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Observations of anthropogenic global warming

Papers on stratospheric ozone measurements

Posted by Ari Jokimäki on October 28, 2014

This is a list of papers on stratospheric ozone measurements. The list is not complete, and will most likely be updated in future in order to make it more thorough and more representative.

Trends in stratospheric ozone derived from merged SAGE II and Odin-OSIRIS satellite observations – Bourassa et al. (2014)
Abstract: “Stratospheric ozone profile measurements from the Stratospheric Aerosol and Gas Experiment~(SAGE) II satellite instrument (1984–2005) are combined with those from the Optical Spectrograph and InfraRed Imager System (OSIRIS) instrument on the Odin satellite (2001–Present) to quantify interannual variability and decadal trends in stratospheric ozone between 60° S and 60° N. These data are merged into a multi-instrument, long-term stratospheric ozone record (1984–present) by analyzing the measurements during the overlap period of 2002–2005 when both satellite instruments were operational. The variability in the deseasonalized time series is fit using multiple linear regression with predictor basis functions including the quasi-biennial oscillation, El Niño–Southern Oscillation index, solar activity proxy, and the pressure at the tropical tropopause, in addition to two linear trends (one before and one after 1997), from which the decadal trends in ozone are derived. From 1984 to 1997, there are statistically significant negative trends of 5–10% per decade throughout the stratosphere between approximately 30 and 50 km. From 1997 to present, a statistically significant recovery of 3–8% per decade has taken place throughout most of the stratosphere with the notable exception between 40° S and 40° N below approximately 22 km where the negative trend continues. The recovery is not significant between 25 and 35 km altitudes when accounting for a conservative estimate of instrument drift.”
Bourassa, A. E., Degenstein, D. A., Randel, W. J., Zawodny, J. M., Kyrölä, E., McLinden, C. A., Sioris, C. E., and Roth, C. Z.: Trends in stratospheric ozone derived from merged SAGE II and Odin-OSIRIS satellite observations, Atmos. Chem. Phys., 14, 6983-6994, doi:10.5194/acp-14-6983-2014, 2014. [FULL TEXT]

Ozone and temperature decadal trends in the stratosphere, mesosphere and lower thermosphere, based on measurements from SABER on TIMED – Huang et al. (2014)
Abstract: “We have derived ozone and temperature trends from years 2002 through 2012, from 20 to 100 km altitude, and 48° S to 48° N latitude, based on measurements from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics (TIMED) satellite. For the first time, trends of ozone and temperature measured at the same times and locations are obtained, and their correlations should provide useful information about the relative importance of photochemistry versus dynamics over the longer term. We are not aware of comparable results covering this time period and spatial extent. For stratospheric ozone, until the late 1990s, previous studies found negative trends (decreasing amounts). In recent years, some empirical and modeling studies have shown the occurrence of a turnaround in the decreasing ozone, possibly beginning in the late 1990s, suggesting that the stratospheric ozone trend is leveling off or even turning positive. Our global results add more definitive evidence, expand the coverage, and show that at mid-latitudes (north and south) in the stratosphere, the ozone trends are indeed positive, with ozone having increased by a few percent from 2002 through 2012. However, in the tropics, we find negative ozone trends between 25 and 50 km. For stratospheric temperatures, the trends are mostly negatively correlated to the ozone trends. The temperature trends are positive in the tropics between 30 and 40 km, and between 20 and 25 km, at approximately 24° N and at 24° S latitude. The stratospheric temperature trends are otherwise mostly negative. In the mesosphere, the ozone trends are mostly flat, with suggestions of small positive trends at lower latitudes. The temperature trends in this region are mostly negative, showing decreases of up to ~ −3 K decade−1. In the lower thermosphere (between ~ 85 and 100 km), ozone and temperature trends are both negative. The ozone trend can approach ~ −10% decade−1, and the temperature trend can approach ~ −3 K decade−1. Aside from trends, these patterns of ozone–temperature correlations are consistent with previous studies of ozone and temperature perturbations such as the quasi-biennial (QBO) and semiannual (SAO) oscillations, and add confidence to the results.”
Huang, F. T., Mayr, H. G., Russell III, J. M., and Mlynczak, M. G.: Ozone and temperature decadal trends in the stratosphere, mesosphere and lower thermosphere, based on measurements from SABER on TIMED, Ann. Geophys., 32, 935-949, doi:10.5194/angeo-32-935-2014, 2014. [FULL TEXT]

Stratospheric ozone trends and variability as seen by SCIAMACHY from 2002 to 2012 – Gebhardt et al. (2014)
Abstract: “Vertical profiles of the rate of linear change (trend) in the altitude range 15–50 km are determined from decadal O3 time series obtained from SCIAMACHY1/ENVISAT2 measurements in limb-viewing geometry. The trends are calculated by using a multivariate linear regression. Seasonal variations, the quasi-biennial oscillation, signatures of the solar cycle and the El Niño–Southern Oscillation are accounted for in the regression. The time range of trend calculation is August 2002–April 2012. A focus for analysis are the zonal bands of 20° N–20° S (tropics), 60–50° N, and 50–60° S (midlatitudes). In the tropics, positive trends of up to 5% per decade between 20 and 30 km and negative trends of up to 10% per decade between 30 and 38 km are identified. Positive O3 trends of around 5% per decade are found in the upper stratosphere in the tropics and at midlatitudes. Comparisons between SCIAMACHY and EOS MLS3 show reasonable agreement both in the tropics and at midlatitudes for most altitudes. In the tropics, measurements from OSIRIS4/Odin and SHADOZ5 are also analysed. These yield rates of linear change of O3 similar to those from SCIAMACHY. However, the trends from SCIAMACHY near 34 km in the tropics are larger than MLS and OSIRIS by a factor of around two.”
Gebhardt, C., Rozanov, A., Hommel, R., Weber, M., Bovensmann, H., Burrows, J. P., Degenstein, D., Froidevaux, L., and Thompson, A. M.: Stratospheric ozone trends and variability as seen by SCIAMACHY from 2002 to 2012, Atmos. Chem. Phys., 14, 831-846, doi:10.5194/acp-14-831-2014, 2014. [FULL TEXT]

