scholarly journals First characterization and validation of FORLI-HNO<sub>3</sub> vertical profiles retrieved from IASI/Metop

2016 ◽  
Author(s):  
Gaétane Ronsmans ◽  
Bavo Langerock ◽  
Catherine Wespes ◽  
James W. Hannigan ◽  
Frank Hase ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Stratospheric Ozone ◽  
Low Noise ◽  
Atmospheric Composition ◽  
Polar Regions ◽  
Vertical Profiles ◽  
Data Set ◽  
Atmospheric Species ◽  
Temporal Sampling ◽  
Signal Peak

Abstract. Knowing the spatial and seasonal distributions of nitric acid (HNO3) around the globe is of great interest to apprehend the processes regulating stratospheric ozone, especially in the polar regions. Thanks to its unprecedented spatial and temporal sampling, the nadir-viewing Infrared Atmospheric Sounding Interferometer (IASI) allows sounding the atmosphere twice a day globally, with good spectral resolution and low noise. With the Fast Optimal Retrievals on Layers for IASI (FORLI) algorithm, we are retrieving, in near-real time, columns as well as vertical profiles of several atmospheric species, amongst which is HNO3. We present in this paper the first characterization of the FORLI-HNO3 profile products, in terms of vertical sensitivity and error budgets. We show that the sensitivity of IASI to HNO3 is highest in the lower stratosphere (10–20 km), where the largest amounts of HNO3 are found, but that the vertical sensitivity of IASI only allows one level of information on the profile (DOFS 1). The sensitivity near the surface is negligible in most cases, and for this reason, a partial column (5–35 km) is used for the analyses. Both vertical profiles and partial columns are compared to FTIR ground-based measurements from the Network for the Detection of Atmospheric Composition Change (NDACC) to characterize the accuracy and precision of the FORLI-HNO3 product. The profile validation is conducted through the smoothing of the raw FTIR profiles by the IASI averaging kernels and gives good results, with a slight overestimation of IASI measurements in the Upper Troposphere-Lower Stratosphere (UTLS) at the 6 chosen stations (Thule, Kiruna, Jungfraujoch, Izaña, Lauder and Arrival Heights). The validation of the partial columns (5–35 km) is also conclusive with a mean correlation of 0.93 between IASI and the FTIR measurements. An initial survey of the HNO3 spatial and seasonal variabilities obtained from IASI measurements for a one year (2011) data set shows that the expected latitudinal gradient of concentrations from low to high latitudes and the large seasonal variability in polar regions (cycle amplitude around 30 % of the seasonal signal, peak-to-peak) are well represented with IASI data.

scholarly journals First characterization and validation of FORLI-HNO<sub>3</sub> vertical profiles retrieved from IASI/Metop

2016 ◽  
Vol 9 (9) ◽  
pp. 4783-4801 ◽  
Author(s):  
Gaétane Ronsmans ◽  
Bavo Langerock ◽  
Catherine Wespes ◽  
James W. Hannigan ◽  
Frank Hase ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Lower Stratosphere ◽  
Stratospheric Ozone ◽  
Low Noise ◽  
Atmospheric Composition ◽  
Polar Regions ◽  
Vertical Profiles ◽  
Data Set ◽  
Atmospheric Species ◽  
Temporal Sampling

