Homogenized total ozone data records from the European sensors GOME/ERS‐2, SCIAMACHY/Envisat, and GOME‐2/MetOp‐A

Abstract

Within the European Space Agency's Climate Change Initiative, total ozone column records from GOME (Global Ozone Monitoring Experiment), SCIAMACHY (SCanning Imaging Absorption SpectroMeter for Atmospheric CartograpHY), and GOME-2 have been reprocessed with GODFIT version 3 (GOME-type Direct FITting). This algorithm is based on the direct fitting of reflectances simulated in the Huggins bands to the observations. We report on new developments in the algorithm from the version implemented in the operational GOME Data Processor v5. The a priori ozone profile database TOMSv8 is now combined with a recently compiled OMI/MLS tropospheric ozone climatology to improve the representativeness of a priori information. The Ring procedure that corrects simulated radiances for the rotational Raman inelastic scattering signature has been improved using a revised semi-empirical expression. Correction factors are also applied to the simulated spectra to account for atmospheric polarization. In addition, the computational performance has been significantly enhanced through the implementation of new radiative transfer tools based on principal component analysis of the optical properties. Furthermore, a soft-calibration scheme for measured reflectances and based on selected Brewer measurements has been developed in order to reduce the impact of level-1 errors. This soft-calibration corrects not only for possible biases in backscattered reflectances, but also for artificial spectral features interfering with the ozone signature. Intersensor comparisons and ground-based validation indicate that these ozone data sets are of unprecedented quality, with stability better than 1% per decade, a precision of 1.7%, and systematic uncertainties less than 3.6% over a wide range of atmospheric states.

Comparison of profile total ozone from SBUV (v8.6) with GOME-type and ground-based total ozone for a 16-year period (1996 to 2011)

“…It incorporates the ozone data products retrieved using the newly developed GOME Direct Fitting algorithm GODFIT (Lerot et al, , 2014Van Roozendael et al, 2012) and covers the period from March 1996 to June 2011.…”

Impact of inter-mission differences and drifts on chlorophyll-atrend estimates

“…In the studies cited above, intermission biases were handled in a variety of ways, from ignoring them in the temporal analyses to specifically accounting for them, or correcting them. These issues have been faced by other disciplines that have developed responses adapted to the characteristics associated with the variable under study, for instance, sea level (Ablain et al 2015), sea surface temperature (Kilpatrick, Podestà, and Evans 2001), or atmospheric ozone (Lerot et al 2014;Pastel et al 2014).…”

The Global Ozone Monitoring Experiment: Review of in-flight performance and new reprocessed 1995–2011 level 1 product

“…to degradation in the reflectance, which may affect for example ozone profile retrievals (van der A et al, 2002;Liu et al, 2007) or the determination of total ozone columns using a direct fitting approach (Lerot et al, 2014), because these algorithms are sensitive to absolutely calibrated reflectances. Correction approaches for the reflectance degradation have been developed in the past which rely on, e.g.…”

“…Correction approaches for the reflectance degradation have been developed in the past which rely on, e.g. the comparison of experimental and simulated data (van der A et al, 2002;Cai et al, 2012), the comparison of satellite reflectance spectra with ground-based reference spectra (Lerot et al, 2014), or the comparison of 15 global average reflectance with respect to global average reflectance from the beginning of the mission (Liu et al, 2007;Tilstra et al, 2012). For the latter approach the underlying assumption is that the global average reflectance does not change in time.…”

“…Fortunately, in this area the impact of the ERS-2 tape recorder failure in June 2003 is quite small, so that the time series are almost complete with only a short gap in 2003. We limit our analysis to two single wavelengths in the UV part of the spectrum (325 and 335 nm, respectively) which mark the lower and upper limit of the fitting window for total ozone retrieval (Loyola 5 et al, 2011;Lerot et al, 2014). All GOME ground pixels with cloud fraction less than 0.2 were extracted that fall into a square area of ±1.5 • in latitude and longitude around the center geolocation of the reference site.…”