Remote Sens. 2013, 5, 4187-4208; doi:10.3390/rs5094187 Remote Sensing ISSN 2072-4292 www.mdpi.com/journal/remotesensing Article Assessing the Sensitivity of the OMI-NO 2 Product to Emission Changes across Europe Martijn Schaap *, Richard Kranenburg, Lyana Curier, Magdalena Jozwicka, Enrico Dammers and Renske Timmermans Dutch Organisation for Applied Scientific Research (TNO), P.O. Box 80015, Utrecht 3508 TA, The Netherlands; E-Mails: Richard.Kranenburg@tno.nl (R.K.); Lyana.Curier@tno.nl (L.C.); Magdalena.Jozwicka@tno.nl (M.J.); Enrico.Dammers@tno.nl (E.D.); Renske.Timmermans@tno.nl (R.T.) * Author to whom correspondence should be addressed; E-Mail: martijn.schaap@tno.nl; Tel.: +31-88-866-2041; Fax: +31-88-866-2044. Received: 14 June 2013; in revised form: 22 August 2013 / Accepted: 22 August 2013 / Published: 27 August 2013 Abstract: The advent of satellite data has provided a source of independent information to monitor trends in tropospheric nitrogen dioxide levels. To interpret these trends, one needs to know the sensitivity of the satellite retrieved NO 2 column to anthropogenic emissions. We have applied a chemistry transport model to investigate the sensitivity of the modeled NO 2 column, sampled at the OMI (Ozone Monitoring Instrument) overpass time and location and weighted by the OMI averaging kernel, to emission sources across Europe. The most important contribution (~35%) in Western Europe is made by road transport. Off-road transport and industrial combustion each contribute 10%–15% across continental Europe. In Eastern Europe, power plant contributions are of comparable magnitude as those of road transport. To answer the question if the OMI-NO 2 trends can be translated directly into emission changes, we assessed the anticipated changes in OMI-NO 2 between 2005 and 2020. Although the results indicated that for many countries, it is indeed possible, for medium- and small-sized coastal countries, the contribution of the increasing shipping emissions in adjacent sea areas may mask a significant part of national emission reductions. This study highlights the need for a combined use of models, a priori emission estimates and satellite data to verify emission trends. OPEN ACCESS