Abstract. Knowing the spatial and seasonal distributions of nitric acid (HNO3) around the globe is of great interest and allows us to comprehend the processes regulating stratospheric ozone, especially in the polar regions. Due to its unprecedented spatial and temporal sampling, the nadir-viewing Infrared Atmospheric Sounding Interferometer (IASI) is capable of sounding the atmosphere twice a day globally, with good spectral resolution and low noise. With the Fast Optimal Retrievals on Layers for IASI (FORLI) algorithm, we are retrieving, in near real time, columns as well as vertical profiles of several atmospheric species, among which is HNO3. We present in this paper the first characterization of the FORLI-HNO3 profile products, in terms of vertical sensitivity and error budgets. We show that the sensitivity of IASI to HNO3 is highest in the lower stratosphere (10–20 km), where the largest amounts of HNO3 are found, but that the vertical sensitivity of IASI only allows one level of information on the profile (degrees of freedom for signal, DOFS;  ∼  1). The sensitivity near the surface is negligible in most cases, and for this reason, a partial column (5–35 km) is used for the analyses. Both vertical profiles and partial columns are compared to FTIR ground-based measurements from the Network for the Detection of Atmospheric Composition Change (NDACC) to characterize the accuracy and precision of the FORLI-HNO3 product. The profile validation is conducted through the smoothing of the raw FTIR profiles by the IASI averaging kernels and gives good results, with a slight overestimation of IASI measurements in the upper troposphere/lower stratosphere (UTLS) at the six chosen stations (Thule, Kiruna, Jungfraujoch, Izaña, Lauder and Arrival Heights). The validation of the partial columns (5–35 km) is also conclusive with a mean correlation of 0.93 between IASI and the FTIR measurements. An initial survey of the HNO3 spatial and seasonal variabilities obtained from IASI measurements for a 1-year (2011) data set shows that the expected latitudinal gradient of concentrations from low to high latitudes and the large seasonal variability in polar regions (cycle amplitude around 30 % of the seasonal signal, peak to peak) are well represented by IASI data.

scholarly journals Improved retrieval of nitrogen dioxide (NO<sub>2</sub>) column densities by means of MKIV Brewer spectrophotometers

2014 ◽  
Vol 7 (11) ◽  
pp. 4009-4022 ◽  
Author(s):  
H. Diémoz ◽  
A. M. Siani ◽  
A. Redondas ◽  
V. Savastiouk ◽  
C. T. McElroy ◽  
...  
Keyword(s):  
Nitrogen Dioxide ◽  
Ad Hoc ◽  
Absorption Spectrometry ◽  
Atmospheric Composition ◽  
Data Sets ◽  
Data Set ◽  
Noise Interference ◽  
Atmospheric Species ◽  
Mass Factor

Abstract. A new algorithm to retrieve nitrogen dioxide (NO2) column densities using MKIV ("Mark IV") Brewer spectrophotometers is described. The method includes several improvements, such as a more recent spectroscopic data set, the reduction of measurement noise, interference by other atmospheric species and instrumental settings, and a better determination of the zenith sky air mass factor. The technique was tested during an ad hoc calibration campaign at the high-altitude site of Izaña (Tenerife, Spain) and the results of the direct sun and zenith sky geometries were compared to those obtained by two reference instruments from the Network for the Detection of Atmospheric Composition Change (NDACC): a Fourier Transform Infrared Radiometer (FTIR) and an advanced visible spectrograph (RASAS-II) based on the differential optical absorption spectrometry (DOAS) technique. To determine the extraterrestrial constant, an easily implementable extension of the standard Langley technique for very clean sites without tropospheric NO2 was developed which takes into account the daytime linear drift of stratospheric nitrogen dioxide due to photochemistry. The measurement uncertainty was thoroughly determined by using a Monte Carlo technique. Poisson noise and wavelength misalignments were found to be the most influential contributors to the overall uncertainty, and possible solutions are proposed for future improvements. The new algorithm is backward-compatible, thus allowing for the reprocessing of historical data sets.

10 years of Polar Stratospheric Clouds lidar measurements at the French antarctic station Dumont d’Urville

2020 ◽  
Author(s):  
Florent Tencé ◽  
Julien Jumelet ◽  
Alain Sarkissian ◽  
Slimane Bekki ◽  
Philippe Keckhut
Keyword(s):  
Stratospheric Ozone ◽  
Atmospheric Composition ◽  
Polar Regions ◽  
Primary Role ◽  
Atmospheric Conditions ◽  
Polar Stratospheric Clouds ◽  
Ice Clouds ◽  
Yearly Average ◽  
Lidar Measurements ◽  
Stratospheric Clouds

