Abstract
Abstract. Stratospheric aerosol extinction profiles have been retrieved from SCIAMACHY/Envisat measurements of limb-scattered solar radiation. The retrieval is an improved version of an algorithm presented earlier. The retrieved aerosol extinction profiles are compared to co-located aerosol profile measurements from the SAGE II solar occultation instrument at a wavelength of 525 nm. Comparisons were carried out with two versions of the SAGE II data set (version 6.2 and the new version 7.0). In a global average sense the SCIAMACHY and the SAGE II version 7.0 extinction profiles agree to within about 10 % for altitudes above 15 km. Larger relative differences (up to 40 %) are observed at specific latitudes and altitudes. We also find differences between the two SAGE II data versions of up to 40 % for specific latitudes and altitudes, consistent with earlier reports. Sample results on the latitudinal and temporal variability of stratospheric aerosol extinction and optical depth during the SCIAMACHY mission period are presented. The results confirm earlier reports that a series of volcanic eruptions is responsible for the increase in stratospheric aerosol optical depth from 2002 to 2012. Above about an altitude of 28 km, volcanic eruptions are found to have negligible impact in the period 2002–2012.
Highlights
Stratospheric sulfate aerosols mainly comprise H2SO4 and H2O, with a H2SO4 weight percentage of 75 % on average
In order to simplify the comparison of our results with these published results we show in Fig. 7 and Fig. 8 stratospheric aerosol optical depth at two wavelengths (525 and 750 nm)
Stratospheric aerosol extinction profiles in the visible spectral range were retrieved from SCIAMACHY limb-scatter observations using an improved retrieval method
Summary
Stratospheric sulfate aerosols mainly comprise H2SO4 and H2O, with a H2SO4 weight percentage of 75 % on average (reviewed by Thomason et al, 2006). The increased stratospheric aerosol load, associated with volcanic eruptions, is one possible mechanism contributing to the recent global warming hiatus, as suggested by Solomon et al (2011) and further outlined in IPCC (2013). Measurement techniques employed to study stratospheric aerosol parameters include in situ particle sampling, e.g., by optical means (e.g., Deshler, 2008), single or multiwavelength LIDAR observations (e.g., Jumelet et al, 2008; Hofmann et al, 2009), satellite solar (e.g., Thomason, 1991; McCormick and Veiga, 1992; Lumpe et al, 1997) or stellar (e.g., Vanhellemont et al, 2010) occultation measurements, as well as satellite observations of limb-scattered solar radiation (Bourassa et al, 2007; Taha et al, 2011; Ovigneur et al, 2011; Ernst et al, 2012). In an earlier study Ernst et al (2012) presented an algorithm description, error budget and validation results for a previous version of the SCIAMACHY stratospheric aerosol retrieval.
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