Drift-corrected trends and periodic variations in MIPAS IMK/IAA ozone measurements – Eckert et al. (2014)
Abstract: “Drifts, trends and periodic variations were calculated from monthly zonally averaged ozone profiles. The ozone profiles were derived from level-1b data of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) by means of the scientific level-2 processor run by the Karlsruhe Institute of Technology (KIT), Institute for Meteorology and Climate Research (IMK). All trend and drift analyses were performed using a multilinear parametric trend model which includes a linear term, several harmonics with period lengths from 3 to 24 months and the quasi-biennial oscillation (QBO). Drifts at 2-sigma significance level were mainly negative for ozone relative to Aura MLS and Odin OSIRIS and negative or near zero for most of the comparisons to lidar measurements. Lidar stations used here include those at Hohenpeissenberg (47.8° N, 11.0° E), Lauder (45.0° S, 169.7° E), Mauna Loa (19.5° N, 155.6° W), Observatoire Haute Provence (43.9° N, 5.7° E) and Table Mountain (34.4° N, 117.7° W). Drifts against the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) were found to be mostly insignificant. The assessed MIPAS ozone trends cover the time period of July 2002 to April 2012 and range from −0.56 ppmv decade−1 to +0.48 ppmv decade−1 (−0.52 ppmv decade−1 to +0.47 ppmv decade−1 when displayed on pressure coordinates) depending on altitude/pressure and latitude. From the empirical drift analyses we conclude that the real ozone trends might be slightly more positive/less negative than those calculated from the MIPAS data, by conceding the possibility of MIPAS having a very small (approximately within −0.3 ppmv decade−1) negative drift for ozone. This leads to drift-corrected trends of −0.41 ppmv decade−1 to +0.55 ppmv decade−1 (−0.38 ppmv decade−1 to +0.53 ppmv decade−1 when displayed on pressure coordinates) for the time period covered by MIPAS Envisat measurements, with very few negative and large areas of positive trends at mid-latitudes for both hemispheres around and above 30 km (~10 hPa). Negative trends are found in the tropics around 25 and 35 km (~25 and 5 hPa), while an area of positive trends is located right above the tropical tropopause. These findings are in good agreement with the recent literature. Differences of the trends compared with the recent literature could be explained by a possible shift of the subtropical mixing barriers. Results for the altitude–latitude distribution of amplitudes of the quasi-biennial, annual and the semi-annual oscillation are overall in very good agreement with recent findings.”
Eckert, E., von Clarmann, T., Kiefer, M., Stiller, G. P., Lossow, S., Glatthor, N., Degenstein, D. A., Froidevaux, L., Godin-Beekmann, S., Leblanc, T., McDermid, S., Pastel, M., Steinbrecht, W., Swart, D. P. J., Walker, K. A., and Bernath, P. F.: Drift-corrected trends and periodic variations in MIPAS IMK/IAA ozone measurements, Atmos. Chem. Phys., 14, 2571-2589, doi:10.5194/acp-14-2571-2014, 2014. [FULL TEXT]

Decadal-scale responses in middle and upper stratospheric ozone from SAGE II version 7 data – Remsberg (2014)
Abstract: “Stratospheric Aerosol and Gas Experiment (SAGE II) version 7 (v7) ozone profiles are analyzed for their decadal-scale responses in the middle and upper stratosphere for 1991 and 1992–2005 and compared with those from its previous version 6.2 (v6.2). Multiple linear regression (MLR) analysis is applied to time series of its ozone number density vs. altitude data for a range of latitudes and altitudes. The MLR models that are fit to the time series data include a periodic 11 yr term, and it is in-phase with that of the 11 yr, solar UV (Ultraviolet)-flux throughout most of the latitude/altitude domain of the middle and upper stratosphere. Several regions that have a response that is not quite in-phase are interpreted as being affected by decadal-scale, dynamical forcings. The maximum minus minimum, solar cycle (SC-like) responses for the ozone at the low latitudes are similar from the two SAGE II data versions and vary from about 5 to 2.5% from 35 to 50 km, although they are resolved better with v7. SAGE II v7 ozone is also analyzed for 1984–1998, in order to mitigate effects of end-point anomalies that bias its ozone in 1991 and the analyzed results for 1991–2005 or following the Pinatubo eruption. Its SC-like ozone response in the upper stratosphere is of the order of 4% for 1984–1998 vs. 2.5 to 3% for 1991–2005. The SAGE II v7 results are also recompared with the responses in ozone from the Halogen Occultation Experiment (HALOE) that are in terms of mixing ratio vs. pressure for 1991–2005 and then for late 1992–2005 to avoid any effects following Pinatubo. Shapes of their respective response profiles agree very well for 1992–2005. The associated linear trends of the ozone are not as negative in 1992–2005 as in 1984–1998, in accord with a leveling off of the effects of reactive chlorine on ozone. It is concluded that the SAGE II v7 ozone yields SC-like ozone responses and trends that are of better quality than those from v6.2.”
Remsberg, E. E.: Decadal-scale responses in middle and upper stratospheric ozone from SAGE II version 7 data, Atmos. Chem. Phys., 14, 1039-1053, doi:10.5194/acp-14-1039-2014, 2014. [FULL TEXT]

