Project Final Report Regional Forest-ABL Coupling: Influence on CO2 and Climate

Ecosystem CO{sub 2} exchange and atmospheric boundary layer (ABL) mixing are correlated diurnally and seasonally. Tracer transport models predict that these covariance signals produce a meridional gradient of annual mean CO{sub 2} concentration in the marine boundary layer that is half as strong as the signal produced by fossil fuel emissions. This rectifier effect has been predicted by many inversion models. However, observations to constrain the strength of the rectifier effect in nature are lacking. The fundamental objective of this project was to measure the strength of these covariance signals between ecosystem CO{sub 2} flux and ABL dynamics by employing ABL profiling systems at eddy flux tower sites. We found that (1) the observed diurnal and seasonal covariance between ecosystem CO{sub 2} fluxes and ABL turbulent mixing are strong; (2) the inversion model underestimates the diurnal and seasonal covariance; (3) the rectifier effect in the model appears to be too weak. However, these results are subject to significant uncertainties associated with the use of a point measurement to represent an area, fair weather bias among the data and instruments, and nonlinear transport processes between continental and marine boundary layers.