-1987. However, for later periods,
the ozoneleveldoesnot riseparallelto the sunspots,
indicating
the superposedozone depletionknown to have occurredin
recenfyears.For our purposeof isolatingthe QBO the nature
of the trend (solar cycleeffect, depletion,etc.) is not important, and the QBO is isolated by subtractingFigure lc from
TOMS ozonein the 5øN-5øSbelt (nearthe equator)andshows
peaksalmostexactlyin the samepositionsas thosefor the 30
mbar wind, indicatingan excellentmatchbetweenthesetwo.
The other plots from the bottom upward are for increasing
latitude belts 5ø-15ø, 15ø-25ø, 25ø-35ø, etc., solid curvesrepresentingnorthern latitudesand crossesrepresentingsouthern
latitudes.The followingmay be noted:
1. The dots on the solid curves represent the northern
latitude maxima,and the spacingin monthsis indicatedby the
numbers.As canbe seen,the spacings
varyin a wide range,and
many are much larger than the wind QBO spacingof 30
months.Someof the spacings
looklike quasi-triennial
oscillation (QTO).
2. The spacings
for similarnorthernand southernlatitudes
are not similar. For example,for 35ø-45øN the spacingswere
36, 39, 24, and 27 months,while for 35ø-45øSthe spacings
(circled numbers)were 27, 27, 33, 30, and 27 months.The
procedureof selectingpeaks is somewhatsubjective.In the
35ø-45øNplot, a peak in the beginningof 1986 rather than at
the end could make the spacings36, 33, 30, and 27 months
somewhatsimilarto the spacingsfor 35ø-45øS.However, some
major differencesremain.In general,spacing•near 30 months
Figure lb. The residualsdesignatedas ozone (12-36) are are seen more often in the southern latitudes than in the
shownin Figure l d. It is interestingto note that the maxima northern latitudes.Thus there are considerablehemispheric
indicatedby dotsare in the samepositionin Figureslb and ld, differences.(Theseresultsare onlycrudelyvalid.Precisespectral analysisis presentedin section5.)
and the peak spacingsare not altered.
3. A strikingfeature is the ozone depressionduring 1985
(markedhatchedin Figure2) whichseemsto haveoccurredat
3. QBO and QTO Characteristics
all southernlatitudes exceeding15ø but not in the northern
by Visual Inspection of Plots
latitudes,aswas also seenin a similar depressionduring 1987
Figure 2 showsa plot of the 4-season(12-month)moving at high southernlatitudes.Ozone is reported to have a relaaverages.The bottom plot is for the 30 mbar stratosphcric tionshipwith the well-knownphenomenonof SouthernOscilwind at Singapore[Pawsonet al., 1993].Bowman[1989] used lation, a representativeof which is the equatorialeasternPadata only for 1979-1987, which contained•3-4 QBO cycles. cific sea surface temperature (SST). Positive temperature
Here, during1979-1992, five QBO cyclesare included,andthe anomalies are associatedwith occurrences of E1 Nifio, which
peak spacingsare 27, 30, 30, 36, and 30 months(all are mul- are warm water episodeson the Peru-Ecuadorcoast.The top
tiplesof 3 as our basicunit is a 3-monthaverage).The second plot in Figure 2 showsthe 12-monthmoving averagesof the
plot from the bottom showsthe 4-seasonmovingaveragesof equatorial eastern Pacific SST. The warm water events of
KANE ET AL.: LATITUDE
DEPENDENCE
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SST
PACIFIC
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N••i• EL
NINeEL
NINe
•
380
OF QBO AND QTO OF TOMS TOTAL OZONE
/'•24ffN 24 ,•,18_,
• 27 21 . 2
TOMS
•6o •x
300
" -•Xx....
xxxxxX•XXx•
•24
(LAI)
•
'N
750-85 ø
xXgxZxxs
• 27 15
310
390
4•
•xS
I'
...........
Xxxx
• x
320
s sso_so
x
360x•XxxxxxxxX•x•xX•..
•x xx• xxxxN 450_550
• 340
•••
m 33o
39•
0
XxxxxX
xxxxX Xs
24
27 •
320
N
0 310•x• 36 xx•
x
•
S
XXxx•
• •xx"•N 35ø-45ø
• 280 • 55A24
x
x
250
•
•x
•
54
-
48
2so_so
27
••
N
-
260250
5øN-5•
-
30 MB
20-
W
•
27
3(
(m/s)O
D
E
-20
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YEAR
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Figure 2. Plotsof 4-season
(12-month)movingaverages.
From top, equatorialeasternPacificseasurface
temperature
(SST),TOMStotalozonein different
latitudebelts,and30mbarequatorial
zonalwind(westerly
positNe,
easterly
negatNe).
Dotsandcircled
crosses
indicate
m•Jmain theplotsofthenorthern
(solidcu•es)
andthesouthern
(crosses)
latitudeozone.Numbersindicatespacings
(in months)be•een successNe
maxima.
1982-1983, 1986-1987, and 1991-1992 are indicatedin black,
and only the 1987 event seemsto have some associationwith
larger(by --•50Dobsonunits(DU) or more) in the northern
latitudes.Second,the variabilityis verydifferentin the northozonechanges
in thesouthern
highlatitudes.
Bojkov[1987]has ern and southernlatitudes.For latitudesexceeding45ø the
discussed some of these associations.
northernlatitudeshave a smalldecline(---2%) from 1980 to
The hemisphericdifferencesare by no meanslimitedto the 1986anda slightlylargerdecline(---3%) from 1986to 1990.In
QBO and QTO characteristics.
Figure3 showsthe long-term the southernhigh latitudes,there is a large decline(---5%)
changes
represented
by the 12-season
(36-month)movingav- from 1980to 1986(evolutionof the Antarcticozonehole) and
eragesfor variouslatitudebelts,solidcurvesrepresenting
the almost a steadylevel or slight increasethereafter. In lower
northernlatitudesand crosses
representingthe southernlati- latitudes the situation seems to have reversed. The northern
tudes.First,the ozonevaluesat highlatitudesareconsiderably latitudeshave a steadydecline from 1980 to 1986, while the
8480
KANE
80
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ET AL.: LATITUDE
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DEPENDENCE
88
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OF QBO AND
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TOTAL
OZONE
Figure 2 and alsowith their corresponding
parameters(12-36)
shownin Figure ld. Correlationswere largerfor the parameter
(12-36), mainly becausethe long-termozone changes(which
may be unrelatedto wind) are eliminatedin this parameter.