Combined SAGE II–GOMOS ozone profile data set for 1984–2011 and trend analysis of the vertical distribution of ozone – Kyrölä et al. (2013)
Abstract: “We have studied data from two satellite occultation instruments in order to generate a high vertical resolution homogeneous ozone time series of 26 yr. The Stratospheric Aerosol and Gas Experiment (SAGE) II solar occultation instrument and the Global Ozone Monitoring by Occultation of Stars (GOMOS) instrument measured ozone profiles in the stratosphere and mesosphere from 1984–2005 and 2002–2012, respectively. Global coverage, good vertical resolution, and the self-calibrating measurement method make data from these instruments valuable for the detection of changes in vertical distribution of ozone over time. As both instruments share a common measurement period from 2002–2005, it is possible to inter-calibrate the data sets. We investigate how well these measurements agree with each other and combine all the data to produce a new stratospheric ozone profile data set. Above 55 km, SAGE II measurements show much less ozone than the GOMOS nighttime measurements as a consequence of the well-known diurnal variation of ozone in the mesosphere. Between 35–55 km, SAGE II sunrise and sunset measurements differ from GOMOS’ measurements to different extents. Sunrise measurements show 2% less ozone than GOMOS, whereas sunset measurements show 4% more ozone than GOMOS. Differences can be explained qualitatively by the diurnal variation of ozone in the stratosphere recently observed by SMILES and modeled by chemical transport models. Between 25–35 km, SAGE II sunrise and sunset measurements and GOMOS measurements agree within 1%.
The observed ozone bias between collocated measurements of SAGE II sunrise/sunset and GOMOS night measurements is used to align the two data sets. The combined data set covers the time period 1984–2011, latitudes 60° S–60° N, and the altitude range of 20–60 km. Profile data are given on a 1 km vertical grid, and with a resolution of 1 month in time and 10° in latitude. The combined ozone data set is analyzed by fitting a time series model to the data. We assume a linear trend with an inflection point (so-called “hockey stick” form). The best estimate for the point of inflection was found to be the year 1997 for ozone between altitudes 35 and 45 km. At all latitudes and altitudes from 35 to 50 km we find a clear change in ozone trend before and after the inflection time. From 38 to 45 km, a negative trend of 4% per decade (statistically significant at 95% level) at the equator has changed to a small positive trend of 0–2% per decade. At mid-latitudes, the negative trend of 4–8% per decade has changed to to a small positive trend of 0–2% per decade. At mid-latitudes near 20 km, the ozone loss has still increased whereas in the tropics a recovery is ongoing.”
Kyrölä, E., Laine, M., Sofieva, V., Tamminen, J., Päivärinta, S.-M., Tukiainen, S., Zawodny, J., and Thomason, L.: Combined SAGE II–GOMOS ozone profile data set for 1984–2011 and trend analysis of the vertical distribution of ozone, Atmos. Chem. Phys., 13, 10645-10658, doi:10.5194/acp-13-10645-2013, 2013. [FULL TEXT]

Measurements of stratospheric ozone at a mid-latitude observing station Valentia, Ireland (51.94° N, 10.25° W), using ground-based and ozonesonde observations from 1994 to 2009 – Tripathi et al. (2013)
Abstract: “Sixteen years (1994 – 2009) of ozone profiling by ozonesondes at Valentia Meteorological and Geophysical Observatory, Ireland (51.94° N, 10.23° W) along with a co-located MkIV Brewer spectrophotometer for the period 1993–2009 are analyzed. Simple and multiple linear regression methods are used to infer the recent trend, if any, in stratospheric column ozone over the station. The decadal trend from 1994 to 2010 is also calculated from the monthly mean data of Brewer and column ozone data derived from satellite observations. Both of these show a 1.5 % increase per decade during this period with an uncertainty of about ±0.25 %. Monthly mean data for March show a much stronger trend of ~ 4.8 % increase per decade for both ozonesonde and Brewer data. The ozone profile is divided between three vertical slots of 0–15 km, 15–26 km, and 26 km to the top of the atmosphere and a 11-year running average is calculated. Ozone values for the month of March only are observed to increase at each level with a maximum change of +9.2 ± 3.2 % per decade (between years 1994 and 2009) being observed in the vertical region from 15 to 26 km. In the tropospheric region from 0 to 15 km, the trend is positive but with a poor statistical significance. However, for the top level of above 26 km the trend is significantly positive at about 4 % per decade. The March integrated ozonesonde column ozone during this period is found to increase at a rate of ~6.6 % per decade compared with the Brewer and satellite positive trends of ~5 % per decade.”
Om P. Tripathi, S. G. Jennings, C. D. O’Dowd, K. P. Lambkin, E. Moran, Journal of Atmospheric Chemistry, December 2013, Volume 70, Issue 4, pp 297-316, DOI: 10.1007/s10874-013-9274-5.

Development of a climate record of tropospheric and stratospheric column ozone from satellite remote sensing: evidence of an early recovery of global stratospheric ozone – Ziemke & Chandra (2012)
Abstract: “Ozone data beginning October 2004 from the Aura Ozone Monitoring Instrument (OMI) and Aura Microwave Limb Sounder (MLS) are used to evaluate the accuracy of the Cloud Slicing technique in effort to develop long data records of tropospheric and stratospheric ozone and for studying their long-term changes. Using this technique, we have produced a 32-yr (1979–2010) long record of tropospheric and stratospheric column ozone from the combined Total Ozone Mapping Spectrometer (TOMS) and OMI. Analyses of these time series suggest that the quasi-biennial oscillation (QBO) is the dominant source of inter-annual variability of stratospheric ozone and is clearest in the Southern Hemisphere during the Aura time record with related inter-annual changes of 30–40 Dobson Units. Tropospheric ozone for the long record also indicates a QBO signal in the tropics with peak-to-peak changes varying from 2 to 7 DU. The most important result from our study is that global stratospheric ozone indicates signature of a recovery occurring with ozone abundance now approaching the levels of year 1980 and earlier. The negative trends in stratospheric ozone in both hemispheres during the first 15 yr of the record are now positive over the last 15 yr and with nearly equal magnitudes. This turnaround in stratospheric ozone loss is occurring about 20 yr earlier than predicted by many chemistry climate models. This suggests that the Montreal Protocol which was first signed in 1987 as an international agreement to reduce ozone destroying substances is working well and perhaps better than anticipated.”
Ziemke, J. R. and Chandra, S.: Development of a climate record of tropospheric and stratospheric column ozone from satellite remote sensing: evidence of an early recovery of global stratospheric ozone, Atmos. Chem. Phys., 12, 5737-5753, doi:10.5194/acp-12-5737-2012, 2012. [FULL TEXT]

