Reconstruction of 3D Ozone Fields Using POAM III During SOLVE
C.E. Randall1, J.D. Lumpe2, R.M. Bevilacqua3, K.W. Hoppel3, M.D. Fromm2, R.J. Salawitch4,
W.H. Swartz5,6, S.A. Lloyd5, E. Kyro7, P. von der Gathen8, H. Claude9, J. Davies10, H.
DeBacker11, H. Dier12, M.J. Molyneux13, and J. Sancho14

1

Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80309-0392. Tel: 303-4928208; Fax: 303-492-6946; email: cora.randall@lasp.colorado.edu. 2 Computational Physics, Inc., 8001 Braddock
Road, Suite 210, Springfield, VA 22151. Tel: 703-764-7501; Fax: 703-764-7500; email: lumpe@cpi.com;
fromm@poamb.nrl.navy.mil. 3 Naval Research Laboratory, Code 7220, Bldg. 2, 4555 Overlook Ave., SW,
Washington, DC 20375-5320. Tel: 202-767-0768; Fax: 202-767-7885; email: bevilacqua@nrl.navy.mil;
karl.hoppel@nrl.navy.mil. 4 Jet Propulsion Laboratory, MS 183-301, 4800 Oak Grove Dr., Pasadena, CA 91109.
Tel: 818-354-0442; Fax: 818-354-5148; email: rjs@caesar.jpl.nasa.gov. 5 The Johns Hopkins University Applied
Physics Laboratory. Tel: 240-228-8462; email: bill.swartz@jhuapl.edu; steven_lloyd@jhuapl.edu. 6 Department
of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742. 7 FMI Sodankylä observatory,
Tähteläntie 71, FIN-99600 Sodankylä, Finland. Tel: +358-16-610 072; fax: +358-16-610 105; email:
esko.kyro@fmi.fi. 8Alfred Wegener Institute for Polar and Marine Research, Research Site Potsdam,
Telegrafenberg A43, D-14473 Potsdam. Tel: +49-331-288-2128; Fax: +49-331-288-2178; email: gathen@awipotsdam.de. 9Hohenpeissenberg Observatory, Deutscher Wetterdienst, Albin-Schwaiger-Weg 10, 82383,
Hohenpeissenberg, Germany. email: hans.claude@dwd.de. 10jonathan.davies@ec.gc.ca. 11Royal Meteorological
Institute of Belgium, Ringlaan 3, B-1180 Brussels, Belgium. Tel: +32-2-3730594; Fax: +32-2-3751259; email:
hugo.debacker@oma.be. 12DWD Meteorological Observatory Lindenberg, Am Observatorium 12, 15864
Lindenberg. Tel: +49-33677-60231; Fax: +49-33677-60280; email: horst.dier@dwd.de. 13Met Office, Beaufort
Park, Easthampstead, Wokingham, Berks, RG40 3DN, United Kingdom; email: mjmolyneux@meto.gov.uk.
14
Izana Atmospheric Observatory, La Marina, 20, PO Box 880, Santa Cruz de Tenerife, Spain, 38071; email:
jsancho@inm.es.

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Abstract
In this paper, we demonstrate the utility of the Polar Ozone and Aerosol Measurement (POAM)
III data for providing semi-global three-dimensional ozone fields during the SAGE III Ozone
Loss and Validation Experiment (SOLVE) winter. As a solar occultation instrument, POAM III
measurements were limited to latitudes of 63°N to 68°N during the SOLVE campaign, but
covered a wide range of potential vorticity. Using established mapping techniques, we have used
the relation between potential vorticity and ozone measured by POAM III to calculate threedimensional ozone mixing ratio fields throughout the northern hemisphere on a daily basis
during the 1999-2000 winter. To validate the results, we have extensively compared profiles
obtained from ozonesondes and the Halogen Occultation Experiment to the proxy O3
interpolated horizontally and vertically to the correlative measurement locations. On average,
the proxy O3 agrees with the correlative observations to better than ~5%, at potential
temperatures below about 900 K and latitudes above about 30°N, demonstrating the reliability of
the reconstructed O3 fields in these regions. We discuss the application of the POAM proxy
ozone profiles for calculating photolysis rates along the ER-2 and DC-8 flight tracks during the
SOLVE campaign, and present a qualitative picture of the evolution of polar stratospheric ozone
throughout the winter.
1. Introduction
The SAGE III Ozone Loss and Validation Experiment (SOLVE) campaign was designed to
investigate the processes causing O3 loss at high northern latitudes, and to provide correlative
data for validating the Stratospheric Aerosol and Gas Experiment (SAGE) III. One of the goals
of SOLVE was to optimize the inference of O3 loss from satellite observations, for those years
when dedicated ground, balloon and/or aircraft campaigns are not feasible. Although the launch
of SAGE III was unfortunately delayed, the Polar Ozone and Aerosol Measurement (POAM) III
instrument, a satellite-based solar occultation instrument with latitude coverage similar to the
planned SAGE III measurements, was (and still is) operational. During the SOLVE campaign,
POAM III provided daily stratospheric profiles of ozone, water vapor, nitrogen dioxide and
aerosol extinction in the northern hemisphere (NH) from 63°N to 68°N with about 1-km vertical
resolution. These measurements are being used to investigate the polar processes responsible for
O3 loss during the 1999-2000 NH winter [e.g., Hoppel et al., 2001; Bevilacqua et al., 2001; both
in this issue].
It is now well established that the 1999-2000 NH polar vortex was unusually cold, with
temperatures often below the threshold for forming Polar Stratospheric Clouds (PSCs) [Manney
and Sabutis, 2000]. O3 decreases inside the polar vortex of 0.04±0.01 ppmv/day were observed
in Microwave Limb Sounder (MLS) data from early February [Santee et al., 2000], and O3
chemical loss of more than 70% by the end of March has been inferred from ozonesonde data at
Ny Ǻlesund, Spitsbergen (79°N, 12°E) [Sinnhuber et al., 2000]. Nevertheless, the precise
mechanisms controlling the magnitude of the O3 loss have yet to be elucidated in detail. Ideally,
a campaign such as SOLVE would be supported by global satellite measurements, with the
ground-based, balloon and aircraft measurements providing detailed but localized information,
and the satellite providing measurements to place this information into a more global context.
Although the Total Ozone Mapping Spectrometer (TOMS) instrument provides an excellent
near-global map of column O3, vertically resolved measurements are often preferable for
mechanistic studies. Unfortunately, no instrument capable of providing global O3 profiles with

