Modelling bi-directional fluxes of methanol and acetaldehyde with the FORCAsT canopy exchange model

Ashworth, Kirsti and Chung, Serena H. and Mckinney, Karena A. and Liu, Ying and Munger, William J. and Martin, Scot T. and Steiner, Allison L. (2016) Modelling bi-directional fluxes of methanol and acetaldehyde with the FORCAsT canopy exchange model. Atmospheric Chemistry and Physics Discussions. pp. 1-48. ISSN 1680-7367

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Abstract

The FORCAsT canopy exchange model was used to investigate the underlying mechanisms governing foliage emissions of methanol and acetaldehyde, two short chain oxygenated volatile organic compounds ubiquitous in the troposphere and known to have strong biogenic sources, at a northern mid-latitude forest site. The explicit representation of the vegetation canopy within the model allowed us to test the hypothesis that stomatal conductance regulates emissions of these compounds to an extent that its influence is observable at the ecosystem-scale, a process not currently considered in regional or global scale atmospheric chemistry models. We found that FORCAsT could only reproduce the magnitude and diurnal profiles of methanol and acetaldehyde fluxes measured at the top of the forest canopy at Harvard Forest if light-dependent emissions were introduced to the model. With the inclusion of such emissions FORCAsT was able to successfully simulate the observed bi-directional exchange of methanol and acetaldehyde. Although we found evidence that stomatal conductance influences methanol fluxes and concentrations at scales beyond the leaf-level, particularly at dawn and dusk, we were able to adequately capture ecosystem exchange without the addition of stomatal control to the standard parameterisations of foliage emissions, suggesting that ecosystem fluxes can be well enough represented by the emissions models currently used.

Item Type:
Journal Article
Journal or Publication Title:
Atmospheric Chemistry and Physics Discussions
ID Code:
82355
Deposited By:
Deposited On:
28 Oct 2016 08:26
Refereed?:
Yes
Published?:
Published
Last Modified:
05 Aug 2020 11:47