Figure 4 showsthe correlation plots for northern latitudes on
the left side and southernlatitudeson the right side.The lags
90
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QTO OF TOMS
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•
NORTHERN
x x x SOUTHERN
DU
370
305
Xxxx
Xxxxxxxxxxx
750_85
ø and leads examined are from -9 to +9 seasons,almost one
QBO cycle(30 months,10 trimesters)on either side,and refer
:585
.•.•__•xXxxxxxx
Xx
xxXXXxxx
xxxxxxxx
xxx
to the parameterwith respectto wind. Positivelag meansthat
:5;•o
XXXxxxx
XXxxxxxx
xxxxxx
x
390
650-75
ø
XXXX
XX
XX
XXXX
XXXXX
XX
xxX
%__
the parameter showedmaxima later than the wind maxima,
and negativelag meansthat the parameter attained maxima
earlier than the wind. The following may be noted:
1. Ozone at 5øN-5øS(top plot) is highlycorrelated(correlations >0.7) with wind, at almostzero lag. In the next belt,
5ø-15ø in both hemispheres,the correlationsreduce to ---0.30.5, but the lag is still almostzero. It may be noted, however,
that Yangand Tung [1995] reported a nodal line for column
ozonenear 10ø-12øof latitude in both the hemispheres,across
which there is a 180ø phasechange.Our latitude range is too
XXXXXXXXXXXxxxXxxxx
xxXXXXxXXXXXXXXXXX
340
xxxxxx
• XI 55ø-65ø
b.I
g
:580
••.•
450-55
ø
:550
XXXXXXXxxxx
XXXXXXxxxXXxxx
xxxXXXXXXX
XX
xxXXXXX
340
broad to detect such a fine structure.
330
2. For higherlatitudesthe correlationsare larger (---0.5),
:520
xxxxxxxxxXXxxx
x •
:55ø-45øbut the phaseshiftsconsiderably,from 0 to -4 seasons.The
xXXXX
300
Xxx
XXxx
xXxxxxxXXXXXXxxXX transitionseemsto be sharp,near 15øin both the hemispheres,
and in agreementwith the findingsof Bowman[1989]and Yang
and Tung [1995], though they reported seasonaldifferences,
which are eliminatedin our analysis.
290
•...,••Xxxxx
xxxX
•xx
xx
x 250__:55
ø
15o__25
o
280
--
270
XXxxxxxx•__
•]
xX
3.
In the northern latitudes, there seems to be another
260xxXXXXXX
xxxxXXXXxxxxx]
5ø- 15
ø
phaseshiftbetweenthe 45o-55øbelt and the 55o-65øbelt, from
XXXXXXXX
XXX
XXX
XxX
XXX
xxX
255
•
25O
5ON_5os -4
•]
seasonsto +2 seasons,which is maintained in the 65o-75ø
belt. Yangand Tung[1995]have mentionedsucha possibility,
SUNSPOT
CORRELATIONS,30MB WIND (VS) TOMS TOTAL OZONE
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-5
90
0
SOUTHERN
5
-5
0
5
YEAR
.5
0
Figure 3. Plots of 12-season(36-month) movingaveragesof
TOMS total ozone in northern (solid curves)and southern
(crosses)latitude belts.The bottom plot is for sunspotnum-
.5
0
bers.
.5
0
southernlatitudes seem to have a steadylevel in 1980-1982,
followed by a decline thereafter up until 1986. From 1986
onward, there is a steadylevel or rising tendency.(In years
after 1992, there is probablya global decline,not discussed
in
this paper.) The bottom plot in Figure 3 showsthe sunspot
numbers.The ozone decline from 1980 to 1986 is parallel to
the sunspotnumbers,but from 1986 onward, ozone did not
increasemuchwith the sunspotnumbers,indicatingthat there
is a long-termozone depletion superposed.
Possiblereasonsfor thesediscrepancies
canbe various.The
equatorial QBO may percolate to higher latitudeswith or
without phaseshifts,but other effectsmay be superposedand
may alter the positionsof the maxima.Alternatively,the peak
spacingsat higherlatitudesmay be due to altogetherdifferent
periodicities.A cross-correlation
and spectrumanalysiscould
give more preciseinformation.
•o
,T.5
Wo
o
z
Oo
_j.5
',,.,
i
Cross-Correlation Analysis
The wind valuesin the bottom plot of Figure 2 were correlated with the 12-month moving averagesof ozone shownin
5ø- 15ON
_
•.
5ø-15øS/
15o__
20ON 15ø-20
.
-.•• '•
25ø-`35øN
•
.35
ø--45
øN
•o
5o-65ON
o
.5
o
.5
o
-.5
I I I I I I I I I
I I I I I I I I I
I I I I I I I I I
I I I I I I I I I
-5
0
5
-5
0
5
SEASONS
Figure 4.
4.
•
Cross correlationsbetween 30 mbar wind and the
parameter(12-36) of TOMS total ozoneat differentlatitudes,
northern on the left side and southernon the right side. Correlation maxima(dots) are joined by connectinglinesto indicate phaseshifts.
KANE
ET AL.' LATITUDE
DEPENDENCE
OF QBO AND
but in the north polar region(750-85ø) the phaserevertsback
to -4 seasons.In the southernhemispherethe phasesat all
latitudes
above 15 ø seem to remain
at -4
to -6
QTO OF TOMS
TOTAL
OZONE
8481
CORRELATIONS,E.E.PACIFICSST (VS) TOMSTOTALOZONE
NORTHERN
-5
seasons.
Figure 5 showsa similar analysisfor correlationsbetween
equatorial eastern Pacific SST and the TOMS ozone data,
usingthe parameter(12-36), for northernlatitudeson the left
side and southern latitudes on the right side. The top plot
(commonto both sides)is for the equatorialregion(_+5ø) and
showslow correlations(---0.3), indicatingeither that the rela-
• o
tionship
between
equatorial
ozoneandSSTispoororthatit is
,.z,
SOUTHERN
0
5
-5
0
5
.5
o
o
overwhelmed
by the relationship
of equatorial
ozonewith ,¾o
stratosphericwind. The next plots are for the latitude belt
5ø-15
ø.Herethecorrelations
arehigher
(---0.5),
eitherbecause 70
therelationship
of ozone
withSSThasimproved
or because
thewindeffectisweaker,aswasindicated
bythelowcorrela- '5,o
tions
forthislatitude
beltinFigure
4.Also,
forhigher
latitudes
the correlations
are higher(---0.5)(againfor the samereason) o
øo
but for the northern latitudesonly. Regarding the phasethe
equatorialozone has a minimum (marked by triangles)near
the SST maximum(zero line), and there is a gradual phase
shift in the northern latitudes,from +3 seasonsat the equator
to -2 seasonsat 35ø.At 350-45 ø,there seemsto be a transition;
o
o
-,5
correlationsare low, and for higher latitudes the phase has
-5
0
5
-5
0
5
SEASONS
shiftedconsiderably.
