Towards scale-invariant aboveground biomass estimation in Savanna ecosystems using small-footprint waveform lidar

Land degradation is becoming an issue of increasing concern in the savanna ecosystems of southern Africa. As a result, there is a growing need to map structural changes at the fine scale, while retaining the ability to aggregate up to landscape level for analysis across land use gradients. Aboveground biomass (AGB) is an important indicator of vegetation structure and therefore is the ideal variable for estimation from light detection and ranging (lidar) data. To avoid the effects of scale, this paper takes a tree-delineation approach for segmentation of the structurally heterogeneous savanna environment. Diameter at breast height (DBH) measurements collected in-field are then regressed against lidar-derived statistics to estimate DBH on a per tree basis, from which biomass follows naturally by allometry. The result is a spatially explicit biomass map of the savanna environment, believed to be one of the first of its kind, that can be scaled by aggregation of per-tree biomass distributions

ECOSTRESS: NASA's next generation mission to measure evapotranspiration from the International Space Station

The ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station ECOSTRESS) was launched to the International Space Station on June 29, 2018. The primary science focus of ECOSTRESS is centered on evapotranspiration (ET), which is produced as level‐3 (L3) latent heat flux (LE) data products. These data are generated from the level‐2 land surface temperature and emissivity product (L2_LSTE), in conjunction with ancillary surface and atmospheric data. Here, we provide the first validation (Stage 1, preliminary) of the global ECOSTRESS clear‐sky ET product (L3_ET_PT‐JPL, version 6.0) against LE measurements at 82 eddy covariance sites around the world. Overall, the ECOSTRESS ET product performs well against the site measurements (clear‐sky instantaneous/time of overpass: r2 = 0.88; overall bias = 8%; normalized RMSE = 6%). ET uncertainty was generally consistent across climate zones, biome types, and times of day (ECOSTRESS samples the diurnal cycle), though temperate sites are over‐represented. The 70 m high spatial resolution of ECOSTRESS improved correlations by 85%, and RMSE by 62%, relative to 1 km pixels. This paper serves as a reference for the ECOSTRESS L3 ET accuracy and Stage 1 validation status for subsequent science that follows using these data