Atkinson

B. J. Connor

D. P. J. Swart

E. J. Brinksma

Fairlie

G. E. Bodeker

G. L. Manney

Hoskins

I. S. Boyd

J. B. Bergwerff

J. B. Liley

J. W. Hovenier

Manney

N. J. Livesey

Parrish

Roscoe

Schoeberl

Sutton

W. Hogervorst

Waugh

Y. J. Meijer

Brinksma, E.J.

Meijer, Y.J.

Connor, B.J.

Manney, G.L.

Bergwerff, J.B.

Bodeker, G.E.

Boyd, I.S.

Liley, J.B.

Hogervorst, W.

Hovenier, J.W.

Livesey, N.J.

Swart, D.P.J.

DSpace at VU

GEOPHYSICAL RESEARCH LETTERS, VOL. 25, NO. 15, PAGES 2785-2788, AUGUST 1, 1998
Analysis of Record-Low Ozone Values During the 1997
Winter over Lauder, New Zealand
E. J. Brinksma1, Y. J. Meijer2, B. J. Connor3, G. L. Manney4,
J. B. Bergwer2, G. E. Bodeker3, I. S. Boyd3, J. B. Liley3, W. Hogervorst1,
J. W. Hovenier1, N. J. Livesey4, D. P. J. Swart2
Abstract. Record-low ozone (O3) column densities (with a
minimum of 222 DU) were observed over the Lauder NDSC
(Network for the Detection of Stratospheric Change) sta-
tion (45S, 170E) in August 1997. Possible causes are ex-
amined using height-resolved O3 measurements over Lauder,
and high-resolution reverse trajectory maps ofO3 (initialised
with Microwave Limb Sounder measurements) and of poten-
tial vorticity. The analysis shows thatO3 poor air originated
from two regions: Below the 550 K isentrope (22 km) sub-
tropical air was observed, while between 600 and 1000 K
(25 { 33.5 km) the polar vortex tilted over Lauder for sev-
eral days. A rapid recovery of the O3 column density was
observed later, due to an O3 rich polar vortex lament mov-
ing over Lauder between 18 and 24 km, while simultaneously
the O3 poor higher vortex moved away.
Introduction
Measurements at Lauder and TOMS satellite data showed
that the 1997 springtime and winter were characterised by
low O3 column densities throughout the Southern Hemi-
sphere mid-latitude region, which could be largely accounted
for by the phase of the Quasi Biennial Oscillation and a long-
term decrease in the average ozone levels [Connor et al.,
submitted to Geoph. Res. Letters]. The August ’97 average
over Lauder was 324 DU, which is 21 DU below the 1985{
1996 August average. In this article, daily observations over
Lauder in early August of 1997 are presented which are even
lower, down to 222 DU. Similar cases in which the O3 col-
umn density dropped abruptly and sharply were observed
in September and October of 1997.
In the late winter of ’97, TOMS observations showed an
unusually distorted polar vortex edge, which was centred o
the pole repeatedly. A perturbed polar vortex is associated
with enhanced planetary wave activity, which may distribute
vortex laments over lower latitudes [e.g., Schoeberl et al.,
1992]. Similarly, laments can be peeled o the subtropi-
cal barrier, and previous studies [e.g., Waugh, 1993] have
linked subtropical stratospheric mixing and disturbances of
the polar vortices in both hemispheres during the winter.
1Vrije Universiteit, Department of Physics and Astronomy,
Amsterdam, The Netherlands.
2National Institute of Public Health and the Environment
(RIVM) Air Research Laboratory, Bilthoven, The Netherlands.
3National Institute of Water and Atmospheric Research Ltd.
(NIWA), Lauder, New Zealand.
4Jet Propulsion Laboratory, California Institute of Technol-
ogy, Pasadena
Copyright 1998 by the American Geophysical Union.
Paper number 98GL52218.
0094-8534/98/98GL-52218$05.00
Exchange between the vortex and mid-latitude air is im-
portant since it influences the amount of chemical processing
of ozone [e.g., Schoeberl et al., 1988]. Only a few obser-
vations of vortex laments at Southern Hemisphere mid-
latitudes have been previously reported [Atkinson et al.,
1989; Atkinson and Plumb, 1997; Fairlie et al., 1997].
August ’97 Observations
Ozone column density measurements were performed by
a Dobson spectrophotometer and an ultraviolet scanning
spectrometer (UVM) at Lauder, and by the Earth Probe
TOMS satellite instrument within 0:25 lat. by 0:30 long.
from Lauder. An oset of −12 DU was applied to the UVM
data presented here to achieve good agreement with the
Dobson data. This is consistent with a study based on long-
term measurements over Lauder [Bodeker et al., submitted
to J. Geoph. Res.].
