Coherence of long-term stratospheric ozone vertical distribution time series   used for the study of ozone recovery at a northern mid-latitude station

Abstract. The coherence of stratospheric ozone time series retrieved from various observational records is investigated at Haute-Provence Observatory (OHP–43.93° N, 5.71° E). The analysis is accomplished through the intercomparison of collocated ozone measurements of Light Detection and Ranging (lidar) with Solar Backscatter UltraViolet(/2) (SBUV(/2)), Stratospheric Aerosol and Gas Experiment II (SAGE~II), Halogen Occultation Experiment (HALOE), Microwave Limb Sounder (MLS) on Upper Atmosphere Research Satellite (UARS) and Aura and Global Ozone Monitoring by Occultation of Stars (GOMOS) satellite observations as well as with in situ ozonesondes and ground-based Umkehr measurements performed at OHP. A detailed statistical study of the relative differences of ozone observations over the whole stratosphere is performed to detect any specific drift in the data. On average, all instruments show their best agreement with lidar at 20–40 km, where deviations are within ±5 %. Discrepancies are somewhat higher below 20 and above 40 km. The agreement with SAGE II data is remarkable since average differences are within ±1 % at 17–41 km. In contrast, Umkehr data underestimate systematically the lidar measurements in the whole stratosphere with a near zero bias at 16–8 hPa (~30 km). Drifts are estimated using simple linear regression for the data sets analysed in this study, from the monthly averaged difference time series. The derived values are less than ±0.5 % yr−1 in the 20–40 km altitude range and most drifts are not significant at the 2σ level. We also discuss the possibilities of extending the SAGE II and HALOE data with the GOMOS and Aura MLS data in consideration with relative offsets and drifts since the combination of such data sets are likely to be used for the study of stratospheric ozone recovery in the future.

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Coherence of long-term stratospheric ozone vertical distribution time series used for the study of ozone recovery at a northern mid-latitude station

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-10-28519-2010 ◽

2010 ◽

Vol 10 (11) ◽

pp. 28519-28564

Author(s):

P. J. Nair ◽

S. Godin-Beekmann ◽

A. Pazmiño ◽

A. Hauchecorne ◽

G. Ancellet ◽

...

Keyword(s):

Time Series ◽

Stratospheric Ozone ◽

Stratospheric Aerosol ◽

Data Sets ◽

Zero Bias ◽

Lidar Measurements ◽

Relative Differences ◽

Difference Time

Abstract. The coherence of stratospheric ozone time series retrieved from various observational records is investigated at Haute–Provence Observatory (OHP–43.93° N, 5.71° E). The analysis is accomplished through the intercomparison of collocated ozone measurements of Light Detection and Ranging (lidar) with Solar Backscatter UltraViolet(/2) (SBUV(/2)), Stratospheric Aerosol and Gas Experiment II (SAGE II), Halogen Occultation Experiment (HALOE), Microwave Limb Sounder (MLS) on Upper Atmosphere Research Satellite (UARS) and Aura and Global Ozone Monitoring by Occultation of Stars (GOMOS) satellite observations as well as with in-situ ozonesondes and ground-based Umkehr measurements performed at OHP. A detailed statistical study of the relative differences of ozone observations is performed to detect any specific drifts in the data. On average, all instruments show their best agreement with lidar at 20–40 km, where deviations are within ±5%. Discrepancies are somewhat higher below 20 and above 40 km. The agreement with SAGE II data is remarkable since average differences are within ±1% at 17–41 km. In contrast, Umkehr data underestimate systematically the lidar measurements in the whole stratosphere albeit a near zero bias is observed at 16–8 hPa (~30 km). Drifts are estimated using simple linear regression for the long-term (more than 10 years long) data sets analysed in this study, from the monthly averaged difference time series. The derived values are less than ±0.5% yr−1 in the 20–40 km altitude range and most drifts are not significant at the 2σ level.

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Evolution of stratospheric ozone and water vapour time series studied with satellite measurements

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-9-1157-2009 ◽

2009 ◽

Vol 9 (1) ◽

pp. 1157-1209 ◽

Cited By ~ 4

Author(s):

A. Jones ◽

J. Urban ◽

D. P. Murtagh ◽

P. Eriksson ◽

S. Brohede ◽

...