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high vertical resolution was operational throughout the SOLVE campaign (although the MLS
was operational for nine days in February and March [Santee et al., 2000]).
In an effort to improve this situation, we have reconstructed daily, semi-global (NH only),
vertically resolved O3 fields from the POAM data. The technique by which this was
accomplished, which we refer to as potential vorticity (PV) mapping, was established more than
a decade ago for use with LIMS [Butchart and Remsberg, 1986] and ER-2 [Schoeberl et al.,
1989] data. This technique makes it possible, under certain conditions, to calculate mixing ratios
over a much wider range of geographic locations than were actually observed. In this paper we
describe the PV mapping technique as applied to the POAM III data, validate the results, and
show how these results are useful for the SOLVE objectives.
The premise behind the PV mapping technique is that PV is a conserved quantity during
adiabatic transport, so it is often used as a tracer of atmospheric motions. Since O3 in the winter
stratosphere is dynamically controlled, a single, well-defined relationship defines its correlation
with PV across the polar vortex anywhere on a given potential temperature (q) surface at any
given point in time [e.g., Leovy et al., 1985, Allaart et al., 1993]. If this relationship is
determined by measuring O3 over a sufficient range of PV/q space, it can thus be used to derive
O3 mixing ratios at geographic locations outside the actual measurement field, as long as the PV
and q values at those locations are known. The technique has been incorporated into studies of
vortex processes in both hemispheres [Schoeberl et al., 1989; Lait et al., 1990; Manney et al.,
1998; 1999], and the underlying concepts have been used to improve satellite data
intercomparisons [Manney et al., 2001; Redaelli et al., 1994]. This paper describes its first
application with POAM III O3 data. POAM III routinely measured O3 profiles over a wide range
of PV during the SOLVE campaign (see section 2). Taking advantage of the PV analyses from
the Met Office (UKMO) [Swinbank and O’Neill, 1994], we were able to reconstruct O3 profiles
on the NH UKMO grid, as described in section 3. We evaluated the NH gridded O3 “proxy”
product by interpolating the profiles vertically and horizontally to the locations of correlative
measurements, to which we compared the proxy profiles. These comparisons are described in
section 4. The initial motivation for performing and validating the PV-mapping with POAM III
data during SOLVE was to derive O3 profiles above the SOLVE aircraft measurements. These
profiles could then be used to determine solar flux transmissions for theoretical calculations of
photolysis reaction rates. This application of the proxy O3 data is the subject of section 5.
2. POAM III Data
Each day, approximately fifteen POAM observations, separated by ~25° in longitude, are made
around a circle of approximately constant latitude in the northern hemisphere (NH) at local
sunset. The average latitude of the observations on each day from 1 November 1999 through 30
April 2000 is shown in Figure 1. At each measurement location, POAM measures profiles of O3
(~10-60 km), aerosol extinction at five wavelengths from 353 nm to 1020 nm (~10-30 km), NO2
(~20-40 km), and H2O (~10-45 km). In this paper, we focus on the version 3.0 POAM III O3
data. Preliminary validation of an earlier version of POAM III O3 was described by Lucke et al.
[1999]. More recent analyses with version 3.0 have been completed by Lumpe et al. [2001, this
issue] and Rusch et al. (Validation of POAM III O3: Comparison to ozonesonde and satellite
data, submitted to J. Geophys. Res., 2001). These show that on average, POAM III O3 profiles in
the NH agree to better than 10% with correlative observations from 12 to 60 km.

C.E. Randall et al., POAM III Ozone during SOLVE

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Because the vortex is often displaced from the pole in the NH, POAM III makes measurements
at a wide range of equivalent latitudes [Butchart and Remsberg, 1986] on a daily basis during the
winter, even though the geographic latitude is essentially constant on a given day. For example,
Plate 1 shows the PV on the 500 K potential temperature surface corresponding to every POAM
measurement in the NH from 1 November 1999 through 30 April 2000. For this figure and
elsewhere in the paper, we use UKMO PV analyses interpolated in time and space to the POAM
measurement locations when necessary. The inner and outer vortex edge boundaries, as defined
by Nash et al. [1996], are denoted in the plot. From late December through mid-March, POAM
sampled in the vortex core, on the vortex edge, and outside the vortex on a near-daily basis. It is
this characteristic of the POAM measurements that allows the analysis described below.
To illustrate how O3 changes with PV, a contour plot of the O3 field generated from
measurements obtained by POAM over a 3-day period from 24-26 December 1999 is given in
Plate 2. Maps such as this were provided to SOLVE campaign participants on a daily basis
throughout the winter. At this particular time and latitude, measurement locations at longitudes
of about 330°E to 60°E were inside the vortex (in-V), with longitudes near 180° well outside the
vortex (out-V), and longitudes near 120°E and 300°E on the edge of the vortex (edge-V). This is
quite typical for the vortex structure and location in the NH. Since O3 is in dynamical control at
this time and latitude, mixing ratios follow the vortex structure. At all altitudes above about 500
K, O3 mixing ratios are significantly higher outside the vortex than inside; this results largely
from transport of O3-rich air from lower latitudes to the polar region outside the vortex [Randall
et al., 1995]. Inside the vortex, air parcels cannot mix as freely with the lower latitude air, so
mixing ratios remain lower than outside the vortex. Near 450 K, where the vertical gradient in
the O3 profile is larger than at the higher altitudes, O3 mixing ratios inside the vortex are slightly
higher than outside. This is due to enhanced diabatic descent inside the vortex. Because O3
mixing ratios increase with altitude here, air parcels descending inside the vortex to 450 K
increase the O3 mixing ratios to values above those outside the vortex, where descent occurs less
rapidly and with more horizontal mixing [e.g., Randall et al., 1995; Manney et al., 1995a, and
references therein].
Whereas Plate 2 illustrates the O3 variation with respect to the vortex that was observed in late
December, Plate 3 presents the temporal variation in O3 that was observed at different locations
with respect to the vortex over the course of the winter. This figure shows the daily average
POAM III O3 mixing ratios segregated according to position with respect to the vortex (e.g.,
inside, outside, or on the edge) using the Nash et al. [1996] vortex definition. Although these
observations were all acquired within the fairly narrow latitude band depicted in Figure 1, they
illustrate some interesting features of the changes in vortex distribution of O3 during the winter at
these latitudes. For instance, at 550 K and 600 K, in-V mixing ratios are persistently lower than
out-V mixing ratios, for the reasons stated above relating to poleward transport of high O3
mixing ratio air from lower latitudes. At 450 K in December, in-V O3 is more than 50% higher
than out-V O3. Again, this was explained above, and results from enhanced diabatic descent
inside the vortex. However, in-V O3 mixing ratios at 450 K begin to decline steeply by midFebruary, so that by early March they are as low as out-V mixing ratios. This is the signature of
chemical O3 loss, and is discussed in more detail by Hoppel et al. [2001, this issue]. By early
March, even edge-V O3 is declining at 450 K. Similar declines in in-V and edge-V O3 are also

