scholarly journals Spatial, temporal, and vertical variability of polar stratospheric ozone loss in the Arctic winters 2004/2005–2009/2010

2010 ◽  
Vol 10 (20) ◽  
pp. 9915-9930 ◽  
Author(s):  
J. Kuttippurath ◽  
S. Godin-Beekmann ◽  
F. Lefèvre ◽  
F. Goutail
Keyword(s):  
Transport Model ◽  
Stratospheric Ozone ◽  
Polar Vortex ◽  
The Arctic ◽  
Model Calculations ◽  
Ozone Loss ◽  
Vertical Range ◽  
Column Ozone ◽  
Catalytic Cycles ◽  
Good Agreement

Abstract. The polar stratospheric ozone loss during the Arctic winters 2004/2005–2009/2010 is investigated by using high resolution simulations from the chemical transport model Mimosa-Chim and observations from Aura Microwave Limb Sounder (MLS), by applying the passive tracer technique. The winter 2004/2005 shows the coldest temperatures, highest area of polar stratospheric clouds and strongest chlorine activation in 2004/2005–2009/2010. The ozone loss diagnosed from both simulations and measurements inside the polar vortex at 475 K ranges from 0.7 ppmv in the warm winter 2005/2006 to 1.5–1.7 ppmv in the cold winter 2004/2005. Halogenated (chlorine and bromine) catalytic cycles contribute to 75–90% of the ozone loss at this level. At 675 K the lowest loss of 0.3–0.5 ppmv is computed in 2008/2009, and the highest loss of 1.3 ppmv is estimated in 2006/2007 by the model and in 2004/2005 by MLS. Most of the ozone loss (60–75%) at this level results from nitrogen catalytic cycles rather than halogen cycles. At both 475 and 675 K levels the simulated ozone and ozone loss evolution inside the vortex is in reasonably good agreement with the MLS observations. The ozone partial column loss in 350–850 K deduced from the model calculations at the MLS sampling locations inside the polar vortex ranges between 43 DU in 2005/2006 and 109 DU in 2004/2005, while those derived from the MLS observations range between 26 DU and 115 DU for the same winters. The partial column ozone depletion derived in that vertical range is larger than that estimated in 350–550 K by 19±7 DU on average, mainly due to NOx chemistry. The column ozone loss estimates from both Mimosa-Chim and MLS in 350–850 K are generally in good agreement with those derived from ground-based ultraviolet-visible spectrometer total ozone observations for the respective winters, except in 2010.

scholarly journals Spatial, temporal, and vertical variability of polar stratospheric ozone loss in the Arctic winters 2004/05–2009/10

2010 ◽  
Vol 10 (6) ◽  
pp. 14675-14711
Author(s):  
J. Kuttippurath ◽  
S. Godin-Beekmann ◽  
F. Lefèvre ◽  
F. Goutail
Keyword(s):  
Transport Model ◽  
Stratospheric Ozone ◽  
Polar Vortex ◽  
Ultra Violet ◽  
The Arctic ◽  
Chemical Transport Model ◽  
Model Calculations ◽  
Ozone Loss ◽  
Catalytic Cycles ◽  
Good Agreement

Abstract. The stratospheric ozone loss during the Arctic winters 2004/05–2009/10 is investigated by using high resolution simulations from the chemical transport model Mimosa-Chim and observations from Microwave Limb Sounder (MLS) on Aura by the passive tracer technique. The winter 2004/05 was the coldest of the series with strongest chlorine activation. The ozone loss diagnosed from both model and measurements inside the polar vortex at 475 K ranges from ~1–0.7 ppmv in the warm winter 2005/06 to 1.7 ppmv in the cold winter 2004/05. Halogenated (chlorine and bromine) catalytic cycles contribute to 75–90% of the accumulated ozone loss at this level. At 675 K the lowest loss of ~0.4 ppmv is computed in 2008/09 from both simulations and observations and, the highest loss is estimated in 2006/07 by the model (1.3 ppmv) and in 2004/05 by MLS (1.5 ppmv). Most of the ozone loss (60–75%) at this level results from cycles catalysed by nitrogen oxides (NO and NO2) rather than halogens. At both 475 and 675 K levels the simulated ozone evolution inside the polar vortex is in reasonably good agreement with the observations. The ozone total column loss deduced from the model calculations at the MLS sampling locations inside the vortex ranges between 40 DU in 2005/06 and 94 DU in 2004/05, while that derived from observations ranges between 37 DU and 111 DU in the same winters. These estimates from both Mimosa-Chim and MLS are in general good agreement with those from the ground-based UV-VIS (ultra violet–visible) ozone loss analyses for the respective winters.