Keyword(s):

Time Series ◽

Water Vapour ◽

Stratospheric Ozone ◽

Stratospheric Aerosol ◽

Data Sets ◽

Quasi Biennial Oscillation ◽

Long Term Stability ◽

Infrared Imager ◽

Scanning Imaging

Abstract. The long term evolution of stratospheric ozone and water vapour has been investigated by extending satellite time series to April 2008. For ozone, we examine monthly average ozone values from various satellite data sets for nine latitude and altitude bins covering 60° S to 60° N and 20–45 km and covering the time period 1979–2008. Data are from the Stratospheric Aerosol and Gas Experiment (SAGE I+II), the HALogen Occultation Experiment (HALOE), the Solar BackscatterUltraViolet-2 (SBUV/2) instrument, the Sub-Millimetre Radiometer (SMR), the Optical Spectrograph InfraRed Imager System (OSIRIS), and the SCanning Imaging Absorption spectroMeter for Atmospheric CHartograpY (SCIAMACHY). Monthly ozone anomalies are calculated by utilising a linear regression model, which also models the solar, quasi-biennial oscillation (QBO), and seasonal cycle contributions. Individual instrument ozone anomalies are combined producing a weighted all instrument average. Assuming a turning point of 1997 and that the all instrument average is represented by good instrumental long term stability, the largest statistically significant ozone declines from 1979–1997 are seen at the mid-latitudes between 35 and 45 km, namely −7.7%/decade in the Northern Hemisphere and −7.8%/decade in the Southern Hemisphere. For the period 1997 to 2008 we find that the southern mid-latitudes between 35 and 45 km show the largest ozone recovery (+3.4%/decade) compared to other global regions, although the estimated trend model error is of a similar magnitude (+2.1%/decade, at the 95% confidence level). An all instrument average is also constructed from water vapour anomalies during 1984–2008, using the SAGE II, HALOE, SMR, and the Microwave Limb Sounder (aura/MLS) measurements. We report that the decrease in water vapour values after 2001 slows down around 2004 in the lower tropical stratosphere (20–25 km), and has even shown signs of increasing values in upper stratospheric mid-latitudes. We show that a similar correlation is also seen with the temperature measured at 100 hPa during this same period.

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Evolution of stratospheric ozone and water vapour time series studied with satellite measurements

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-6055-2009 ◽

2009 ◽

Vol 9 (16) ◽

pp. 6055-6075 ◽

Cited By ~ 87

Author(s):

A. Jones ◽

J. Urban ◽

D. P. Murtagh ◽

P. Eriksson ◽

S. Brohede ◽

...

Keyword(s):

Time Series ◽

Water Vapour ◽

Stratospheric Ozone ◽

Stratospheric Aerosol ◽

Data Sets ◽

Model Errors ◽

Quasi Biennial Oscillation ◽

Sigma Level ◽

Scanning Imaging

Abstract. The long term evolution of stratospheric ozone and water vapour has been investigated by extending satellite time series to April 2008. For ozone, we examine monthly average ozone values from various satellite data sets for nine latitude and altitude bins covering 60° S to 60° N and 20–45 km and covering the time period of 1979–2008. Data are from the Stratospheric Aerosol and Gas Experiment (SAGE I+II), the HALogen Occultation Experiment (HALOE), the Solar BackscatterUltraViolet-2 (SBUV/2) instrument, the Sub-Millimetre Radiometer (SMR), the Optical Spectrograph InfraRed Imager System (OSIRIS), and the SCanning Imaging Absorption spectroMeter for Atmospheric CHartograpY (SCIAMACHY). Monthly ozone anomalies are calculated by utilising a linear regression model, which also models the solar, quasi-biennial oscillation (QBO), and seasonal cycle contributions. Individual instrument ozone anomalies are combined producing an all instrument average. Assuming a turning point of 1997 and that the all instrument average is represented by good instrumental long term stability, the largest statistically significant ozone declines (at two sigma) from 1979–1997 are seen at the mid-latitudes between 35 and 45 km, namely −7.2%±0.9%/decade in the Northern Hemisphere and −7.1%±0.9%/in the Southern Hemisphere. Furthermore, for the period 1997 to 2008 we find that the same locations show the largest ozone recovery (+1.4% and +0.8%/decade respectively) compared to other global regions, although the estimated trend model errors indicate that the trend estimates are not significantly different from a zero trend at the 2 sigma level. An all instrument average is also constructed from water vapour anomalies during 1991–2008, using the SAGE II, HALOE, SMR, and the Microwave Limb Sounder (Aura/MLS) measurements. We report that the decrease in water vapour values after 2001 slows down around 2004–2005 in the lower tropical stratosphere (20–25 km) and has even shown signs of increasing until present. We show that a similar correlation is also seen with the temperature measured at 100 hPa during this same period.