C.E. Randall et al., POAM III Ozone during SOLVE

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evident at 500 K. Another interesting feature is that until about mid-January, edge-V mixing
ratios at 500 K are higher than both in-V and out-V. We believe that this can be explained
primarily by a variation across the edge of the vortex in the O3 profile vertical gradient near 500
K. Examination of POAM III profiles in October and November reveals that edge-V and out-V
O3 mixing ratio profiles exhibited a steep gradient from 400 to 600 K. Enhanced diabatic
descent on the edge of the vortex would have resulted in higher edge-V O3 than out-V, just as at
450 K. However, whereas in-V O3 mixing ratios followed a similarly steep gradient from 400 to
500 K, they were roughly constant near 3.0 ppmv or less above about 500 K. Thus, enhanced
diabatic descent inside the vortex produced little change in the in-V O3 mixing ratios at this time,
resulting in edge-V O3 mixing ratios that were higher than both in-V and out-V. There may also
be a contribution from faster diabatic descent along the edge of the vortex compared to inside.
Reverse trajectory calculations performed elsewhere (G. Manney, private communication, 2001)
showed that air parcels at 500 K on 5 January would have descended ~10 K further on the edge
of the vortex than inside during the preceding 40 days .
3. Method
As mentioned above, the fact that PV is conserved during adiabatic transport allows us to use it
to follow the motion of tracers (such as O3 under many conditions) on isentropic surfaces. This
concept can be applied to approximate O3 at geographic locations distant from actual
measurements, as long as the measurements themselves adequately constrain the relationship
between PV and O3, and the PV values at the remote locations are well known [e.g., Schoeberl et
al., 1989]. As shown above, POAM III measurements span a wide range of PV values daily
throughout the NH winter, and clearly document variations in O3 expected from the changing
PV. For every day during the SOLVE campaign, we thus calculated an analytic (quadratic)
expression relating PV to O3 using the POAM III O3 profiles and the UKMO PV values
interpolated in time and space to the POAM measurement locations. In practice, we actually
used O3 and PV data corresponding to the 7-day interval centered on the day of interest. We
found by trial and error that this interval length corresponded to the optimum balance for
defining the PV/O3 relation. Including more days introduces error due to varying PV/O3
correlations, particularly in times of rapid vortex evolution. Including fewer days results in
poorer statistics - in general the quadratic fits in these cases were qualitatively similar to the 7day analyses, but suffered from more noise. For each day during the SOLVE winter, we then
applied this relation to the daily 12:00 UT NH UKMO PV field to generate proxy O3 mixing
ratios on the same latitude/longitude grids as the UKMO data (for this work these grids spanned
the NH in 2.5-degree increments in latitude and 3.75-degree increments in longitude).
Our method is illustrated in Plate 4 for 1 January 2000 at 650 K. Plate 4a shows the POAM III
O3 mixing ratios from 29 December through 4 January plotted against the UKMO PV
interpolated to the POAM III measurement locations on the 650 K surface. For this altitude and
time, high PV values correspond to the lowest values of O3, and low PV values to the highest
values of O3, since O3 outside the vortex is higher than inside, as discussed above.
Superimposed on the data is a quadratic fit. We calculated a proxy O3 field for this day by
multiplying the 650 K UKMO PV grid for January 1 by the quadratic coefficients defining the fit
in Plate 4a. Plate 4b shows a contour map of the UKMO PV, clearly depicting the vortex as
having an oval shape with its long axis oriented along 90°E-270°E longitude, and its center
displaced from the pole toward Greenland and Scandinavia. Over the 7-day period from 29

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December to 4 January the POAM measurements spanned the latitude circle near 63°, in fairly
regular longitude intervals of about five degrees. The measurements occurred well outside and
inside the vortex, missing only the region with the very highest values of PV. The proxy O3
field, calculated from the PV field in Plate 4b and the quadratic coefficients defining the fit in
Plate 4a, is plotted in Plate 4c. As expected from the monotonic PV/O3 relation in Plate 4a, the
O3 field is essentially the reverse of the PV field – with low O3 inside the vortex, and high O3
outside the vortex.
Extending this illustration to other days, Plate 5 shows the POAM III O3 mixing ratios at 500 K
and quadratic PV/O3 fits for four different days during the SOLVE campaign. This figure
illustrates the gradually changing PV/O3 relation over the course of the winter. Although similar
information about the data can be derived from Plate 3, we focus here on the quadratic fits to the
data. The most salient point about this figure is that for all of these days, a quadratic fit appears
to match the data quite well, on average. On 20 December, edge and in-V mixing ratios are
higher than out-V, due to enhanced diabatic descent inside the vortex. The fit shows a slight
enhancement of edge mixing ratios over in-V mixing ratios, but this is somewhat uncertain since,
as shown in Plate 1, only a small fraction of the POAM measurements at this time occurred
inside the inner edge of the vortex. Thus, extrapolation of this quadratic to substantially higher
values of PV is expected to be less certain than, for instance, extrapolation to lower values of PV.
By the end of January, the enhancement of edge O3 mixing ratios over those both outside and
inside the vortex is clear, the result of enhanced diabatic descent on the edge bringing down O3rich air. By late February, the fits indicate mixing ratios inside the vortex that are significantly
less than outside, a result expected only in the presence of chemical O3 loss. On 20 March, even
though POAM sampled a wide range of PV, fewer points define the quadratic inside the vortex,
suggesting higher uncertainty for the fit at this time.
Applying the fits shown in Plate 5 to the UKMO PV fields, we generated the proxy O3 maps
shown in Plate 6. Overall, these maps are consistent with the interpretation of the plots at the
POAM latitudes discussed above. That is, areas of highest O3 in December through February
form a collar near the vortex edge, where descent of O3-rich air dominates. The areas of lowest
O3 in February lie inside the vortex, and signify chemical O3 loss during the winter. On March
20, the vortex was elongated and split into two areas of high PV (and relatively low O3),
resulting in the double-lobed appearance to this map. These maps also illustrate, however, the
potential for error when using the mapping technique to infer O3 at latitudes far from the original
measurements. Consider, for instance, the map for 20 January 2000. The apparent intrusion of
air with high O3 mixing ratios from the vortex edge to the pole near Greenland is an artifact due
to anomalous structure in the UKMO PV field for this day. Indeed, the proxy O3 mixing ratio at
500 K on 20 January, interpolated to the location of Eureka (79.9°N, -85°E), was higher by about
15% than the sonde measurement for that day.
At the other extreme, the very low (~2.2 ppmv) proxy O3 mixing ratios on 20 January near 80°N
latitude are also an artifact, and are lower than actual measurements, for instance at Ny Ǻlesund
(see section 4). These low mixing ratios result from an extrapolation of the PV/O3 relation to
higher PV values and latitudes than were observed. The primary reason for this is that because
of the dynamically induced higher O3 on the edge of the vortex, the mapping technique causes
O3 to monotonically decrease at higher values of PV that are not sampled by POAM, rather than

