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A comparison of CMAX-DOAS measurements and satellite retrievals of NO2 in an urban environment.

Louisa Kramer(1), Roland Leigh(1) and Paul Monks(2)

(1) EOS, Space Research Centre, Leicester, LE1 7RH, United Kingdom
(2) Department of Chemistry, University of Leicester, LE1 7RH, United Kingdom


The Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) technique has been advanced by several groups over the last few years, primarily using a motorised telescope or mirror assembly to take sequential images along different viewing geometries. The Leicester based UV/visible Concurrent MAX-DOAS (CMAX-DOAS) system is based on the concept of observing several viewing geometries simultaneously, utilising an instrument that images from multiple viewing angles using a single CCD with an imaging spectrometer and a multi-track fibre-optic cable, giving an instrument that offers temporal resolution of a minute or less.

The Leicester CMAX-DOAS instrument has previously been tested during the NAMBLEX (North Atlantic Marine Boundary Layer Experiment) in Ireland in 2002 and more recently formed part of the NDSC inter-comparison campaign in And√łya, Norway in 2003. The system is now installed on the Space Research Centre roof at the University of Leicester performing measurements of nitrogen dioxide, ozone and other trace gas species.

Global NO2 data have been retrieved from measurements performed by SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric CHartographY) operating on the European satellite ENVISAT and the Ozone Monitoring Instrument (OMI), launched onboard the NASA satellite Aura in July 2004. Both SCIAMACHY and OMI have good spatial resolutions making the instruments suitable for comparisons with measurements on an urban scale.

In this presentation, an overview of the instrumental setup will be given and the current performance and potential of the instrument discussed. Finally, a comparison of CMAX-DOAS retrievals and data from the SCIAMACHY and OMI instruments will be presented, examining the full range of spatial scales available for urban air quality monitoring.


Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry