Total column amounts (in DU) for tropospheric O3 at Sable Island derived from ozonesonde vertical profiles (dashed line) and from the Aura/OMI satellite (solid line). Total tropospheric O3 amounts from all ozonesonde profiles collected in 2006 are being used to validate measurements collected by satellites, including the Ozone Monitoring Instrument (OMI) on Aura. Aura in one of NASA’s Earth Observing System (EOS) satellites. [Figure Anne Thompson, Penn State University]