A characteristic analysis of fog using GPS-derived integrated water vapour

Abstract

In order to determine the plausibility of GPS-derived Integrated Water Vapour (IWV) as a fog detector, the relationship between GPS IWV and meteorological observations during fog was studied in a time domain. In this research, it is assumed that fog is a simple function of water vapour and cloud water based on non-precipitation warm cloud in the bulk water-continuity model and that, during fog, the atmosphere over the fog layer is horizontally homogeneous.The case of dense fog was chosen, for which the visibility observed by the human eye ('synop') was < 1 km with the regular observation at co-located GPS sites. Preliminary results showed that GPS IWV could detect the microphysical and dynamical process of fog, such as conversion of the water vapour into cloud water and inflow of water vapour into GPS observation sites. Furthermore, it could potentially be found that GPS IWV reflected unceasingly and quantitatively the state of fog after saturation.To mitigate limitations of the temporal resolution and the inaccuracy of 'synop' visibility data, a GPS receiver and a visibility meter were operated at the same site simultaneously. This experiment revealed definitively that typical radiation fog was more suitable than other types of fog for detection by GPS IWV.Based on these results, it is suggested that GPS IWV can be considered as a supplementary technique in detecting fog processes and improving fog predictability. Copyright © 2010 Royal Meteorological Society.