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to level off to some extent inside the vortex. Using higher order polynomials for the PV/O3 fits
can alleviate this type of problem somewhat, but introduces other artifacts into the analysis. This
effect is exacerbated by the fact that the return of sunlight to the POAM measurement latitude
(~64°N) in January caused some chemical loss at 500 K (see Plate 3; also [Hoppel et al., this
issue]) inside the vortex. Even though such loss could not yet have occurred at the higher
latitudes still in darkness, the mapping technique generalizes it to the entire vortex, and in fact
extrapolates to even lower O3 values at the higher PV values. In the next section, we explore in
detail the effects of such errors on the validity of the reconstructed fields.
4. Validation of the Method
To validate the PV mapping technique with POAM data, we have extensively compared the
proxy O3 profiles generated using the method above to profiles obtained from balloon-based
electrochemical concentration cell and Brewer-Mast ozonesondes and the Halogen Occultation
Experiment (HALOE). Comparisons were made by interpolating the proxy O3 horizontally and
vertically to the correlative measurement locations. These comparisons included locations both
well north and well south of the actual POAM III measurement locations, and both outside and
inside the polar vortex. Ozonesonde profiles were obtained from a sonde network operating
within the framework of the THESEO 2000-EuroSOLVE project. For this work, we used data
from 29 stations in Europe, North America, and Russia. Station locations and the number of
profiles used from each are listed in Table 1. All data incorporated in our analysis have been
quality controlled in real time during the SOLVE campaign, by daily visual inspection of
profiles. The time series data from Ny Ǻlesund (see below) have also passed a more rigorous,
post-mission quality control process. HALOE version 19 O3 data were obtained from the
HALOE home page (http://haloedata.larc.nasa.gov/). The O3 profiles were placed on potential
temperature grids using the temperatures and pressures provided with the sonde (measured by
radiosonde) and HALOE (NCEP) data sets.
Plate 7 shows representative comparisons between individual ozonesonde profiles at three
different locations and the proxy O3 profiles (determined by interpolation of the proxy O3 field
on the UKMO grid to the sonde location). For this example, we have chosen to show results
from stations that were roughly 14° north (Ny Ǻlesund), 17° south (Hohenpeissenberg), and 37°
south (Izana) of the POAM measurements. In general the agreement with the sondes is
excellent, with the proxy even capturing the steep lower stratospheric gradient in the O3 profile at
Izana (28.4°N). The discrepancy above 700 K in the Izana comparisons is primarily due to the
fact that at this low latitude and these high altitudes, O3 is no longer a passive tracer.
To quantify the sonde results, we have carried out a statistical analysis, calculating the average
differences between the proxy and the sonde profiles for each of the measurements listed in
Table 1. Plate 8 shows the average difference profile for these comparisons, as well as the
individual differences and standard deviation of the mean (which is equivalent to the uncertainty
in the mean). These results show that for the early to mid-winter data included here, the proxy
O3 profiles on average agree with the sondes to better than 5% below about 800 K. This
agreement is particularly noteworthy given the large range of sonde locations compared to the
relatively localized POAM measurement latitudes. Approximately 4.4% of the comparisons
shown in Plate 8 include proxy O3 data that were derived from an extrapolation of the PV/O3
quadratic fit beyond the range of PV values actually sampled by POAM (75 points out of 1720).

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The comparisons including these extrapolated points are fairly evenly distributed among the
entire set of comparisons, and do not significantly affect the overall averages.
To better understand the latitude dependence of the quality of the proxy profiles, we have
compared the proxy O3 to more than nine hundred O3 profiles measured by HALOE, at the
latitudes and times shown in Figure 2. The latitude dependence of the differences between
HALOE and the proxy O3 is shown in Plate 9 for four different potential temperature levels.
These comparisons show that between 500 K and 850 K, the proxy O3 generally agrees with the
HALOE data remarkably well at latitudes poleward of 30°N (see below), but more poorly at
equatorial latitudes. The larger differences at the lower latitudes probably have two causes.
First, increasing uncertainty in the UKMO PV field at these latitudes is likely to contribute to
errors in the PV/O3 analysis. Second, these latitudes correspond to PV values well outside the
range sampled by POAM, where the quadratic relation may no longer hold (note that
comparisons where the proxy O3 was determined from an extrapolation of the PV/O3 quadratic
fit beyond the PV range sampled by POAM are denoted in black). At 650 K and above, the
results at the lower latitudes may also be affected by the fact that increasing sunlight will cause
O3 to transition away from a dynamically controlled situation [Garcia and Solomon, 1985],
increasing the error in the PV/O3 analysis. Although agreement is worse at 1250 K than at the
lower altitudes, it is still quite reasonable poleward of 30°N.
To quantify these comparisons, Figure 3 shows the statistical results for all events (724)
poleward of 30°N. Comparisons including proxy O3 derived from an extrapolation of the PV/O3
quadratic fit beyond the PV range sampled by POAM constitute about 20% of the data points at
latitudes poleward of 30°N; their removal does not significantly alter the conclusions stated here.
Like the sonde comparisons, agreement is impressive, with differences often less than 5% below
1100 K. The differences increase at the highest altitudes, most likely because of the lack of
dynamical control at these altitudes as sunlight returns to the polar region. The large differences
at 400 K in part reflect real differences between the POAM and HALOE data which have not yet
been resolved (Rusch et al., Validation of POAM III O3: Comparison to ozonesonde and
satellite data, submitted to J. Geophys. Res., 2001). However, near 400 K the documented
differences between POAM and HALOE are only at the 10% level, and cannot entirely explain
either the average differences seen in Figure 3, or the marked increase in the variability of the
comparisons at 400 K. We believe the deterioration in the comparisons at 400 K may result from
increased mixing of air parcels at and below this altitude, where the effective diffusivity is
generally higher than at higher altitudes [Haynes and Shuckburgh, 2000]. Variable small-scale
mixing could change the PV/O3 relationship as a function of geographic location, so that the fit
derived from the POAM data would not necessarily apply to the location of the HALOE (or
sonde) measurements. This would suggest that for the SOLVE winter, the lower altitude limit
for the PV mapping technique employed here is around 400-450 K. Confirming this speculation
requires more investigation, and is beyond the scope of this paper.
To probe more deeply into the quality of the PV/O3 reconstruction at latitudes poleward of the
POAM measurements, and to evaluate the proxy O3 in regions of chemical O3 loss, we have
compared in detail the proxy O3 to ozonesonde measurements made at Ny Ǻlesund. At 78.9°N
and 12°E, this station is often located under the center of the NH vortex, where one might expect
O3 loss to maximize. Indeed, as noted earlier, O3 loss of more than 70% during the SOLVE

