Advanced space-borne imagers such as the low earth-orbiting Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua and Terra spacecraft can be very useful for (1) validation of existing derived products from lower resolution instruments such as the Geostationary Operational Environmental Satellite (GOES) Imagers, and (2) assessing the capabilities of future polar (National Polar Orbiting Environmental Satellite Prototype, 2006) or geostationary (GOES Advanced Baseline Imager, 2013), which will have vastly improved multi-spectral sensors. The MODIS has 36 spectral bands with 1 km resolution infrared (IR) and 0.25-0.5 km visible and near-IR imagery. By comparison, the current GOES Imager has 4 IR channels (4 km resolution) and a visible band (1 km resolution).

This paper describes how imagery and derived products from MODIS compared with those from GOES-8 and 10 for a case of orographic fog and stratus clouds during the night of 4-5 March 2001. This event resulted in widespread low ceilings and visibilities over the High Plains from Kansas to eastern Montana. The derived products compared were: (1) imagery derived from the brightness temperature difference (BTD) between IR bands centered near 4 µm and 11 µm wavelengths (a.k.a. “Fog product”), (2) fog depth estimates based on the magnitude of BTD’s, and (3) a Low Cloud Base product to show areas where ceilings below 1000 ft Above Ground Level are likely. The latter product is estimated with the aid of both satellite IR and surface shelter temperatures.

There were some significant, fine scale features observable in the MODIS data not readily seen by GOES, such as better definition of a narrow band of fog in the James River Valley of South Dakota, although the overall area coverages were similar from both systems. There was also a striking difference in the quality of the bi-spectral imagery, due to the very low instrument noise in the shortwave IR (4 µm) band from MODIS.