Calibrated geo-located HIRS Channel 11 radiances. High radiance values are related to the red and the yellow coloured pixels, and low values are marked by magenta. HIRS channel 11 is sensitive to atmospheric water vapour (7.3 microns) in the mid-troposphere (roughly 700 hPa, corresponding to about 3 km). Thus, for low surface altitudes, the main contributors to the radiance signal are clouds and atmospheric humidity. Data recorded on 21 November 2006.