Reconciling differences in stratospheric ozone composites

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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Reconciling differences in stratospheric ozone composites

10.5194/acp-2017-142 ◽

2017 ◽

Author(s):

William T. Ball ◽

Justin Alsing ◽

Daniel J. Mortlock ◽

Eugene V. Rozanov ◽

Fiona Tummon ◽

...

Keyword(s):

Particle Filter ◽

Particle Filtering ◽

Sequential Monte Carlo ◽

Stratospheric Ozone ◽

Filter Method ◽

Data Series ◽

Robust Estimate ◽

Source Data ◽

Decadal Trend

Abstract. To accurately estimate decadal trends in stratospheric ozone requires stable long-term observations. Recently, several ozone composites have been published that combine observations from multiple instruments to span more than three decades. Despite this, trends disagree by latitude and altitude, even between composites built upon the same instrument data. We confirm that the leading causes of differences in decadal trend estimates lie in (i) steps in the composite timeseries 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 lead to inaccurate trend estimates. Here, we aim to remove these artefacts by applying particle filtering, sequential Monte Carlo Bayesian estimation, which uses only the data itself in addition to prior knowledge about ozone variability and known problems during instrument operation. We apply the particle filter to stratospheric ozone in 10° bands from 60° S–60° N and from 46–1 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. To analyse the new data series, we use dynamical linear modelling (DLM), which provides a more robust estimate of long-term changes through Bayesian inference than MLR. Particle filtering 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 mid-latitudes, in all four composites analysed, and particularly in the new particle filter composite. The particle filter results also show no hemispheric difference in the recovery at mid-latitudes, in contrast to a feature that is present, but not consistent, in the four composites. We recommend using the particle filter method to construct a new composite based not on existing composites, as we do here, but on the original instrument data: such a product would provide a further advance for the estimation of decadal changes in stratospheric ozone.

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Seasonal stratospheric ozone trends over 2000–2018 derived from several merged data sets

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-7035-2020 ◽

2020 ◽

Vol 20 (11) ◽

pp. 7035-7047 ◽

Cited By ~ 1

Author(s):

Monika E. Szeląg ◽

Viktoria F. Sofieva ◽

Doug Degenstein ◽

Chris Roth ◽

Sean Davis ◽

...

Keyword(s):

Stratospheric Ozone ◽

Equatorial Region ◽

Data Sets ◽

Opposite Pattern ◽

The North ◽

Stratospheric Temperature ◽

Temperature Trends ◽

Ozone Trends ◽

Seasonal Dependence

Abstract. In this work, we analyze the seasonal dependence of ozone trends in the stratosphere using four long-term merged data sets, SAGE-CCI-OMPS, SAGE-OSIRIS-OMPS, GOZCARDS, and SWOOSH, which provide more than 30 years of monthly zonal mean ozone profiles in the stratosphere. We focus here on trends between 2000 and 2018. All data sets show similar results, although some discrepancies are observed. In the upper stratosphere, the trends are positive throughout all seasons and the majority of latitudes. The largest upper-stratospheric ozone trends are observed during local winter (up to 6 % per decade) and equinox (up to 3 % per decade) at mid-latitudes. In the equatorial region, we find a very strong seasonal dependence of ozone trends at all altitudes: the trends vary from positive to negative, with the sign of transition depending on altitude and season. The trends are negative in the upper-stratospheric winter (−1 % per decade to −2 % per decade) and in the lower-stratospheric spring (−2 % per decade to −4 % per decade), but positive (2 % per decade to 3 % per decade) at 30–35 km in spring, while the opposite pattern is observed in summer. The tropical trends below 25 km are negative and maximize during summer (up to −2 % per decade) and spring (up to −3 % per decade). In the lower mid-latitude stratosphere, our analysis points to a hemispheric asymmetry: during local summers and equinoxes, positive trends are observed in the south (+1 % per decade to +2 % per decade), while negative trends are observed in the north (−1 % per decade to −2 % per decade). We compare the seasonal dependence of ozone trends with available analyses of the seasonal dependence of stratospheric temperature trends. We find that ozone and temperature trends show positive correlation in the dynamically controlled lower stratosphere and negative correlation above 30 km, where photochemistry dominates. Seasonal trend analysis gives information beyond that contained in annual mean trends, which can be helpful in order to better understand the role of dynamical variability in short-term trends and future ozone recovery predictions.

