Advances in the Detection and Analysis of Fog at Night Using GOES Multispectral Infrared Imagery

A technique is described for the detection of fog and low clouds at night using multispectral infrared (IR) imagery from Geostationary Operational Environmental Satellites (GOES). The technique requires subtraction and enhancement of digital data from IR window channels at 3.9- and 10.7–11.2-µm wavelengths. Resulting images show stratiform clouds over any type of terrain for a wide range of surface temperature conditions. The bispectral difference images are a considerable improvement over the use of enhanced images for a single window IR channel. An image enhancement technique that displays the approximate depth of fog was developed based on the correlation of brightness differences in the two IR channels to cloud-top heights reported by aircraft. The improved resolution and greater frequency provided by the GOES I-M satellites will result in a substantial improvement in the ability to monitor areas of reduced ceilings and visibilities at night.