2012-10-05: Monitoring volcanic ash aerosol height from GOME-2 Oxygen A band measurements

Large volcanic ash plumes can have a serious impact on aviation. The height of the ash layer is an relevant parameter in the derivation of aerosol mass concentration which can be harmful for aircraft engines in case of high concentration. Recently Wang et al. (2012) demonstrate that it is possible to derive aerosol height from Oxygen A band measurement for absorbing aerosols such as volcanic ash plumes, biomass burning aerosols and desert dust aerosols.

The Fast Retrieval Scheme for Clouds from the Oxygen A band (FRESCO) algorithm is an operational cloud retrieval algorithm for GOME-2 on board METOP A/B. According to simulations and GOME-2 measurements, FRESCO can be used to derive aerosol layer height, especially for optically thick absorbing aerosols in clear-sky scenes. For extremely thick volcanic ash plumes, the aerosol height can even be derived for cloudy scenes. Combining FRESCO and absorbing aerosol index (AAI) data, an estimate for the aerosol layer height can be given.

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The Puyehue volcanic ash plume on 6 June 2011: (a) GOME-2 AAI image, (b) MODIS RGB image, (c) GOME-2 cloud pressure, (d) GOME-2 scene pressure, (e) GOME-2 effective cloud fraction, (f) GOME-2 scene albedo. The location of the plume is indicated with a box in the GOME-2 images. The plumes in the left and right boxes were measured around 14:10 and 10:45 UTC, respectively. The MODIS image was measured at 14:25 UTC.