Interannual variability and trends in tropical ozone derived from SAGE II satellite data and SHADOZ ozonesondes – Randel & Thompson (2011)
Abstract: “Long-term observations of stratospheric ozone from the Stratospheric Aerosol and Gas Experiment II (SAGE II) satellite (1984–2005) are combined with ozonesonde measurements from the Southern Hemisphere Additional Ozonesondes (SHADOZ) network (1998–2009) to study interannual variability and trends in tropical ozone. Excellent agreement is found comparing the two data sets for the overlap period 1998–2005, and the data are combined to form a continuous time series covering 1984–2009. SHADOZ measurements also provide temperature profiles, and interannual changes in ozone and temperature are highly correlated throughout the tropical lower stratosphere (16–27 km). Interannual variability in stratospheric ozone is dominated by effects of the quasi-biennial oscillation and El Niño–Southern Oscillation, and there are also significant negative trends (−2 to −4% per decade) in the tropical lower stratosphere (over 17–21 km). These tropical ozone trends are consistent with results from chemistry-climate model simulations, wherein the trends result from increases in upwelling circulation in the tropical lower stratosphere.”
Randel, W. J., and A. M. Thompson (2011), Interannual variability and trends in tropical ozone derived from SAGE II satellite data and SHADOZ ozonesondes, J. Geophys. Res., 116, D07303, doi:10.1029/2010JD015195. [FULL TEXT]

Ozone and temperature trends in the upper stratosphere at five stations of the Network for the Detection of Atmospheric Composition Change – Steinbrecht et al. (2009)
Abstract: “Upper stratospheric ozone anomalies from the satellite-borne Solar Backscatter Ultra-Violet (SBUV), Stratospheric Aerosol and Gas Experiment II (SAGE II), Halogen Occultation Experiment (HALOE), Global Ozone Monitoring by Occultation of Stars (GOMOS), and Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) instruments agree within 5% or better with ground-based data from lidars and microwave radiometers at five stations of the Network for the Detection of Atmospheric Composition Change (NDACC), from 45°S to 48°N. From 1979 until the late 1990s, all available data show a clear decline of ozone near 40 km, by 10%–15%. This decline has not continued in the last 10 years. At some sites, ozone at 40 km appears to have increased since 2000, consistent with the beginning decline of stratospheric chlorine. The phaseout of chlorofluorocarbons after the International Montreal Protocol in 1987 has been successful, and is now showing positive effects on ozone in the upper stratosphere. Temperature anomalies near 40 km altitude from European Centre for Medium Range Weather Forecast reanalyses (ERA-40), from National Centers for Environmental Prediction (NCEP) operational analyses, and from HALOE and lidar measurements show good consistency at the five stations, within about 3 K. Since about 1985, upper stratospheric temperatures have been fluctuating around a constant level at all five NDACC stations. This non-decline of upper stratospheric temperatures is a significant change from the more or less linear cooling of the upper stratosphere up until the mid-1990s, reported in previous trend assessments. It is also at odds with the almost linear 1 K per decade cooling simulated over the entire 1979–2010 period by chemistry–climate models (CCMs). The same CCM simulations, however, track the historical ozone anomalies quite well, including the change of ozone tendency in the late 1990s.”
W. Steinbrecht, H. Claude, F. Schönenborn, I. S. McDermid, T. Leblanc, S. Godin-Beekmann, P. Keckhut, A. Hauchecorne, J. A. E. Van Gijsel, D. P. J. Swart, G. E. Bodeker, A. Parrish, I. S. Boyd, N. Kämpfer, K. Hocke, R. S. Stolarski, S. M. Frith, L. W. Thomason, E. E. Remsberg, C. Von Savigny, A. Rozanov & J. P. Burrows, International Journal of Remote Sensing, Volume 30, Issue 15-16, 2009, DOI:10.1080/01431160902821841.

A stratospheric ozone profile data set for 1979–2005: Variability, trends, and comparisons with column ozone data – Randel & Wu (2007)
Abstract: “A global stratospheric ozone data set for 1979–2005 is described. Interannual variations are derived from analysis of Stratospheric Aerosol and Gas Experiment (SAGE I and II) profile measurements, combined with polar ozonesonde data from Syowa (69°S) and Resolute (75°N). These interannual changes are combined with a seasonally varying ozone climatology from Fortuin and Kelder [1998] to provide a monthly global data set. These data are intended for use in global modeling studies and for analysis of global variability and trends. In order to generate continuous fields from the gappy SAGE data, we use a regression fit that includes decadal trends, solar cycle, and QBO terms, and the spatial structure of these variations is studied in detail. Decadal trends are modeled using an equivalent effective stratospheric chlorine proxy. Ozone variability from the vertically integrated SAGE/sonde data set is compared with results derived from a merged Total Ozone Mapping Spectrometer/solar backscatter ultraviolet column ozone data set, showing good overall agreement (in particular for trends in extratropics). We also compare the SAGE data with ozonesonde measurements over Northern Hemisphere midlatitudes and find excellent agreement for lower stratospheric variability and trends. In the tropics, the SAGE ozone data show relatively large percentage decreases in the lower stratosphere. However, the vertically integrated SAGE data do not agree with column ozone trends in the tropics, so there is less confidence in the SAGE results in this region.”
William J. Randel and Fei Wu, Journal of Geophysical Research: Atmospheres (1984–2012), Volume 112, Issue D6, 27 March 2007, DOI: 10.1029/2006JD007339. [FULL TEXT]

