Abstract:
An objective classification of radiation fog in distinct evolutionary stages during its life cycle based on reliable
criteria is essential for various applications, for example for numerical fog modelling and fog forecasting.
However, there have been up to now merely qualitative approaches for the distinction of different
evolutionary stages in radiation fog. Measurements of the microphysical fog properties with an optical particle
counter obtained from droplet measurement technologies together with recordings of the horizontal visibility
(VIS) are statistically analyzed to determine individual evolutionary stages of radiation fog with consistent
microphysical properties. The developed three-stage approach is based on a statistical change point analysis of
the double sum curves of the VIS, the liquid water content, the droplet concentration and the mean radius of
the drop size distributions. It could be shown that each of the three recorded radiation fog occurrences could
be split into three consecutive phases from formation to dissipation, regardless whether the VIS or the
microphysical properties were considered. Having featured consistent microphysical patterns, it could be
assumed that the three separated phases of the single fog occurrence could be aggregated for radiation fog.
Although this classification is statistically reliable, the dataset still has to be extended for a generalization
concerning the separated evolutionary stages.
