Multi-decadal estimates of aboveground biomass estimated from repeat airborne waveform lidar acquisitions

The NASA Land, Vegetation, Ice Sensor (LVIS), a f ull waveform airborne lidar instrument, has acquired repeat observations over temperate and tropical forest sites, specifically the Appalachian Mountains (USA) in 1999 and 2019 and in Costa Rica in 1999, 2005, and 2019 . These acquisitions will expand the number of coincident observations from NASA Global Ecosystem Dynamics Investigation (GEDI) orbits and existing ground plot networks for calibration and validation, and provide reference data on long-term (> 10 years) accumulation and fluxes of terrestrial forest carbon stocks. Here we present estimates of aboveground biomass and associated uncertainty carbon stocks for each lidar acquisition and discuss the implications and next steps for estimation of carbon gains and losses over the interval between acquisitions. We follow methods developed for the AfriSAR mission and the GEDI Level 4A footprint aboveground biomass product, and that are aligned with recommendations from the forthcoming Committee on Earth Observation Satallites (CEOS) Land Product Validation best practices protocol for aboveground biomass. Our results can inform validation of carbon fluxes to be developed from spaceborne active remote sensing missions, such as the recently launched GEDI, and forthcoming SAR missions such as NASA/ISRO NISAR.