Long-term evolution of upper stratospheric ozone at selected stations of the Network for the Detection of Stratospheric Change (NDSC) – Steinbrecht et al. (2006)
Abstract: “The long-term evolution of upper stratospheric ozone has been recorded by lidars and microwave radiometers within the ground-based Network for the Detection of Stratospheric Change (NDSC), and by the space-borne Solar Backscatter Ultra-Violet instruments (SBUV), Stratospheric Aerosol and Gas Experiment (SAGE), and Halogen Occultation Experiment (HALOE). Climatological mean differences between these instruments are typically smaller than 5% between 25 and 50 km. Ozone anomaly time series from all instruments, averaged from 35 to 45 km altitude, track each other very well and typically agree within 3 to 5%. SBUV seems to have a slight positive drift against the other instruments. The corresponding 1979 to 1999 period from a transient simulation by the fully coupled MAECHAM4-CHEM chemistry climate model reproduces many features of the observed anomalies. However, in the upper stratosphere the model shows too low ozone values and too negative ozone trends, probably due to an underestimation of methane and a consequent overestimation of ClO. The combination of all observational data sets provides a very consistent picture, with a long-term stability of 2% or better. Upper stratospheric ozone shows three main features: (1) a decline by 10 to 15% since 1980, due to chemical destruction by chlorine; (2) two to three year fluctuations by 5 to 10%, due to the Quasi-Biennial Oscillation (QBO); (3) an 11-year oscillation by about 5%, due to the 11-year solar cycle. The 1979 to 1997 ozone trends are larger at the southern mid-latitude station Lauder (45°S), reaching −8%/decade, compared to only about −6%/decade at Table Mountain (35°N), Haute Provence/Bordeaux (≈45°N), and Hohenpeissenberg/Bern(≈47°N). At Lauder, Hawaii (20°N), Table Mountain, and Haute Provence, ozone residuals after subtraction of QBO- and solar cycle effects have levelled off in recent years, or are even increasing. Assuming a turning point in January 1997, the change of trend is largest at southern mid-latitude Lauder, +11%/decade, compared to +7%/decade at northern mid-latitudes. This points to a beginning recovery of upper stratospheric ozone. However, chlorine levels are still very high and ozone will remain vulnerable. At this point the most northerly mid-latitude station, Hohenpeissenberg/Bern differs from the other stations, and shows much less clear evidence for a beginning recovery, with a change of trend in 1997 by only +3%/decade. In fact, record low upper stratospheric ozone values were observed at Hohenpeissenberg/Bern, and to a lesser degree at Table Mountain and Haute Provence, in the winters 2003/2004 and 2004/2005.”
W. Steinbrecht, H. Claude, F. Schönenborn, I. S. McDermid, T. Leblanc, S. Godin, T. Song, D. P. J. Swart, Y. J. Meijer, G. E. Bodeker, B. J. Connor, N. Kämpfer, K. Hocke, Y. Calisesi, N. Schneider, J. de la Noë, A. D. Parrish, I. S. Boyd, C. Brühl, B. Steil, M. A. Giorgetta, E. Manzini, L. W. Thomason, J. M. Zawodny, M. P. McCormick, J. M. Russell III, P. K. Bhartia, R. S. Stolarski and S. M. Hollandsworth-Frith, Journal of Geophysical Research: Atmospheres (1984–2012), Volume 111, Issue D10, 27 May 2006, DOI: 10.1029/2005JD006454. [FULL TEXT]

Enhanced upper stratospheric ozone: Sign of recovery or solar cycle effect? – Steinbrecht et al. (2004)
Abstract: “Ozone data measured since 1987 in the 35- to 45-km altitude region by differential absorption laser-radar (DIAL) at Hohenpeissenberg (47.8°N, 11.0°E) confirm the long-term ozone decline observed by the satellite-borne Stratospheric Aerosol and Gas Experiment (SAGE) and Halogen Occultation Experiment (HALOE) instruments, as well as interannual ozone fluctuations. Analysis of the DIAL data indicates that the amplitude of ozone variations related to the 11-year solar cycle might reach up to 7%, much larger than 4% reported in other studies. Higher ozone values observed in the years 2001 to 2003 might, therefore, be a consequence of the ending solar maximum and not necessarily indicate a beginning recovery of upper stratospheric ozone. Much clearer evidence for a recovery is expected in a few years, near the end of the solar minimum starting now.”
W. Steinbrecht, H. Claude and P. Winkler, Journal of Geophysical Research: Atmospheres (1984–2012), Volume 109, Issue D2, 27 January 2004, DOI: 10.1029/2003JD004284. [FULL TEXT]

Evidence for slowdown in stratospheric ozone loss: First stage of ozone recovery – Newchurch et al. (2003)
Abstract: “Global ozone trends derived from the Stratospheric Aerosol and Gas Experiment I and II (SAGE I/II) combined with the more recent Halogen Occultation Experiment (HALOE) observations provide evidence of a slowdown in stratospheric ozone losses since 1997. This evidence is quantified by the cumulative sum of residual differences from the predicted linear trend. The cumulative residuals indicate that the rate of ozone loss at 35–45 km altitudes globally has diminished. These changes in loss rates are consistent with the slowdown of total stratospheric chlorine increases characterized by HALOE HCl measurements. These changes in the ozone loss rates in the upper stratosphere are significant and constitute the first stage of a recovery of the ozone layer.”
Newchurch, M. J., E.-S. Yang, D. M. Cunnold, G. C. Reinsel, J. M. Zawodny, and J. M. Russell III (2003), Evidence for slowdown in stratospheric ozone loss: First stage of ozone recovery, J. Geophys. Res., 108, 4507, doi:10.1029/2003JD003471, D16. [FULL TEXT]

Trend analysis of upper stratospheric Umkehr ozone data for evidence of turnaround – Reinsel (2002)
Abstract: “Recent upper stratospheric (~35–45 km) Umkehr ozone data from three high-quality stations have been examined, with residual and change-in-trend analyses performed. These data show a consistent feature of mildly positive tendency in values for the recent several years. Trend analyses of these data yield significant positive change-in-trend estimates of about 0.75% per year since 1996 relative to negative trends of about -0.55% per year existing prior to 1996, leading to a (nonsignificant) estimate of about 0.2% per year positive trend for the recent 5-year period since the 1996 change-in-trend date.”
Reinsel, G. C., Trend analysis of upper stratospheric Umkehr ozone data for evidence of turnaround, Geophys. Res. Lett., 29(10), doi:10.1029/2002GL014716, 2002. [FULL TEXT]

