The Impacts of Wildfire on Surface Albedo and Surface Roughness: Implications for Modeling Evapotranspiration (Awardee)

Climate change has increased the frequency of wildfire occurrences, especially in Western regions of the U.S. Vegetation phenology, which characterizes both physical changes (e.g. leaf development and abscission) in vegetation structure and the inherent seasonality of mass and energy flux, is considered to be a crucial signature of ecosystem processes and feedbacks to climate. In 2002, a micrometeorological flux tower was installed at the Appleton-Whittle Research Ranch (AWRR) in southern Arizona, about 60 km to the southeast of Tucson. Since the early 1970’s, the 3238 ha ranch has had limited grazing. The wildfire burned nearly 90% of the ranch area, with little vegetation left at the surface. The installation of the tower just after the fire provided an unique opportunity to make direct observations of the solar shortwave and visible albedo over the ground without vegetation and evaluate the changes over the next few years. In addition, from the micrometeorological observations, we were able to also quantify the changes the wildfire had on the surface roughness, and determine how long it took for the grassland to recover back to a quasi-baseline state. The observations were then combined with model results to assess the implications of how this could have affected the estimates of evapotranspiration over the next several years.