If ozonemaxima(marked by circles)are
considered,there seemsto be a gradual phase propagation, Figure 5. Crosscorrelationsbetween equatorial easternPafrom +9 seasonsat the equator to approximately-8 seasons cific SST and the parameter (12-36) of TOMS total ozone at
at the poles.In the southernhemispherethe phasesare almost different latitudes, northern on the left side and southern on
constant,with ozone minima within 2 seasonsof the zero line, the right side. Correlation maxima (circles)and minima (triand ozone maxima occurring4 seasonslater. However, the angles)are joined by connectinglinesto indicatephaseshifts.
correlationsin southernlatitudes are generally low (---0.3),
indicatinga poor relationshipbetweenozoneand SST. Let us
now examinethe spectralcharacteristics
of all theseparameters. their standarderrors by a least squaresfit. From these,re and
their standarderror • (commonfor all re in this methodology)
canbe calculated,and anyre exceeding2• would be significant
5. Spectrum Analysis
at a 95% (a priori) confidencelevel.
To decipher the periodicitiesinvolved, a power spectrum
Some aspectsof this methodologyneed to be emphasized
analysiswas conductedby using maximum entropy spectral here. First, MESA peak detectionis very, very accurate.For
analysis(MESA) [Burg,1967;Ulrychand Bishop,1975],which example,the presentdata are seasonalvalues(four valuesper
detectsperiodicitiesmuch more accuratelythan the conven- year) for ---13years(i.e., 52 data points).In the conventional
tional [Blackmanand Tukey,1958] (hereinafterreferred to as BT method,with a generallyrecommendedlag m of 25% of
BT) method.Similarto the parameterlagm in BT, MESA has the data length(in thiscase,m = 13), onlycertainfrequencies
a parameter called the length of the prediction error filter k/2m canbe investigated(i.e., 1/26,2/26, ßßß, and 13/26,where
(LPEF), whichcanbe chosen.With low LPEF, only low peri- the foldingfrequencyis 0.5). In termsof periodicitiestheseare
odicitiesare resolved.Larger LPEF resolvelarger periodici- 26, 13,.-., 2.36, 2.16, and 2.00. Thus, if the periodicity was
ties,eventhoseapproachingthe data length,but the errorsare 2.25, it would be missed. In MESA, there is no such restriction.
larger and low periodicitiesshowpeak splitting.An LPEF of Any frequency(of course,lessthan the foldingfrequency0.5)
---50%of the data lengthis generallyadequateandwasusedin canbe investigated,and the stepsare a matter of choice.Thus,
the presentanalysis.
between 2.0 and 3.0, ---70 stepswere investigated,and the
MESA hasa drawback,namely,the power estimatesare not periodicitiescould have an accuracyof 0.01. This was earlier
reliable [Kaneand Trivedi,1982].Hence MESA was usedonly checkedby feeding artificial samples[seeKane, 1977, 1979].
to identifythe possibleperiodicitiesTe, whichwere then used MESA resolvespeaks even slightly better than the criterion
in the expression
mentionedby Ulrychand Bishop[1975],namely,two frequencies,f• andf2, canbe resolvedif the data lengthexceeds1/ (f•
- f2). Since the amplitudesare finally estimatedby MRA
f(t) = Ao+ • [aksin(2rrt/TO+ b• cos(2rrt/TO]+ E
(MESA is used only for locatingperiodicitiesT), the main
rt
k=l
restriction
rt
= A0+ • r• sin(2rrt/T•+ rkk)+ E
(1)
k=l
wheref(t) is the observedseriesand E is the error factor. A
multipleregression
analysis(MRA) [Bevington,
1969]wasthen
carried out to obtain the best estimatesof Ao, (ae, be), and
comes from
MRA.
Here
the standard
error of all
periodicitiesis equal. However, if two periodicitiesare too
close,the method giveslarger standarderrorsfor both those
periodicities.In general, a separationof 0.10 (e.g., 2.50 and
2.60) is enoughfor resolution.
MESA doesnot need any filtering and can reveal all peaks
even if these are in a wide range. Figure 6 showsthe spectra
(i.e., amplitudes of the various periodicities detected by
8482
KANE
ET AL.: LATITUDE
DEPENDENCE
OF QBO AND
QTO OF TOMS
TOTAL
OZONE
SPECTRA OF TOTAL OZONE (TOMS)'35ø-45øN
ot(a)
.oo
,.-- 2__..0
:::5 J...69.
,,,4
,2
n
0
b.J
4
(20m)
I
2.66
1.67
,,
.,
,.
!
4.02
,.
,,
,.!
2.67
12- MONTH
MOVING
AVERAGE
4.00
1.67
IT
Z
o
N
(15m)
. 1.24
b)
i.-
3 - MONTHLY
(32rn)
(C)
27:5
1.67
'1
(12--36
)
:597
,2
o
0
LOG
--wO.mO
o.I
T--•
1.0
o.2 oils o.4 io.5
2.0
5.0
PERIODICITY
o;6 ore.7io.8
4.0
5.0
6.0
T (YEARS)
Figure 6. Amplitudesof the variousperiodicitiesin the 35ø-45øNTOMS total ozone seriesdetectedby
MESA for (a) 3-monthaverages,(b) 4-season(12-month)movingaverages,
and (c) the parameter(12-36).
Numbersindicateperiodicitiesin years(thosein parenthesisindicatein months).
MESA) for the TOMS (35ø-45øN)ozoneplot shownearlierin
Figure 1. Figure 6a showsspectrafor the 3-month averages,
and, as expected,the strongestperiodicityis the annualwave
(T = 1.00 year). The hatchedportion showsthe 2rr limit.
From the sum and difference periods of 8.3 and 21 months
mentionedby Bowman [1989] and Tungand Yang [1994a,b]
the period 0.69 years(---8 months)is hardlysignificant,probablybecausewe haveused3-month averages.However,small
but significantpeaksare seenat 1.24years(15 m), 1.67years
(20 m), 2.66years(32 m, QBO), and 4.02years.In Figure6b
for 12-month moving averagesthe 1.67 year peak becomes
insignificant,but 2.67 and 4.00 year peaks stand out significantly.In spectrafor parameter(12-36) in Figure6c the same
peaks appear. In addition, the 1.67 year peak also becomes
significant.Thus the parameter(12-36) is a very goodrepresentativeof QBO, in all aspects.Hence, for further spectral
analysis,only the parameter(12-36) is used.