Upper-stratospheric ozone trends 1979–1998 – Newchurch et al. (2000)
Abstract: “Extensive analyses of ozone observations between 1978 and 1998 measured by Dobson Umkehr, Stratospheric Aerosol and Gas Experiment (SAGE) I and II, and Solar Backscattered Ultraviolet (SBUV) and (SBUV)/2 indicate continued significant ozone decline throughout the extratropical upper stratosphere from 30–45 km altitude. The maximum annual linear decline of -0.8±0.2 % yr-1 (2s) occurs at 40 km and is well described in terms of a linear decline modulated by the 11-year solar variation. The minimum decline of -0.1±0.1% yr-1 (2s) occurs at 25 km in midlatitudes, with remarkable symmetry between the Northern and Southern Hemispheres at 40 km altitude. Midlatitude upper-stratospheric zonal trends exhibit significant seasonal variation (±30% in the Northern Hemisphere, ±40% in the Southern Hemisphere) with the most negative trends of -1.2% yr-1 occurring in the winter. Significant seasonal trends of -0.7 to -0.9% yr-1 occur at 40 km in the tropics between April and September. Subjecting the statistical models used to calculate the ozone trends to intercomparison tests on a variety of common data sets yields results that indicate the standard deviation between trends estimated by 10 different statistical models is less than 0.1% yr-1 in the annual-mean trend for SAGE data and less than 0.2% yr-1 in the most demanding conditions (seasons with irregular, sparse data) [World Meteorological Organization (WMO), 1998]. These consistent trend results between statistical models together with extensive consistency between the independent measurement-system trend observations by Dobson Umkehr, SAGE I and II, and SBUV and SBUV/2 provide a high degree of confidence in the accuracy of the declining ozone amounts reported here. Additional details of ozone trend results from 1978 to 1996 (2 years shorter than reported here) along with lower-stratospheric and tropospheric ozone trends, extensive intercomparisons to assess relative instrument drifts, and retrieval algorithm details are given by WMO [1998].”
Newchurch, M. J., et al. (2000), Upper-stratospheric ozone trends 1979–1998, J. Geophys. Res., 105(D11), 14625–14636, doi:10.1029/2000JD900037. [FULL TEXT]

Northern middle-latitude ozone profile features and trends observed by SBUV and Umkehr, 1979–1990 – DeLuisi et al. (1994)
Abstract: “A comparison of Umkehr ozone profile data with the reprocessed solar backscatter ultraviolet (SBUV) ozone profile data in the northern middle-latitude region, 30° to 50°N, is reported. Although significant biases exist between the two types of observations, the long-term variations and least squares linear regression trends agree remarkably well over the comparison period of 1979 to 1990. The ozone trend in the upper stratosphere is of the order of -0.9% yr-1. Near 25 km, little if any trend appears, but a larger negative trend is seen in the lower stratosphere near 15 km. Comparisons show that the average annual ozone cycles in the profiles also agree well. The upper stratospheric ozone results are consistent with photochemical model predictions of ozone depletion near 40 km that are due to the release of anthropogenically produced chlorofluorocarbons. The lower stratospheric ozone trend results are in reasonable agreement with published ozonesonde data trends. It is shown that the ozone trends in the lower stratospheric layers impact significantly on the total ozone trend of the order of -0.47% yr-1. The good agreement now seen between the two types of observations suggests that the combined ground-based and satellite approach could provide a valuable database for long-term monitoring of stratospheric ozone for trends and extraordinary variations.”
DeLuisi, J. J., C. L. Mateer, D. Theisen, P. K. Bhartia, D. Longenecker, and B. Chu (1994), Northern middle-latitude ozone profile features and trends observed by SBUV and Umkehr, 1979–1990, J. Geophys. Res., 99(D9), 18901–18908, doi:10.1029/94JD01518. [FULL TEXT]

Comparison of SBUV and SAGE II ozone profiles: Implications for ozone trends – McPeters et al. (1994)
Abstract: “Solar backscattered ultraviolet (SBUV) ozone profiles have been compared with Stratospheric Aerosol and Gas Experiment (SAGE) II profiles over the period October 1984 through June 1990, when data are available from both instruments. SBUV measurements were selected to closely match the SAGE II latitude/longitude measurement pattern. There are significant differences between the SAGE II sunrise and the sunset zonal mean ozone profiles in the equatorial zone, particularly in the upper stratosphere, that may be connected with extreme SAGE II solar azimuth angles for tropical sunrise measurements. Calculation of the average sunset bias between SBUV and SAGE II ozone profiles shows that allowing for diurnal variation in Umkehr layer 10, SBUV and SAGE II agree to within ±5% for the entire stratosphere in the northern midlatitude zone. The worst agreement is seen at southern midlatitudes near the ozone peak (disagreements of ±10%), apparently the result of the SBUV ozone profile peaking at a lower altitude than SAGE. The integrated ozone columns (cumulative above 15 km) agree very well, to within ±2.3% in all zones for both sunset and sunrise measurements. A comparison of the time dependence of SBUV and SAGE II shows that there was less than ±5% relative drift over the 5.5 years for all altitudes except below 25 km, where the SBUV vertical resolution is poor. The best agreement with SAGE is seen in the integrated column ozone (cumulative above 15 km), where SAGE II has a 1% negative trend relative to SBUV over the comparison period. There is a persistent disagreement of the two instruments in Umkehr layers 9 and 10 of ±4% over the 5.5-year comparison period. In the equatorial zone this disagreement may be caused in part by a large positive trend (0.8°K per year) in the National Meteorologica Center temperatures used to convert the SAGE II measurement of ozone density versus altitude to a pressure scale for comparison with SBUV. In the middle stratosphere (30–40 km), SBUV shows a 2–4% negative drift relative to SAGE II. If the actual ozone trends are considered, SBUV and SAGE II agree in showing little ozone change (less than 2%) between 1984 and 1990, except in layer 3 where SAGE II measures a large ozone decrease. But over 11 years, SBUV measured a 7% per decade ozone decrease between 40 and 50 km, decreasing in magnitude at lower altitudes, in good agreement with 11-year trends derived from the average of 5 Umkehr stations.”
McPeters, R. D., T. Miles, L. E. Flynn, C. G. Wellemeyer, and J. M. Zawodny (1994), Comparison of SBUV and SAGE II ozone profiles: Implications for ozone trends, J. Geophys. Res., 99(D10), 20513–20524, doi:10.1029/94JD02008.