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Merged SAGE II, Ozone_cci and OMPS ozone profile dataset and evaluation of ozone trends in the stratosphere

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-12533-2017 ◽

2017 ◽

Vol 17 (20) ◽

pp. 12533-12552 ◽

Cited By ~ 25

Author(s):

Viktoria F. Sofieva ◽

Erkki Kyrölä ◽

Marko Laine ◽

Johanna Tamminen ◽

Doug Degenstein ◽

...

Keyword(s):

Climate Change ◽

Stratospheric Ozone ◽

European Space Agency ◽

Space Agency ◽

Ozone Profile ◽

Ozone Trends ◽

Stratospheric Cooling ◽

The Individual ◽

Good Agreement

Abstract. In this paper, we present a merged dataset of ozone profiles from several satellite instruments: SAGE II on ERBS, GOMOS, SCIAMACHY and MIPAS on Envisat, OSIRIS on Odin, ACE-FTS on SCISAT, and OMPS on Suomi-NPP. The merged dataset is created in the framework of the European Space Agency Climate Change Initiative (Ozone_cci) with the aim of analyzing stratospheric ozone trends. For the merged dataset, we used the latest versions of the original ozone datasets. The datasets from the individual instruments have been extensively validated and intercompared; only those datasets which are in good agreement, and do not exhibit significant drifts with respect to collocated ground-based observations and with respect to each other, are used for merging. The long-term SAGE–CCI–OMPS dataset is created by computation and merging of deseasonalized anomalies from individual instruments. The merged SAGE–CCI–OMPS dataset consists of deseasonalized anomalies of ozone in 10° latitude bands from 90° S to 90° N and from 10 to 50 km in steps of 1 km covering the period from October 1984 to July 2016. This newly created dataset is used for evaluating ozone trends in the stratosphere through multiple linear regression. Negative ozone trends in the upper stratosphere are observed before 1997 and positive trends are found after 1997. The upper stratospheric trends are statistically significant at midlatitudes and indicate ozone recovery, as expected from the decrease of stratospheric halogens that started in the middle of the 1990s and stratospheric cooling.

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An exploration of ozone changes and their radiative forcing prior to the chlorofluorocarbon era

Atmospheric Chemistry and Physics ◽

10.5194/acp-2-363-2002 ◽

2002 ◽

Vol 2 (5) ◽

pp. 363-374 ◽

Cited By ~ 14

Author(s):

D. T. Shindell ◽

G. Faluvegi

Keyword(s):

Ozone Depletion ◽

Tropospheric Ozone ◽

Radiative Forcing ◽

Stratospheric Ozone ◽

Data Sets ◽

Independent Data ◽

Spatial Coverage ◽

Ozone Trends ◽

Ozone Trend

Abstract. Using historical observations and model simulations, we investigate ozone trends prior to the mid-1970s onset of halogen-induced ozone depletion. Though measurements are quite limited, an analysis based on multiple, independent data sets (direct and indirect) provides better constraints than any individual set of observations. We find that three data sets support an apparent long-term stratospheric ozone trend of -7.2 ± 2.3 DU during 1957-1975, which modeling attributes primarily to water vapor increases. The results suggest that 20th century stratospheric ozone depletion may have been roughly 50% more than is generally supposed. Similarly, three data sets support tropospheric ozone increases over polluted Northern Hemisphere continental regions of 8.2 ± 2.1 DU during this period, which are mutually consistent with the stratospheric trends. As with paleoclimate data, which is also based on indirect proxies and/or limited spatial coverage, these results must be interpreted with caution. However, they provide the most thorough estimates presently available of ozone changes prior to the coincident onset of satellite data and halogen dominated ozone changes. If these apparent trends were real, the radiative forcing by stratospheric ozone since the 1950s would then have been -0.15 ± 0.05 W/m2, and -0.2 W/m2 since the preindustrial. For tropospheric ozone, it would have been 0.38 ± 0.10 W/m2 since the late 1950s. Combined with even a very conservative estimate of tropospheric ozone forcing prior to that time, this would be larger than current estimates since 1850 which are derived from models that are even less well constrained. These calculations demonstrate the importance of gaining a better understanding of historical ozone changes.

