High upward fluxes of formic acid from a boreal forest canopy

Author/Creator ORCID

Date

2016-08-26

Department

Program

Citation of Original Publication

Schobesberger, S., et al. (2016 ), Highupward fluxes of formic acid from aboreal forest canopy, Geophys. Res. Lett.,43, 9342–9351, doi:10.1002/2016GL069599

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©2016. American Geophysical Union. All Rights Reserved

Subjects

Abstract

Eddy covariance fluxes of formic acid, HCOOH, were measured over a boreal forest canopy in spring/summer 2014. The HCOOH fluxes were bidirectional but mostly upward during daytime, in contrast to studies elsewhere that reported mostly downward fluxes. Downward flux episodes were explained well by modeled dry deposition rates. The sum of net observed flux and modeled dry deposition yields an upward “gross flux” of HCOOH, which could not be quantitatively explained by literature estimates of direct vegetative/soil emissions nor by efficient chemical production from other volatile organic compounds, suggesting missing or greatly underestimated HCOOH sources in the boreal ecosystem. We implemented a vegetative HCOOH source into the GEOS‐Chem chemical transport model to match our derived gross flux and evaluated the updated model against airborne and spaceborne observations. Model biases in the boundary layer were substantially reduced based on this revised treatment, but biases in the free troposphere remain unexplained.