Figure 7 showsthe spectrafor all parameters,for northern
latitudeson the left side and southernlatitudeson the right
side.The top plots(commonto both sides)are for the 30 mbar
wind and showone strongpeak at 2.57 years(31 m) and a
muchsmallerpeak at 5.0 years.The nextplots,alsocommonto
both sides,are for the equatorialozone (5øN-5øS)and show
one prominentpeak at 2.52 years and a smallerpeak at 4.00
years. The good correlation(>0.7) betweenthe equatorial
wind and ozoneis mainly due to the similarityof the 2.57 and
2.52 year peaks and the correlationis not perfect (nearing
1.00), mainlybecausethe other smallperiodicitiesof 5.0 and
4.0 years are not similar. In the succeedingplots both the
northern and southernlatitudes show a small peak near 1.7
years(20-21 m) and a largerpeak near 2.4-2.6 years.MESA
is very accuratein this region, and experimentswith artificial
samples[Kane, 1977, 1979] show that peaks can be distinguished easily, if differing by 0.05 or more. Hence 2.42 is
different from 2.58 and certainlydifferent from 2.73. In general, the amplitudesincreasefrom low latitudes to middle
latitudes,but the amplitude in the equatorial region is also
large. The periodicitynear 1.70 yearsis smalland insignificant
in the equatorial region, appearingonly at exequatoriallatitudes in both the hemispheres,and has been emphasizedby
Tungand Yang[1994a]as a distinguishing
factor of the extratropicalozone.However,our spectrashowanotherequally(or
probablymore) substantialperiodicitynear 3.7-4.0 years in
the northern latitudes, which is almost absent in the southern
latitudes.This is an additionalreasonwhy the plots for the
southernlatitudesin Figure 2 havepeak spacingsnearerto 30
months,while spacingsin the plots for the northernlatitudes
are often
wide
off the mark.
In our view
this is the most
importanthemisphericdifference.Yangand Tung [1994] refer
to a three-peakspectrumof extratropicalozone QBO, but the
peaksare near 30, 20, and 8 monthsand there is no reference
to a peak near 4.0 years. However, Hasebe [1980, 1983] did
report a 4-year oscillationand namedit FYO. Shiotani[1992]
examinedthe TOMS equatorialozone data and found a variation
associated
with
the
E1 Nifio-Southern
Oscillation
(ENSO) cycle(---4years).
Yangand Tung[1995]mentionthat the QBO signalis strongestin the middle and high latitudes.Sincewe have the amplitudes for specificperiodicities,it would be interestingto
checktheir latitude dependence.Figure 8a showsthe latitude
distributionof the amplitudes.As mentionedearlier, MESA is
very accuratein the QBO and QTO region if the data series
havemore than 50 points,as in the presentcase(14 years,56
trimester points). In Figure 7, all the periodicitiesare not
exactlyalike. For example,the ---20-monthperiod hasa range
of 1.64-1.90years(20-23 m), and the ---30-monthperiodhas
a rangeof 2.29-2.73years(27-33 m). Thesemayor maynotbe
the sameperiods.Assumingthat they are, Figure 8a showsthe
latitudedependence.Larger amplitudesare at largerlatitudes,
exceptfor the 30-monthperiod,whichshowsa large amplitude
at the equator also.Someperiodsthat are very different from
the respectivegroupare markedwith rectangles,and comparing their amplitudeswith the rest may or may not be justified.
For the ---4-yeargroup,there are no observations
in the southern latitudes.
Regardingphaseshiftswith latitude,Angell and Korshover
[1962] reported a meridionalpropagationof the QBO at the
phasespeedof 0.2 m/sfrom 10øto 47øNandmuchsloweror no
propagationfarther north.Hasebe[1980]found a phasereversalbetweentheselatitudes.Later, Hasebe[1983] and recently
KANE
ET AL.: LATITUDE
DEPENDENCE
OF QBO AND
Zerefoset al. [1992]reportedpolewardphasepropagationfrom
the northernand southernmidlatitudes.Yangand Tung[1995]
reexaminedground-basedand satellitedata in detail and concludedthat there were three distinctregions,namely,tropical,
midlatitudinal,and polar,in eachof whichthe phasewasfairly
constant,and largephaseshiftsoccurredonly in the transition
regions.In our Figure 4 this behavioris roughlyconfirmedfor
the general QBO pattern. It would be interesting to see
whether a similar pattern is obtainedfor the individualperiodicitiesnear 1.70years(--•21m), 2.50years(--•30m), and 3.80
years seen in Figure 7, though the periodicitiesdo not tally
exactly.Figure 8b showsthe results.For the period near 1.7
years,there is no data point at the equator,but the phasesare
verydifferentin the northernandsouthernlatitudes.Tungand
Yang[1994a,p. 2706,1994b]havemadea detailedstudyof this
(20 m) periodicityandmentionthat"it is almostantisymmetric
betweenthe two hemispheres,suggestive
of a circulationcomponentthat has a globalpattern from one hemisphereto another." Someantisymmetryis seenin our Figure 8b, top plot.
For the period near 2.50 years(30 m) (Figure 8b, middle
plot) the phasesshiftconsiderably
(3 rad, half a cycle)from the
equatorto --•40ølatitude.In the northernhemispherethe shift
is rapid from 00-20ø and sloweror uncertainthereafter. In the
southernhemispherethe shiftis almostgradual.The nodalline
at 10ø-12ølatitude,acrosswhichthere is a reported180øphase
change[Yangand Tung, 1995], is included here but crudely
becauseof the wide latitudebelts(10ø width). Above 40ø the
southernlatitude phasesremain constantup to the polar region, but in the northern latitudesthe phasechangesare indicative of distinct regions as indicated by Yang and Tung
[1995].Also, the --•30-mperiod changesconsiderably,to 2.38
years(29 m) at 50ø,3.01years(36 m) at 60ø,and 3.34years(40
m) at 70ø.In the northernpolarregion(75ø-85ø),thereare two
periods,2.27years(27 m) and 3.69years,very differentfrom
the QBO and QTO at lower latitudes.For this polar region,
Yangand Tung [1995] mention possiblecomplicationsdue to
the presenceor absenceof midwintersuddenwarmings,but
suchan effect is not expectedin 12-monthmovingaverages.In
any case,some complications
probablydue to local (polar)
circulationpatternsare indicated.
For the 3.8-yearperiodicitythe pattern is seenonly in the
northernhemisphere,and the phaseshift with latitude seems
to be gradual,from 1.5to 5 rad from 0øto 50ølatitudeand from
5 back to 1 rad from 50ø to the southpolar region.This is in
contrastto the observationsof Hasebe[1983], who reported
that the FYO wasalmostsymmetricto the equator(we do not
seeit in the southernhemisphere).A spectralanalysisof the
equatorialeasternPacificSST anomalies[Angell,1981, also
private communication,1981-1997]showeda very prominent
peak at 4.2 years (shownin our Figure 7, bottom plot), not
exactlythe sameasthe --•3.8-yearpeaksin the ozoneplots,and
the phasewasthe sameas the phaseof ozoneat --•30øN.Thus
midlatitude
ozone maxima are associated with SST maxima.
