GOES Low-Cloud/Fog product--CIRA (Cooperative Institute for Research in the Atmosphere)

Note: This dataset is no longer available; it was lost in a disk crash. It's documented here as part of the process used in creating other datasets. The Low-Cloud/Fog satellite imagery product was developed at CIRA (Cooperative Institute for Research in the Atmosphere) to assist in the design of algorithms for GOES-R, the next generation weather satellite scheduled for a 2015 orbit. The Low-Cloud/Fog layer is computed from two GOES Imager bands , the 3.9um (shortwave) and 10.7 um (longwave) infrared window bands. The reflected component of the shortwave infrared window band is the key to the product. In the shortwave portion of the spectrum, ice clouds and snow are not very reflective, unlike water-droplet clouds which are highly reflective. This characteristic leads to an easy way to distinguish between ice and water clouds. Although this distinction is seen in the shortwave infrared window band alone, subtracting the emitted component of the shortwave highlights/enhances the reflected component for the user of this product. The GOES Low-Cloud/Fog product cannot by itself distinguish between a low cloud and a fog layer (where the latter is simply a low cloud whose base is in contact with the surface). Low clouds cannot be seen when high clouds obscure the lower clouds below. Especially at night, thin cirrus will appear black and can mask low clouds. The Pacific Coastal Fog project alleviated the severity of this constraint by limiting the use of the Low-Cloud/Fog product to summer months when fog and low stratus clouds are the predominant atmospheric feature.