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The Impact of Non-uniform Sampling on Stratospheric Ozone Trends Derived from Occultation Instruments

10.5194/acp-2017-575 ◽

2017 ◽

Author(s):

Robert P. Damadeo ◽

Joseph M. Zawodny ◽

Ellis E. Remsberg ◽

Kaley A. Walker

Keyword(s):

Stratospheric Ozone ◽

Primary Source ◽

Data Sets ◽

Sampled Data ◽

Uniform Sampling ◽

Ozone Trends ◽

Long Term Trends ◽

Non Uniform Sampling ◽

The Impact

Abstract. This paper applies a recently developed technique for deriving long-term trends in ozone from sparsely sampled data sets to multiple occultation instruments simultaneously without the need for homogenization. The technique can compensate for the non-uniform temporal, spatial, and diurnal sampling of the different instruments and can also be used to account for biases and drifts between instruments. These problems have been noted in recent international assessments as being a primary source of uncertainty that clouds the significance of derived trends. Results show potential recovery trends of ~ 2–3 %/decade in the upper stratosphere at mid-latitudes, which are similar to other studies, and also how sampling biases present in these data sets can create differences in derived "recovery" trends of up to ~ 1 %/decade if not properly accounted for. Limitations inherent to all techniques (e.g., relative instrument drifts) and their impacts (e.g., trend differences up to ~ 2 %/decade) are also described and a potential path forward towards resolution is presented.

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Merged SAGE II, Ozone_cci and OMPS ozone profiles dataset and evaluation of ozone trends in the stratosphere

10.5194/acp-2017-598 ◽

2017 ◽

Cited By ~ 1

Author(s):

Viktoria F. Sofieva ◽

Erkki Kyrölä ◽

Marko Laine ◽

Johanna Tamminen ◽

Doug Degenstein ◽

...

Keyword(s):

Climate Change ◽

Linear Regression ◽

Multiple Linear Regression ◽

Stratospheric Ozone ◽

European Space Agency ◽

Space Agency ◽

Ozone Trends ◽

The Individual ◽

Good Agreement

Abstract. In this paper, we present a merged dataset of ozone profiles from several satellite instruments: SAGE II on ERBS, GOMOS, SCIAMACHY and MIPAS on Envisat, OSIRIS on Odin, ACE-FTS on SCISAT, and OMPS on Suomi-NPP. The merged dataset is created in the framework of European Space Agency Climate Change Initiative (Ozone_cci) with the aim of analyzing stratospheric ozone trends. For the merged dataset, we used the latest versions of the original ozone datasets. The datasets from the individual instruments have been extensively validated and inter-compared; only those datasets, which are in good agreement and do not exhibit significant drifts with respect to collocated ground-based observations and with respect to each other, are used for merging. The long-term SAGE-CCI-OMPS dataset is created by computation and merging of deseasonalized anomalies from individual instruments. The merged SAGE-CCI-OMPS dataset consists of deseasonalized anomalies of ozone in 10° latitude bands from 90° S to 90° N and from 10 to 50 km in steps of 1 km covering the period from October 1984 to July 2016. This newly created dataset is used for evaluating ozone trends in the stratosphere through multiple linear regression. Negative ozone trends in the upper stratosphere are observed before 1997 and positive trends are found after 1997. The upper stratospheric trends are statistically significant at mid-latitudes in the upper stratosphere and indicate ozone recovery, as expected from the decrease of stratospheric halogens that started in the middle of the 1990s.

