Title: A new method for describing long-term changes in total ozone

Authors: HARRIS, J.M., S.J. OLTMANS, P.P. TANS, R.D. EVANS, and D.L.
QUINCY

Source: Geophysical Research Letters,28, 24, 4535-4538, 2001

Document Type: Journal Article

Abstract: A new method for describing long-term changes in total ozone
was developed so that variations on time scales greater than that of the
QBO may be examined. The technique fits a flexible tendency curve to
total ozone data after explained variations have been removed. The
derivative of the tendency curve is the growth rate curve. The average
along this curve is comparable to total ozone trends reported in the
past. Statistical uncertainty of the growth rate is determined using
bootstrap techniques. Dobson column ozone measurements with long-term
(30+ years) records from the NOAA/CMDL Cooperative Dobson Network were
analyzed. Total ozone decreases ranged from 1-2%/decade since the 1960s
and from 2-4%/decade since 1979 at all sites except Mauna Loa where
results were not significant. The tendency curves indicate that the
total ozone decline began in the 1970s and that there are no clear signs
of recovery as of the end of 2000.

Title: Evidence for slowdown in stratospheric ozone loss: First stage of
ozone recovery

Author(s): Newchurch MJ, Yang ES, Cunnold DM, Reinsel GC, Zawodny JM,
Russell JM

Source: JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 108 (D16): Art. No.
4507 AUG 23 2003

Abstract: Global ozone trends derived from the Stratospheric Aerosol and
Gas Experiment I and II (SAGE I/II) combined with the more recent
Halogen Occultation Experiment (HALOE) observations provide evidence of
a slowdown in stratospheric ozone losses since 1997. This evidence is
quantified by the cumulative sum of residual differences from the
predicted linear trend. The cumulative residuals indicate that the rate
of ozone loss at 35 45 km altitudes globally has diminished. These
changes in loss rates are consistent with the slowdown of total
stratospheric chlorine increases characterized by HALOE HCl
measurements. These changes in the ozone loss rates in the upper
stratosphere are significant and constitute the first stage of a
recovery of the ozone layer.

Author Keywords: stratospheric ozone trends; CFCs; Montreal Protocol

Title: Trends of ozone in the troposphere

Authors: OLTMANS, S.J., A.S. Lefohn, H.E. Scheel, J.M. HARRIS, H. Levy
II, I.E. Galbally, E.-G. Brunke, C.P. Meyer, J.A. LATHROP, B.J. JOHNSON,
D.S. Shadwick, E. Cuevas, F.J. Schmidlin, D.W. Tarasick, H. Claude, J.B.
Kerr, O. Uchino, and V. Mohnen

Source: Geophysical Research Letters,25, 2, 139-142, 1998

Document Type: Journal Article

Abstract: Using a set of selected surface ozone (nine stations) and
ozone vertical profile measurements (from six stations), we have
documented changes in tropospheric ozone at a number of locations. From
two stations at high northern hemisphere (NH) latitudes there has been a
significant decline in ozone amounts throughout the troposphere since
the early 1980s. At midlatitudes of the NH where data are the most
abundant, on the other hand, important regional differences prevail. The
two stations in the eastern United States show that changes in ozone
concentrations since the early 1970s have been relatively small. At the
two sites in Europe, however, ozone amounts increased rapidly into the
mid-1980s, but have increased less rapidly (or in some places not at
all) since then. Increases at the Japanese ozonesonde station have been
largest in the lower troposphere, but have slowed in the recent decade.
The tropics are sparsely sampled but do not show significant changes.
Small increases are suggested at southern hemisphere (SH) midlatitudes
by the two surface data records. In Antarctica large declines in the
ozone concentration are noted in the South Pole data, and like those at
high latitudes of the NH, seem to parallel the large decreases in the
stratosphere.

Title: Detecting the recovery of total column ozone

Authors: Weatherhead, E.C., G.C. Reinsel, G.C. Tiao, C.H. Jackman, L.
Bishop, S.M. Hollandsworth-Frith, J. DeLuisi, T. Keller, S.J. OLTMANS,
E.L. Fleming, D.J. Wuebbles, J.B. Kerr, A.J. Miller, J. Herman, R.
McPeters, R.M. Nagatani, and J.E. Frederick

Source: Journal of Geophysical Research,105, D17, 22,201-22,210, 2000

Document Type: Journal Article

Abstract: International agreements for the limitation of ozone-depleting
substances have already resulted in decreases in concentrations of some
of these chemicals in the troposphere. Full compliance and understanding
of all factors contributing to ozone depletion are still uncertain;
however, reasonable expectations are for a gradual recovery of the ozone
layer over the next 50 years. Because of the complexity of the processes
involved in ozone depletion, it is crucial to detect not just a decrease
in ozone-depleting substances but also a recovery in the ozone layer.
The recovery is likely to be detected in some areas sooner than others
because of natural variability in ozone concentrations. On the basis of
both the magnitude and autocorrelation of the noise from Nimbus 7 Total
Ozone Mapping Spectrometer ozone measurements, estimates of the time
required to detect a fixed trend in ozone at various locations around
the world are presented. Predictions from the Goddard Space Flight
Center (GSFC) two-dimensional chemical model are used to estimate the
time required to detect predicted trends in different areas of the
world. The analysis is based on our current understanding of ozone
chemistry, full compliance with the Montreal Protocol and its
amendments, and no intervening factors, such as major volcanic eruptions
or enhanced stratospheric cooling. The results indicate that recovery of
total column ozone is likely to be detected earliest in the Southern
Hemisphere near New Zealand, southern Africa, and the southern South
America and that the range of time expected to detect recovery for most
regions of the world is between 15 and 45 years. Should the recovery be
slower than predicted by the GSFC model, owing, for instance, to the
effect of greenhouse gas emissions, or should measurement sites be
perturbed, even longer times would be needed for detection

