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PI-Submitted Research Highlights for
Terrestrial Ecosystem Science Program

Seeing the Vegetation Canopy from Wind Measurements

Dennis Baldocchi

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Temporally dynamic canopy heights derived from momentum flux data across AmeriFlux sites.

The Science 
This study evaluates an innovative and robust method for deriving the canopy height, a key descriptor of the Earth surface, from continuously measured wind statistics and momentum fluxes. Researchers from the University of California, Berkeley show its applicability for tracking the temporal dynamics of vegetation canopies, including plant growth, harvest, land-use change, and disturbance.

The Impact
Networks of eddy covariance tower sites (i.e., meteorological observation towers with high-frequency measurements of wind speed and surface fluxes) have collected ~108 hours of turbulent flux data worldwide. This study demonstrates the great potential of the flux-derived canopy heights for providing a new benchmark for regional and global Earth system models and satellite remote sensing of canopy structure.

Summary
Vegetation canopy height is a key descriptor of the Earth surface and is in use by many modeling and conservation applications. However, large-scale and time-varying data of canopy heights are often unavailable. This synthesis evaluates the calculation of canopy heights from the momentum flux data measured at eddy covariance flux tower sites. This study shows that the aerodynamic estimation of canopy heights robustly predicts the site-to-site and year-to-year differences in canopy heights across a wide variety of forests. The weekly canopy heights successfully capture the dynamics of vegetation canopies over growing seasons at cropland and grassland sites. These results demonstrate the potential of the flux-derived canopy heights for tracking the seasonal, interannual, and/or decadal dynamics of vegetation canopies including growth, harvest, land-use change, and disturbance. Given the amount of data collected and the diversity of vegetation covered by the global networks of eddy covariance flux tower sites, the flux-derived canopy height has great potential for providing a new benchmark for regional and global ESMs and satellite remote sensing of canopy structure.

Contacts
BER Program Manager
Daniel Stover
SC-23.1
Terrestrial Ecosystem Science
Daniel.Stover@science.doe.gov

Principal Investigator
Dennis Baldocchi
University of California, Berkeley
baldocchi@berkeley.edu

Housen Chu
Lawrence Berkeley National Laboratory
Berkeley, CA 94720
hchu@lbl.gov

Funding
This study is supported by FLUXNET and AmeriFlux Management Project, hosted by the Lawrence Berkeley National Laboratory, which is sponsored by the U.S. Department of Energy Office of Science (DE-SC0012456 and DE-AC02-05CH11231).

Publications
Chu, H. et al. “Temporal dynamics of aerodynamic canopy height derived from eddy covariance momentum flux data across North American Flux Networks.” Geophysical Research Letters 45(17), 9275–9287 (2018). [DOI:10.1029/2018GL079306]

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