Reduced visibility by foggy events greatly affects road, marine and aviation transportation. Understanding formation of fog leads to reduction of financial losses and casualties. The purpose of this study is physical-statistical analysis of the fog types at the Ardebil airport. For this purpose, synoptic data of the airport meteorology station were used in a 13-year period (2004-2016). For statistical analysis, frequency of fog events in various time intervals has been investigated. Then, using physical analysis, the type of fog was studied at different synoptic hours. Results indicate the physical processes of radiation cooling and humidity advection are main physical mechanisms for formation of fog and low stratus clouds respectively at 21, 00, 03, 06 (UTC) and 09, 12, 15 (UTC) and both of them at18 UTC.