18th Conference on Weather and Forecasting, 14th Conference on Numerical Weather Prediction, and Ninth Conference on Mesoscale Processes

Monday, 30 July 2001
Model sensitivity to wildfire-induced changes in soil albedo, vegetation cover, and soil moisture
Elizabeth Mulvihill Page, NOAA/NWS, Boulder, CO; and W. R. Cotton
Wildfires and forest fires in particular leave behind greatly altered land surfaces including lowered surface albedos, reduced vegetation coverage, and dry soils. For extended periods following wildfires, the burned areas will absorb more solar radiation, have reduced transpiration from vegetation, and reduced evaporation from dried soils leading to enhanced sensible heating of the burned areas. During conditionally unstable periods following wildfires, the burned areas should thereby become "hotspots" relative to surrounding unburned areas for development of deep convective storms and thereby increase the chances of storm-induced enhanced runoff on land-surfaces now prone to erosion.

To examine this hypothesis, the Regional Atmospheric Modeling System (RAMS) developed at Colorado State University is employed. The versatility of this model allows surface parameters to vary over the domain in order to replicate sharp boundaries in surface characteristics that are believed to be important in antecedent fire-induced mesoscale circulations.

Sensitivity tests are structured to the application of mesoscale circulations developing due to surface changes caused by fire. The surface parameters to be tested include surface albedo, degree of slope, vegetation type and coverage, and soil moisture. The variations in surface parameters follow the expected effects from large fires. Changes to the surface parameters over the burned region include decreases in vegetation coverage, soil moisture, and albedo. Initially, the model is run using flat terrain with a large burned area. Subsequent simulations model the effects of the burn area over sloped terrain. Preliminary results will be presented at the conference.

Supplementary URL: