Variability in the Stratospheric Aerosol Load from SCIAMACHY Limb-scatter Observations
Brinkhoff, Lena A.1; Ernst, Florian1; Rozanov, Alexei1; von Savigny, Christian2; Hommel, René1; Bovensmann, Heinrich1; Burrows, John P.1
1Institute of Environmental Physics and Remote Sensing, University of Bremen, GERMANY; 2Ernst-Moritz-Arndt-University of Greifswald, GERMANY

Stratospheric aerosols are of scientific interest, as they primarily scatter solar radiation, and therefore increase the Earth's planetary albedo. The permanent aerosol background in the stratosphere is due to tropical injection of tropospheric air containing SO2, COS and sulphate particles, which are precursors for stratospheric aerosols. An additional contribution is sporadically caused by an uplift of SO2 after a strong volcanic eruption. Especially after strong volcanic eruptions, the consequential effect of stratospheric aerosols on the Earth's radiation budget is stratospheric warming and tropospheric cooling. Furthermore, they have an impact on stratospheric chemistry: Stratospheric aerosols are precursors for polar stratospheric clouds and thus support the destruction of ozone inside the polar vortex. They even lead to a halogen-driven ozone destruction outside polar vortices. On account of these properties, stratospheric aerosols belong to the so-called Essential Climate Variables.
We retrieve stratospheric aerosol extinction coefficients from SCIAMACHY limb-scatter measurements. SCIAMACHY was one of ten instruments onboard the ENVISAT spacecraft, detecting the sunlight in the wavelength range from 214 to 2386 nm with three different viewing geometries: nadir, limb and occultation. Limb-scatter measurements have the advantage of high vertical resolution, compared to nadir measurements, and a near-global coverage on the dayside of the Earth, in contrast to solar occultation measurements. The present SCIAMACHY limb aerosol product from Aug. 2002 to April 2012 (loss of ENVISAT) will be presented. It shows, for example, signatures of volcanic eruption and bushfire events in the tropopause region, a very pronounced seasonal cycle in the aerosol load at about 27 km altitude, which is mainly caused by the Brewer-Dobson Circulation, and additionally a biennial variation in the aerosol load at about 32 km altitude due to the QBO.