A Combined Sensor Method for Detecting Frost Formation

Since frost is not associated with any type of observable precipitation, can't be observed by radar or satellite, and isn't reported by ASOS/AWOS or in the METARS, it can be a difficult phenomenon to automatically detect. One instrument currently used by ASOS that has shown some limited capability for detecting frost is the freezing rain sensor. A freezing precipitation algorithm for this instrument does account for frost, but has been observed to only report in instances of very heavy frost (Ramsey, A. C., 1999). Another sensor that has shown promise for detecting frost is the leaf-wetness sensor (LWS). Combining these sensors with several other sensors (visibility, precipitation gauges, temperature, ceilometer, radiation, wind speed and relative humidity) has the potential to detect active frost formation. Several case studies will be presented showing how a combination of sensors can be used to detect frost formation.