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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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Dissolved Oxygen Balance Model for Neris

Nonlinear Analysis Modelling and Control ◽

10.15388/na.2001.6.1.15228 ◽

2001 ◽

Vol 6 (1) ◽

pp. 105-131 ◽

Cited By ~ 2

Author(s):

Gaudenta

Keyword(s):

Time Series ◽

Time Series Analysis ◽

Dissolved Oxygen ◽

Biochemical Oxygen Demand ◽

Oxygen Demand ◽

Point Sources ◽

Balance Model ◽

Oxygen Balance ◽

Source Data

We consider a dissolved oxygen balance model for Neris, which includes biochemical oxygen demand, nitrification, sedimentation, algae respiration and photosynthesis. The load from point sources, tributaries and distributed sources are taken into account. Long-term systematic components such as drift and seasonal components are analysed by applying time series analysis. The model is adapted according to the State Environmental Monitoring, and source data of controlled pollution covering the period 1978-1998.

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Stratospheric ozone trends for 1985–2018: sensitivity to recent large variability

10.5194/acp-2019-243 ◽

2019 ◽

Author(s):

William T. Ball ◽

Justin Alsing ◽

Johannes Staehelin ◽

Sean M. Davis ◽

Lucien Froidevaux ◽

...

Keyword(s):

Seasonal Variability ◽

Lower Stratosphere ◽

Stratospheric Ozone ◽

Montreal Protocol ◽

Regression Analyses ◽

Large Variability ◽

Ozone Trends ◽

Ozone Depleting Substances ◽

Made In

Abstract. The Montreal Protocol has successfully prevented catastrophic losses of stratospheric ozone, and signs of recovery are now evident. Nevertheless, recent work suggests that ozone in the lower stratosphere ( 95 %, 30° S–30° N) decreases dominate the quasi-global integrated decrease (99 % probability); the integrated tropical stratospheric column (1–100 hPa, 30° S–30° N) displays a significant overall decrease, with 95 % probability. These decreases do not reveal an inefficacy of the Montreal Protocol. Rather, they suggest other effects to be at work, mainly dynamical variability on long or short timescale, counteracting the protocol's regulation of halogenated ozone depleting substances (hODS). We demonstrate that large inter-annual mid-latitude variations (30° –60° ), such as the 2017 resurgence, are driven by non-linear QBO phase-dependent seasonal variability. However, this variability is not represented in current regression analyses. To understand if observed lower stratospheric decreases are a transient or long-term phenomenon, progress needs to be made in accounting for this dynamically-driven variability.

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Validation and Trend Analysis of Stratospheric Ozone Data from Ground-Based Observations at Lauder, New Zealand

Remote Sensing ◽

10.3390/rs13010109 ◽

2020 ◽

Vol 13 (1) ◽

pp. 109

Author(s):

Leonie Bernet ◽

Ian Boyd ◽

Gerald Nedoluha ◽

Richard Querel ◽

Daan Swart ◽

...

Keyword(s):

New Zealand ◽

Stratospheric Ozone ◽

Microwave Radiometer ◽

Detailed Comparison ◽

Reanalysis Data ◽

Montreal Protocol ◽

Atmospheric Composition ◽

Ozone Trends ◽

Institute Of Technology

Changes in stratospheric ozone have to be assessed continuously to evaluate the effectiveness of the Montreal Protocol. In the southern hemisphere, few ground-based observational datasets exist, making measurements at the Network for the Detection of Atmospheric Composition Change (NDACC) station at Lauder, New Zealand invaluable. Investigating these datasets in detail is essential to derive realistic ozone trends. We compared lidar data and microwave radiometer data with collocated Aura Microwave Limb sounder (MLS) satellite data and ERA5 reanalysis data. The detailed comparison makes it possible to assess inhomogeneities in the data. We find good agreement between the datasets but also some possible biases, especially in the ERA5 data. The data uncertainties and the inhomogeneities were then considered when deriving trends. Using two regression models from the Long-term Ozone Trends and Uncertainties in the Stratosphere (LOTUS) project and from the Karlsruhe Institute of Technology (KIT), we estimated resulting ozone trends. Further, we assessed how trends are affected by data uncertainties and inhomogeneities. We find positive ozone trends throughout the stratosphere between 0% and 5% per decade and show that considering data uncertainties and inhomogeneities in the regression affects the resulting trends.

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