In Fig. 1, the O3 column densities measured over Lauder
in August 1997 and their 1985{1996 daily averages are com-
pared. The presented UVM observations were performed
at local noon (0:45 UT), while Dobson spectrophotome-
ter results are representative daily values. Apparently, from
August 7 to 10 the measured values were over 2 standard
deviations below the average. The record value of 222 DU
was observed on August 9, 22 UT (not shown). A rapid re-
covery was observed on August 10, up to 340 DU at the
start of August 11.
220
240
260
280
300
320
340
360
380
400
420
3 1 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3
O
zo
ne
 C
ol
um
n 
De
ns
ity
 (D
U)
Jul                            Aug '97
Figure 1. Results of O3 column density measurements
over Lauder in August of 1997 by UVM (squares), Dob-
son spectrophotometer (circles) and TOMS (triangles) are
presented, compared to the daily ozone column densities av-
eraged over 1985{1996 (grey line). The -mark denotes the
August 10 lidar measurement at 10 UT.
2785
2786 BRINKSMA ET AL.: LOW WINTER OZONE OVER LAUDER, NEW ZEALAND
1 0
1 4
1 8
2 2
2 6
3 0
3 4
0 3 6 9 1 2 1 5 1 8 2 1
Ozone Number Density (1012 cm-3)
A
lti
tu
de
 (k
m)
Aug 
5 6
Jul 
3 1 1 31 07
Figure 2. Height proles of O3 number density measured
over Lauder from July 31 to August 13, 1997, by lidar (black
lines) and sondes (thick grey lines). The mean prole for
July 31 - August 10, derived from sonde measurements be-
tween 1986 and 1996, is superposed on all proles as a ref-
erence (dashed lines). The proles have been oset succes-
sively by 3  1012cm−3. On August 5 the lidar and sonde
measurements were simultaneous, while on August 13 the
lidar measurement was performed several hours before the
sonde launch.
Height-resolved O3 measurements over Lauder were mea-
sured by a stratospheric lidar [Swart et al., 1994; 1995, ],
electrochemical concentration cell sondes, and a microwave
radiometer [Parrish et al., 1992]. The observations yield
bothO3 number density as a function of height (Fig. 2) and
O3 mixing ratio as a function of potential temperature ()
(Fig. 3). Fig. 2 illustrates clearly the changes in the O3
column density. On the other hand, the O3 mixing ratio is
conserved on constant -surfaces (isentropes) in the absence
of chemical and diabatic processes, and therefore, Fig. 3 is
better suited to reveal O3 variations caused by transport.
Note that mixing ratio changes at low heights contribute
strongly to the O3 column density.
Ozone poor air (i.e., air with a low O3 mixing ratio) was
observed in two regions: A ‘low region’, from =350{550
K (13{22 km, the lower boundary is determined by the
minimum height of the lidar measurements), and a ‘high
region’, between =600 K and 1000 K (25{33.5 km). The
microwave measurements, which are available above 20 km
( ’500 K), conrm the lidar observations of reduced ozone,
but are not included in these gures for clarity. Comparing
the August 7 with the August 10 lidar observation shows
that theO3 number densities increased signicantly between
18.5 and 33.5 km ( ’ 470{1000 K), causing the fast
recovery observed on August 10 between 0 and 10 UT.
Using the lidar measurements, the evolution of the O3
number density solely due to adiabatic ascent or descent
of the air was computed. This was done by converting
number density to mixing ratio, evaluating the evolution of
the heights of the isentropes, and converting back to num-
ber density. These calculations showed that the observed
changes could not be explained by adiabatic ascent or de-
scent, except from August 10 to 13 between 18 and 23 km.
Analysis
Potential Vorticity (PV) on isentropic surfaces behaves
as a dynamical tracer in the absence of diabatic eects, and
can be a powerful tool for understanding transport processes
that aect O3 [Hoskins et al., 1985]. The polar vortex is
identied by high absolute PV values, and a region of strong
isentropic PV gradients, associated with the polar night jet,
demarks its boundary. High-resolution PV and O3 maps
on selected isentropic surfaces for August 4{10 were con-
structed using a reverse trajectory procedure [Sutton et al.,
1994; Manney et al., 1998]. Maps were initialised with PV,
or with O3 reconstructed from Upper Atmosphere Research