In
contrast,the equatorialozoneis approximatelyhalf a cycleout
of phase,and henceequatorialozoneminima would be associatedwith SST maxima.These resultsfor the equatorialregion are in general agreementwith the dynamicalresponses
discussed
by Hasebe[1993].
However, as shownin Figure 2 (top plot) for equatorial
easternPacificSST representingthe E1 Nifio-SouthernOscillation (ENSO) phenomenon,theseeventsare not cyclicand
occurabruptly,lastingfor a year or so,and do not seemto have
a one-to-onerelationshipwith ozoneat anylatitude.As shown
QTO OF TOMS
2
I
3
2.571
4
I
I
- ,-
TOTAL
OZONE
2
3
4
I
2.57 I
I
I
- - .
8483
I
%o
5
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3o MB WIND
2.52
OZONE
I
4.0,5øN-5øS
5oN-15ON
_.
1.76
I
2.46
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,, ,,,
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3
PERIODICITY T (YEARS)
I
4
5
6
Figure 7. •p]itudes of the variousperiodicitiesdetectedby
m•mum entropyspectralanalysis(MESA) in the 12-month
movingaveragesof 30 mbarwind (top plot), equatorialeastern
Pacificsea surfacetemperature(SST) (bottomplot), and the
parameter(12-36) for the TOMS total ozoneat different]atitudes,for northern on the ]eft side and southernon the right
side. The numbersrepresentperiodicitiesT in years. The
hatchedportionsindicatethe 2c limits.
by Bojkov [1987] in his detailed studyof the 1983 and 1985
ozone distributionanomalies,there are two major complicating factors,namely,the QBO and volcaniceruptions,and the
QBO "setsthe stage"for major ozone deficiencies,while circulationchangesdue to the ENSO eventsand volcaniceruptionsserveto augmentthe effect.Zerefoset al. [1992]examined
the ENSO effectsin ozone and found an inphaserelationship
between SouthernOscillationIndex (SOI) (representedby
Tahiti minusDarwin atmosphericpressure)and tropicaltotal
ozonebut an insignificantrelationshipwith high-latitudeozone
unlessthe ENSO eventwas very strong(e.g., 1982-1983),in
which case, low-ozone values at middle and polar latitudes
followedthe ENSO eventwithin a few months.Krzyscin[1994]
considerstheseapproachesincompleteand statesthat not only
the phaseof the QBO but the phaseof the solaractivity(high
or low) and the time of the ENSO appearance(cold or warm
season)need to be consideredsimultaneously.
6.
Possible
Distortions
Due to the Use
of 12-Month Moving Averages
In the analysisso far, 12-monthmovingaverageshave been
used, mainly to reduce the effect of the annual wave. Could
this procedurehaveaffectedsomecharacteristics
of the QBO
waves?Many workers have such an apprehension,probably
basedon the warningsof somespecialists[e.g.,Mitchellet al.,
8484
KANE
ET AL.: LATITUDE
S
- 80
i
IO
i
DEPENDENCE
- 60
i
i
- 40
i
OF QBO AND
- 2.0
I
i
0
i
20
i
I
I
1'85•.89
I ,52
ß•- '•'
40
I
I
80
I
I
N
I
172
1.67
1.76
1.8y (a)
?_.52
?--•1•
?_.44
?_.46
?_.58
_ 4F•
z
I
1.76
I•.,•be,•:: -
%?_.37
4
60
I
OZONE
1.87_
1'6•68
I
TOTAL
1'9,,•
•
'"• 1.71
E•
QTO OF TOMS
40zr• 31-•
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
•
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
0
<[
n-
2-
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3.69
0
S
-80
- 60
- 40
- 20
0
20
40
60
I
80
I
N
LATITUDE
Figure 8. Latitude dependenceof (a) the amplitudesand (b) the phasesof the periodicitiesdetectedby
MESA in the TOMS total ozone series.The numbersindicate the periodicitiesinvolved,the numbersin
rectanglesindicatingperiodicitiesoff the mark in that groupand henceunreliable.In Figures8a and 8b the
top plot is for the periodicity-1.70 years(20 m), the middleplot is for the periodicity-2.50 years(30 m), and
the bottom plot is for the periodicity-4 years.
1966] that the moving average procedure introducessome
sidelobes.Mathematically,a 12-monthmovingaverageeliminates the 12-monthwave (and its harmonicsat 6, 4, and 3
months,etc.) completelybut also reducesthe amplitudesof
higher periodicities,for example, that of a 2-year wave to
-65% and that of a 3-yearwave to -85%, and has almostno
effect on higher periodicities[seeKane, 1996]. In Figure 6 it
wasshownthat in the spectraof original(3-monthly)valuesthe
annual wave predominated,dwarfing all other periodicities.
However, in the spectraof 12-monthlymoving averagesthe
annual wave disappearsand other periodicitiesstand out,
thoughwith reducedamplitudes.To checkthe effecton other
characteristics
(e.g., phases),the whole analysiswasrepeated,
using3-monthlyoriginalvalues(not 12-monthmovingaverages). Also, values were used for smaller latitude intervals,
namely, 5ø latitude belts, insteadof the 10ø belts used so far.
The resultsof a spectrumanalysisare shownin Figure 9, for
northernhemisphereon the left sideand southernhemisphere
on the right side.In the top panelsthe dotsindicatethe strong
peak at 2.57 years and the weak peaks at -2.0 and 5.0 years,
observedin 30 mbar wind (thesepeaks are slightlydifferent
from thoseof Figure 7, as 3-monthlyvalueswere usedinstead
of the 12-monthlymoving averagesused in Figure 7). The
trianglesindicatethe weak peak at 2.35 yearsand the strong
peak at 4.2 years in equatorial eastern Pacific SST. For the
peaksin ozone a comparisonof Figure 9 with Figure 7 indicatesthe following:
1. At almostall latitudesthe strongestpeak in Figure 9 is
the annual wave (1.00 years). MESA indicated this as 3.99
seasons,which is 1.00 years, correct to the seconddecimal
place. This indicatesthe accuracywith which MESA detects
peaks.Hence all otherpeaksindicatedshouldbe accurateto at
least 0.02. In contrastto Figure 7 the annualwave has now a
very large amplitude,reachingvalues up to 90 DU in the
northern polar region. If the ordinate scaleis chosenas to
accommodatesuch magnitudes,all other peaks would be
dwarfed into insignificance.Hence the ordinate scale in all
panelsis restrictedto within 0-20 DU, and the amplitudeof
the annual wave is marked with one arrow for amplitudes
between 15 and 30 DU, two arrows for 30-60 DU, and three
arrowsfor amplitudes>60 DU. In MRA the amplitudeof the
strongestpeak alsodictatesthe standarderror, whichis com-
KANE ET AL.: LATITUDE DEPENDENCE OF QBO AND QTO OF TOMS TOTAL OZONE
8485
LAT.
