Detecting ground fog from space – a microphysics-based approach

Abstract

The detection of ground fog from satellite data is of interest in operational nowcasting applications, as well as in studies of the climate system. A discrimination between fog at the ground and other low-stratus situations from satellite data requires information on cloud vertical geometry to establish whether the cloud touches the ground. This article introduces a technique that allows for the discrimination between low stratus and (ground) fog on the basis of geostationary satellite imagery. The cloud-base height is derived using a subadiabatic model of cloud microphysics. In this model, the cloud base is varied until model liquid–water path matches that retrieved from satellite data. The performance of this technique is shown to be good in a comparison with METeorological Aerodrome Report data comprising 1030 satellite scenes. With a hit rate of 81% and a threat score of 0.62, the skill is satisfactory.

Acknowledgements

The authors thank ESA and the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) for early access to MSG data within the ESA MSG Principal Investigator Programme. Funding for satellite-data evaluation was provided by DFG in grants Be 1780/8-1, Be 1780/8-3 and Be 1780/14-1. European Union (EU) Cooperation in Science and Technology (COST) action 722 provided a valuable framework for the discussion of the satellite products. The helpful comments of two anonymous reviewers are gratefully acknowledged.