Improving control of smoke from prescribed fire using Low Visibility Occurrence Risk Index

Abstract

Wildland fires produce smoke that contributes to reduced visibility over roadways with potentially tragic consequences. Land managers need to reduce this potential hazard. Two indices are described that correlate with conditions associated with roadway hazard. The Dispersion Index (DI) depends on surface and upper air meteorological data and describes the atmosphere's capacity to reduce smoke concentrations to acceptably low levels downwind from fire. The Low Visibility Occurrence Risk Index (LVORI) is a combination of DI and relative humidity. LVORI expresses the likelihood of low visibility due to smoke and/ or fog being reported at a roadway accident site. LVORI is expressed as a function of estimated weather at each accident site, as determined from National Weather Service reports.