scholarly journals Chemical ozone loss and ozone mini-hole event during the Arctic winter 2010/2011 as observed by SCIAMACHY and GOME-2

2014 ◽  
Vol 14 (7) ◽  
pp. 3247-3276 ◽  
Author(s):  
R. Hommel ◽  
K.-U. Eichmann ◽  
J. Aschmann ◽  
K. Bramstedt ◽  
M. Weber ◽  
...  
Keyword(s):  
Transport Model ◽  
Polar Vortex ◽  
The Arctic ◽  
Optical Absorption Spectroscopy ◽  
Late Winter ◽  
Total Column Ozone ◽  
Bromine Oxide ◽  
Ozone Loss ◽  
Catalytic Cycles ◽  
Total Column

Abstract. Record breaking loss of ozone (O3) in the Arctic stratosphere has been reported in winter–spring 2010/2011. We examine in detail the composition and transformations occurring in the Arctic polar vortex using total column and vertical profile data products for O3, bromine oxide (BrO), nitrogen dioxide (NO2), chlorine dioxide (OClO), and polar stratospheric clouds (PSC) retrieved from measurements made by SCIAMACHY (Scanning Imaging Absorption SpectroMeter for Atmospheric CHartography) on-board Envisat (Environmental Satellite), as well as total column ozone amount, retrieved from the measurements of GOME-2 (Global Ozone Monitoring Experiment) on MetOp-A (Meteorological Experimental Satellite). Similarly we use the retrieved data from DOAS (Differential Optical Absorption Spectroscopy) measurements made in Ny-Ålesund (78.55° N, 11.55° E). A chemical transport model (CTM) has been used to relate and compare Arctic winter–spring conditions in 2011 with those in the previous year. In late winter–spring 2010/2011 the chemical ozone loss in the polar vortex derived from SCIAMACHY observations confirms findings reported elsewhere. More than 70% of O3 was depleted by halogen catalytic cycles between the 425 and 525 K isentropic surfaces, i.e. in the altitude range ~16–20 km. In contrast, during the same period in the previous winter 2009/2010, a typical warm Arctic winter, only slightly more than 20% depletion occurred below 20 km, while 40% of O3 was removed above the 575 K isentrope (~23 km). This loss above 575 K is explained by the catalytic destruction by NOx descending from the mesosphere. In both Arctic winters 2009/2010 and 2010/2011, calculated O3 losses from the CTM are in good agreement to our observations and other model studies. The mid-winter 2011 conditions, prior to the catalytic cycles being fully effective, are also investigated. Surprisingly, a significant loss of O3 around 60%, previously not discussed in detail, is observed in mid-January 2011 below 500 K (~19 km) and sustained for approximately 1 week. The low O3 region had an exceptionally large spatial extent. The situation was caused by two independently evolving tropopause elevations over the Asian continent. Induced adiabatic cooling of the stratosphere favoured the formation of PSC, increased the amount of active chlorine for a short time, and potentially contributed to higher polar ozone loss later in spring.

Record springtime stratospheric ozone depletion at 80°N in 2020

2021 ◽  
Author(s):  
Ramina Alwarda ◽  
Kristof Bognar ◽  
Kimberly Strong ◽  
Martyn Chipperfield ◽  
Sandip Dhomse ◽  
...  
Keyword(s):  
Ozone Depletion ◽  
Transport Model ◽  
Stratospheric Ozone ◽  
Polar Vortex ◽  
The Arctic ◽  
Optical Absorption Spectroscopy ◽  
Chemical Transport Model ◽  
Polar Stratospheric Clouds ◽  
Ozone Loss ◽  
Stratospheric Clouds

