Quantifying Changes in Surface Properties in Environment Affected by Wildfire Using MODIS Products

Droughts and wildfires have increased in both frequency and intensity across the western US. Several notable extremes from recent years serve as witness. These events threaten life and property, modify ecosystem functioning and services, and potentially impose feedbacks on the broader earth system. The main aim of this study was to document ecosystem responses to severe wildfire event to assess how these disturbances are altering terrestrial ecosystems and how they are changing surface-atmosphere exchanges using a case study of Rim fire that occurred in 2013. The Rim fire was burned on the west slope of the Sierra Nevada and was large enough to have impacts on the local exchanges of carbon, water, and energy between land and atmosphere.

We analyzed several MODIS and other products to estimate land surface temperature (LST), vegetation cover (VC), evapotranspiration (ET), and gross primary productivity (GPP) before, during, and after disturbance events to examine how these variables change from pre- to post-burning relative to undisturbed counterparts. Results showed lower LST and higher ET and GPP in the control site compared to the Rim fire. The change in LST, ET, and GPP was much more pronounced when wildfire event was accompanied by severe drought. For example, in 2014, peak year of drought in California, LST increased by 6 ℃ and ET and GPP decreased by around 50% in Rim fire perimeter compared to year 2013. Rim fire, accompanied by severe drought, was impactful to alter local climate, with potential for secondary modifications to atmospheric circulations, cloud formation, and precipitation. In addition, severe wildfires like Rim fire that replace forest stands with grass and herbaceous vegetation types might act to amplify droughts and heatwaves, thus making them more common or more severe.