&lt;p&gt;&lt;span&gt;Polar Stratospheric Clouds (PSCs) play a primary role in polar stratospheric ozone depletion processes. &lt;/span&gt;&lt;span&gt;Aside from recent improvements in both spaceborne PSCs monitoring as well as investigations on PSCs microphysics and modeling, there are still uncertainties associated to solid particle formation and their denitrification potential. In that regard, groundbased instruments deliver detailed and valuable measurements that complement the global spaceborne coverage.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;Operated since 1989 at the French antarctic station Dumont d&amp;#8217;Urville (DDU) in the frame of the international Network for the Detection of Atmospheric Composition Change (NDACC), the Rayleigh/Mie/Raman lidar provides over the years a solid dataset to feed both process and classification studies, by monitoring cloud and aerosol occurrences in the upper troposphere and lower stratosphere. Located on antarctic shore (66&amp;#176;S - 140&amp;#176;E), the station has a privileged access to polar vortex dynamics. Measurements are weather-dependent with a yearly average of 130 nights of monitoring. Expected PSC formation temperatures are used to evaluate the whole PSC season occurrences.&lt;/p&gt;&lt;p&gt;We hereby present a consolidated dataset from 10 years of lidar measurements using the 532nm backscatter ratio, the aerosol depolarisation and local atmospheric conditions to help in building an aerosol/cloud classification. Using the different PSC classes and associated optical properties thresholds established in the recent PSC CALIOP classification, we build a picture of the 2007-2019 events, from march to october.&lt;/p&gt;&lt;p&gt;Overall, the DDU PSC pattern is very consistent with expected typical temperature controlled microphysical calculations. Outside of background sulfate aerosols and anomalies related to volcanic activity (like in 2015), Supercooled Ternary Solution (STS) particles are the most observed particle type, closely followed by Nitric Acid Trihydrate (NAT). ICE clouds are less but regularly observed. ICE clouds also have to be cleary separated from cirrus clouds, raising the issue of accurate dynamics tropopause calculations.&lt;/p&gt;&lt;p&gt;&lt;span&gt;Validation of the spaceborne measurements as well as multiple signatures of volcanic or even biomass originated aerosol plumes strengthens the need for groundbased monitoring &lt;/span&gt;&lt;span&gt;especially in polar regions where instrumental facilities remain sparse.&lt;/span&gt;&lt;/p&gt;

scholarly journals The CAMS interim Reanalysis of Carbon Monoxide, Ozone and Aerosol for 2003–2015

2017 ◽  
Vol 17 (3) ◽  
pp. 1945-1983 ◽  
Author(s):  
Johannes Flemming ◽  
Angela Benedetti ◽  
Antje Inness ◽  
Richard J. Engelen ◽  
Luke Jones ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Weather Forecasting ◽  
Stratospheric Ozone ◽  
Nitrogen Monoxide ◽  
Horizontal Resolution ◽  
Atmospheric Composition ◽  
Strong Impact ◽  
Temporal Consistency ◽  
Emission Data ◽  
Data Set

Abstract. A new global reanalysis data set of atmospheric composition (AC) for the period 2003–2015 has been produced by the Copernicus Atmosphere Monitoring Service (CAMS). Satellite observations of total column (TC) carbon monoxide (CO) and aerosol optical depth (AOD), as well as several TC and profile observations of ozone, have been assimilated with the Integrated Forecasting System for Composition (C-IFS) of the European Centre for Medium-Range Weather Forecasting. Compared to the previous Monitoring Atmospheric Composition and Climate (MACC) reanalysis (MACCRA), the new CAMS interim reanalysis (CAMSiRA) is of a coarser horizontal resolution of about 110 km, compared to 80 km, but covers a longer period with the intent to be continued to present day. This paper compares CAMSiRA with MACCRA and a control run experiment (CR) without assimilation of AC retrievals. CAMSiRA has smaller biases than the CR with respect to independent observations of CO, AOD and stratospheric ozone. However, ozone at the surface could not be improved by the assimilation because of the strong impact of surface processes such as dry deposition and titration with nitrogen monoxide (NO), which were both unchanged by the assimilation. The assimilation of AOD led to a global reduction of sea salt and desert dust as well as an exaggerated increase in sulfate. Compared to MACCRA, CAMSiRA had smaller biases for AOD, surface CO and TC ozone as well as for upper stratospheric and tropospheric ozone. Finally, the temporal consistency of CAMSiRA was better than the one of MACCRA. This was achieved by using a revised emission data set as well as by applying careful selection and bias correction to the assimilated retrievals. CAMSiRA is therefore better suited than MACCRA for the study of interannual variability, as demonstrated for trends in surface CO.

