Combined SAGE II-GOMOS ozone profile data set 1984–2011 and trend analysis of the vertical distribution of ozone

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 Experimen (SAGE) II solar occultation instrument from 1984–2005 and the Global Ozone Monitoring by Occultation of Stars instrument (GOMOS) from 2002–2012 measured ozone profiles in the stratosphere and mesosphere. 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 intercalibrate 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 each other. 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 modelled by chemical transport models. For 25–35 km SAGE II sunrise and sunset and GOMOS agree within 1%. <br></br> 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&deg; S–60&deg; N and the altitude range of 20–60 km. Profile data are given on a 1 km vertical grid, and with a resolution of one month in time and ten degrees 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 inflexion point (so-called "hockey stick" form). The best estimate for the point of inflexion was found to be the year 1997 for ozone between altitudes 35 and 45 km. At all latitudes and altitudes from 25 km to 50 km we find a clear change in ozone trend before and after the inflexion time. From 38 km to 45 km a negative trend of 0–3% per decade at the equator has changed to a small positive trend of 0–2% per decade except in the altitude range of 30–35 km where the ozone loss has even increased. At mid-latitudes the negative trend of 4–10% per decade has changed to to a small positive trend of 0–2% per decade

Subtropical and midlatitude ozone trends in the stratosphere: Implications for recovery

“…These estimates are in good agreement with those estimated at northern midlatitudes (30–60 ∘ N) from satellite measurements in 1979–1997 by Jones et al [], as they also find statistically significant trends of about −0.38 ± 0.08% yr −1 at 20–25 km, −0.33 ± 0.07% yr −1 at 25–35 km, and −0.72 ± 0.09% yr −1 at 35–45 km. Similarly, our estimates are comparable to those evaluated from the combined SAGE II and Global Ozone Monitoring by Occultation of Stars (GOMOS) data for the northern midlatitudes in 1984–1997 (e.g., −0.7% yr −1 at 35–45 km) by Kyrölä et al [], as listed in Table (extracted from their Figure 14). Our upper stratospheric estimate is also in accordance with that found from satellite measurements by Cunnold et al [] and Wang et al [] at midlatitudes and from ground‐based and space‐based measurements by Steinbrecht et al [] and Nair et al [] for the midlatitude lidar stations, with the trends being around −0.75 ± 0.12% yr −1 .…”

“…In general, the comparisons between lidars and SAGE II and lidars and HALOE show drifts of about ±0.3 to ±0.4%yr −1 . The drifts derived from the combined time series over the lidar stations are insignificant and are of the order of ±0.2% yr −1 at 20–40 km [e.g., Nair et al , ], indicating the importance of creating merged data sets, to reduce the individual data biases and instrumental drifts in short‐term data sets, to produce quality long‐term data for meaningful trend studies [e.g., Nair et al , ; Jones et al , ; Kyrölä et al , ; Steinbrecht et al , ].…”

Ozone ProfilE Retrieval Algorithm (OPERA) for nadir-looking satellite instruments in the UV–VIS

“…Kyrölä et al , 2013;Gebhardt et al , 2014) show that the ozone trend over the last 20 years is of the order of a few percent per decade at altitudes over 20 km. Above 45 km, the observed trends are much smaller than the observed differences between the retrievals with and without the additive offset.…”

“…Other instruments followed, e.g. the SCanning Imaging Absorption spectroMeter for Atmospheric CartograpHY (SCIA-MACHY; see Bovensmann et al, 1999), which was launched aboard ENVISAT in 2002; the Ozone Monitoring Instrument (OMI; see Levelt et al, 2006), launched in 2004 aboard Aura; and GOME-2 (Callies et al, 2000), launched in 2006 aboard the first of EUMETSAT's Metop series.…”

ALTIUS: a spaceborne AOTF-based UV-VIS-NIR hyperspectral imager for atmospheric remote sensing

“…mainly in the tropics and Northern mid-latitudes, below the ozone maximum. [3][4][5] Recently, several reprocessing activities have been undertaken, namely the Stratosphere-troposphere Processes And their Role in Climate (SPARC) Data Initiative or the ozone Climate Change Initiative (O3CCI) among others. Their goal is to prepare and possibly merge datasets from various instruments in order to perform trend analyses, assess possible biases or build consistent datasets for atmospheric models.…”