Analysis of weather conditions for fog in Hefei

The monthly and seasonal variation of fog in Hefei and related surface weather elements characteristics were analyzed using conventional observation data from 2005 to 2009.Back-trajectory and cluster analyses were used to study the large scale transport characteristics on fog days.The results show that the number of fog days was the muximum in December,but it was the minimum in July.The weather conditions of fog can be characterized by high humidity,breeze and easterly or northwest wind.The fog occurrence was closely related to the transport pattern.The fog was associated with easterly(from east) trajectory at the ground level(10m),southwesterly and local trajectory at upper boundary layer(1000m).