Satellite Microwave Limb Sounder (MLS) observations. The
MLS O3 data used here dier from those used by Manney
et al. [1998] as the instrument obtained pressure informa-
tion dierently, and climatological temperature data and an
unpublished retrieval algorithm (prototype MLS version 5)
were used. The trajectory calculations [Manney et al., 1998]
were run with horizontal winds and estimates of diabatic
descent rates computed from UKMO (United Kingdom Me-
teorological Oce) data.
Maps at =420 and 500 K (16 and 20 km) indicate that
in the lower stratosphereO3 poor air with a low-latitude ori-
gin (i.e., with a low absolute value of the PV) mixed into
mid-latitudes during the rst week of August. In Fig. 4 re-
gions where subtropical air is pulled up around the vortex
are shown (right panel, mixing ratios of 0.5{0.6 ppmv, while
the 1986{1996 average over Lauder at 420 K in early Au-
gust was 0.7 ppmv). Evidently, these laments are folded
together with relatively O3 rich laments from the vortex
edge region (mixing ratios above 0.8 ppmv). The lament
which is seen on August 9, was present over Lauder between
August 7 and 10, with the lowest mixing ratio (0.55 ppmv)
observed at =420 K on August 9.
350
450
550
650
750
850
950
1050
0 3 6 9 1 2 1 5 1 8 2 1 2 4
Ozone Mixing Ratio (ppmv)
Po
t. 
Te
m
pe
ra
tu
re
 (K
)
350
550
750
950
A
pp
ro
x.
 A
lti
tu
de
 (k
m)
Aug 
5 6
Jul 
3 1 1 31 07
1 5
2 2
2 9
3 3
Figure 3. Potential temperature versus ozone mixing ratio
between July 31 and August 13, 1997. The plotting conven-
tions from Fig. 2 have been maintained. The approximate
height scale on the right axis was derived from the lidar
potential temperatures on August 5, and may vary consid-
erably from day to day. Here, the proles have been oset
successively by 3 ppmv.
BRINKSMA ET AL.: LOW WINTER OZONE OVER LAUDER, NEW ZEALAND 2787
(a) (b)
= 420 K
PV from UKMO Ozone (ppmv) from PV/    space
        reconstruction
Θ
Θ
1000 UT, 9 Aug 1997
Figure 4. Maps of (a) the PV calculated by advection of UKMO PV from July 28, 1997, and (b) the O3 mixing ratio
calculated by advection of a PV/-space reconstruction of MLS observations for July 28, 1997. Both maps are for Aug 9,
10 UT, =420 K. The colourscale in (a) is in units of 10−4Km2kg−1s−1, in (b) the units are ppmv. The South Pole is
situated in the centre of the maps, with New Zealand just left of the upward pointing dateline.
In the middle stratosphere the air had a distinctly dif-
ferent origin. Fig. 5 shows a map of the PV at =850 K
(31 km) on August 9, with the vortex clearly situated over
Lauder. Further study shows that the polar vortex moved
over Lauder between August 5 and 6, rst above =660 K
(27.5 km), but on August 9 down to =600 K (25 km).
Above  ’580 K, the polar vortex is O3 poor as indicated by
MLS O3 data (not shown). On August 10 from =600 K{
1100 K (25{35 km) the vortex had been replaced by vortex
edge air. Higher up the vortex moved away during the next
days.
On August 10, the O3 mixing ratios between 18 and 25
km ( ’450{600 K) over Lauder increased abruptly (e.g.,
PV at      = 850 K
1000 UT, 9 Aug 1997
Θ
Figure 5. Map of the PV at =850 K on August 9, 10 UT,
calculated by advection of UKMO PV from July 28, 1997.
Plotting conventions as in Fig. 4.
from 2.2 ppmv on Aug 9 to 2.8 ppmv on Aug 10 at =500 K,
while the 1986{1996 average was 2.4 ppmv). This was due
to a passing lament ofO3 rich vortex edge air, which can be
identied on the maps at 485 K and 500 K (cf. Fig. 6). At
520 K, the lament was visible to the north of New Zealand
on August 10, and likely passed over Lauder earlier that
day. At 420 K (16 km), the lament remained south of
New Zealand.
The high-resolution PV maps were compared with daily
UKMO PV data over Lauder for consistency. The daily data
are spatial interpolations of the PV calculated from temper-
ature and winds with 2.5 lat. by 3.75 long. resolution, at
12 UT, and are thus not expected to show the details of la-
PV at      = 500 K
1000 UT, 10 Aug 1997
Θ
Figure 6. Map of the PV at =500 K on August 10,
10 UT, calculated by advection of interpolated data of July
29, 1997. Plotting conventions as in Fig. 4.
2788 BRINKSMA ET AL.: LOW WINTER OZONE OVER LAUDER, NEW ZEALAND
N
or
m
a
liz
e
d 
O
zo
n
e
 
