Best Practices for Road Weather Management Version 2.0
Bridge Frost Occurrence and Prediction
Frost on bridges can present hazardous conditions to motorists, particularly if it occurs when adjacent roadways are clear of frost. Accurate forecasts of bridge frost onset times, frost intensity, and frost disappearance (e.g., melting or sublimation) are needed to help roadway maintenance personnel decide when, where, and how much frost-suppression chemical to use. We have developed a finite-difference algorithm (BridgeT) that simulates vertical heat transfer in a bridge based on evolving meteorological conditions at its top and bottom as supplied by a weather forecast model. This algorithm simulates bridge deck surface temperature at 1-min intervals and calculates volume per unit area (i.e., depth) of frost deposited, melted, or sublimed. From this we produce forecasts of frost onset time, frost "depth," and duration of frost on the bridge. Evaluation of forecast methods for predicting frost on bridges and roadways is difficult because of a lack of observations of frost occurrences. Early morning observations of untreated bridges near Ames, Iowa, were made during two winter seasons to establish a database of bridge frost occurrences and nonoccurrences. When frost was detected, observations were continued until the frost disappeared and thereby provided additional information on duration and timing of onset and demise of frost. Bridge frost predictions as well as predictions of air temperature, dew-point temperature, bridgetop surface temperature, and wind speed, are compared with observed and measured values to assess skill in forecasting bridge frost and associated conditions.
6th International Symposium on Snow Removal and Ice Control Technology, Transportation Research Circular, No. E-C063
Greenfield, et al
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