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winter has been inferred above Ny Ǻlesund [Sinnhuber et al., 2000]. Figure 4 shows the
evolution of O3 mixing ratios measured by sonde above Ny Ǻlesund at four different potential
temperature levels between 450 and 750 K, from late November through April. Superimposed
are the proxy O3 values, interpolated to the latitude and longitude of Ny Ǻlesund. Throughout
most of the winter, at all of these potential temperature levels, the agreement is remarkable, with
mean differences ranging from about +5% to –7%. These results indicate that even at latitudes
significantly poleward of the POAM measurements, and well inside the vortex, the PV mapping
yields reasonable O3 values. In particular, the proxy field captures the variations in O3 at 450 K
until early March and at 500 K until late March, including the decline caused by chemical loss
processes. There are two noteworthy regions of disagreement. At 450 K and 500 K, proxy O3
values at the end of January and beginning of February are generally somewhat lower than the
sonde data. As discussed above with regard to Plate 6, this results from errors in the in-V
reconstruction stemming largely from the fact that the air parcels sampled by POAM have been
exposed to more sunlight, and thus more chemical processing leading to O3 loss, than air over Ny
Ǻlesund, even if they are at similar equivalent latitudes. In two cases, this is compounded by an
extrapolation of the PV/O3 curve beyond the range of PV sampled by POAM. This comparison
thus emphasizes the need for caution when interpreting the proxy O3 results in regions where
geographic gradients due to photochemistry are significant, particularly if the proxy is derived
from extrapolations beyond the sampled range of PV. The other notable disagreement occurs at
450 K near day 90, where proxy O3 is significantly higher than sonde O3. At this time, POAM
was sampling primarily on the edge of the vortex, and the mapping thus failed to capture the
morphology of the substantial O3 loss that occurred at higher equivalent latitudes. Furthermore,
the vortex was evolving rapidly at this time, increasing the uncertainty in the PV mapping
analysis. Note, however, that the increase in O3 near day 80 (20 March), as the vortex shifted
away from Ny Ǻlesund, was captured fairly well by the PV/O3 analysis.
The comparisons presented here show that overall, the proxy O3 profiles are in excellent
agreement with correlative observations, and can be used extensively for scientific
investigations. Caution is required, however, when there are significant errors in our knowledge
of the PV/q fields, or in our knowledge of the PV/O3 relation. The latter error, which is the most
prevalent, can arise for a number of different reasons. First, this will often result when the range
of PV sampled by the instrument is too narrow to adequately extrapolate outside this range.
Second, the PV/O3 relation may not follow closely enough the quadratic curve that we use to
define it, instead being better defined by another analytic form. Third, if the PV/q field is
changing rapidly (e.g., through diabatic processes), the PV/O3 relation defined by a seven-day
period will average over these PV variations. Fourth, it may simply be inappropriate to assume a
single (quadratic or otherwise) PV/O3 relation. This will be the case, for instance, when O3 is in
photochemical control, and is thus not expected to strictly correlate with PV. For example, we
expect the analysis to work less well in the middle to upper stratosphere in summer, and also in
the presence of the anticyclonic low O3 pockets that occur in the winter middle stratosphere
[Manney et al., 1995b; Nair et al., 1998; Morris et al., 1998]. For the latter situation, there may
be a perfectly valid quadratic that describes the PV/O3 relation everywhere except near the low
O3 pockets, where the proxy O3 would overestimate the observed O3. Note, however, that even
in the presence of chemical changes, such as polar O3 loss, the mapping technique will produce
valid results as long as O3 and PV are well-correlated within the time period of the analysis, and

C.E. Randall et al., POAM III Ozone during SOLVE

10

as long as the observations fulfill the other requirements such as adequate sampling of the PV/q
field (e.g., Figure 4).
5. Application of the Method
The results above confirm the validity of the PV mapping technique for deriving proxy O3 values
from the POAM III data at most times and locations during the NH winter poleward of 30°N.
These results can be used for a variety of purposes, and are particularly relevant in times (such as
the SOLVE winter) when high vertical resolution, global, O3 measurements are lacking. In
general, using the proxy O3 will improve analyses that rely on climatological profiles for lack of
actual data. For instance, the proxy O3 data have been used to initialize calculations for
investigations of O3 photochemical loss during the winter [Hoppel et al., this issue], and can be
used to improve satellite data retrievals which require a priori O3 profiles, such as those from the
TOMS instrument. When combined with data from other instruments such as HALOE or SAGE,
the analysis can be improved at the lower latitudes. We are currently using this strategy as one
means of generating global stratospheric O3 fields for inclusion in the Navy’s operational
weather prediction system (NOGAPS [Hogan and Rosmund, 1991]). In this section, we describe
the application of POAM PV mapping results to calculations of photolysis rates relevant to
SOLVE investigations.
One of the primary goals of the SOLVE campaign was to investigate O3 loss processes using the
numerous measurements of stratospheric species along the DC-8 and ER-2 flight paths. To put
those measurements into the context of a detailed photochemistry scheme requires knowledge of
the rate coefficients for the relevant photolytic reactions; i.e., the j-values. The j-values can be
calculated most directly if one measures the solar actinic flux that is transmitted through the
atmosphere to the aircraft location from all directions, at the appropriate wavelengths. This is
accomplished by the Scanning Actinic Flux Spectroradiometer (SAFS) instruments [Shetter and
Müller, 1999] on the DC-8 for fifteen molecules of interest. A more indirect determination of
the j-values is to measure the O3 column above the aircraft, and to use this information to deduce
the transmission through the atmosphere of the radiation responsible for the photolysis. The
principal sources of overhead O3 information during previous ER-2 campaigns have been the insitu Composition and Photodissociative Flux Measurement (CPFM) [McElroy, 1995], and the
TOMS satellite measurements (from which a climatological tropospheric column must be
subtracted) [McPeters et al., 1998]. A drawback to using these measurements, however, is that
they become much less reliable or unavailable at high solar zenith angles (SZAs). Thus,
accurately determining O3 columns over the ER-2 at high SZAs was one of the primary
motivating factors for applying the PV mapping technique to the POAM III data.
The POAM III reconstructed O3 fields have been used to create consistent j-value data sets for
the entire campaign, independent of limitations at high SZAs. This has been done independently
by two different groups, at the Applied Physics Laboratory (APL) and at the Jet Propulsion
Laboratory (JPL). In order to calculate accurate j-values, it is necessary that the reconstructed O3
at and above the aircraft flight track be accurate. The validation discussion above showed that
statistically, the reconstructed profiles interpolated to ozonesonde and HALOE measurement
locations compared very well to the observations. We investigated the reliability of the PV
mapping results for determining O3 at the aircraft location by comparing the proxy O3 to in situ
O3 measurements from the ozone photometer onboard the ER-2 [Proffit and McLaughlin, 1983;