<p>The Arctic winter of 2019-2020 was characterized by an unusually persistent polar vortex and temperatures in the lower stratosphere that were consistently below the threshold for the formation of polar stratospheric clouds (PSCs). These conditions led to ozone loss that is comparable to the Antarctic ozone hole. Ground-based measurements from a suite of instruments at the Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka, Canada (80.05°N, 86.42°W) were used to investigate chemical ozone depletion. The vortex was located above Eureka longer than in any previous year in the 20-year dataset and lidar measurements provided evidence of polar stratospheric clouds (PSCs) above Eureka. Additionally, UV-visible zenith-sky Differential Optical Absorption Spectroscopy (DOAS) measurements showed record ozone loss in the 20-year dataset, evidence of denitrification along with the slowest increase of NO<sub>2</sub> during spring, as well as enhanced reactive halogen species (OClO and BrO). Complementary measurements of HCl and ClONO<sub>2</sub> (chlorine reservoir species) from a Fourier transform infrared (FTIR) spectrometer showed unusually low columns that were comparable to 2011, the previous year with significant chemical ozone depletion. Record low values of HNO<sub>3</sub> in the FTIR dataset are in accordance with the evidence of PSCs and a denitrified atmosphere. Estimates of chemical ozone loss were derived using passive ozone from the SLIMCAT offline chemical transport model to account for dynamical contributions to the stratospheric ozone budget.</p>

scholarly journals Stratospheric ozone loss in the Arctic winters between 2005 and 2013 derived with ACE-FTS measurements

2019 ◽  
Vol 19 (1) ◽  
pp. 577-601 ◽  
Author(s):  
Debora Griffin ◽  
Kaley A. Walker ◽  
Ingo Wohltmann ◽  
Sandip S. Dhomse ◽  
Markus Rex ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Stratospheric Ozone ◽  
Polar Vortex ◽  
The Arctic ◽  
Estimation Methods ◽  
Mixing Ratio ◽  
Total Column Ozone ◽  
Ozone Loss ◽  
Column Ozone ◽  
First Time

Abstract. Stratospheric ozone loss inside the Arctic polar vortex for the winters between 2004–2005 and 2012–2013 has been quantified using measurements from the space-borne Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS). For the first time, an evaluation has been performed of six different ozone loss estimation methods based on the same single observational dataset to determine the Arctic ozone loss (mixing ratio loss profiles and the partial-column ozone losses between 380 and 550 K). The methods used are the tracer-tracer correlation, the artificial tracer correlation, the average vortex profile descent, and the passive subtraction with model output from both Lagrangian and Eulerian chemical transport models (CTMs). For the tracer-tracer, the artificial tracer, and the average vortex profile descent approaches, various tracers have been used that are also measured by ACE-FTS. From these seven tracers investigated (CH4, N2O, HF, OCS, CFC-11, CFC-12, and CFC-113), we found that CH4, N2O, HF, and CFC-12 are the most suitable tracers for investigating polar stratospheric ozone depletion with ACE-FTS v3.5. The ozone loss estimates (in terms of the mixing ratio as well as total column ozone) are generally in good agreement between the different methods and among the different tracers. However, using the average vortex profile descent technique typically leads to smaller maximum losses (by approximately 15–30 DU) compared to all other methods. The passive subtraction method using output from CTMs generally results in slightly larger losses compared to the techniques that use ACE-FTS measurements only. The ozone loss computed, using both measurements and models, shows the greatest loss during the 2010–2011 Arctic winter. For that year, our results show that maximum ozone loss (2.1–2.7 ppmv) occurred at 460 K. The estimated partial-column ozone loss inside the polar vortex (between 380 and 550 K) using the different methods is 66–103, 61–95, 59–96, 41–89, and 85–122 DU for March 2005, 2007, 2008, 2010, and 2011, respectively. Ozone loss is difficult to diagnose for the Arctic winters during 2005–2006, 2008–2009, 2011–2012, and 2012–2013, because strong polar vortex disturbance or major sudden stratospheric warming events significantly perturbed the polar vortex, thereby limiting the number of measurements available for the analysis of ozone loss.

scholarly journals Stratospheric ozone loss in the Arctic winters between 2005 and 2013 derived with ACE-FTS measurements

2018 ◽  
Author(s):  
Debora Griffin ◽  
Kaley A. Walker ◽  
Ingo Wohltmann ◽  
Sandip S. Dhomse ◽  
Markus Rex ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Stratospheric Ozone ◽  
Correlation Method ◽  
Polar Vortex ◽  
The Arctic ◽  
Estimation Methods ◽  
Mixing Ratio ◽  
Total Column Ozone ◽  
Ozone Loss ◽  
Column Ozone