Title: Trends in the vertical distribution of ozone: A comparison of two
analyses of ozonesonde data

Author(s): Logan JA, Megretskaia IA, Miller AJ, Tiao GC, Choi D, Zhang
L, Stolarski RS, Labow GJ, Hollandsworth SM, Bodeker GE, Claude H, De
Muer D, Kerr JB, Tarasick DW, Oltmans SJ, Johnson B, Schmidlin F,
Staehelin J, Viatte P, Uchino O

Source: JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 104 (D21):
26373-26399 NOV 20 1999

Abstract: We present the results of two independent analyses of trends
in the vertical distribution of ozone. For most of the ozonesonde
stations we use data that were recently reevaluated and reprocessed to
improve their quality and internal consistency. The two analyses give
similar results for trends in ozone. We attribute differences in results
primarily to differences in data selection criteria, rather than in
statistical trend models. We find significant decreases in stratospheric
ozone at all stations in middle and high latitudes of the Northern
Hemisphere from 1970 to 1996, with the largest decreases located between
12 and 2i km, and trends of -3 to -10 %/decade near 17 km. The decreases
are largest at the Canadian and the most northerly Japanese station and
are smallest at the European stations and at Wallops Island. The mean
midlatitude trend is largest, -7 %/decade, from 12 to 18 km for
1970-1996, and the decrease in ozone is significant from 10.5 to 25 km.
For 1980-1996, the decrease is more negative by 1-2 %/decade, with a
maximum trend of -9%/decade in the lowermost stratosphere. The trends
vary seasonally from about 10 to 17 km, with largest ozone decreases in
winter and spring. Trends in tropospheric ozone are highly variable and
depend on the region. There are decreases or zero trends at the Canadian
stations for 1970-1996, and decreases of -2 to -8 %/decade for the
mid-troposphere for 1980-1996; the three European stations show
increases for 1970-1996, but trends are close to zero for two stations
for 1980-1996 and positive for one; there are increases in ozone for the
three Japanese stations for 1970-1996, but trends are either positive or
zero for 1980-1996. The United States stations show zero or slightly
negative trends in tropospheric ozone after 1980. It is not possible to
define reliably a mean tropospheric ozone trend for northern
midlatitudes, given the small number of stations and the large
variability in trends. The integrated column trends derived from the
sonde data are consistent with trends derived from both surface-based
and satellite measurements of the ozone column.

Title: Tropospheric Ozone Over the North Pacific From Ozonesonde
Observations

Authors: Oltmans, S. J. , B. J. Johnson, J. M. Harris, A. M. Thompson,
H. Y. Liu, H. Vömel, C. Y. Chan, T. Fujimoto, V. G. Brackett, W. L.
Chang, J.-P. Chen, J. H. Kim, L. Y. Chan, and H.-W. Chang.

Source: Journal Geophysical Research,109, 10.1029/2003JD003466, 2004

Document Type:

Abstract: \[ 1\] As part of the Transport and Chemical Evolution over
the Pacific (TRACE-P) mission, ozonesondes were used to make ozone
vertical profile measurements at nine locations in the North Pacific. At
most of the sites there is a multiyear record of observations. From
locations in the western Pacific ( Hong Kong; Taipei; Jeju Island,
Korea; and Naha, Kagoshima, Tsukuba, and Sapporo, Japan), a site in the
central Pacific ( Hilo, Hawaii), and a site on the west coast of the
United States ( Trinidad Head, California) both a seasonal and event
specific picture of tropospheric ozone over the North Pacific emerges.
Ozone profiles over the North Pacific generally show a prominent spring
maximum throughout the troposphere. This maximum is tied to the location
of the jet stream and its influence on stratosphere-troposphere exchange
and the increase in photochemical ozone production through the spring.
Prominent layers of enhanced ozone in the middle and upper troposphere
north of about 30degrees N seem to be more closely tied to stratospheric
intrusions while biomass burning leads to layers of enhanced ozone in
the lower and upper troposphere at Hong Kong (22 degreesN) and Taipei
(25 degreesN). The lower free tropospheric layers at Hong Kong are
associated with burning in SE Asia, but the upper layer may be
associated with either equatorial Northern Hemisphere burning in Africa
or SE Asian biomass burning. In the boundary layer at Taipei very high
mixing ratios of ozone were observed that result from pollution
transport from China in the spring and local urban pollution during the
summer. At the ozonesonde site near Tokyo ( Tsukuba, 36 degreesN) very
large enhancements of ozone are seen in the boundary layer in the summer
that are characteristic of urban air pollution. At sites in the mid and
eastern Pacific the signature of transport of polluted air from Asia is
not readily identifiable from the ozonesonde profile. This is likely due
to the more subtle signal and the fact that from the ozone profile and
meteorological data by themselves it is difficult to identify such a
signal. During the TRACE-P intensive campaign period (February - April
2001), tropospheric ozone amounts were generally typical of those seen
in the long-term records of the stations with multiyear soundings. The
exception was the upper troposphere over Hong Kong and Taipei where
ozone amounts were lower in 2001.