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Intercomparison of stratospheric ozone profiles for the assessment of the upgraded GROMOS radiometer at Bern

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-6-6097-2013 ◽

2013 ◽

Vol 6 (4) ◽

pp. 6097-6146 ◽

Cited By ~ 13

Author(s):

S. Studer ◽

K. Hocke ◽

M. Pastel ◽

S. Godin-Beekmann ◽

N. Kämpfer

Keyword(s):

Time Series ◽

Stratospheric Ozone ◽

Microwave Radiometer ◽

Mean Difference ◽

Atmospheric Composition ◽

Time Period ◽

Lidar Measurements ◽

Mesospheric Ozone ◽

Relative Differences

Abstract. Since November 1994, the GROund-based Millimeter-wave Ozone Spectrometer (GROMOS) measures stratospheric and lower mesospheric ozone in Bern, Switzerland (47.95° N, 7.44° E). GROMOS is part of the Network for the Detection of Atmospheric Composition Change (NDACC). In July 2009, a Fast-Fourier-Transform spectrometer (FFTS) has been added as backend to GROMOS. The new FFTS and the original filter bench (FB) measured parallel for over two years. In October 2011, the FB has been turned off and the FFTS is now used to continue the ozone time series. For a consolidated ozone time series in the frame of NDACC, the quality of the stratospheric ozone profiles obtained with the FFTS has to be assessed. The FFTS results from July 2009 to December 2011 are compared to ozone profiles retrieved by the FB. FFTS and FB of the GROMOS microwave radiometer agree within 5% above 20 hPa. A later harmonization of both time series will be realized by taking the FFTS as benchmark for the FB. Ozone profiles from the FFTS are also compared to coinciding lidar measurements from the Observatoire Haute Provence (OHP), France. For the time period studied a maximum mean difference (lidar – GROMOS FFTS) of +3.8% at 3.1 hPa and a minimum mean difference of +1.4% at 8 hPa is found. Further, intercomparisons with ozone profiles from other independent instruments are performed: satellite measurements include MIPAS onboard ENVISAT, SABER onboard TIMED, MLS onboard EOS Aura and ACE-FTS onboard SCISAT-1. Additionally, ozonesondes launched from Payerne, Switzerland, are used in the lower stratosphere. Mean relative differences of GROMOS FFTS and these independent instruments are less than 10% between 50 and 0.1 hPa.

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Merging of ozone profiles from SCIAMACHY, OMPS and SAGE II observations to study stratospheric ozone changes

Atmospheric Measurement Techniques ◽

10.5194/amt-12-2423-2019 ◽

2019 ◽

Vol 12 (4) ◽

pp. 2423-2444

Author(s):

Carlo Arosio ◽

Alexei Rozanov ◽

Elizaveta Malinina ◽

Mark Weber ◽

John P. Burrows

Keyword(s):

