Characterizing fog occurrences in the northeastern United States using historical data

Although increased understanding of fog has been obtained through previous field experiments and modeling studies, a comprehensive description of the fog life cycle and processes leading to its temporal and spatial variability in a complex environment remain elusive. One such environment is the New York area, as it is characterized by a complex coastline, variability of land surface characteristics and high levels of pollution. Poor visibility associated with fog is a common phenomenon in the New York area and lead to significant disruptions in air travel at some of the world’s busiest airports, as well as to hazardous flying conditions for the general aviation pilots and to difficult driving conditions on the area’s crowded highways.

A climatological study, based on the identification of fog events from historical hourly surface observations, aims at identifying and characterizing the various regimes leading to fog formation in a region centered on New York City. Over a period of 20 years, the number of events shows a clear minimum in urban centers, while coastal locations tend to experience the most fog. Fog events are also categorized according to fog types. Results show that the area experiences various fog regimes, under the influence of a variety of synoptic weather patterns. The most common fog type is fog associated with precipitation, while fog onset resulting from cloud base lowering, either associated with frontal clouds or marine boundary layer clouds, also occurs frequently in the area. A significant number of advection fog events occur in coastal areas mostly during spring, while radiation fog occurs predominantly in suburban and rural inland areas during fall. An analysis of local conditions at the onset of fog events is performed to identify important influences.