M
ix
in
g 
Ra
tio
Po
te
nt
ia
l V
or
tic
ity
 [1
0-4
Km
2 k
g-
1 s
-
1 ]
840 K 
1.00
1.10
1.20
1.30
1.40
-4.90
-3.90
-2.90
-1.90
1 0Jul Aug8 1 23 1 642
465 K 
0.75
0.95
1.15
-0.20
-0.17
-0.14
Figure 7. Time series of the daily UKMO PV (right ver-
tical axis, solid line), and O3 mixing ratio (left vertical axis)
measured by lidar (diamonds), microwave (circles) and son-
des (squares), at =840 K (top panel) and 465 K (bot-
tom panel). The mixing ratios plotted for each instrument
have been normalised to the 5 August measurement by the
same instrument. The sonde and lidar O3 data have been
smoothed to a potential temperature resolution of 100 K.
The microwave O3 data have been linearly interpolated to
the shown values.
mentation seen on the high-resolution maps. In the bottom
panel of Fig. 7 the daily data are shown at =465 K (18
km), along with the observed O3 mixing ratios. Evidently
they did not capture the lament of subtropical air well,
but showed an overall decrease in the absolute value of the
PV. This was also observed at 420 K and 520 K (21 km),
though not at 585 K (24 km). Also, an increase around
August 10 was revealed, when the O3 rich vortex lament
passed over Lauder. In the daily PV data, the lament ex-
tended down to 485 K, but not to 420 K, and extended up
to 520 K, but not to 585 K, in agreement with the results
of the high-resolution calculations. Note that absolute PV
and O3 mixing ratios are correlated.
The top panel of Fig. 7 shows daily UKMO PV data
and O3 at 840 K (30.5 km), which represents the region
between 585 K and 1000 K (33.5 km). Evidently, air that
originated from the polar vortex (high absolute PV) was O3
poor. The only exception to this is August 10, when the PV
at 840 K reaches a maximum while the O3 mixing ratio has
already started to increase. This likely reflects inaccuracies
associated with the coarse resolution of the UKMO PV data.
Conclusions
A decrease of the O3 column density over Lauder in
excess of 100 DU can be attributed to a juxtaposition of
O3 poor air with a low-latitude origin in the lower strato-
sphere, and O3 poor air from the polar vortex above about
25 km. Combined with the background conditions, which
were 20 DU below average in August [Connor et al., sub-
mitted to Geoph. Res. Letters] this resulted in the lowest O3
values on record. The episode of low O3 values ended when
an O3 rich lower vortex lament replaced the subtropical air
over Lauder, while simultaneously the polar vortex moved
away.
TOMS observations in the late winter show an unusually
disturbed polar vortex, indicating enhanced planetary wave
activity. This enhanced activity was the likely cause of the
unusual dynamical situation over Lauder.
Acknowledgments. We are grateful to the UARS MLS
team for providing their O3 data, Dr. R. L. McKenzie for provid-
ing the UVM data, K. F. Boersma for writing lidar temperature
software, and Drs. D. P. Donovan, J. F. de Haan, F. Alkemade,
and G. J. M. Velders for useful comments. This work was partly
funded by the New Zealand Foundation for Research, Science
and Technology contract C01633. Research at the Jet Propulsion
Laboratory, California Institute of Technology, was done under
contract with NASA. The University of Wyoming funded the Aug
5 sonde.
References
Atkinson, R. J., W. A. Matthews, P. A. Newman, and R. A.
Plumb, Evidence of the mid-latitude impact of Antarctic ozone
depletion, Nature, 340, 290-294, 1989.
Atkinson, R. J., and R. A. Plumb, Three-dimensional ozone trans-
port during the ozone hole breakup in December 1987, J. Geo-
phys. Res., 102, no. D1, 1451-1466, 1997.
Fairlie, T. D., R. B. Pierce, W. L. Grose, G. Lingenfelser,
M. Loewenstein, and J. R. Podolske, Lagrangian forecasting
during ASHOE/MAESA: Analysis of predictive skill for ana-
lyzed and reverse-domain-lled potential vorticity, J. Geophys.
Res., 102, no. D11, 13,160-13,182, 1997.
Hoskins, B. J., M. E. McIntyre, and A. W. Robertson, On the
use and signicance of isentropic potential vorticity maps, Q.
J. R. Meteorol. Soc., 111, no. 470, 877-946, 1985.
Manney, G. L., J. C. Bird, D. P. Donovan, T. J. Duck,
J. A. Whiteway, S. R. Pal, and A. I. Carswell, Modeling ozone
laminae in ground-based Arctic wintertime observations using
trajectory calculations and satellite data, J. Geophys. Res.,
103, no. d5, 5797-5814, 1998.
Parrish, A., B. J. Connor, J. J. Tsou, I. S. McDermid, W. P. Chu,
Ground-Based Microwave Monitoring of Stratospheric Ozone,
J. Geophys. Res., 97, 2541-2546, 1992.
Roscoe, H. K., A. E. Jones, A. M. Lee, Midwinter Start to Antarc-
tic Ozone Depletion: Evidence from Observations and Models,
Science, 270, 93-96, 1997.
Schoeberl, M. R., Dynamics weaken the polar hole, Nature, 336,
420-421, 1988.
Schoeberl, M. R., L. R. Lait, P. A. Newman, and J. E. Roseneld,
The Structure of the Polar Vortex, J. Geophys. Res., 97, no.
D8, 7859-7882, 1992.
Swart, Daan P. J., Jan Spakman, and Hans B. Bergwer, RIVM’s
Stratospheric Ozone Lidar for NDSC Station Lauder: System
Description and First Results. Abstracts of Papers of the 17th
International Laser Radar Conference, Sendai, Japan, 405-408,
1994.
Swart, D. P. J., J. Spakman, J. B. Bergwer, E. J. Brinksma,
and F. T. Ormel, RIVM Stratospheric Ozone Lidar for NDSC
Station Lauder, New Zealand, NOP Report, RIVM, Bilthoven,
The Netherlands, 57 pages, 1995.
Sutton, R. T., H. MacLean, R. Swinbank, A. O’Neill, F. W. Tay-
lor, High-resolution stratospheric tracer elds estimated from
satellite observations using Lagrangian trajectory calculations,
J. Atmos. Sci., 51, 2995-3005, 1994.
Waugh, D. W., Subtropical stratospheric mixing linked to distur-
bances in the polar vortices, Nature, 365, 533-535, 1993.
E. J. Brinksma, Vrije Universiteit, Faculty of Physics & As-
tronomy, De Boelelaan 1081, 1081 HV Amsterdam, The Nether-
lands. email: ellen@nat.vu.nl
(Received May 11, 1998; revised June 19, 1998;
accepted June 23, 1998.)