Abstract. Stratospheric ozone loss inside the Arctic polar vortex for the winters between 2004/2005 and 2012/2013 has been quantified using measurements from the space-borne Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS). Six different methods, including tracer-tracer correlation, artificial tracer correlation, average vortex profile descent, and passive subtraction with model output from both Lagrangian and Eulerian chemical transport models (CTMs), have been employed to determine the Arctic ozone loss (mixing ratio loss profiles and the partial column ozone losses between 380 and 550 K). For the tracer-tracer, the artificial tracer, and the average vortex profile descent approaches, various tracers have been used. Here, we show that CH4, N2O, HF, and CFC-12 are suitable tracers for investigating polar stratospheric ozone depletion with ACE-FTS. The ozone loss estimates (in terms of the mixing ratio as well as total column ozone) are generally in good agreement between the different methods and among the different tracers. However, the tracer-tracer correlation method does not agree with the other estimation methods in March 2005 and using the average vortex profile descent technique typically leads to smaller maximum losses compared to all other methods. The passive subtraction method using output from CTMs generally results in smaller uncertainties and slightly larger losses compared to the techniques that use ACE-FTS measurements only. The ozone loss computed, using both measurements and models, shows the greatest loss during the 2010/2011 Arctic winter. For that year, our results show that maximum ozone loss (2.1–2.7 ppmv) occurred at 460 K. The estimated partial column ozone loss inside the polar vortex (between 380 K and 550 K) is 66–103 DU, 61–95 DU, 59–96 DU, 41–89 DU, and 85–122 DU for March 2005, 2007, 2008, 2010, and 2011, respectively. Ozone loss is difficult to diagnose during 2005/2006, 2008/2009, 2011/2012, and 2012/2013 because strong polar vortex disturbance or major sudden stratospheric warming events significantly perturbed the polar vortex thereby limiting the number of measurements available for the analysis.

scholarly journals The use of SMILES data to study ozone loss in the Arctic winter 2009/2010 and comparison with Odin/SMR data using assimilation techniques

2014 ◽  
Vol 14 (23) ◽  
pp. 12855-12869 ◽  
Author(s):  
K. Sagi ◽  
D. Murtagh ◽  
J. Urban ◽  
H. Sagawa ◽  
Y. Kasai
Keyword(s):  
Ozone Depletion ◽  
Transport Model ◽  
Space Station ◽  
Polar Vortex ◽  
The Arctic ◽  
Mixing Ratio ◽  
Weather Forecasts ◽  
Ozone Loss ◽  
Medium Range ◽  
Assimilation Model

Abstract. The Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) on board the International Space Station observed ozone in the stratosphere with high precision from October 2009 to April 2010. Although SMILES measurements only cover latitudes from 38° S to 65° N, the combination of data assimilation methods and an isentropic advection model allows us to quantify the ozone depletion in the 2009/2010 Arctic polar winter by making use of the instability of the polar vortex in the northern hemisphere. Ozone data from both SMILES and Odin/SMR (Sub-Millimetre Radiometer) for the winter were assimilated into the Dynamical Isentropic Assimilation Model for OdiN Data (DIAMOND). DIAMOND is an off-line wind-driven transport model on isentropic surfaces. Wind data from the operational analyses of the European Centre for Medium- Range Weather Forecasts (ECMWF) were used to drive the model. In this study, particular attention is paid to the cross isentropic transport of the tracer in order to accurately assess the ozone loss. The assimilated SMILES ozone fields agree well with the limitation of noise induced variability within the SMR fields despite the limited latitude coverage of the SMILES observations. Ozone depletion has been derived by comparing the ozone field acquired by sequential assimilation with a passively transported ozone field initialized on 1 December 2009. Significant ozone loss was found in different periods and altitudes from using both SMILES and SMR data: The initial depletion occurred at the end of January below 550 K with an accumulated loss of 0.6–1.0 ppmv (approximately 20%) by 1 April. The ensuing loss started from the end of February between 575 K and 650 K. Our estimation shows that 0.8–1.3 ppmv (20–25 %) of O3 has been removed at the 600 K isentropic level by 1 April in volume mixing ratio (VMR).

scholarly journals A Match-based approach to the estimation of polar stratospheric ozone loss using Aura Microwave Limb Sounder observations