Time Series ◽

Stratospheric Ozone ◽

Multivariate Regression Analysis ◽

Stratospheric Aerosol ◽

Montreal Protocol ◽

Inversion Algorithm ◽

Data Set ◽

Large Variability ◽

Stratospheric Temperature

Abstract. This paper presents vertically and zonally resolved merged ozone time series from limb measurements of the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) and the Ozone Mapping and Profiler Suite (OMPS) Limb Profiler (LP). In addition, we present the merging of the latter two data sets with zonally averaged profiles from Stratospheric Aerosol and Gas Experiment (SAGE) II. The retrieval of ozone profiles from SCIAMACHY and OMPS-LP is performed using an inversion algorithm developed at the University of Bremen. To optimize the merging of these two time series, we use data from the Microwave Limb Sounder (MLS) as a transfer function and we follow two approaches: (1) a conventional method involving the calculation of deseasonalized anomalies and (2) a “plain-debiasing” approach, generally not considered in previous similar studies, which preserves the seasonal cycles of each instrument. We find a good correlation and no significant drifts between the merged and MLS time series. Using the merged data set from both approaches, we apply a multivariate regression analysis to study ozone changes in the 20–50 km range over the 2003–2018 period. Exploiting the dense horizontal sampling of the instruments, we investigate not only the zonally averaged field, but also the longitudinally resolved long-term ozone variations, finding an unexpected and large variability, especially at mid and high latitudes, with variations of up to 3 %–5 % per decade at altitudes around 40 km. Significant positive linear trends of about 2 %–4 % per decade were identified in the upper stratosphere between altitudes of 38 and 45 km at mid latitudes. This is in agreement with the predicted recovery of upper stratospheric ozone, which is attributed to both the adoption of measures to limit the release of halogen-containing ozone-depleting substances (Montreal Protocol) and the decrease in stratospheric temperature resulting from the increasing concentration of greenhouse gases. In the tropical stratosphere below 25 km negative but non-significant trends were found. We compare our results with previous studies and with short-term trends calculated over the SCIAMACHY period (2002–2012). While generally a good agreement is found, some discrepancies are seen in the tropical mid stratosphere. Regarding the merging of SAGE II with SCIAMACHY and OMPS-LP, zonal mean anomalies are taken into consideration and ozone trends before and after 1997 are calculated. Negative trends above 30 km are found for the 1985–1997 period, with a peak of −6 % per decade at mid latitudes, in agreement with previous studies. The increase in ozone concentration in the upper stratosphere is confirmed over the 1998–2018 period. Trends in the tropical stratosphere at 30–35 km show an interesting behavior: over the 1998–2018 period a negligible trend is found. However, between 2004 and 2011 a negative long-term change is detected followed by a positive change between 2012 and 2018. We attribute this behavior to dynamical changes in the tropical middle stratosphere.

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Relative drifts and stability of satellite and ground-based stratospheric ozone profiles at NDACC lidar stations

Atmospheric Measurement Techniques ◽

10.5194/amt-5-1301-2012 ◽

2012 ◽

Vol 5 (6) ◽

pp. 1301-1318 ◽

Cited By ~ 32

Author(s):

P. J. Nair ◽

S. Godin-Beekmann ◽

L. Froidevaux ◽

L. E. Flynn ◽

J. M. Zawodny ◽

...

Keyword(s):

Stratospheric Ozone ◽

Measurement Techniques ◽

Data Sets ◽

Data Set ◽

Meteorological Observatory ◽

The Stability ◽

Combined Time Series ◽

Relative Differences ◽

Term Data

Abstract. The long-term evolution of stratospheric ozone at different stations in the low and mid-latitudes is investigated. The analysis is performed by comparing the collocated profiles of ozone lidars, at the northern mid-latitudes (Meteorological Observatory Hohenpeißenberg, Haute-Provence Observatory, Tsukuba and Table Mountain Facility), tropics (Mauna Loa Observatory) and southern mid-latitudes (Lauder), with ozonesondes and space-borne sensors (SBUV(/2), SAGE II, HALOE, UARS MLS and Aura MLS), extracted around the stations. Relative differences are calculated to find biases and temporal drifts in the measurements. All measurement techniques show their best agreement with respect to the lidar at 20–40 km, where the differences and drifts are generally within ±5% and ±0.5% yr−1, respectively, at most stations. In addition, the stability of the long-term ozone observations (lidar, SBUV(/2), SAGE II and HALOE) is evaluated by the cross-comparison of each data set. In general, all lidars and SBUV(/2) exhibit near-zero drifts and the comparison between SAGE II and HALOE shows larger, but insignificant drifts. The RMS of the drifts of lidar and SBUV(/2) is 0.22 and 0.27% yr−1, respectively at 20–40 km. The average drifts of the long-term data sets, derived from various comparisons, are less than ±0.3% yr−1 in the 20–40 km altitude at all stations. A combined time series of the relative differences between SAGE II, HALOE and Aura MLS with respect to lidar data at six sites is constructed, to obtain long-term data sets lasting up to 27 years. The relative drifts derived from these combined data are very small, within ±0.2% yr−1.

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Relative drifts and stability of satellite and ground-based stratospheric ozone profiles at NDACC lidar stations

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-5-471-2012 ◽

2012 ◽

Vol 5 (1) ◽

pp. 471-516

Author(s):

P. J. Nair ◽

S. Godin-Beekmann ◽

L. Froidevaux ◽

L. E. Flynn ◽

J. M. Zawodny ◽

...