Analysis of Record-Low Ozone Values During the 1997 Winter over Lauder, New Zealand.

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Analysis of record-low ozone values during the 1997 winter over Lauder, New Zealand

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VU Research PortalAnalysis of Record-Low Ozone Values During the 1997 Winter over Lauder, NewZealand.Brinksma, E.J.; Meijer, Y.J.; Connor, B.J.; Manney, G.L.; Bergwerff, J.B.; Bodeker, G.E.;Boyd, I.S.; Liley, J.B.; Hogervorst, W.; Hovenier, J.W.; Livesey, N.J.; Swart, D.P.J.published inGeophysical Research Letters1998DOI (link to publisher)10.1029/98GL52218document versionPublisher's PDF, also known as Version of recordLink to publication in VU Research Portalcitation for published version (APA)Brinksma, E. J., Meijer, Y. J., Connor, B. J., Manney, G. L., Bergwerff, J. B., Bodeker, G. E., Boyd, I. S., Liley, J.B., Hogervorst, W., Hovenier, J. W., Livesey, N. J., & Swart, D. P. J. (1998). Analysis of Record-Low OzoneValues During the 1997 Winter over Lauder, New Zealand. Geophysical Research Letters, 25, 2785-2788.https://doi.org/10.1029/98GL52218General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright ownersand it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.            • Users may download and print one copy of any publication from the public portal for the purpose of private study or research.            • You may not further distribute the material or use it for any profit-making activity or commercial gain            • You may freely distribute the URL identifying the publication in the public portal ?Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.E-mail address:vuresearchportal.ub@vu.nlDownload date: 13. Dec. 2021GEOPHYSICAL RESEARCH LETTERS, VOL. 25, NO. 15, PAGES 2785-2788, AUGUST 1, 1998Analysis of Record-Low Ozone Values During the 1997Winter over Lauder, New ZealandE. J. Brinksma1, Y. J. Meijer2, B. J. Connor3, G. L. Manney4,J. B. Bergwerff2, G. E. Bodeker3, I. S. Boyd3, J. B. Liley3, W. Hogervorst1,J. W. Hovenier1, N. J. Livesey4, D. P. J. Swart2Abstract. Record-low ozone (O3) column densities (with aminimum of 222 DU) were observed over the Lauder NDSC(Network for the Detection of Stratospheric Change) sta-tion (45◦S, 170◦E) in August 1997. Possible causes are ex-amined using height-resolved O3 measurements over Lauder,and high-resolution reverse trajectory maps ofO3 (initialisedwith Microwave Limb Sounder measurements) and of poten-tial vorticity. The analysis shows thatO3 poor air originatedfrom two regions: Below the 550 K isentrope (∼22 km) sub-tropical air was observed, while between 600 and 1000 K(∼25 – 33.5 km) the polar vortex tilted over Lauder for sev-eral days. A rapid recovery of the O3 column density wasobserved later, due to an O3 rich polar vortex filament mov-ing over Lauder between 18 and 24 km, while simultaneouslythe O3 poor higher vortex moved away.IntroductionMeasurements at Lauder and TOMS satellite data showedthat the 1997 springtime and winter were characterised bylow O3 column densities throughout the Southern Hemi-sphere mid-latitude region, which could be largely accountedfor by the phase of the Quasi Biennial Oscillation and a long-term decrease in the average ozone levels [Connor et al.,submitted to Geoph. Res. Letters]. The August ’97 averageover Lauder was 324 DU, which is 21 DU below the 1985–1996 August average. In this article, daily observations overLauder in early August of 1997 are presented which are evenlower, down to 222 DU. Similar cases in which the O3 col-umn density dropped abruptly and sharply were observedin September and October of 1997.In the late winter of ’97, TOMS observations showed anunusually distorted polar vortex edge, which was centred offthe pole repeatedly. A perturbed polar vortex is associatedwith enhanced planetary wave activity, which may distributevortex filaments over lower latitudes [e.g., Schoeberl et al.,1992]. Similarly, filaments can be peeled off the subtropi-cal barrier, and previous studies [e.g., Waugh, 1993] havelinked subtropical stratospheric mixing and disturbances ofthe polar vortices in both hemispheres during the winter.1Vrije Universiteit, Department of Physics and Astronomy,Amsterdam, The Netherlands.2National Institute of Public Health and the Environment(RIVM) Air Research Laboratory, Bilthoven, The Netherlands.3National Institute of Water and Atmospheric Research Ltd.