2008-06-02: The eye of the beholder

The Ozone Monitoring Instrument (OMI) uses reflected sunlight to retrieve concentrations of trace gases in the atmosphere, like O3 and NO2. These retrieved trace gas amounts must be corrected for the presence of clouds in the atmosphere. Cloud heights are derived from OMI observations of scattered light in the UV-visible range. However, satellite imagers like MODIS use thermal infra-red radiation, emitted by the clouds themselves. The two observation methods give a different view of clouds: OMI sees the middle of the cloud, whereas MODIS sees the top of the cloud.
For more details see Sneep et al. [2008]
Cloud pressure in the hurricane Ileana off the coast of Mexico, on 23 August 2006. Left and middle: OMI cloud pressure from O2-O2 and Raman scattering methods. Right: PARASOL O2 cloud pressure. Different retrieval methods give different cloud pressures.