Nabro volcano aerosol in the stratosphere over Georgia, South Caucasus from ground-based spectrometry of twilight sky brightness

摘要

Ground-based spectral measurements of twilight sky brightness were carriedout between September 2009 and August 2011 in Georgia, South Caucasus. Thealgorithm which allowed to retrieve the lower stratospheric and uppertropospheric aerosol extinction profiles was developed. The Monte-Carlotechnique was used to correctly represent multiple scattering in a sphericalatmosphere. The estimated stratospheric aerosol optical depths at awavelength of 780 nm were: 6 × 10?3 ± 2 × 10?3(31 August 2009–29 November 2009), 2.5 × 10?3 ± 7 × 10−4(20 March 2010–15 January 2011) and 8 × 10?3 ± 3 × 10?3(18 July 2011–3 August 2011). The opticaldepth values correspond to the moderately elevated stratospheric aerosollevel after the Sarychev eruption in 2009, background stratospheric aerosollayer, and the volcanically disturbed stratospheric aerosol layer after theNabro eruption in June 2011.