(NIWA), Lauder, New Zealand.4Jet Propulsion Laboratory, California Institute of Technol-ogy, PasadenaCopyright 1998 by the American Geophysical Union.Paper number 98GL52218.0094-8534/98/98GL-52218$05.00Exchange between the vortex and mid-latitude air is im-portant since it influences the amount of chemical processingof ozone [e.g., Schoeberl et al., 1988]. Only a few obser-vations of vortex filaments at Southern Hemisphere mid-latitudes have been previously reported [Atkinson et al.,1989; Atkinson and Plumb, 1997; Fairlie et al., 1997].August ’97 ObservationsOzone column density measurements were performed bya Dobson spectrophotometer and an ultraviolet scanningspectrometer (UVM) at Lauder, and by the Earth ProbeTOMS satellite instrument within 0.25◦ lat. by 0.30◦ long.from Lauder. An offset of −12 DU was applied to the UVMdata presented here to achieve good agreement with theDobson data. This is consistent with a study based on long-term measurements over Lauder [Bodeker et al., submittedto J. Geoph. Res.].In Fig. 1, the O3 column densities measured over Lauderin August 1997 and their 1985–1996 daily averages are com-pared. The presented UVM observations were performedat local noon (∼0:45 UT), while Dobson spectrophotome-ter results are representative daily values. Apparently, fromAugust 7 to 10 the measured values were over 2 standarddeviations below the average. The record value of 222 DUwas observed on August 9, 22 UT (not shown). A rapid re-covery was observed on August 10, up to 340 DU at thestart of August 11.2202402602803003203403603804004203 1 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3Ozone Column Density (DU)Jul                            Aug '97Figure 1. Results of O3 column density measurementsover Lauder in August of 1997 by UVM (squares), Dob-son spectrophotometer (circles) and TOMS (triangles) arepresented, compared to the daily ozone column densities av-eraged over 1985–1996 (grey line). The ×-mark denotes theAugust 10 lidar measurement at 10 UT.27852786 BRINKSMA ET AL.: LOW WINTER OZONE OVER LAUDER, NEW ZEALAND1 01 41 82 22 63 03 40 3 6 9 1 2 1 5 1 8 2 1Ozone Number Density (10 12 cm -3)Altitude (km)Aug 5 6Jul 3 1 1 31 07Figure 2. Height profiles of O3 number density measuredover Lauder from July 31 to August 13, 1997, by lidar (blacklines) and sondes (thick grey lines). The mean profile forJuly 31 - August 10, derived from sonde measurements be-tween 1986 and 1996, is superposed on all profiles as a ref-erence (dashed lines). The profiles have been offset succes-sively by 3 × 1012cm−3. On August 5 the lidar and sondemeasurements were simultaneous, while on August 13 thelidar measurement was performed several hours before thesonde launch.Height-resolved O3 measurements over Lauder were mea-sured by a stratospheric lidar [Swart et al., 1994; 1995, ],electrochemical concentration cell sondes, and a microwaveradiometer [Parrish et al., 1992]. The observations yieldbothO3 number density as a function of height (Fig. 2) andO3 mixing ratio as a function of potential temperature (Θ)(Fig. 3). Fig. 2 illustrates clearly the changes in the O3column density. On the other hand, the O3 mixing ratio isconserved on constant Θ-surfaces (isentropes) in the absenceof chemical and diabatic processes, and therefore, Fig. 3 isbetter suited to reveal O3 variations caused by transport.Note that mixing ratio changes at low heights contributestrongly to the O3 column density.Ozone poor air (i.e., air with a low O3 mixing ratio) wasobserved in two regions: A ‘low region’, from Θ=350–550K (∼13–22 km, the lower boundary is determined by theminimum height of the lidar measurements), and a ‘highregion’, between Θ=600 K and 1000 K (∼25–33.5 km). Themicrowave measurements, which are available above 20 km(Θ '500 K), confirm the lidar observations of reduced ozone,but are not included in these figures for clarity. Comparingthe August 7 with the August 10 lidar observation showsthat theO3 number densities increased significantly between∼18.5 and 33.5 km (Θ ' 470–1000 K), causing the fastrecovery observed on August 10 between 0 and 10 UT.Using the lidar measurements, the evolution of the O3number density solely due to adiabatic ascent or descentof the air was computed. This was done by convertingnumber density to mixing ratio, evaluating the evolution ofthe heights of the isentropes, and converting back to num-ber density. These calculations showed that the observedchanges could not be explained by adiabatic ascent or de-scent, except from August 10 to 13 between 18 and 23 km.AnalysisPotential Vorticity (PV) on isentropic surfaces behavesas a dynamical tracer in the absence of diabatic effects, andcan be a powerful tool for understanding transport processesthat affect O3 [Hoskins et al., 1985]. The polar vortex isidentified by high absolute PV values, and a region of strongisentropic PV gradients, associated with the polar night jet,demarks its boundary. High-resolution PV and O3 mapson selected isentropic surfaces for August 4–10 were con-structed using a reverse trajectory procedure [Sutton et al.,1994; Manney et al., 1998]. Maps were initialised with PV,or with O3 reconstructed from Upper Atmosphere ResearchSatellite Microwave Limb Sounder (MLS) observations. TheMLS O3 data used here differ from those used by Manneyet al. [1998] as the instrument obtained pressure informa-tion differently, and climatological temperature data and anunpublished