C.E. Randall et al., POAM III Ozone during SOLVE

11

Richard et al., 2001]. For these comparisons, some representative examples of which are shown
in Plate 10, the proxy O3 was interpolated horizontally and vertically to the ER-2 flight tracks.
Plate 10 reveals excellent agreement between the proxy O3 and ER-2 observations, even during
the rapid altitude changes (dips) of the aircraft, as expected from the comparisons shown above.
To illustrate the reliability of the j-value calculations themselves, Figure 5 compares the APL
calculations [Swartz et al., 1999] appropriate for the DC-8 flight on 3 March 2000 to the j-values
derived using actinic flux measurements from the SAFS measurement, for the O3 → O(1D)
reaction. The j-values derived from the POAM reconstruction analysis match those derived from
the SAFS measurements quite well, generally agreeing to within 10% or better. Also shown are
the j-values determined using TOMS measurements of total ozone. These also match the SAFS
determinations well, although not quite as well as the POAM-based calculations for this
particular flight. It should be noted that for the TOMS calculations, climatological O3 profiles
were scaled to the TOMS total column, so that the O3 column below the DC-8 could be
subtracted off. Likewise, climatological profiles were used to extend the POAM measurements
down to the DC-8 flight altitude. When averaged over the entire campaign, the APL(TOMS)
calculations of j(O3) at SZA>85° exceeded determinations based on the SAFS data by ~13±3%.
The APL(POAM) calculations on average agreed better with the SAFS determinations,
exceeding them by only 3±2%. With regard to these results, however, it is important to note that
the TOMS total O3 retrieval has not been optimized for the high latitudes and SZAs encountered
during the SOLVE campaign. At lower SZAs, APL(TOMS) and APL(POAM) provided more
comparable levels of agreement with SAFS.
Plate 11 demonstrates the utility of the j-value calculations based on the POAM reconstruction
for ER-2 flights. In this figure we compare JPL j-value calculations for the photolysis of Cl2O2
based on column O3 determined from the POAM reconstruction and the CPFM measurements.
We show two different derivations for the POAM reconstruction, including calculations based
solely on the POAM proxy data, as well as calculations based on the proxy data scaled to the
TOMS total column O3. For the latter case, the reconstructed O3 profiles are scaled such that the
total column abundance of the proxy profile, which is extended below the POAM measurements
with a climatological profile, matches the TOMS total column. For this case, the proxy, scaled
proxy and CPFM j-value determinations match quite well throughout most of the flight.
However, at the highest SZAs, between about 11.5 and 14 GMT, the CPFM values are
unavailable. Thus, the proxy determination serves to fill in this time gap. Similar results are
seen for other flights and other j-values: in general, there is good agreement between estimates
of overhead ozone, and thus j-values, based on the POAM reconstruction and the CPFM data, for
SZA less than about 85°. For the largest SZA, however, the reconstruction with POAM data
provides a more accurate method of determining j-values than simply relying on climatological
data, as has been the practice in the past.
6. Summary
For each day during the 1999-2000 winter, we have used the relation between PV and O3 mixing
ratio to calculate semi-global (NH only) three-dimensional O3 fields. The work presented here
represents the first demonstration of the PV mapping technique applied to solar occultation
measurements at high equivalent latitudes over the course of an entire winter. We have
extensively compared the proxy O3 so generated to profiles obtained from ozonesondes and

C.E. Randall et al., POAM III Ozone during SOLVE

12

HALOE. Comparisons were made by interpolating the proxy O3 horizontally and vertically to
the correlative measurement locations. These comparisons included locations both well north
and well south of the actual POAM III measurement locations, and both outside and inside the
polar vortex. On average, the proxy O3 agrees with the correlative observations to better than
~5%, at potential temperatures below about 900 K, and at latitudes above about 30°N (i.e., in the
region where O3 is dynamically controlled). These results demonstrate the reliability of the
reconstructed global fields using the PV mapping technique. The POAM III proxy ozone fields
have been used to estimate O3 profiles for the computation of photolysis rates along the SOLVE
aircraft flight tracks.
Finally, Plate 12 shows the proxy fields at 500 K throughout the SOLVE winter in 5-day
increments. This figure graphically illustrates the changing ozone field as dynamical and
chemical processes perturb the polar region over the course of the winter. Air descending in and
on the edge of the vortex causes O3 mixing ratios to increase at 500 K, and is responsible for the
ring at the edge of the vortex that is so prominent in most of the panels. Persistent chemical O3
loss inside the vortex begins in late January at POAM latitudes, and continues through March, as
indicated by the transition toward the blue end of the color scale. Toward the end of March the
vortex begins to break down at 500 K, and the two pockets of low ozone on 21 March coincide
with the two branches of the vortex at this time. Even as late as 20 April, there are persistently
low O3 mixing ratios coinciding with the highest PV values, presumably remnants of the low-O3
regions which formed during the winter inside the vortex. As noted above, detailed
interpretation of the proxy fields requires caution when mechanisms responsible for ozone
variability depend on factors other than equivalent latitude. In spite of this caveat, and other
potential errors discussed above, the proxy fields illustrate the versatility and applicability of the
solar occultation observations for O3 loss investigations. Furthermore, by presenting a 3D
picture of the changing Arctic O3, they provide information easily accessible to the general
public. The proxy fields present a qualitative picture of semi-global, vertically resolved O3
variations throughout the winter in the lower stratosphere, a picture that is not directly available
from any of the currently operational satellite instruments. This method is easily extended to
other winters measured by POAM II and POAM III, and will be applicable to measurements
from SAGE III once it is launched. Ideally, POAM III data will be combined with HALOE or
SAGE II to improve results at the lower latitudes, and with future SAGE III measurements to
improve PV-sampling at the highest latitudes.

C.E. Randall et al., POAM III Ozone during SOLVE

13

Acknowledgements
This work was supported by NASA grant N00014-97-1-G018 and by the NASA Scientific Data
Purchase program through contract # NAS13-99031. We thank G. Manney for helpful
discussions, R. Shetter for providing the SAFS data, and M. Rex for providing easy access to
ozonesonde data during the SOLVE campaign. Version 3.0 POAM III data can be obtained
from the NASA Langley Research Center EOSDIS Distributed Active Archive Center. We
would like to acknowledge the following providers of ozonesonde data: V. Dorokhov (Central
Aerological Observatory, Russia), M. Gil (Icelandic Meteorological Office and Instituto
Nacional de Tecnica Aeroespacial), I. S. Mikkelsen (Danish Meteorological Institute;
Jaegersborg, Scoresbysund, Thule), Z. Litynska (IMWM, Legionowo), R. Stubi
(Meteoswiss/Payerne), T. Turunen (Finnish Meteorological Institute, Sodankyla), and G.
Vaughan (University of Wales, Aberystwyth).

