Branch Seminar Series: Wenge Ni-Meister

Hunter College of The City, University of New York
The 2007 National Decadal Survey report identified the need to measure the horizontal and vertical structure of ecosystems for estimating global carbon storage and ecosystem response to climate change and human land use. The Decadal Survey recommended the use of lidar observations to obtain these data, either from the lidar mission like the Ice, Cloud, and Land Elevation Satellite-II (ICESat-II), or a combined lidar and radar mission like the Deformation, Ecosystem Structure, and Dynamic of Ice (DESDynI). A physical based approach is required to assess the tradeoffs of the vegetation height and the above ground biomass retrieval requirements for the future lidar missions. We developed a physical based approach to estimate vegetation height, cover, biomass and their errors as functions of vegetation structure, surface topography, off-nadir viewing, footprint size, pulse width and surface roughness. The key of the methodology lies in using the well developed Geometric Optical and Radiative Transfer (GORT) model which describes the laser pulse interactions with vegetation structure and underneath surface topography. It directly characterizes the impacts of footprint size, underneath surface topography/roughness, off-nadir viewing and laser pulse width on lidar waveforms and vegetation height retrieval. Using this physical based approach allows us to assess the vegetation height and above ground biomass retrieval accuracies at different footprint sizes over different slope terrains for different vegetation characteristics.