Keyword(s):

Stratospheric Ozone ◽

Measurement Techniques ◽

Data Sets ◽

Data Set ◽

Meteorological Observatory ◽

The Stability ◽

Combined Time Series ◽

Relative Differences ◽

Term Data

Abstract. The long-term evolution of stratospheric ozone at different stations in the low and mid-latitudes is investigated. The analysis is performed by comparing the collocated profiles of ozone lidars, at the northern mid-latitudes (Meteorological Observatory Hohenpeißenberg, Haute-Provence Observatory, Tsukuba and Table Mountain Facility), tropics (Mauna Loa Observatory) and southern mid-latitudes (Lauder), with ozonesondes and space-borne sensors (SBUV(/2), SAGE II, HALOE, UARS MLS and Aura MLS), extracted around the stations. Relative differences are calculated to find biases and temporal drifts in the measurements. All measurement techniques show their best agreement with respect to the lidar at 20–40 km, where the differences are within ±3% and drifts are less than ±0.3% yr−1 at all stations. In addition, the stability of the long-term ozone observations (lidar, SBUV(/2), SAGE II and HALOE) is evaluated by the cross-comparison of each data set. In general, all lidars and SBUV(/2) exhibit near zero drifts and the comparison between SAGE II and HALOE shows larger, but insignificant drifts. The RMS of the drifts of lidar and SBUV(/2) is 0.22 and 0.27% yr−1, respectively. The average drifts of the long-term data sets, derived from various comparisons, are less than ±0.3% yr−1 in 20–40 km at all stations. A combined time series of the relative differences between SAGE II, HALOE and Aura MLS with respect to lidar data at six sites is constructed, to obtain long-term data sets lasting up to 27 yr. The relative drifts derived from these combined data are very small, within ±0.2% yr−1.

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Intercomparison of in-situ aircraft and satellite aerosol measurements in the stratosphere

Scientific Reports ◽

10.1038/s41598-019-52089-6 ◽

2019 ◽

Vol 9 (1) ◽

Author(s):

Oscar S. Sandvik ◽

Johan Friberg ◽

Bengt G. Martinsson ◽

Peter F. J. van Velthoven ◽

Markus Hermann ◽

...

Keyword(s):

Stratospheric Aerosol ◽

Aerosol Composition ◽

Tropospheric Aerosol ◽

Lidar Measurements ◽

Northern Hemispheric ◽

Extratropical Tropopause ◽

Passenger Aircraft ◽

First Time

Abstract Aerosol composition and optical scattering from particles in the lowermost stratosphere (LMS) have been studied by comparing in-situ aerosol samples from the IAGOS-CARIBIC passenger aircraft with vertical profiles of aerosol backscattering obtained from the CALIOP lidar aboard the CALIPSO satellite. Concentrations of the dominating fractions of the stratospheric aerosol, being sulphur and carbon, have been obtained from post-flight analysis of IAGOS-CARIBIC aerosol samples. This information together with literature data on black carbon concentrations were used to calculate the aerosol backscattering which subsequently is compared with measurements by CALIOP. Vertical optical profiles were taken in an altitude range of several kilometres from and above the northern hemispheric extratropical tropopause for the years 2006-2014. We find that the two vastly different measurement platforms yield different aerosol backscattering, especially close to the tropopause where the influence from tropospheric aerosol is strong. The best agreement is found when the LMS is affected by volcanism, i.e., at elevated aerosol loadings. At background conditions, best agreement is obtained some distance (>2 km) above the tropopause in winter and spring, i.e., at likewise elevated aerosol loadings from subsiding aerosol-rich stratospheric air. This is to our knowledge the first time the CALIPSO lidar measurements have been compared to in-situ long-term aerosol measurements.

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Merging of ozone profiles from SCIAMACHY, OMPS and SAGE II observations to study stratospheric ozone changes

10.5194/amt-2018-275 ◽

2018 ◽

Author(s):

Carlo Arosio ◽

Alexei Rozanov ◽

Elizaveta Malinina ◽

Mark Weber ◽

John P. Burrows

Keyword(s):

