NOAA-NESDIS
Regional And Mesoscale Meteorology Team
Daily Satellite Discussion
Thursday June 12, 1997

    The feature for today focuses on detection of African dust in the 1745 GMT Visible imagery and the corresponding signature as seen in the product from the GOES-8 "split window" infrared channels. The 10.7 - 12.0 micron difference product was created the same way the fog product is created: the brightness temperature differences are taken and then scaled for viewing. The 12.0 micron channel is sensitive to certain types of aerosols. Dust particles originating from the Sahara Desert have a higher emissivity in 12.0 micron than in 10.7 micron. This creates a negative difference (10.7 -12.0).

    Compare these regions of dust with the sunglint region around Central America. We see sunglint in the Visible imagery because of the reflected energy off the ocean waters. We do not see this feature in the differenced product because neither channels are sensitive to the reflected energy. Another characteristic of 12.0 micron imagery is it's sensitivity to low level moisture. The 12.0 micron channel is slightly cooler than the 10.7 micron channel due to absorption of low level moisture. Note the positive regions in the difference product.

    RAMSDIS sites do not currently receive this product. It is under investigation for future use.

    Bernadette Connell

    We welcome your comments and discussion at ramsdis@comet.ucar.edu