The influence of simple chemistry on scalar variance and vertical-flux budgets above and within a forest canopy

A large-eddy simulation is modified to include multiple scalars emitted by a plant canopy. Each of these scalars is subjected to varying rates of chemical loss. A detailed comparison between conserved species and species undergoing simple first- and second-order chemical loss will be presented. Profiles of mean mixing ratio, mixing ratio variance and vertical mixing ratio flux reveal the influence of chemical reactivity. Budgets of mixing ratio variance and flux elucidate the mechanisms through which chemistry modifies each.

For variance production, the largest chemical impact is on the gradient term, while for flux production, chemistry has an even larger effect on the buoyancy term. With regards to variance destruction, chemistry has the largest influence on the SGS dissipation term, while the pressure-scalar destruction term is most affected in the flux budget. The mean mixing ratio regime is shown to dominate the net contribution of the chemistry terms in the budgets of the second-order species.