Two new approaches for the detection of fog/low stratus during daylight are presented. The methods are
based on second generation space technology from the polar (TERRA/AQUA MODIS) and geostationary
(MSG-SEVIRI) orbits. The MODIS approach makes use of a threshold technique which relies on eight
spectral bands. Minimum and maximum fog thresholds are determined by spectral threshold functions
which are derived from radiative transfer calculations. Validation with SYNOP data points to a good
performance of the algorithm. The SEVIRI approach profits from spectral and spatial cloud characteristics.
Fog detection is performed by using dynamic thresholding and a test due to cloud homogeneity.