retrieval algorithm (prototype MLS version 5)were used. The trajectory calculations [Manney et al., 1998]were run with horizontal winds and estimates of diabaticdescent rates computed from UKMO (United Kingdom Me-teorological Office) data.Maps at Θ=420 and 500 K (∼16 and 20 km) indicate thatin the lower stratosphereO3 poor air with a low-latitude ori-gin (i.e., with a low absolute value of the PV) mixed intomid-latitudes during the first week of August. In Fig. 4 re-gions where subtropical air is pulled up around the vortexare shown (right panel, mixing ratios of 0.5–0.6 ppmv, whilethe 1986–1996 average over Lauder at 420 K in early Au-gust was 0.7 ppmv). Evidently, these filaments are foldedtogether with relatively O3 rich filaments from the vortexedge region (mixing ratios above 0.8 ppmv). The filamentwhich is seen on August 9, was present over Lauder betweenAugust 7 and 10, with the lowest mixing ratio (0.55 ppmv)observed at Θ=420 K on August 9.35045055065075085095010500 3 6 9 1 2 1 5 1 8 2 1 2 4Ozone Mixing Ratio (ppmv)Pot. Temperature (K)350550750950Approx. Altitude (km)Aug 5 6Jul 3 1 1 31 071 52 22 93 3Figure 3. Potential temperature versus ozone mixing ratiobetween July 31 and August 13, 1997. The plotting conven-tions from Fig. 2 have been maintained. The approximateheight scale on the right axis was derived from the lidarpotential temperatures on August 5, and may vary consid-erably from day to day. Here, the profiles have been offsetsuccessively by 3 ppmv.BRINKSMA ET AL.: LOW WINTER OZONE OVER LAUDER, NEW ZEALAND 2787(a) (b)= 420 KPV from UKMO Ozone (ppmv) from PV/    space        reconstructionΘΘ1000 UT, 9 Aug 1997Figure 4. Maps of (a) the PV calculated by advection of UKMO PV from July 28, 1997, and (b) the O3 mixing ratiocalculated by advection of a PV/Θ-space reconstruction of MLS observations for July 28, 1997. Both maps are for Aug 9,10 UT, Θ=420 K. The colourscale in (a) is in units of 10−4Km2kg−1s−1, in (b) the units are ppmv. The South Pole issituated in the centre of the maps, with New Zealand just left of the upward pointing dateline.In the middle stratosphere the air had a distinctly dif-ferent origin. Fig. 5 shows a map of the PV at Θ=850 K(∼31 km) on August 9, with the vortex clearly situated overLauder. Further study shows that the polar vortex movedover Lauder between August 5 and 6, first above Θ=660 K(∼27.5 km), but on August 9 down to Θ=600 K (∼25 km).Above Θ '580 K, the polar vortex is O3 poor as indicated byMLS O3 data (not shown). On August 10 from Θ=600 K–1100 K (∼25–35 km) the vortex had been replaced by vortexedge air. Higher up the vortex moved away during the nextdays.On August 10, the O3 mixing ratios between 18 and 25km (Θ '450–600 K) over Lauder increased abruptly (e.g.,PV at      = 850 K1000 UT, 9 Aug 1997ΘFigure 5. Map of the PV at Θ=850 K on August 9, 10 UT,calculated by advection of UKMO PV from July 28, 1997.Plotting conventions as in Fig. 4.from 2.2 ppmv on Aug 9 to 2.8 ppmv on Aug 10 at Θ=500 K,while the 1986–1996 average was 2.4 ppmv). This was dueto a passing filament ofO3 rich vortex edge air, which can beidentified on the maps at 485 K and 500 K (cf. Fig. 6). At520 K, the filament was visible to the north of New Zealandon August 10, and likely passed over Lauder earlier thatday. At 420 K (∼16 km), the filament remained south ofNew Zealand.The high-resolution PV maps were compared with dailyUKMO PV data over Lauder for consistency. The daily dataare spatial interpolations of the PV calculated from temper-ature and winds with 2.5◦ lat. by 3.75◦ long. resolution, at12 UT, and are thus not expected to show the details of fila-PV at      = 500 K1000 UT, 10 Aug 1997ΘFigure 6. Map of the PV at Θ=500 K on August 10,10 UT, calculated by advection of interpolated data of July29, 1997. Plotting conventions as in Fig. 4.2788 BRINKSMA ET AL.: LOW WINTER OZONE OVER LAUDER, NEW ZEALANDNormalized Ozone Mixing RatioPotential Vorticity [10-4Km2 kg-1 s-1]840 K 1.001.101.201.301.40 -4.90-3.90-2.90-1.901 0Jul Aug8 1 23 1 642465 K 0.750.951.15-0.20-0.17-0.14Figure 7. Time series of the daily UKMO PV (right ver-tical axis, solid line), and O3 mixing ratio (left vertical axis)measured by lidar (diamonds), microwave (circles) and son-des (squares), at Θ=840 K (top panel) and 465 K (bot-tom panel). The mixing ratios plotted for each instrumenthave been normalised to the 5 August measurement by thesame instrument. The sonde and lidar O3 data have beensmoothed to a potential temperature resolution of 100 K.The microwave O3 data have been linearly interpolated tothe shown values.mentation seen on the high-resolution maps. In the bottompanel of Fig. 7 the daily data are shown at Θ=465 K (∼18km), along with the observed O3 mixing ratios. Evidentlythey did not capture the filament of subtropical air well,but showed an overall decrease in the absolute value of thePV. This was also observed at 420 K and 520 K (∼21 km),though not