Light Pollution and Meteorology – Cloud Base Height Estimation at Night Based on Sky Camera Measurements

Abstract

Base height of low-level clouds is a critical parameter in aviation meteorology. We introduce a new observation method for determining cloud base height at night. The technique is based on processing sky camera pictures and it is analogous to the triangulation principle of searchlight ceilometer. We show that light pollution (the upward component of artificial lights) could be used passively as cloud ceiling projector in various environments. The method was tested in one year period from one observation site in central Budapest. We found that the base height could be estimated with reasonable accuracy in the case of homogeneous stratus cloud sheets, via the illumination of the clouds from the stronger ornamental lights in the city. Case studies with different local light pollution characteristics (e.g. smaller settlements, different observation distances) will be presented. Limitations of the method will be discussed.