Trends in fog frequency and duration in the Southeast United States

Dense fog is a frequently occurring phenomenon across the Southeast United States. The National Weather Service designates horizontal visibility of 1/4 mile or less as dense fog. The objective of this research is to compile fog data and to analyze the frequency and duration of dense fog events across the southeast for the period 1948-2003. Southeast states include Virginia, North Carolina, South Carolina, Georgia, Florida, and Alabama. A day with at least one hour of horizontal visibility of 1/4 mile or less is considered a fog event day. The hourly dataset (TD3280) is used to determine the number of fog event days and the duration of each event. Any seasonal and yearly trends are examined to determine if the frequency and/or length of fog events are changing with time. The TD3280 dataset uses first-order stations and should, therefore, provide information about trends in-or-near urban areas.