C.E. Randall et al., POAM III Ozone during SOLVE

14

References
Allaart, M.A.F., H. Kelder, and L.C. Heijboer, On the relation between ozone and potential
vorticity, Geophys. Res. Lett. 20, 811-814, 1993.
Bevilacqua, R.M., et al., POAM III PSC observations during the 1999/2000 northern hemisphere
winter, J. Geophys. Res., 2001 (this issue).
Butchart, N. and E.E. Remsberg, The area of the stratospheric polar vortex as a diagnostic for
tracer transport on an isentropic surface, J. Atmos. Sci. 43, 1319-1339, 1986.
Garcia, R.R., and S. Solomon, The effect of breaking gravity waves on the dynamics and
chemical composition of the mesosphere and lower thermosphere, J. Geophys. Res. 90, 38503868, 1985.
Haynes, P. and E. Shuckburgh, Effective diffusivity as a diagnostic of atmospheric transport, 1.
Stratosphere, J. Geophys. Res. 105, 22,777-22,794, 2000.
Hogan, T. and T. Rosmund, The description of the Navy Operational Global Atmospheric
Prediction Systems spectral forecast model, Mon. Weather Rev. 119, 1786-1815, 1991.
Hoppel, K.W., et al., POAM III observations of Arctic ozone loss for the 1999/2000 winter, J.
Geophys. Res., 2001 (this issue).
Lait, L.R., An alternative form for potential vorticity, J. Atmos. Sci. 51, 1754-1759, 1994.
Lait, L.R., et al., Reconstruction of O3 and N2O fields from ER-2, DC-8, and balloon
observations, Geophys. Res. Lett. 17, 521-524, 1990.
Leovy, C.B., C-R. Sun, M.H. Hitchman, E.E. Remsberg, J.M. Russell, III, L.L. Gordley, J.C.
Gille, and L.V. Lyjak, Transport of ozone in the middle stratosphere: Evidence for planetary
wave breaking, J. Atmos. Sci. 42, 230-244, 1985.
Lucke, R.L., et al., The Polar Ozone and Aerosol Measurement (POAM) III instrument and early
validation results, J. Geophys. Res. 104, 18757-18799, 1999.
Lumpe, J.D., et al., Comparison of POAM III ozone measurements with correlative aircraft and
balloon data during SOLVE, J. Geophys. Res., 2001 (this issue).
Manney, G.L., et al., Comparison of satellite ozone observations in coincident air masses in early
November 1994, J. Geophys. Res. 106, 9923-9943, 2001.
Manney, G.L., and J.L. Sabutis, Development of the polar vortex in the 1999-2000 Arctic winter
stratosphere, Geophys. Res. Lett. 27, 2589-2592, 2000.
Manney, G.L., H.A. Michelsen, M.L. Santee, M.R. Gunson, F.W. Irion, A.E. Roche, and N.J.
Livesey, Polar vortex dynamics during spring and fall diagnosed using trace gas observations

C.E. Randall et al., POAM III Ozone during SOLVE

15

from the Atmospheric Trace Molecule Spectroscopy instrument, J. Geophys. Res. 104, 18,84118,866, 1999.
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, 5797-5814, 1998.
Manney, G.L., L. Froidevaux, J.W. Waters and R.W. Zurek, Evolution of microwave limb
sounder ozone and the polar vortex during winter, J. Geophys. Res. 100, 2953-2972, 1995a.
Manney, G.L., et al., Formation of low ozone pockets in the middle stratosphere anticyclone
during winter, J. Geophys. Res. 100, 13,939-13,950, 1995b.
McElroy, C. T., A spectroradiometer for the measurement of direct and scattered solar irradiance
from on-board the NASA ER-2 high-altitude research aircraft, Geophys. Res. Lett., 22, 13611364, 1995.
McPeters, R., et al., Earth Probe Total Ozone Mapping Spectrometer (TOMS) data products
user's guide, NASA/TP-1998-206895, NASA, Goddard Space Flight Center, Greenbelt,
Maryland, 1998.
Morris, G.A., S.R. Kawa, A.R. Douglass, M.R. Schoeberl, L. Froidevaux, and J. Waters, Lowozone pockets explained, J. Geophys. Res. 103, 3599-3610, 1998.
Nair, H., M. Allen, L. Froidevaux, and R.W. Zurek, Localized rapid ozone loss in the northern
winter stratosphere: An analysis of UARS observations, J. Geophys. Res. 103, 1555-1571, 1998.
Nash, E.R., P.A. Newman, J.E. Rosenfield, and M.R. Schoeberl, An objective determination of
the polar vortex using Ertel’s potential vorticity, J. Geophys. Res. 101, 9471-9478, 1996.
Proffitt, M. H., and R. J. McLaughlin, Fast-response dual-beam UV absorption ozone
photometer suitable for use on stratospheric balloons, Rev. Sci. Instrum., 54, 1719-1728, 1983.
Randall, C.E., et al., Preliminary results from POAM II: Stratospheric ozone at high northern
latitudes, Geophys. Res. Lett. 22, 2733-2736, 1995.
Redaelli, G., et al., UARS MLS O3 soundings compared with lidar measurements using the
conservative coordinates reconstruction technique, Geophys. Res. Lett. 21, 1535-1538, 1994.
Richard, E.C., et al., Severe chemical ozone loss inside the Arctic polar vortex during winter
1999-2000 inferred from in-situ airborne measurements, Geophys. Res. Lett., 28, 2197-2200,
2001.
Santee, M.L., G.L. Manney, N.J. Livesey, and J.W. Waters, UARS Microwave Limb Sounder
observations of denitrification and ozone loss in the 2000 Arctic winter, Geophys. Res. Lett. 27,
3213-3216, 2000.

C.E. Randall et al., POAM III Ozone during SOLVE

16

Schoeberl, M.R., et al., Reconstruction of the constituent distribution and trends in the Antarctic
polar vortex from ER-2 flight observations, J. Geophys. Res. 94, 16,815-16,845, 1989.
Shetter, R. E., and M. Müller, Photolysis frequency measurements using actinic flux
spectroradiometry during the PEM-Tropics mission: Instrumentation description and some
results, J. Geophys. Res., 104, 5647-5661, 1999.
Sinnhuber, B.-M., et al., Large loss of total ozone during the Arctic winter of 1999/2000,
Geophys. Res. Lett. 27, 3473-3476, 2000.
Swartz, W. H., S. A. Lloyd, T. L. Kusterer, D. E. Anderson, C. T. McElroy, and C. Midwinter, A
sensitivity study of photolysis rate coefficients during POLARIS, J. Geophys. Res., 104, 26,72526,735, 1999.
Swinbank, R., and A. O’Neill, A stratosphere-troposphere data assimilation system, Mon.
Weather Rev., 122, 686-702, 1994.

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17

Figures

Figure 1. Latitudes of the NH POAM measurements from 1 November 1999 through 30 April
2000.

