Academic journal article The Geographical Bulletin

A Fog Climatology of the Delmarva Peninsula

Academic journal article The Geographical Bulletin

A Fog Climatology of the Delmarva Peninsula

Article excerpt

INTRODUCTION

Across most of the United States, public school delays due to fog are rare . However, for parents and students residing on the Delmarva Peninsula school delays due to fog are commonplace The Delmarva Peninsula consists of Delaware and the eastern portions of Maryland and Virginia (Fig . 1). The Peninsula is bordered to the east by the Atlantic Ocean and to the west by the Chesapeake Bay. Salisbury and Dover are the main population centers, resort towns line much of the Atlantic coast, and the rest of the Peninsula is predominantly rural . The Atlantic and Chesapeake both play a role in influencing the climate of the region including the vary- ing seasonality and characteristics of fog on a mesoscale . In Wicomico County, Maryland, over a recent five-year period (2011-2016) there was an average of five (one- or twohour) school delays caused by fog per year (WCBOE 2016). Prior to 1997 Delmarva schools were rarely delayed for fog . However, a fatal school bus accident in Easton, Maryland during low visibility fog conditions on October 31, 1997 (The Daily Times 1997) changed the way that foggy conditions are treated in this region with regard to school safely School delays due to fog are now issued whenever relatively dense fog conditions develop overnight and are expected to persist into the normal morning school bus route times The preponderance of school delays along with the economic impact to coastal cities makes an examination of the climatology of fog conditions across the Delmarva region especially relevant

Fog can form either by the cooling of nearsurface air down to its dew point or by the addition of moisture to the air. The fog type (classification) depends upon the method of formation There are five types of fog, three that result from cooling of the air and two that result from the addition of moisture to the air. The three types of fog that form from cooling are radiation fog, advection fog, and upslope fog It is well known that radiation fog forms on calm and clear nights due to radiational cooling and is most common in the early morning hours surrounding sunrise (Westcott 2007). Advection fog forms when relatively warm, humid air moves over a colder surface such as cold water or snow. This fog type is common during the spring in coastal regions . Upslope fog forms due to the gentle uplift and cooling of air along a sloping surface . The two types of fog that result from the addition of moisture to the air are steam fog and frontal fog . Steam fog forms when cool air is present over a relatively warm water surface and is especially common during autumn . Frontal fog forms when light precipitation falls through a layer of cool air and typically is associated with a warm front (Ahrens 2013, Aguado and Burt 2013).

Fog occurrence is often a function of local, regional, and synoptic scale conditions and strongly varies with geographical location (Croft et al. 1995; Garcia-Garcia and Zarraluqui 2008). Forecasting fog is challenging due to the complex interplay of various atmospheric processes (Tardif and Rasmussen 2010). Despite advances in weather forecasting due to improvements of modelling techniques, accurate fog forecasting remains difficult (Bergot and Guedalia 1994).

Although fog is not often considered a newsworthy event, its impacts are often costly and can even be deadly (Croft et al. 1995, Haeffelin et al. 2010; Ashley et al . 2015) . Delays in aviation, marine and surface transportation are the most well recognized (Garmon et al . 1996). It can also have less explicit, location-specific economic impacts; fog can make tourist destinations undesirable and drive away business These effects have been studied for tourism in mountainous regions by Bürki et al . (2003) and more generally by Gómez Martín (2005). In spite of their importance, fog impacts have not been properly assessed throughout the world (Garcia-Garcia and Zarraluqui 2008) Fog has received relatively little attention compared to many other meteorological elements such as temperature, precipitation and wind

Recent fog-related research has primarily focused on fog detection using satellite imagery (Ellrod 1995; Bendix 2002; Bendix et al 2006; Cermak and Bendix 2008) and modelling techniques to predict the occurrence and characteristics of fog (Bergot and Guedalia 1994; Teixeira and Miranda 2001). …

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