Temporal dynamics of aerodynamic canopy height derived from eddy covariance momentum flux data across North American Flux Networks

Authors: CHU, HOUSEN - Lawrence Berkeley National Laboratory; BALDOCCHI, DENNIS - University Of California; POINDEXTER, CRISTINA - California State University; ABRAHA, MICHAEL - Michigan State University; DESAI, ANKUR - University Of Wisconsin; BOHRER, GIL - The Ohio State University; ARAIN, M ALTAF - McMaster University; GRIFFIS, TIMOTHY - University Of Minnesota; BLANKEN, PETER - University Of Colorado; O'HALLORAN, THOMAS - Clemson University; Hatfield, Jerry; Prueger, John; Baker, John

Submitted to: Geophysical Research Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/19/2018
Publication Date: 8/24/2018
Citation: Chu, H., Baldocchi, D., Poindexter, C., Abraha, M., Desai, A., Bohrer, G., Arain, M., Griffis, T., Blanken, P., O'Halloran, T., Hatfield, J.L., Prueger, J.H., Baker, J.M. 2018. 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. https://doi.org/10.1029/2018GL079306.
DOI: https://doi.org/10.1029/2018GL079306

Interpretive Summary: Assessing the ability of a plant canopy to exchange gases with the atmosphere requires an understanding of the fundamental properties of the canopy. We conducted an analyses across multiple sites to determine if there were uniform relationships in the canopy properties related to their aerodynamic characteristics. We found that canopies could be quantified using the variation in height throughout the year and these could be incorporated into energy exchange models. This information provides the basis for improving large scale models of plant canopies as part of the regional scale assessments by climate and hydrologic modelers and is valuable for policy assessments of land use change.

Technical Abstract: Aerodynamic canopy height (ha) is the effective height of a vegetation canopy for its influence on atmospheric fluxes and is a key parameter of surface-atmosphere coupling. However, methods to estimate ha from data are limited. This synthesis evaluates the applicability and robustness of the calculation of ha from eddy covariance momentum flux data. At 69 forest sites (111 site- years), annual ha robustly predicted site-to-site and year-to-year differences in canopy heights (R2 = 0.88). At 23 cropland/grassland sites, weekly ha successfully captured the dynamics of vegetation canopies over growing seasons (R2 > 0.70 in 74 site-years). Together, this evidence demonstrates the potential of flux-derived ha for tracking the seasonal, interannual, and/or decadal dynamics of vegetation canopies including growth, harvest, land use change, and disturbance. The large-scale and time-varying ha derived from flux networks worldwide provides a new benchmark for regional and global Earth system models and satellite remote sensing canopy structure.