T'--""
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26 3.4
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PERIODICITY
O.Z
0.4
0.6
O.a
I
56
I
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1.0
I
I
I
10
T (YEARS)
Figure9. Amplitudes
of thevarious
periodicities
detected
byMESAof theoriginal
values
(fourseasonal
values
peryear)ofTOMSozone
atdifferent
latitudes,
northern
ontheleftsideandsouthern
ontherightside.
Thenumbers
represent
periodicities
T inyears.
Thehatched
portions
indicate
the2(rlimits.
In thetoppanel,
dotsindicate
theperiodicities
2.00,2.54,and5.2years
observed
in30mbarequatorial
zonal
wind,andtriangles
indicate
2.35and4.2yearsobserved
in equatorial
eastern
Pacific
SST.Fortheannual
wave(1.00years)the
amplitude
isoutofscale,
andonearrow
indicates
amplitude
15-30DU,twoarrows
indicate
30-60DU,and
three arrows indicate >60 DU.
(or barelysignificant)
at a 2(r level.Thus
monto all otherperiodicities.
In the presentcasethe ampli- more significant
tude of the annual wave was a few Dobson units at low latistudying
otherperiodicities
in thepresence
of a strongannual
Figure7 clearlyshowsthe advantage
of
tudes,and the standarderror was ---1 DU. So, whereasthe waveis not desirable.
for thispurpose.
annualwavewas very significant,
other periodicitieshaving using12-monthlymovingaverages
2. In bothhemispheres,
thereis a peakat ---0.7years(8-9
amplitudes
of a few Dobsonunitswerealsosignificant
at or
abovea 2(r level,indicatedby the hatchedmarking.At higher months),often insidethe hatchedmarking,and hencenot
at a 2(r level.However,it is consistently
thereat
latitudesthe annual wave has a larger amplitude,and the significant
andisprobably
the8.3-month
QBOstandarderror is also larger (---2-3 DU). So, whereasthe middleandhighlatitudes
peakmentioned
byBowman[1989].
annualwaveis stillhighlysignificant,
the otherperiodicities
of annualwavemodulation
low statistical
significance,
this
a few Dobsonunitsamplitudes
startlosingtheir significance. So,in spiteof its apparently
to be genuine.
Thispeakwasabsentin Figure7
At veryhighlatitudes
theannualwavein northern
latitudes
has peakseems
the procedure
of 12-monthaveraging
destroys
sucha
an amplitudeof ---90+ 5 DU andis highlysignificant.
How- because
ever,otherperiodicities
of amplitudes
up to even10DU areno peak.
8486
KANE
ET AL.: LATITUDE
DEPENDENCE
OF QBO AND
3. There is a peak at 1.23-1.30years(15-16 months)which
is apparentlynot significant(or barelysignificant)but appears
persistentlyat low latitudes, more so in the northern hemisphere. At higher latitudes it seemsto shift to ---1.45 years
(17-18 months)in the northernhemisphereandto ---1.50-1.60
years (18-19 months) in the southernhemisphere.These
peaks at 15-19 months do not seem to be mentioned in the
literature. However, another much more persistentpeak is
near 1.70years(20-21 months)and is probablythe 21-month
QBO-annual wave modulation peak mentioned by Bowman
[1989].However,thesepeaksare presentat equatorialand low
latitudes also. So, the modulation is not necessarilyonly in
middle and high latitudes.Incidentally, these peakswere absentin Figure 7 as they are destroyedby the 12-monthmoving
averageprocedure.
4. There is a QBO peak at all latitudes, strong at the
equator also,with a periodicityof 2.49 years,similar but not
quite equal to the strong2.54-yearperiodicityof the 30 mbar
wind. One could ignore the differencebut for the fact that the
ozone periodicityis not the sameat all latitudes.Also, there is
the addedcomplicationthat 30 mbarwind hasanother,smaller
peak at ---2.00years and ENSO (representedby equatorial
easternPacific SST) also has a peak near 2.35 years.These
ozonepeakshave amplitudesof -5 DU and at higherlatitudes
where the standarderror is a few DU these peaks become
QTO OF TOMS TOTAL
OZONE
30ølatitudeand thereafterhasan almostconstantamplitudeof
2-3 DU, with uncertainbehaviorin the polar region. These
striking changesin the periodicitiesat higher latitudes, seen
earlier in Figure 7 also, seem to be features not detected
before.
Figure 10b showsthe phasechanges.For the annual wave
(1.00 years), there is an asymmetricchangedue to reverse
seasonsin the two hemispheres.For the 1.70-yearperiodicity
the phasechangesare similarto thosein Figure 7, indicating
the hemisphericantisymmetryreferred to by Tungand Yang
[1994a,b]. For the 2.50-yearQBO in the northernhemisphere
the phasechangesrapidly by -3 rad (180ø) from 0ø to 15ø,
remainssteadyup to ---30ø,revertsbackto the equatorialphase
for ---30ø-50
ø latitude, and changesagain to the 30ø phase
thereafter.The pattern is similar to that mentionedby Yang
and Tung[1995], exceptthat insteadof three distinctregions,
namely, tropical, midlatitudinal, and polar, mentioned by
them, there seemto be four distinctregions,equatorial,low
latitudinal,midlatitudinal,and polar. In contrast,in the southern hemispherethe phasechangeseemsto be gradual,-5 rad
from 0ø to -60 ø and a steadyphasethereafter.The patterns
are certainlydifferentin the two hemispheres.Earlier, Figure
8 gave similar indications.For the 4-year periodicityin the
northern hemispherethe phasechangesgraduallyby ---180ø
from 0ø to ---50ø and is very erratic thereafter. In the southern
insignificant.
Similarpeakswereseenin Figure7 alsoandwere hemispherethisperiodicityis missingfor 15ø-30ølatitude,but
significant.So, the 12-monthlyaveragesdemonstratethese there is a sharpphasechangefrom 0ø to 15ø latitude and the
peaks in a better way.
phase is constantup to --•70ø, and erratic thereafter. Some
5. There is a peak near 4 years, more persistentin the inkling of this was seenin Figure 8 also.
northern hemispherelow and middle latitudes.At higher latitudesit shiftsto --•3.5years.The amplitudesare significantat
7.
Conclusions and Discussion
low latitudesbut becomeinsignificantat higherlatitudes.Figure 7 also showed these characteristics.
The 3-monthlyTOMS ozonevalueswere subjectedto 4-seaThus the 12-monthmovingaveragesshowthesepeaksin a son (12-month)movingaverages,designatedas ozone (12).
better way.