2015 ◽  
Vol 15 (17) ◽  
pp. 9945-9963 ◽  
Author(s):  
N. J. Livesey ◽  
M. L. Santee ◽  
G. L. Manney
Keyword(s):  
Stratospheric Ozone ◽  
Potential Temperature ◽  
Polar Vortex ◽  
Rate Of Change ◽  
The Arctic ◽  
Air Mass ◽  
Ozone Loss ◽  
Chemical Destruction ◽  
Induced Changes ◽  
The Impact

Abstract. The well-established "Match" approach to quantifying chemical destruction of ozone in the polar lower stratosphere is applied to ozone observations from the Microwave Limb Sounder (MLS) on NASA's Aura spacecraft. Quantification of ozone loss requires distinguishing transport- and chemically induced changes in ozone abundance. This is accomplished in the Match approach by examining cases where trajectories indicate that the same air mass has been observed on multiple occasions. The method was pioneered using ozonesonde observations, for which hundreds of matched ozone observations per winter are typically available. The dense coverage of the MLS measurements, particularly at polar latitudes, allows matches to be made to thousands of observations each day. This study is enabled by recently developed MLS Lagrangian trajectory diagnostic (LTD) support products. Sensitivity studies indicate that the largest influence on the ozone loss estimates are the value of potential vorticity (PV) used to define the edge of the polar vortex (within which matched observations must lie) and the degree to which the PV of an air mass is allowed to vary between matched observations. Applying Match calculations to MLS observations of nitrous oxide, a long-lived tracer whose expected rate of change is negligible on the weekly to monthly timescales considered here, enables quantification of the impact of transport errors on the Match-based ozone loss estimates. Our loss estimates are generally in agreement with previous estimates for selected Arctic winters, though indicating smaller losses than many other studies. Arctic ozone losses are greatest during the 2010/11 winter, as seen in prior studies, with 2.0 ppmv (parts per million by volume) loss estimated at 450 K potential temperature (~ 18 km altitude). As expected, Antarctic winter ozone losses are consistently greater than those for the Arctic, with less interannual variability (e.g., ranging between 2.3 and 3.0 ppmv at 450 K). This study exemplifies the insights into atmospheric processes that can be obtained by applying the Match methodology to a densely sampled observation record such as that from Aura MLS.

scholarly journals Observations of filamentary structures near the vortex edge in the Arctic winter lower stratosphere

2013 ◽  
Vol 13 (21) ◽  
pp. 10859-10871 ◽  
Author(s):  
C. Kalicinsky ◽  
J.-U. Grooß ◽  
G. Günther ◽  
J. Ungermann ◽  
J. Blank ◽  
...  
Keyword(s):  
Cross Sections ◽  
Transport Model ◽  
Stratospheric Ozone ◽  
Polar Vortex ◽  
Lagrangian Model ◽  
The Arctic ◽  
Small Scale ◽  
Air Mass ◽  
Mixing Ratios ◽  
Passive Tracers

Abstract. The CRISTA-NF (Cryogenic Infrared Spectrometers and Telescope for the Atmosphere – New Frontiers) instrument is an airborne infrared limb sounder operated aboard the Russian research aircraft M55-Geophysica. The instrument successfully participated in a large Arctic aircraft campaign within the RECONCILE (Reconciliation of essential process parameters for an enhanced predictability of Arctic stratospheric ozone loss and its climate interactions) project in Kiruna (Sweden) from January to March 2010. This paper concentrates on the measurements taken during one flight of the campaign, which took place on 2 March in the vicinity of the polar vortex. We present two-dimensional cross-sections of derived volume mixing ratios for the trace gases CFC-11, O3, and ClONO2 with an unprecedented vertical resolution of about 500 to 600 m for a large part of the observed altitude range (≈ 6–19 km) and a dense horizontal sampling along flight direction of ≈ 15 km. The trace gas distributions show several structures, for example a part of the polar vortex and a vortex filament, which can be identified by means of O3–CFC-11 tracer–tracer correlations. The observations made during this flight are interpreted using the chemistry and transport model CLaMS (Chemical Lagrangian Model of the Stratosphere). Comparisons of the observations with the model results are used to assess the performance of the model with respect to advection, mixing, and the chemistry in the polar vortex. These comparisons confirm the capability of CLaMS to reproduce even very small-scale structures in the atmosphere, which partly have a vertical extent of only 1 km. Based on the good agreement between simulation and observation, we use artificial (passive) tracers, which represent different air mass origins (e.g. vortex, tropics), to further analyse the CRISTA-NF observations in terms of the composition of air mass origins. These passive tracers clearly illustrate the observation of filamentary structures that include tropical air masses. A characteristic of the Arctic winter 2009/10 was a sudden stratospheric warming in December that led to a split of the polar vortex. The vortex re-established at the end of December. Our passive tracer simulations suggest that large parts of the re-established vortex consisted to about 45% of high- and mid-latitude air.

