Comparison of OMI UV observations with ground-based measurements at high northern latitudes G. Bernhard, A. Arola, A. Dahlback, V. Fioletov, A. Heikkilä, B. Johnsen, T. Koskela, K. Lakkala, T. Svendby, and J. Tamminen Biospherical Instruments, San Diego, California, USA Finnish Meteorological Institute, Helsinki, Finland Department of Physics, University of Oslo, Oslo, Norway Environment Canada...