Thesevalueswere subjectedto further 12-season
(36-month)
The latitude dependenceof the amplitudesand the phases movingaverages,designatedas ozone (36). When these 36of some of these periodicitiesare shownin Figures 10a and month averageswere subtractedfrom the 12-monthaverages,
10b. Figure 10a showsthe amplitudes.The 0.7- and 1.30-year the residualsdesignatedas ozone(12-36) gavea goodrepreperiodicitiesare insignificantor barely significantat all lati- sentationof the QBO and QTO (quasi-biennialand quasitudes and are not considered.Amplitudes of the annualwave triennial oscillations)of ozone. The characteristicsof these
(1.00 years)are a few DU near the equator,increasingmono- were studiedand comparedwith thoseof stratosphericwinds
tonicallyto -90 DU near the northernpolar regionbut onlyto and ENSO phenomena.A similar analysiswas done by using
-50 DU near the southernpolar region. Amplitudesof the the original 3-monthlyTOMS valuesalso.The resultsmay be
- 1.70year(20 month)periodicityare ---1 DU nearthe equator
and rise almost monotonicallyto ---10 DU near the polar
regions,wherethe periodicitiesalsochange(increase)considerablyto ---1,85years(22 months).Amplitudesof the ---2.50year (30-month)periodicityare ---7 DU near the equatorbut
fall rapidlyto ---2DU near 15ø-20ølatitude and increasethereafter to -6-8 DU, with latitudesup to •--50ø in the northern
hemisphereand 40ø in the southernhemisphere.Amplitudes
fall thereafterto -4 DU up to -70 øand rise thereafterto ---10
DU. In the northernhemispherethe periodicitychangesconsiderably,increasingto ---2.85years (34 months)at latitudes
550-65ø and decreasingto ---2.30years(28 months)at higher
latitudes. In the southern hemispherealso the periodicity
changesto ---2.30years(28 months)in the polar region.Amplitudesof the ---4-yearperiodicity,seenmore consistentlyin
the northernhemisphere,are ---2-3 DU near the equator,rise
to ---6 DU near 55ø, and have a sharp drop to ---2 DU thereafter, followedby a rise to ---8 DU near the poles,where the
periodicityalso decreasesconsiderablyto ---3.5years.In the
southernhemispherethisperiodicityis almostabsentin -10 ø-
summarized
as follows:
1. The plots of the 12-month averagesof the 30 mbar
equatorial zonal wind (westerlypositive, easterlynegative)
matchedwell with thoseof the low-latitude(5øN-5øS)ozone,
with peak spacingsof ---30months.At other latitudesthe peak
spacingswere very irregular,differingwidelyfrom the average
of ---30 months,more so in the northern hemisphere.For the
same latitude belt, peaks in the northern and southernlatitudesdid not tally. The long-termvariabilityof ozonewasalso
very different at different latitudes and different for similar
northern
and southern
latitudes.
2. A cross-correlation
analysisof the 30 mbar equatorial
zonalwind (westerlypositive,easterlynegative)with the ozone
in the various
latitude
belts showed that the maximum
corre-
lation was high (>0.7) at almostzero lag for the equatorial
ozone(westerlywind maximacoincidingwith ozonemaxima),
low (---0.3)but almostwith no lagfor the 5ø-15ølatitudebelt in
both hemispheres(this belt includesthe nodal line at 10ø-12ø
acrosswhich there is reporteda 180ø phasechange,seeYang
and Tung[1995]),and medium(-0.5) with a largephaseshift
KANE
ET AL.: LATITUDE
DEPENDENCE
OF QBO AND
QTO OF TOMS
SOUTH
-90
-80
-70
-60
-50
TOTAL
OZONE
NORTH
-40
-:50
-20
-I0
0
0
I0
2_.0
$0
40
50
60
70
•
u•
'
8-
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6-
•
x-
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/
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,
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-30
,
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-I0
0
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!0
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40
50
60
70
80
90
NORTH
Figure 10. Plot of (a) amplitudesin Dobsonunits and (b) phasesin radians,of the variousperiodicities
(indicatedby numbers)versuslatitude.Periodicities
that are slightlydifferentfrom the groupare marked.
(approximately-4 seasons)
for a wide latituderange15ø-45ø
in both hemispheres.For higher latitudes in the southern
hemispherethe phaseremainedconstantup to the polar region,but for highernorthernlatitudesthe phaseshiftedfrom
-4 seasonsto +4 seasonsfrom 45ø to 85ø latitude, indicating
complicating
factorsin the northernhighlatitudes.Thusthere
was considerablehemisphericdifference.
3. A cross-correlationanalysisof the equatorial eastern
Pacificseasurfacetemperaturewith ozoneshowedlow correlation in the equatorialregion and highercorrelationsat non-
8488
KANE ET AL.: LATITUDE
DEPENDENCE
OF QBO AND QTO OF TOMS TOTAL
OZONE
to _+15øof the equator,thoughPlumbandBell [1982]produced
a model in which the QBO circulationcould extendup to 30ø.
4. The 30 mbar wind and the equatorial ozone had one Second,the seasonallyvaryingmean meridional circulation
strongpeak at --•2.50years(30 m) and anothersmallpeak at (global MMC) may transportequatorialQBO ozone anoma5.0 yearsin wind and 4.0 yearsin ozone.At other latitudes, lies into the subtropics[Holton,1989].Here the extratropical
ozonehad a smallbut significantpeak near 1.70years(20 m) QBO would have the same characteristicsas the equatorial
in both the hemispheres
and a peaknear 2.4-2.6 yearsin both QBO. Third, there could be a combination of the two mechathe hemispheres
up to --•55ø latitude.At higherlatitudesthis nismsmentionedabove.The equatorial QBO would have a
branch(out of phasewith the equatorialbranch),
peak disappeared
in the northernlatitudes,and peaksnear 3 subtropical
years appeared,while in the southern latitudes this peak whichcouldbe carriedto higherlatitudesby the climatological
shiftedto --•2.35years.There were peaksnear 4 yearsin the mean and eddycirculations[Grayand Pyle,1989;ChipperfieM
northernhemispherebut rarely in the southernhemisphere. and Gray, 1992; Gray and Ruth, 1993]. A different type of
5. The amplitudesof the variouspeaksshoweda gradual theory [Holton and Tan, 1980] suggeststhat the equatorial
increasewith latitude,exceptthat at the equatorthe 30-mpeak zonalwind QBO couldchangethe backgroundflow and affect
was as strongas thoseat the polar latitudes.The 20-m peak the vertical and meridional propagation of planetary-scale
had oppositephasesin the northernand southernlatitudes. waves.Hamilton [1989] suggestedthat a connectionbetween
The 30-m peaksshowedan almostgradualphaseshift from ozoneat the equatorand the subtropicscouldbe due to stronmixingof ozonein the lowerstratosphere
00-40ølatitude, but with someindicationof an abruptchange gerquasi-horizontal
wavesduringthewesterlyphaseof the equafrom 0ø to 20ø, particularlyin the northern hemisphere.At byplanetary-scale
higherlatitudesthe phaseremainedconstantin the southern torial QBO. From his studyof TOMS (1979-1987) data,Bowhemisphere
but waserraticin the northernhemisphere,
where man [1989]hadconcludedthat the abruptphaseshiftsin ozone
the periodsalsochanged.The 4-yearpeak seenmostlyin the anomaliesat --•10ø latitudeprecludethe possibilitythat extratransportof
northernlatitudeshad a phasechangefrom 1 to 5 rad from tropicalQBO was the resultof quasi-horizontal
00-50 ø latitude and from 5 back to 1 rad from 50 ø to the north
equatorialozone anomaliesto higher latitudes.Instead,the
ozone anomaliesresembleda seasonallymodulatedstanding
polar region.