scholarly journals Evidence for a continuous decline in lower stratospheric ozone offsetting ozone layer recovery

2018 ◽  
Vol 18 (2) ◽  
pp. 1379-1394 ◽  
Author(s):  
William T. Ball ◽  
Justin Alsing ◽  
Daniel J. Mortlock ◽  
Johannes Staehelin ◽  
Joanna D. Haigh ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Stratospheric Ozone ◽  
Ozone Layer ◽  
Montreal Protocol ◽  
Downward Trend ◽  
Polar Regions ◽  
Total Column Ozone ◽  
Ozone Depleting Substances ◽  
Column Ozone ◽  
Total Column

Abstract. Ozone forms in the Earth's atmosphere from the photodissociation of molecular oxygen, primarily in the tropical stratosphere. It is then transported to the extratropics by the Brewer–Dobson circulation (BDC), forming a protective ozone layer around the globe. Human emissions of halogen-containing ozone-depleting substances (hODSs) led to a decline in stratospheric ozone until they were banned by the Montreal Protocol, and since 1998 ozone in the upper stratosphere is rising again, likely the recovery from halogen-induced losses. Total column measurements of ozone between the Earth's surface and the top of the atmosphere indicate that the ozone layer has stopped declining across the globe, but no clear increase has been observed at latitudes between 60° S and 60° N outside the polar regions (60–90°). Here we report evidence from multiple satellite measurements that ozone in the lower stratosphere between 60° S and 60° N has indeed continued to decline since 1998. We find that, even though upper stratospheric ozone is recovering, the continuing downward trend in the lower stratosphere prevails, resulting in a downward trend in stratospheric column ozone between 60° S and 60° N. We find that total column ozone between 60° S and 60° N appears not to have decreased only because of increases in tropospheric column ozone that compensate for the stratospheric decreases. The reasons for the continued reduction of lower stratospheric ozone are not clear; models do not reproduce these trends, and thus the causes now urgently need to be established.

Evaluation of CAM-Chem VSLBr model performance during SouthTRAC campaign

2021 ◽  
Author(s):  
Lucas Berná ◽  
Ana Isabel Lopez-Noreña ◽  
Enrique Puliafito ◽  
Javier Alejandro Barrera ◽  
Andreas Engel ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Pearson Correlation ◽  
Stratospheric Ozone ◽  
Model Performance ◽  
National Research Council ◽  
Reaction Rates ◽  
Atmospheric Composition ◽  
Climate Simulation ◽  
Phase Reaction ◽  
Upper Troposphere