Plate 1. Potential vorticity of the NH POAM measurements from 1 November 1999 through 30
April 2000. The inner and outer boundaries of the vortex edge region are denoted in blue and
red, respectively.

C.E. Randall et al., POAM III Ozone during SOLVE

18

Plate 2. Representative contour map made from POAM III O3 measurements from 24-26
December 1999, at a latitude of 63.5°. The temperature (K) and modified PV (10-6 K m2 kg-1 s-1)
[Lait, 1994] derived from UKMO data are superimposed as solid and dotted lines, respectively.
POAM profile locations are given by the red marks above the top horizontal axis.

Plate 3. Daily average POAM III O3 mixing ratios inside the vortex (red), on the edge of the
vortex (blue) and outside the vortex (black) from 1 December 1999 through 31 March 2000, at
the potential temperatures noted in each panel.

C.E. Randall et al., POAM III Ozone during SOLVE

19

Plate 4. (a) POAM III O3 mixing ratios at 650 K from 29 December through 4 January 2000
(red asterisks), plotted against the UKMO PV interpolated in time and space to the POAM
measurement locations. Superimposed is a quadratic fit to the data. (b) UKMO PV field on 1
January 2000 on the 650 K potential temperature surface. Latitude lines are drawn at 30°N and
60°N, and East longitudes increase counterclockwise from 0° on the right. POAM measurement
locations from 29 December 1999 to 4 January 2000 are denoted by the black dots. Solid
(dashed) white contours denote the geographic boundaries inside (outside) of which the PV
values were higher (lower) than those sampled by POAM. (c) The proxy O3 field for 1 January
2000, calculated as described in the text. The color scales refer to PV (10-6 m2 kg-1 s-1 K) in (b)
and to O3 mixing ratio (ppmv) in (c).

Plate 5. As in Plate 4a, but for the 500 K potential temperature level, for the days noted in each
panel.

C.E. Randall et al., POAM III Ozone during SOLVE

20

Plate 6. As in Plate 4c, but corresponding to the plots in Plate 5.

Plate 7. Representative examples of individual profile comparisons between the proxy O3
interpolated to the sonde location (red, +) and the sonde profile (black) at Ny Ålesund (Ny),
Hohenpeissenberg (Ho), and Izana (Iz), on the dates (yymmdd) shown in each panel.

C.E. Randall et al., POAM III Ozone during SOLVE

21

Plate 8. Statistical results for all ozonesonde comparisons between 22 November 1999 and 1
February 2000 shown as the average difference profile (solid line with dots) and the standard
deviation of the mean (dotted lines), with the individual differences overplotted as red points
(black x marks denote individual differences where the proxy O3 was derived from an
extrapolation of the PV/O3 quadratic fit beyond the range of PV values actually sampled by
POAM). The number of comparisons included at each potential temperature level is given on
the right vertical axis.

Figure 2. HALOE measurement latitudes in the NH during SOLVE, from late November, 1999
through March, 2000.

C.E. Randall et al., POAM III Ozone during SOLVE

22

Plate 9. Latitude dependence of the differences between HALOE and the proxy O3 for events
noted in Figure 2, at the potential temperature levels denoted in each panel. Comparisons
including proxy O3 derived from extrapolation of the PV/O3 fit beyond the range of PV sampled
by POAM are indicated in black; all other comparisons are indicated in red.

Figure 3. Statistical differences (heavy solid line) for events north of 30°N in the proxy-HALOE
comparisons. Dotted lines are the standard deviation of the distribution. The standard deviations
of the mean are approximately the thickness of the heavy solid line. Dashed lines are plotted at
±10% for guidance.

C.E. Randall et al., POAM III Ozone during SOLVE

23

Figure 4. Evolution of O3 mixing ratios measured by ozonesonde over Ny Ǻlesund (plus
symbols), at the different potential temperature levels noted in each panel, compared to the proxy
O3 derived for the location of this station (open circles). Proxy O3 data derived from
extrapolation of the PV/O3 quadratic fit beyond the range of PV sampled by POAM are denoted
by the filled circles.

Plate 10. Comparison of the reconstructed O3 interpolated to the ER-2 flight location (red) and
the in-situ measurements from the ozone photometer onboard the ER-2 (black) during the flight
on the date (yymmdd) noted in each panel. The sharp dips in the O3 measurements correspond to
rapid altitude changes by the ER-2.

C.E. Randall et al., POAM III Ozone during SOLVE

24

Figure 5. Comparison of O3 photolysis j-values determined by the APL group based on the
POAM reconstructed O3 (solid) and the TOMS total column measurements (dotted) to
calculations based on SAFS actinic flux observations (+) for the DC-8 flight on 3 March 2000.
The SZA variation along the flight track is denoted by the dashed line.

Plate 11. Comparison of Cl2O2 photolysis j-values determined by the JPL group based on the
POAM reconstructed O3 (green) and the POAM reconstructed O3 scaled to the TOMS
measurements (black), to calculations based on the CPFM data (red) for the ER-2 flight on 26
February 2000. The SZAs of the measurements are noted in the top panel.

C.E. Randall et al., POAM III Ozone during SOLVE

25

Plate 12. Proxy O3 maps on the 500 K potential temperature level, as in Plate 6, for the dates
shown in each panel. Note that the final panel succeeds the previous one by one month.

C.E. Randall et al., POAM III Ozone during SOLVE

26

Table 1. Ozonesonde stations used in the statistical validation analysis. The number of
comparisons from each station that were included in the results shown in Plate 8 is listed in the
last column. Profiles were obtained between 22 November 1999 and 1 February 2000.
Station
Aberystwyth
Alert
Andoya
Churchill
De Bilt
Stonyplain
Eureka
Gardermoen
Goose Bay
Hohenpeissenberg
Izana
Jaegersborg
Jokioinen
Lerwick
Lindenberg
Legionowo
Ny Ǻlesund
Orland
Payerne
Prague
Keflavik
Resolute
Salekhard
Scoresbysund
Sodankyla
Thule
Uccle
Valentia
Yakutsk

Latitude
52.40
82.50
69.30
58.74
52.10
53.55
79.99
60.11
53.18
47.80
28.46
55.77
60.80
60.13
52.13
52.40
78.93
63.42
46.80
50.02
63.97
74.71
66.70
70.50
67.39
76.53
50.80
51.93
62.03

Longitude
-4.10
-62.3
16.11
-94.00
5.18
-114.
-85.9
11.04
-60.2
11.00
-16.2
12.53
23.50
-1.18
14.07
20.97
11.95
9.24
6.95
14.45
-22.60
-94.90
66.70
-22.00
26.65
-68.70
4.35
-10.20
129.60
Total:

C.E. Randall et al., POAM III Ozone during SOLVE

# Comparisons
5
8
6
6
7
5
17
3
4
27
2
1
12
22
6
15
29
14
30
12
4
12
10
10
19
5
23
6
5
325