6. The resultsof an analysisof the originalvalues(not the oscillation,
possibly
dueto a quasi-biennial
waveforcingof the
MMC and the associated
verticaladvectionof
12-monthmovingaverages)were very similarto thoseof the planetary-scale
that the
analysisof the 12-month moving averages.In the northern ozone.Recently,TungandYang[1994a,b] emphasized
hemispherethe phase of the 2.50-year (30 month) peak extratropicalozoneQBO had only 20-30% of the equatorial
changedabruptly(roughlysimilarto Yangand Tung[1995]).In 30-month QBO and a considerableportion was in the 20the southernhemisphere,there was an almostgradualphase monthperiod,whichcouldbe thoughtof asthe modulationof
change.
the seasonal
anomaly(12-mpnthperiod)by the 30-monthpe7. The analysisof originalvaluesalso revealedpersistent riod and henceneededthe presenceof an extratropicalQBO
peaksat 0.7 years(8-9 months),which are probablythe --•8- anomalyin the transportingcirculation.They proposeda simmodelbasedon the hypothesis
that the extramonth QBO-annual wave modulation peaks mentionedby ple mechanistic
seasonal
circulation
Bowman[1989].Persistentpeakswere alsoobservedat --•1.30 tropicalQBO wascausedby an anomalous
years(16 months)in low latitudes,whichshiftedto --•1.45years inducedby an anomalousEliassen-Palm(E-P) flux divergence,
(17-18 months) at higher latitudes. The other peaks also which may be causedin turn by the relative poleward and
showed latitudinal
shifts.
downwardshiftof the regionof irreversiblemixing(breaking)
The characteristics
of equatorial stratosphericzonal wind of the extratropicalplanetarywavesduringthe easterlyphase
are well established.The wind oscillatesbetweenwesterlyand of the equatorialQBO as comparedto its westerlyphase.A
easterlydirectionswith a periodvaryingfrom 22 to 34 months. highertendencyfor the planetarywavesto breakin the easterly
A time-heightcrosssection[Naujokat, 1986] showsthe pro- phasehasbeenreported[e.g.,O'SullivanandSalby,1990].This
gressivedescentof the easterlyand westerlywinds and an model involvesthe indirect effect of the equatorialQBO in
asymmetrybetweentheir descending
phases.The zonalwindis modulatingthe seasonalcycleof the extratropicalcirculation
confinedto --•+_15øof the equator and is not stronglylinked to anomalyandhenceresultsin the twoperiods20 and30 months
the seasonalcycle[Wallace,1973].Accordingto the theoryof in high-latitudeozone,with the maximumamplitudeof the
Lindzenand Holton [1968] and Holton and Lindzen [1972]the anomalyoccurringduringwinter in the northernhemisphere
alternatelydescendingwesterliesand easterliesare drivenby and duringlate winter and earlyspringin the southernhemiabsorptionin the stratosphereof verticallypropagatingequa- sphere.In the presentpaper, evidenceis presentedto show
torial Kelvin and Rossbygravitywavesgeneratedin the tro- that the 16-month,20-month, 30-month, and 4-year periods
withlatitude,someto higherperiods,
posphere.The wave drivingof the zonal flow producesa sec- changetheirperiodicities
This is an
ondarymean meridionalcirculation(MMC), with descending someto lower periods,in both the hemispheres.
motion alongthe equatorduringperiodsof westerlyshearand abnormalfeature and needsfurther investigation.Regarding
ascending
motionduringeasterlyshear[PlumbandBell, 1982]. the phasethe 30-monthequatorialcomponentseemsto extend
with an almost
The descending
motionbringsozone-richair from the higher up to --•50ø latitudein both the hemispheres,
stratosphereand increasesthe total ozone,which depictsa gradualphaseshiftin the southernhemispherebut with four
QBO similar to that of the wind. Thus the occurrence of QBO
abruptchangesin the northernhemisphere.Part of it should
in equatorialozone as well as temperatureis well explained. be due to a combinedeffect of the equatorialQBO and its
However, the mechanismsfor a QBO in the extratropicalre- subtropicalbranch.The 4-yearperiodseemsto be seenmore
gion seemto be controversial.Severalmechanisms
havebeen in the northernlatitudes.For the equatorialregionthe ENSO
proposed.First, the equatorialQBO circulationcouldextend effect is rather weak, overwhelmedby the wind effect. Neverto higherlatitudes.Thisis not favoredbecauseof its restriction theless,Shiotani[1992]usedequatorialozonedata at different
equatoriallatitudes.There was considerable
hemisphericdif-
ference.
KANE
ET AL.: LATITUDE
TOMS
I
I
I
I
I
OZONE
I
I
I
DEPENDENCE
OF QBO AND
35ø--45øN
I
I
I
4OO
I
3-
I
I
I
I
I
MONTHLY
35O
300
::5 300
, v v u,,,,v wvww
•40
•20
•20
••
I
I
78
45OE
I
I
80
I
I
82
I
I
84
I
I
86
YEAR
I
I
88
I
I
90
I
I
92
QTO OF TOMS
TOTAL
OZONE
8489
In this paper, the TOMS data usedwere for 45øWlongitude.
For the equatorialregionwe testedone more longitude,and
the 12-monthlyplotswere similarto thosefor 45øW.Also, our
resultstallywith thoseof otherworkers[Yandand Tung,1995].
For other latitudes,Figure 11 showsa plot for 35ø-45øN,for
longitudes45øW and 45øE.Both the 3-monthlyvaluesas well
as the 12-monthlymoving averagesare similar. Presently,a
rigorousdetailed analysisis in progressfor checkingwhether
the characteristicshave any longitudedependence.
I
94
Acknowledgment. This work was partially supportedby FNDCT,
Brazil, under contract FINEP-537/CT.
Figure 11. TOMS total ozone at 35ø-45øN for two longitudes,45øW and 45øE.Top plot is for 3-monthlyvalues,and
bottom plot is for 12-monthmovingaverage.
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(ReceivedSeptember4, 1997;revisedDecember8, 1997;
acceptedDecember11, 1997.)