&lt;p&gt;In the framework of the SouthTRAC Campaign (Transport and Composition of the Southern Hemisphere Upper Troposphere and Lower Stratosphere) based on Rio Grande, Argentina, a local research group from CONICET (Argentine National Research Council) &amp;#160;joined the German consortium maintaining the HALO research aircraft (High-Altitude and LOng-range aircraft) &amp;#160;to help with the flight planning and evaluation of the chemical composition of the upper troposphere and lower stratosphere within the ozone hole periphery. The SouthTRAC aircraft campaign was carried out in two phases which took place in September and November 2019, respectively. With the purpose of providing additional information of the atmospheric composition of brominated Very Short-Lived (VSL&lt;sup&gt;Br&lt;/sup&gt;) species and compare with HALO observations during the transfer and campaign flights, a CAM-Chem (Community Atmosphere Model with Chemistry) global chemistry-climate simulation was conducted. The model setup used in the halogenated CAM-Chem simulation had a 1&amp;#176; x 1.25&amp;#176; lat-lon resolution, 56 hybrid vertical levels from the surface to the middle stratosphere and considered assimilated meteorology from MERRA, including an explicit treatment of VSL&lt;sup&gt;Br&lt;/sup&gt; sources and chemistry. Model output of VSL&lt;sup&gt;Br&lt;/sup&gt;, long-lived bromine and chlorine (LL&lt;sup&gt;Br&lt;/sup&gt; and LL&lt;sup&gt;Cl&lt;/sup&gt;) species and ozone mixing ratios, as well as the main inorganic halogen reactive and reservoir species and gas/heterogeneous phase reaction rates affecting lowermost stratospheric ozone were analyzed in horizontal domains and vertical cross-sections across each flightpath. The model performance with respect to the HALO observations has a general good agreement, presenting better results for mid latitudes (between 30&amp;#186; S and 50&amp;#186; S) than for southern latitudes (&gt;50&amp;#186; S). In particular, CAM-Chem timeseries consistently reproduced the spatio-temporal variation of the main VSLBr species (CH&lt;sub&gt;2&lt;/sub&gt;Br&lt;sub&gt;2&lt;/sub&gt; and CHBr&lt;sub&gt;3&lt;/sub&gt;), including the sharp variations observed across the tropopause. For both VSL&lt;sup&gt;Br&lt;/sup&gt; as well as for LL&lt;sup&gt;Cl&lt;/sup&gt; compounds such as CFC-12, the Pearson correlation coefficient r obtained during each of the flights ranged between 0.7 and 0.9, while the Normalized Mean Bias (NMB) was smaller than 8% for almost every flight. Regarding LL&lt;sup&gt;Br&lt;/sup&gt; CH&lt;sub&gt;3&lt;/sub&gt;Br, the correlation with the aircraft observations is high (r&gt;0.9) but the inter-hemispheric variability during transfer flights is not fully captured. For Ozone, the model presents mid to high correlation with respect to measures (0.5&lt;r&lt;0.95) with a variable overestimation ranging from 10% to at most 40% in some flights.&lt;/p&gt;

1-D photochemical model predicts oxygen isotope anomalies in early Earth atmospheres

2020 ◽  
Author(s):  
Bethan Gregory ◽  
Mark Claire ◽  
Sarah Rugheimer
Keyword(s):  
Oxygen Isotope ◽  
Atmospheric Oxygen ◽  
Stratospheric Ozone ◽  
Atmospheric Composition ◽  
Geological Time ◽  
Geological Record ◽  
Oxygen Levels ◽  
Atmospheric Species ◽  
Photochemical Model ◽  
Modelling Studies

&lt;p&gt;Atmospheric oxygen and ozone over geological time have been constrained using various geochemical proxies and modelling studies, but ambiguity remains. Triple oxygen isotope measurements from Phanerozoic and Proterozoic rocks (e.g. Crockford et al., 2019) provide a direct record of ancient atmospheric composition, and as such are an exciting novel proxy. The only known source of mass-independent fractionation of oxygen isotopes (O-MIF) on Earth is in the formation of stratospheric ozone. A large positive O-MIF signal is imparted to ozone, while the larger reservoir of oxygen gains a much smaller negative O-MIF signal. These species interact with other gases in the atmosphere, and oxidised end products including nitrate, sulphate and perchlorate can persist in various geological archives such as ice, arid desert soil, and marine evaporites. As a result, the magnitude of the O-MIF signature detected in the geological record could be used to quantify levels of atmospheric ozone (and closely-related molecular oxygen) over certain time intervals. Here we develop a one-dimensional photochemical model to incorporate the three isotopes of oxygen, in order to trace oxygen isotope anomalies from stratospheric ozone through other atmospheric species, and into the geological record. This model, &amp;#8216;Atmos,&amp;#8217; has been calibrated over 40 years to provide credible estimates of atmospheric composition deviating from the modern. We use the model to show the lowest oxygen levels at which the anomaly can be produced and transferred, putting a potential lower limit on oxygen levels for parts of the Phanerozoic and mid-Proterozoic.&lt;/p&gt;&lt;p&gt;Reference:&lt;/p&gt;&lt;p&gt;Crockford, P.W., Kunzmann, M., Bekker, A., Hayles, J., Bao, H., Halverson, G.P., Peng, Y., Bui, T.H., Cox, G.M., Gibson, T.M. and W&amp;#246;rndle, S., 2019. Claypool continued: Extending the isotopic record of sedimentary sulfate.&amp;#160;Chemical Geology.&lt;/p&gt;

