Retrieval of stratospheric and tropospheric BrO profiles and columns using ground-based zenith-sky DOAS observations at Harestua, 60° N

• Main Authors: Hendrick, F., van Roozendael, M., Chipperfield, M. P., Dorf, M., Goutail, Florence, Yang, X., Fayt, C., Hermans, C., Pfeilsticker, K., Pommereau, Jean-Pierre, Pyle, J. A., Theys, N., de Mazière, M.
• Other Authors: Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique (BIRA-IASB), Institute for Atmospheric Science Leeds, School of Earth and Environment Leeds (SEE), University of Leeds-University of Leeds, Institute of Environmental Physics Heidelberg (IUP), Universität Heidelberg Heidelberg = Heidelberg University, Service d'aéronomie (SA), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre for Atmospheric Science Cambridge, UK, University of Cambridge UK (CAM)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2007
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Norway; Sea ice
• Online Access: https://hal.science/hal-00328206; https://hal.science/hal-00328206/document; https://hal.science/hal-00328206/file/acpd-7-8663-2007.pdf

International audience A profiling algorithm based on the optimal estimation method is applied to ground-based zenith-sky UV-visible measurements from Harestua, Southern Norway (60° N, 11° E) in order to retrieve BrO vertical profiles. The sensitivity of the zenith-sky observations to the tropospheric BrO detection is increased by using for the spectral analysis a constant reference spectrum corresponding to clear-sky noon summer conditions. The information content and retrieval errors are characterized and it is shown that the retrieved stratospheric profiles and total columns are consistent with correlative balloon and satellite observations, respectively. Tropospheric BrO columns are derived from profiles retrieved at 80° solar zenith angle during sunrise and sunset for the 2000–2006 period. They show a marked seasonality with mean column value ranging from 1.52±0.51×10 13 molec/cm 2 in late winter/early spring to 0.92±0.31×10 13 molec/cm 2 in summer, which corresponds to 1.0±0.3 and 0.6±0.2 pptv, respectively, if we assume that BrO is uniformly mixed in the troposphere. These column values are also consistent with previous estimates made from balloon, satellite, and other ground-based observations. Daytime (10h30 local time) tropospheric BrO columns are compared to the p -TOMCAT 3-D tropospheric chemical transport model (CTM) for the 2002–2003 period. p -TOMCAT shows a good agreement with the retrieved columns except in late winter/early spring where an underestimation by the model is obtained. This feature could be explained by the non-inclusion of sea-ice bromine sources in the current version of p -TOMCAT, which can therefore not reproduce the possible transport from the polar region to Harestua of air-masses with enhanced BrO concentration due to bromine explosion events in late winter/early spring. The corresponding daytime stratospheric BrO columns are compared to the SLIMCAT 3-D stratospheric CTM. The model run used, which assumes 21.2 pptv for the Br y loading (15 pptv for long-lived bromine ...