Stratospheric and tropospheric NO2 observed by SCIAMACHY: first results Original Research Article

Observations from the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) onboard Envisat are used to quantifying the vertical distribution of stratospheric nitrogen dioxide (11–41 km) from limb scattering geometry and the tropospheric column from limb–nadir matching. SCIAMACHY is validated with spatially and temporally coincident observations from Optical Spectrograph and Infrared Imager System (OSIRIS) and from Halogen Occultation Experiment (HALOE). Comparison with the Canadian Middle Atmosphere Model provides a further check of consistency. Errors in pointing are detected and corrected using the recently developed `spectral kneeʹ technique. An instrumental artifact, presumably a tangent-height-dependent wavelength drift, is causing fine spectral structure but can be taken into account as a pseudo-absorber in the least squares fitting. Extending the fitting window to longer wavelengths than those currently employed by other optical satellite-borne NO2 sensors allows for the retrieval to penetrate the lower stratosphere. This extended fitting window is used to retrieve lower stratospheric NO2 in the denoxified Antarctic polar vortex. Finally, tropospheric NO2 columns, retrieved from limb–nadir matching, are presented.