13th Conference on Aviation, Range and Aerospace Meteorology


Statistical characteristics of the wind dependence of snow and freezing fog events at several major airports for improving Runway Visual Range (RVR) performance

Thomas A. Seliga, Volpe National Transportation Systems Center, Cambridge, MA; and D. A. Hazen and S. Burnley

Snow and ice clogging of forward scatter visibility sensors (VS) as well as shadowing by sensor mounting structures in forward scattering systems are of serious concern to airport operations, since these conditions typically can possibly result in loss of service of the affected sensors or cause underestimates of extinction coefficients. Such measurements would result in higher values of RVR being reported to controllers. Clogging can arise when blowing snow or freezing rain enters into sensor heads and aggregate, leading to blockage of the affected sensor's optical window. Shadowing can occur when the sensor structure leads to free flow blockage of snow into the scattering volume, leading to less concentrated amounts of snowfall than would be representative of ambient conditions Heated sensor heads and windows, look-down, slightly skewed geometries and cylindrically-shaped arms for mounting the sensor transmitter and receiver are employed to minimize related risks. This study investigates the possibility of further reducing such risks by examining the feasibility of orienting the sensors in a direction that would minimize the probability of a sensor experiencing combinations of wind, snow and freezing rain that might lead to clogging or shadowing.

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Poster Session 1, Convection, Decision Support Systems, and Air Traffic Management Posters
Monday, 21 January 2008, 2:30 PM-4:00 PM, Exhibit Hall B

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