Satellite measurements of NO₂ from international shipping emissions

Abstract

Measurements from the SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) instrument on board the ENVISAT satellite have been analyzed for tropospheric NO 2 signatures of shipping emissions. Clear indication for NO 2 produced from ship emissions has been found over the Red Sea and along the main shipping lane to the southern tip of India, to Indonesia and north towards China and Japan where the signal is lost. Using simple assumptions for the NO x loss, emission strengths were estimated and compared to an updated ship emission inventory. Good agreement was found in the spatial distribution and the absolute values for the Red Sea agree within a factor of 2, but larger discrepancies exist in other areas. Although the fluxes calculated still have large uncertainties, the results highlight the importance of ship emissions for the marine boundary layer and at the same time demonstrate the potential of satellite observations.