A three-dimensional model comparison of PSC processing during the Arctic winters of 1991/1992 and 1992/1993

1994 ◽  
Vol 12 (4) ◽  
pp. 342-354 ◽  
Author(s):  
M. P. Chipperfield
Keyword(s):  
Model Comparison ◽  
Transport Model ◽  
Three Dimensional ◽  
Polar Vortex ◽  
The Arctic ◽  
Three Dimensional Model ◽  
Polar Stratospheric Clouds ◽  
Ozone Loss ◽  
Stratospheric Clouds ◽  
Compare And Contrast

Abstract. A three-dimensional transport model has been used to compare and contrast the extent of processing by polar stratospheric clouds during the northern hemisphere winters of 1991/1992 and 1992/1993. The model has also been used to compare the potential for ozone loss between these two winters. The TOMCAT off-line model is forced using meteorological analyses from the ECMWF. During winter 1992/1993 polar stratospheric clouds (PSCs) in the model persisted into late February/early March, which is much later than in 1991/1992. This persistence of PSCs should have resulted in much more ozone loss in the later winter. Interestingly, however, the extent of PSC processing and ozone loss was greater in January 1992 than January 1993. In January 1992 PSCs occurred at the edge of a distorted polar vortex whilst in January 1993 the PSCs were located at the centre of a much more zonally symmetrical vortex. In March 1993, distortions of the vortex led to the tearing off of vortex air and its mixing into midlatitudes.

scholarly journals Evolution of stratospheric ozone during winter 2002/2003 as observed by a ground-based millimetre wave radiometer at Kiruna, Sweden

2005 ◽  
Vol 5 (5) ◽  
pp. 1399-1407 ◽  
Author(s):  
U. Raffalski ◽  
G. Hochschild ◽  
G. Kopp ◽  
J. Urban
Keyword(s):  
Lower Stratosphere ◽  
Stratospheric Ozone ◽  
Polar Vortex ◽  
Space Physics ◽  
Solar Irradiation ◽  
The Arctic ◽  
Strong Mixing ◽  
Millimetre Wave ◽  
Cold Temperatures ◽  
Ozone Loss

Abstract. We present ozone measurements from the millimetre wave radiometer installed at the Swedish Institute of Space Physics (Institutet för rymdfysik, IRF) in Kiruna (67.8° N, 20.4° E, 420 m asl). Nearly continuous operation in the winter of 2002/2003 allows us to give an overview of ozone evolution in the stratosphere between 15 and 55 km. In this study we present a detailed analysis of the Arctic winter 2002/2003. By means of a methodology using equivalent latitudes we investigate the meteorological processes in the stratosphere during the entire winter/spring period. During the course of the winter strong mixing into the vortex took place in the middle and upper stratosphere as a result of three minor and one major warming event, but no evidence was found for significant mixing in the lower stratosphere. Ozone depletion in the lower stratosphere during this winter was estimated by measurements on those days when Kiruna was well inside the Arctic polar vortex. The days were carefully chosen using a definition of the vortex edge based on equivalent latitudes. At the 475 K isentropic level a cumulative ozone loss of about 0.5 ppmv was found starting in January and lasting until mid-March. The early ozone loss is probably a result of the very cold temperatures in the lower stratosphere in December and the geographical extension of the vortex to lower latitudes where solar irradiation started photochemical ozone loss in the pre-processed air. In order to correct for dynamic effects of the ozone variation due to diabatic subsidence of air masses inside the vortex, we used N2O measurements from the Odin satellite for the same time period. The derived ozone loss in the lower stratosphere between mid-December and mid-March varies between 1.1±0.1 ppmv on the 150 ppbv N2O isopleth and 1.7±0.1 ppmv on the 50 ppbv N2O isopleth.

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