New Observations of Vertical Canopy Structure and Dynamics from GEDI across Earths Tropical and Temperate Forests

The NASA Global Ecosystem Dynamics Investigation (GEDI) lidar launched to the International Space Station (ISS) on December 5, 2018, has been collecting science data since April 2019, and is expected to continue operation into 2023. Approximately 9.5 billion land surface measurements have been acquired between 51°N and 51°S in the first two years of operation, which is orders of magnitude more than has previously been available to the science community for quantifying canopy structure and biomass. GEDI has delivered footprint level canopy products describing the vertical distribution of cover and Plant Area Volume Density (PAVD) for all land surface shots as the L2B product, which is arguably the most important product for a flagship terrestrial ecology mission designed to measure canopy structure. Calibration and validation is undertaken through a global collation and standardization of community contributed in situ and Airborne Laser Scanning (ALS) datasets, which are collocated with on-orbit GEDI data. High fidelity airborne waveform measurements from the NASA Land Vegetation and Ice Sensor (LVIS) have also been collected coincident with GEDI, with deployments in Gabon (2016), USA / Costa Rica (2019), and French Guiana (2021). Using these data, we assess the performance of Level 2B algorithms for modeling the directional canopy gap probability profile in conditions up to 95% and 98% canopy cover for the coverage and power beams, respectively, and assess the spatial distribution of uncertainty in cover and PAVD estimates at the footprint and 1 km scales. We show that GEDI uniquely captures the spatial distribution of high canopy cover areas and, despite a limited mission lifetime, is also providing an unprecedented global view of phenological and disturbance induced changes in vertical canopy structure.