Comparison of trend analyses for Umkehr data using new and previous inversion algorithms – Reinsel et al. (1994)
Abstract: “Ozone vertical profile Umkehr data for layers 3–9 obtained from 12 stations, using both previous and new inversion algorithms, were analyzed for trends. The trends estimated for the Umkehr data from the two algorithms were compared using two data periods, 1968–1991 and 1977–1991. Both nonseasonal and seasonal trend models were fitted. The overall annual trends are found to be significantly negative, of the order of -5% per decade, for layers 7 and 8 using both inversion algorithms. The largest negative trends occur in these layers under the new algorithm, whereas in the previous algorithm the most negative trend occurs in layer 9. The trend estimates, both annual and seasonal, are substantially different between the two algorithms mainly for layers 3, 4, and 9, where trends from the new algorithm data are about 2% per decade less negative, with less appreciable differences in layers 7 and 8. The trend results from the two data periods are similar, except for layer 3 where trends become more negative, by about -2% per decade, for 1977–1991.”
Gregory C. Reinsel, Wing-Kuen Tam and Lisa H. Ying, Geophysical Research Letters, Volume 21, Issue 11, pages 1007–1010, 1 June 1994, DOI: 10.1029/94GL00980.

Measured Trends in Stratospheric Ozone – Stolarski et al. (1992)
Abstract: “Recent findings, based on both ground-based and satellite measurements, have established that there has been an apparent downward trend in the total column amount of ozone over mid-latitude areas of the Northern Hemisphere in all seasons. Measurements of the altitude profile of the change in the ozone concentration have established that decreases are taking place in the lower stratosphere in the region of highest ozone concentration. Analysis of updated ozone records, through March of 1991, including 29 stations in the former Soviet Union, and analysis of independently calibrated satellite data records from the Total Ozone Mapping Spectrometer and Stratospheric Aerosol and Gas Experiment instruments confirm many of the findings originally derived from the Dobson record concerning northern midlatitude changes in ozone. The data from many instruments now provide a fairly consistent picture of the change that has occurred in stratospheric ozone levels.”
Richard Stolarski, Rumen Bojkov, Lane Bishop, Christos Zerefos, Johannes Staehelin, Joseph Zawodny, Science 17 April 1992: Vol. 256 no. 5055 pp. 342-349, DOI: 10.1126/science.256.5055.342. [FULL TEXT]

An analysis of northern middle-latitude Umkehr measurements corrected for stratospheric aerosols for 1979–1986 – DeLuisi et al. (1989)
Abstract: “Umkehr observations of ozone profile for five northern middle-latitude Dobson spectrophotometer stations are objectively corrected for stratospheric aerosol during the period 1979–1986. The corrections are done by means of theoretical calculations, using observations of stratospheric ozone and aerosols. Stratospheric ozone and aerosol profile data to correct the Umkehr measurements are derived from ozonesonde observations and observations provided by five lidar stations in the northern hemisphere middle latitudes. Optical properties of the stratospheric aerosol existing during and after the major injection by El Chichón are derived from surface and aircraft photometric observations and in situ aircraft observations of aerosol size distribution. The corrected Umkehr data display some noteworthy ozone reductions in the upper stratosphere. The magnitude of these reductions does not seem to be extraordinary when considering features seen in long-term Umkehr data. However, the rates may be extraordinary, for example, in layers 8 and 9, in which decreases in ozone concentration during 1979–1986 were 9% and 15% respectively, using corrected data.”
DeLuisi, J. J., D. U. Longenecker, C. L. Mateer, and D. J. Wuebbles (1989), An analysis of northern middle-latitude Umkehr measurements corrected for stratospheric aerosols for 1979–1986, J. Geophys. Res., 94(D7), 9837–9846, doi:10.1029/JD094iD07p09837.

Statistical analysis of total ozone and stratospheric Umkehr data for trends and solar cycle relationship – Reinsel et al. (1987)
Abstract: “We report on trend analysis of Dobson total ozone data through 1984 and stratospheric Umkehr profile ozone data through 1981, including an examination of the relationship between ozone and long-term solar cycle activity using the 10.7-cm solar flux data. The estimate of the overall global trend in total ozone during the period 1970–1984, with associated 95% confidence (two standard error) limits, is (-0.26±0.92)% per decade, which indicates no significant overall trend. Based on use of the 10.7-cm flux measurements, an overall estimate of the total ozone-solar flux relationship is (1.18±0.66)% change in total ozone from solar cycle minimum to maximum, which indicates a statistically significant positive relationship. Trend analysis of Umkehr data through 1981 yields statistically significant negative trends on the order of (-0.30±0.17)% per year in layers 7 and 8 (~34–43 km), with Mauna Loa transmission data being used to account for volcanic aerosol effects on the Umkehr data. The analysis also indicates significant relationships between Umkehr data and solar flux in layers 6 and 7 (~29–38 km) of (2.57±1.25)% and (3.40±2.16)% change, respectively, from solar cycle minimum to maximum, with no significant relationship detected in the higher layers 8 and 9 where the estimates are more variable. Comparison of these empirical estimates with theoretical model calculations is discussed. Trend analysis of Umkehr data using data through 1984 is not reported in this paper because of the severe impact of volcanic aerosols from El Chichon on the Umkehr measurements during 1982–1984, although further research on methods for adjustment of Umkehr data for aerosol effects during this period is continuing.”
Reinsel, G. C., G. C. Tiao, A. J. Miller, D. J. Wuebbles, P. S. Connell, C. L. Mateer, and J. J. Deluisi (1987), Statistical analysis of total ozone and stratospheric Umkehr data for trends and solar cycle relationship, J. Geophys. Res., 92(D2), 2201–2209, doi:10.1029/JD092iD02p02201.

