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Operational GOME-2 trace gas column measurements of NO2, BrO and SO2

Pieter Valks(1), Nan Hao(1), Meike Rix(1), Jean-Christopher Lambert(2), Gaia Pinardi(2), Michel Van Roozendael(2), Nicolas Theys(2), Jos van Geffen(2) and Diego Loyola(1)

(1) DLR, Muenchnerstrasse 20, 82234 Wessling, Germany
(2) BIRA-IASB, Av Circulaire 3, B-1180 Brussels, Belgium

Abstract

This contribution focuses on the operational GOME-2 trace-gas column products in the framework of EUMETSAT’s Satellite Application Facility on Ozone and Atmospheric Chemistry Monitoring (O3M-SAF). We present the algorithms and exemplary results of total and tropospheric NO2, BrO and SO2. These trace-gas column products are retrieved from GOME-2 solar backscattered measurements in the UV/VIS wavelength region, using the Differential Optical Absorption Spectroscopy (DOAS) method.

Total NO2 is routinely retrieved with the GOME Data Processor (GDP) version 4.2 using the 425-450 nm wavelength region. An additional algorithm is applied to derive the tropospheric NO2 column for polluted conditions: after subtracting the estimated stratospheric component from the total column, the tropospheric NO2 column is determined using an air mass factor based on monthly climatological NO2 profiles from the MOZART-2 model. SO2 emissions from both anthropogenic and volcanic sources can be measured by GOME-2 using the UV wavelength region around 320 nm. For the GOME-2 retrieval of the total BrO column, current research focuses on the optimisation of the DOAS fitting window in the UV wavelength region. BrO columns retrieved from the baseline GOME fitting window (344.6-359 nm) show relatively large noise levels. Therefore, the use of an alternative fitting window has been analysed.

More than two years of NO2, BrO and SO2 column measurements are now available from GOME-2. We present initial validation results using ground-based measurements, as well as comparisons with other satellite products, such as those from SCIAMACHY and OMI. The use of tropospheric NO2 columns for air quality applications will be presented. We will show examples of BrO from volcanic eruptions and under polar winter conditions. Finally, exemplary GOME-2 measurements of SO2 from anthropogenic emissions will be shown, as well as from volcanic eruptions.