Tropospheric and stratospheric BrO and NO2 columns derived by use of satellite observations and 3D CTM FinROSE
Piia Post(1), Leif Backman(2), Laura Thölix(2), Michel Van Roozendael(3) and Caroline Fayt(3)
(1) Univesity of Tartu, Ulikooli 18, 50090 Tartu, Estonia
(2) Finnish Meteorological Institute, Erik Palmen aukio 1, 00560 Helsinki, Finland
(3) Belgian Institute for Space Aeronomy, Avenue Circulaire 3, 1180 Bruxelles, Belgium
From satellite nadir measurements (GOME; SCIAMACHY; OMI) the total slant column densities (SCD) of NO2 and BrO can be retrieved using DOAS technique. In order to obtain tropospheric vertical column densities (VCD) two key problems arise: the quantification of the stratospheric column and the calculation of the tropospheric air mass factor (AMF). This work aims at combining satellite observations and chemical transport modelling to overcome these problems and to gain accurate tropospheric columns.
Stratospheric NO2 and BrO columns are derived at the instrument’s overpass time by means of a stratospheric chemistry transport model, i.e. FinROSE-CTM, to take into account the stratospheric variability of these trace gases. To avoid a bias, the resulting stratospheric NO2 analysis is scaled to “clean” observation conditions by means of a reference sector. Reference pixels with optically thick and high clouds are selected for scaling the stratospheric model BrO output. In order to gain the trace gas tropospheric column the stratospheric slant column is subtracted from the DOAS slant column retrieval. The latter is taken from BIRA-IASB GOME product for BrO and KNMI GOME product NO2 slant columns.
Keywords: ESA European
Space Agency - Agence spatiale europeenne,
observation de la terre, earth observation,
satellite remote sensing,
teledetection, geophysique, altimetrie, radar,
chimique atmospherique, geophysics, altimetry, radar,