Evaluating large scale forest disturbance resulting from Hurricane Katrina using the Geoscience Laser Altimeter System (GLAS) LiDAR

Scientists are actively trying to understand the role of forest disturbance and recovery in the global carbon cycle and budget using a variety of methods. Hurricane Katrina has created an opportunity for scientist to further understand hurricanes impacts on forest systems and the carbon cycle. Recent estimates of forest damage resulting from hurricane Katrina have relied primarily on optical remote sensing. GLAS lidar aboard the NASA satellite ICESat have been used to measure forest structure in diverse landscapes over large areas and to assess forest regrowth after large magnitude disturbances. This study uses GLAS, in combination with other data, to improve the detection and modeling of both the impacts and recovery of ecosystems from hurricanes by providing more direct measurements of changes in structure. Three GLAS campaigns were chosen representing fall, winter and spring for the year preceding and following Katrina. GLAS waveforms were compared to wind speed, forest cover, and damage maps to analyze sampling, and structure patterns. Preliminary results show an average decrease in mean canopy height of ~4m in forests experiencing category two winds, a ~2meter decrease in areas experiencing category one winds, and less than a meter change in areas hit by tropical storm winds. Changes in structure were converted into carbon estimates using the Ecosystem Demography (ED) model and compared to prior independent estimates based on field and optical remote sensing. Results are synthesized to help inform the needed characteristics (e.g. accuracy, sampling) for future data on vegetation structure from space.