Large losses of total ozone in Antarctica reveal seasonal ClOx/NOx interaction – Farman et al. (1985)
Abstract: “Recent attempts to consolidate assessments of the effect of human activities on stratospheric ozone (O3) using one-dimensional models for 30° N have suggested that perturbations of total O3 will remain small for at least the next decade. Results from such models are often accepted by default as global estimates. The inadequacy of this approach is here made evident by observations that the spring values of total O3 in Antarctica have now fallen considerably. The circulation in the lower stratosphere is apparently unchanged, and possible chemical causes must be considered. We suggest that the very low temperatures which prevail from midwinter until several weeks after the spring equinox make the Antarctic stratosphere uniquely sensitive to growth of inorganic chlorine, Clx, primarily by the effect of this growth on the NO2/NO ratio. This, with the height distribution of UV irradiation peculiar to the polar stratosphere, could account for the O3 losses observed.”
J. C. Farman, B. G. Gardiner & J. D. Shanklin, Nature 315, 207 – 210 (16 May 1985); doi:10.1038/315207a0.

Analysis of upper stratospheric Umkehr ozone profile data for trends and the effects of stratospheric aerosols – Reinsel et al. (1984)
Abstract: “A statistical analysis of stratospheric ozone profile data from the Umkehr method is considered for the detection of trends which may be associated with the release of chlorofluoromethanes (CFMs), where possible effects of atmospheric aerosols on the Umkehr measurements are also taken into account. In the statistical trend analysis, time series models have been estimated using monthly averages of Umkehr data over the past 15 to 20 years through 1980 at each of 13 Umkehr stations and at each of the five highest Umkehr layers, 5–9, which cover an altitude range of approximately 24–48 km. The time series regression models incorporate seasonal, trend, and noise factors and an additional factor to explicitly account for the effects of atmospheric aerosols on the Umkehr measurements. At each Umkehr station, the explanatory series used in the statistical model to account for the aerosol effect is a 5 month running average of the monthly atmospheric transmission data at Mauna Loa, Hawaii, the only long running aerosol data available. A random effects model is used to combine the 13 individual station trend estimates from the time series models to form an overall estimate of trend for each Umkehr layer. The analysis indicates statistically significant trends in the upper Umkehr layers 7 and 8 of the order of -0.2 to -0.3% per year over the period 1970–1980, with little trend in the lower layers 5 and 6. The results of the estimation of trends as well as aerosol effects for the Umkehr data are compared with recent corresponding theoretical predictions.”
Reinsel, G. C., G. C. Tiao, J. J. DeLuisi, C. L. Mateer, A. J. Miller, and J. E. Frederick (1984), Analysis of upper stratospheric Umkehr ozone profile data for trends and the effects of stratospheric aerosols, J. Geophys. Res., 89(D3), 4833–4840, doi:10.1029/JD089iD03p04833.

Comparison of seasonal variations of upper stratospheric ozone concentrations revealed by Umkehr and Nimbus 4 BUV observations – DeLuisi et al. (1979)
Abstract: “This paper reports the results of a comparison between upper stratospheric ozone concentration profiles in the region between 22 and 1.4 mbar, as determined from surface-based Umkehr observations and satellite Nimbus 4 BUV observations. The Umkehr data, consisting of monthly averages of observations extending over several years or longer, were obtained at three stations located in the northern hemisphere and two in the southern hemisphere. The BUV data were obtained during the period from May 1970 to March 1971. Aside from some bias in the magnitudes of the Umkehr and BUV data, marked annual cycles of ozone concentration in the upper stratosphere are clearly revealed. Above 4 mbar the profiles show a summer minimum and a winter maximum, while below 4 mbar the annual variation is reversed from this pattern. In the northern hemisphere the winter maximum is accompanied by a secondary minimum of 1- to 2-month duration near 3 mbar. This short-term minimum is much less obvious in the southern hemisphere data. Some of the problem of attempting to monitor long-term changes in the upper stratosphere are discussed briefly.”
DeLuisi, J. J., C. L. Mateer, and D. F. Heath (1979), Comparison of seasonal variations of upper stratospheric ozone concentrations revealed by Umkehr and Nimbus 4 BUV observations, J. Geophys. Res., 84(C7), 3728–3732, doi:10.1029/JC084iC07p03728.

Preliminary comparison of satellite BUV and surface-based Umkehr observations of the vertical distribution of ozone in the upper stratosphere – DeLuisi & Nimira (1977)
Abstract: “Data from surface-based Umkehr and satellite ultraviolet backscatter observations of the vertical distribution of ozone in the upper stratosphere are compared. The satellite data are limited to four single-pass observations of the vertical-meridional distribution of ozone at different seasons of the year during 1970. The Umkehr data are climatological means over several years of observations. Although most of the observations made with the surface and satellite systems do not coincide in time, they nevertheless show a general agreement in seasonal variations that clearly appear in the more complete set of Umkehr data. Average values of ozone concentrations for satellite and Umkehr observations and a standard ozone profile are intercompared and show some significant differences.”
DeLuisi, J. J., and J. Nimira (1978), Preliminary comparison of satellite BUV and surface-based Umkehr observations of the vertical distribution of ozone in the upper stratosphere, J. Geophys. Res., 83(C1), 379–384, doi:10.1029/JC083iC01p00379.

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