Thursday, 7 October 2004
Widespread, dense fog can be both hazardous and disrupt commercial transport. Such fog events in the central U.S. were initially examined in the early and mid-1900s. During the last few decades, radiation fog and coastal advection fog events have been extensively studied in other regions, but not in the central U.S. Early studies suggested that dense and widespread fogs of the central U.S. were largely related to fronts, either pre-warm frontal or post-cold frontal events. More recently, however, fogs are more commonly described in the literature as occurring in associated with the advection of warm moist air over cold or snowy surfaces or with radiational cooling. The purpose of this study is to document the synoptic and surface conditions associated with of fogs of this region.
The environmental conditions associated with dense fog events that occurred at Peoria, IL for the period 1948-1996 will be presented. This study is based on hourly surface observations of horizontal visibility, winds, temperature, humidity and prevailing weather, and also on regional observations of daily snow depth and rainfall. The synoptic setting for fog events also has been examined for dense fog events occurring during the 25-year period from 1970 to1994, primarily employing 3-hr surface charts. The fog events have been categorized by the duration of the event in an attempt to discern conditions that are most relevant for long-lasting dense fog events.
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