Study of Probability of Fog Occurrences at Different Temperature Ranges (Case study: Synoptic Stations in Kurdistan Province)

In this study probability of fog occurrence at a certain location has been estimated by finding a logical relationship between temperature and fog frequency conditions at that location. The available data, till 2006, for 7 synoptic stations in Kurdistan province have been used as case study. First, relative and cumulative frequencies of fog occurrences in different temperature ranges have been determined for each station. Then, their monthly and seasonal cumulative frequencies for a common 15 years period (1992- 2006) among those stations have been calculated. In order to reduce the risk of fog occurrence, necessary preparedness, and prevention of this hazard, their threshold temperatures at each station have been estimated. The results show that except in Ghorve station which the maximum fog frequency has occurred in -8°C to -6°C range and its amount was 71, in the other stations the most frequency of fog occurrences has been observed in -2°C to 0°C temperature range. From total number of fog observations, at Ghorve station 13.3%, Marivan 34%, Sanandaj 30%, Zarineh Obato19%, Saghez 39%, and at Bijar 26% occurred in positive temperatures. In all stations, the fog frequency was considerable in November, December, January and February months and it was inconsiderable in April, May and October. During the remaining months of the year (Jun., July, Aug., Sep.) fog didn’t happen. During the 15 years common period, the maximum fog frequency was 177 which have occurred in Zarineh station in December. In winter, because of low temperatures and relative humidity rising, fog occurrences were more than the other seasons of year in all stations.