scholarly journals Validation of MIPAS IMK/IAA V5R_O3_224 ozone profiles

2014 ◽  
Vol 7 (11) ◽  
pp. 3971-3987 ◽  
Author(s):  
A. Laeng ◽  
U. Grabowski ◽  
T. von Clarmann ◽  
G. Stiller ◽  
N. Glatthor ◽  
...  
Keyword(s):  
Stratospheric Ozone ◽  
Michelson Interferometer ◽  
Vertical Profiles ◽  
Data Set ◽  
Solar Occultation ◽  
Time Period ◽  
Research Level ◽  
Precision Assessment ◽  
High Bias ◽  
Recent Version

Abstract. We present the results of an extensive validation program of the most recent version of ozone vertical profiles retrieved with the IMK/IAA (Institute for Meteorology and Climate Research/Instituto de Astrofísica de Andalucía) MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) research level 2 processor from version 5 spectral level 1 data. The time period covered corresponds to the reduced spectral resolution period of the MIPAS instrument, i.e., January 2005–April 2012. The comparison with satellite instruments includes all post-2005 satellite limb and occultation sensors that have measured the vertical profiles of tropospheric and stratospheric ozone: ACE-FTS, GOMOS, HALOE, HIRDLS, MLS, OSIRIS, POAM, SAGE II, SCIAMACHY, SMILES, and SMR. In addition, balloon-borne MkIV solar occultation measurements and ground-based Umkehr measurements have been included, as well as two nadir sensors: IASI and SBUV. For each reference data set, bias determination and precision assessment are performed. Better agreement with reference instruments than for the previous data version, V5R_O3_220 (Laeng et al., 2014), is found: the known high bias around the ozone vmr (volume mixing ratio) peak is significantly reduced and the vertical resolution at 35 km has been improved. The agreement with limb and solar occultation reference instruments that have a known small bias vs. ozonesondes is within 7% in the lower and middle stratosphere and 5% in the upper troposphere. Around the ozone vmr peak, the agreement with most of the satellite reference instruments is within 5%; this bias is as low as 3% for ACE-FTS, MLS, OSIRIS, POAM and SBUV.

scholarly journals Validation of GOME ozone profiles by means of the ALOMAR ozone lidar

2003 ◽  
Vol 21 (8) ◽  
pp. 1879-1886 ◽  
Author(s):  
G. Hansen ◽  
K. Bramstedt ◽  
V. Rozanov ◽  
M. Weber ◽  
J. P. Burrows
Keyword(s):  
Middle Atmosphere ◽  
Stratospheric Ozone ◽  
Atmospheric Composition ◽  
Vertical Profiles ◽  
Composition And Structure ◽  
Calibration Problem ◽  
Lidar Measurements ◽  
Instruments And Techniques ◽  
The Right ◽  
The University