Time Series ◽

Stratospheric Ozone ◽

Multivariate Regression Analysis ◽

Stratospheric Aerosol ◽

Montreal Protocol ◽

Data Sets ◽

Data Set ◽

Vertical Range ◽

Scanning Imaging ◽

Ozone Depleting Substances

Abstract. This paper presents vertically and zonally resolved merged ozone time series from limb measurements of the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) and the Ozone Mapping and Profiler Suite (OMPS). In addition, we present the merging of the latter two data sets with zonally averaged profiles from the Stratospheric Aerosol and Gas Experiment (SAGE) II. The retrieval of ozone profiles from SCIAMACHY and OMPS is performed at the University of Bremen. Within the merging procedure of these two time series we use data from the Microwave Limb Sounder (MLS) as a transfer function and we follow two approaches: (1) a standard method involving the calculation of deseasonalized anomalies and (2) a plain-debiasing approach, generally not considered in previous similar studies, which preserves the seasonal cycles of each instrument. We find a good correlation and no significant drifts between the merged and MLS time series. Using the merged data set, we apply a multivariate regression analysis to study ozone changes over the 2003–2018 period in the 20–50 km vertical range. Exploiting the high horizontal sampling of the instruments, we investigate not only the zonally averaged field but also the longitudinally resolved long-term ozone variations, finding a remarkable variability, especially at mid- and high-latitudes. Significant positive linear trends of about 2–4 % per decade were identified in the upper stratosphere between 38 and 45 km at mid-latitudes. This is in agreement with the predicted recovery of upper stratospheric ozone, which is attributed both to the adoption of measures to limit the release of halogen-containing ozone-depleting substances included in the Montreal protocol and to the increasing concentration of greenhouse gases. In the tropical stratosphere below 25 km negative but non-significant trends were found. We compare our results with similar previous studies and with short-term trends calculated over the SCIAMACHY period: while a general agreement is found, some discrepancies are seen in the tropical mid-stratosphere. Regarding the merging of SAGE II with SCIAMACHY and OMPS, zonal mean anomalies are taken into consideration and ozone trends after and before 1997 are shown. Negative trends above 30 km are found for the 1985–1997 period, with a peak of −6 % per decade at mid-latitudes, in agreement with previous studies. The increase of ozone concentration in the upper stratosphere is confirmed considering the 1998–2018 period. Trends in the middle and lower tropical stratosphere are found to be non-significant.

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Reconciling differences in stratospheric ozone composites

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-12269-2017 ◽

2017 ◽

Vol 17 (20) ◽

pp. 12269-12302 ◽

Cited By ~ 22

Author(s):

William T. Ball ◽

Justin Alsing ◽

Daniel J. Mortlock ◽

Eugene V. Rozanov ◽

Fiona Tummon ◽

...

Keyword(s):

Time Series ◽

Likelihood Function ◽

Stratospheric Ozone ◽

Gaussian Mixture ◽

Robust Estimate ◽

Mixture Density ◽

Source Data ◽

Ozone Trends ◽

Decadal Trend

Abstract. Observations of stratospheric ozone from multiple instruments now span three decades; combining these into composite datasets allows long-term ozone trends to be estimated. Recently, several ozone composites have been published, but trends disagree by latitude and altitude, even between composites built upon the same instrument data. We confirm that the main causes of differences in decadal trend estimates lie in (i) steps in the composite time series when the instrument source data changes and (ii) artificial sub-decadal trends in the underlying instrument data. These artefacts introduce features that can alias with regressors in multiple linear regression (MLR) analysis; both can lead to inaccurate trend estimates. Here, we aim to remove these artefacts using Bayesian methods to infer the underlying ozone time series from a set of composites by building a joint-likelihood function using a Gaussian-mixture density to model outliers introduced by data artefacts, together with a data-driven prior on ozone variability that incorporates knowledge of problems during instrument operation. We apply this Bayesian self-calibration approach to stratospheric ozone in 10° bands from 60° S to 60° N and from 46 to 1 hPa (∼ 21–48 km) for 1985–2012. There are two main outcomes: (i) we independently identify and confirm many of the data problems previously identified, but which remain unaccounted for in existing composites; (ii) we construct an ozone composite, with uncertainties, that is free from most of these problems – we call this the BAyeSian Integrated and Consolidated (BASIC) composite. To analyse the new BASIC composite, we use dynamical linear modelling (DLM), which provides a more robust estimate of long-term changes through Bayesian inference than MLR. BASIC and DLM, together, provide a step forward in improving estimates of decadal trends. Our results indicate a significant recovery of ozone since 1998 in the upper stratosphere, of both northern and southern midlatitudes, in all four composites analysed, and particularly in the BASIC composite. The BASIC results also show no hemispheric difference in the recovery at midlatitudes, in contrast to an apparent feature that is present, but not consistent, in the four composites. Our overall conclusion is that it is possible to effectively combine different ozone composites and account for artefacts and drifts, and that this leads to a clear and significant result that upper stratospheric ozone levels have increased since 1998, following an earlier decline.

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