at 585 K (∼24 km). Also, an increase aroundAugust 10 was revealed, when the O3 rich vortex filamentpassed over Lauder. In the daily PV data, the filament ex-tended down to 485 K, but not to 420 K, and extended upto 520 K, but not to 585 K, in agreement with the resultsof the high-resolution calculations. Note that absolute PVand O3 mixing ratios are correlated.The top panel of Fig. 7 shows daily UKMO PV dataand O3 at 840 K (∼30.5 km), which represents the regionbetween ∼585 K and 1000 K (∼33.5 km). Evidently, air thatoriginated from the polar vortex (high absolute PV) was O3poor. The only exception to this is August 10, when the PVat 840 K reaches a maximum while the O3 mixing ratio hasalready started to increase. This likely reflects inaccuraciesassociated with the coarse resolution of the UKMO PV data.ConclusionsA decrease of the O3 column density over Lauder inexcess of 100 DU can be attributed to a juxtaposition ofO3 poor air with a low-latitude origin in the lower strato-sphere, and O3 poor air from the polar vortex above about25 km. Combined with the background conditions, whichwere 20 DU below average in August [Connor et al., sub-mitted to Geoph. Res. Letters] this resulted in the lowest O3values on record. The episode of low O3 values ended whenan O3 rich lower vortex filament replaced the subtropical airover Lauder, while simultaneously the polar vortex movedaway.TOMS observations in the late winter show an unusuallydisturbed polar vortex, indicating enhanced planetary waveactivity. This enhanced activity was the likely cause of theunusual dynamical situation over Lauder.Acknowledgments. We are grateful to the UARS MLSteam for providing their O3 data, Dr. R. L. McKenzie for provid-ing the UVM data, K. F. Boersma for writing lidar temperaturesoftware, and Drs. D. P. Donovan, J. F. de Haan, F. Alkemade,and G. J. M. Velders for useful comments. This work was partlyfunded by the New Zealand Foundation for Research, Scienceand Technology contract C01633. Research at the Jet PropulsionLaboratory, California Institute of Technology, was done undercontract with NASA. The University of Wyoming funded the Aug5 sonde.ReferencesAtkinson, R. J., W. A. Matthews, P. A. Newman, and R. A.Plumb, Evidence of the mid-latitude impact of Antarctic ozonedepletion, Nature, 340, 290-294, 1989.Atkinson, R. J., and R. A. Plumb, Three-dimensional ozone trans-port during the ozone hole breakup in December 1987, J. Geo-phys. Res., 102, no. D1, 1451-1466, 1997.Fairlie, T. D., R. B. Pierce, W. L. Grose, G. Lingenfelser,M. Loewenstein, and J. R. Podolske, Lagrangian forecastingduring ASHOE/MAESA: Analysis of predictive skill for ana-lyzed and reverse-domain-filled potential vorticity, J. Geophys.Res., 102, no. D11, 13,160-13,182, 1997.Hoskins, B. J., M. E. McIntyre, and A. W. Robertson, On theuse and significance of isentropic potential vorticity maps, Q.J. R. Meteorol. Soc., 111, no. 470, 877-946, 1985.Manney, G. L., J. C. Bird, D. P. Donovan, T. J. Duck,J. A. Whiteway, S. R. Pal, and A. I. Carswell, Modeling ozonelaminae in ground-based Arctic wintertime observations usingtrajectory calculations and satellite data, J. Geophys. Res.,103, no. d5, 5797-5814, 1998.Parrish, A., B. J. Connor, J. J. Tsou, I. S. McDermid, W. P. Chu,Ground-Based Microwave Monitoring of Stratospheric Ozone,J. Geophys. Res., 97, 2541-2546, 1992.Roscoe, H. K., A. E. Jones, A. M. Lee, Midwinter Start to Antarc-tic Ozone Depletion: Evidence from Observations and Models,Science, 270, 93-96, 1997.Schoeberl, M. R., Dynamics weaken the polar hole, Nature, 336,420-421, 1988.Schoeberl, M. R., L. R. Lait, P. A. Newman, and J. E. Rosenfield,The Structure of the Polar Vortex, J. Geophys. Res., 97, no.D8, 7859-7882, 1992.Swart, Daan P. J., Jan Spakman, and Hans B. Bergwerff, RIVM’sStratospheric Ozone Lidar for NDSC Station Lauder: SystemDescription and First Results. Abstracts of Papers of the 17thInternational Laser Radar Conference, Sendai, Japan, 405-408,1994.Swart, D. P. J., J. Spakman, J. B. Bergwerff, E. J. Brinksma,and F. T. Ormel, RIVM Stratospheric Ozone Lidar for NDSCStation Lauder, New Zealand, NOP Report, RIVM, Bilthoven,The Netherlands, 57 pages, 1995.Sutton, R. T., H. MacLean, R. Swinbank, A. O’Neill, F. W. Tay-lor, High-resolution stratospheric tracer fields estimated fromsatellite observations using Lagrangian trajectory calculations,J. Atmos. Sci., 51, 2995-3005, 1994.Waugh, D. W., Subtropical stratospheric mixing linked to distur-bances in the polar vortices, Nature, 365, 533-535, 1993.E. J. Brinksma, Vrije Universiteit, Faculty of Physics & As-tronomy, De Boelelaan 1081, 1081 HV Amsterdam, The Nether-lands. email: ellen@nat.vu.nl(Received May 11, 1998; revised June 19, 1998;accepted June 23, 1998.)

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Analysis of Record-Low Ozone Values During the 1997 Winter over Lauder, New Zealand.

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