Abstract. Ozone vertical profiles derived from nadir measurements of the GOME instrument on board the ERS-2 satellite, by means of the FURM algorithm of the University of Bremen, are validated against measurements with the stratospheric ozone lidar at the ALOMAR facility in North-Norway. A set of 43 measurements, taken in the period August 1996 to September 1999 with a maximum distance between the ground-based site and the GOME pixel centre of 650 km, is used. The comparison shows a satisfactory agreement within less than ± 7% in the altitude range 15 to 30 km, independent of the season of the year. At lower altitudes, average deviations of the GOME profiles from lidar measurements of up to - 15% occur in spring, the reason for which has to be found in the FURM algorithm, while the agreement is within ± 5% in both winter and summer/autumn months. At altitudes above 30 km, significant seasonally varying discrepancies occur, being largest in winter ( - 40% on average at 40 km altitude) and smallest in summer (less than - 10%). The source of these deviations is most likely related to a radiance and irradiance calibration problem in the GOME data below 300 nm, which are used to derive ozone at the highest altitudes. The validation also shows that it is very important to choose the right ozone climatology for initialisation. Satisfactory results in spring 1997, when the polar stratospheric vortex was very stable, are only achieved, if a winter (vortex) profile is used.Key words. Atmospheric composition and structure (middle atmosphere-composition and chemistry; instruments and techniques; general or miscellaneous)

scholarly journals Variability and trends in total and vertically resolved stratospheric ozone based on the CATO ozone data set

2006 ◽  
Vol 6 (12) ◽  
pp. 4985-5008 ◽  
Author(s):  
D. Brunner ◽  
J. Staehelin ◽  
J. A. Maeder ◽  
I. Wohltmann ◽  
G. E. Bodeker
Keyword(s):  
Regression Model ◽  
Ozone Depletion ◽  
Lower Stratosphere ◽  
Stratospheric Ozone ◽  
Potential Temperature ◽  
Volcanic Eruptions ◽  
Quasi Biennial Oscillation ◽  
Data Set ◽  
Lower Altitude ◽  
Ozone Data

Abstract. Trends in ozone columns and vertical distributions were calculated for the period 1979–2004 based on the ozone data set CATO (Candidoz Assimilated Three-dimensional Ozone) using a multiple linear regression model. CATO has been reconstructed from TOMS, GOME and SBUV total column ozone observations in an equivalent latitude and potential temperature framework and offers a pole to pole coverage of the stratosphere on 15 potential temperature levels. The regression model includes explanatory variables describing the influence of the quasi-biennial oscillation (QBO), volcanic eruptions, the solar cycle, the Brewer-Dobson circulation, Arctic ozone depletion, and the increase in stratospheric chlorine. The effects of displacements of the polar vortex and jet streams due to planetary waves, which may significantly affect trends at a given geographical latitude, are eliminated in the equivalent latitude framework. The QBO shows a strong signal throughout most of the lower stratosphere with peak amplitudes in the tropics of the order of 10–20% (peak to valley). The eruption of Pinatubo led to annual mean ozone reductions of 15–25% between the tropopause and 23 km in northern mid-latitudes and to similar percentage changes in the southern hemisphere but concentrated at altitudes below 17 km. Stratospheric ozone is elevated over a broad latitude range by up to 5% during solar maximum compared to solar minimum, the largest increase being observed around 30 km. This is at a lower altitude than reported previously, and no negative signal is found in the tropical lower stratosphere. The Brewer-Dobson circulation shows a dominant contribution to interannual variability at both high and low latitudes and accounts for some of the ozone increase seen in the northern hemisphere since the mid-1990s. Arctic ozone depletion significantly affects the high northern latitudes between January and March and extends its influence to the mid-latitudes during later months. The vertical distribution of the ozone trend shows distinct negative trends at about 18 km in the lower stratosphere with largest declines over the poles, and above 35 km in the upper stratosphere. A narrow band of large negative trends extends into the tropical lower stratosphere. Assuming that the observed negative trend before 1995 continued to 2004 cannot explain the ozone changes since 1996. A model accounting for recent changes in equivalent effective stratospheric chlorine, aerosols and Eliassen-Palm flux, on the other hand, closely tracks ozone changes since 1995.

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