Dynamics-aerosol-chemistry-cloud interactions in West Africa
Research Publications
09 May 2018
LES study of the impact of moist thermals on the oxidative capacity of the atmosphere in southern West Africa
Publication: Atmos. Chem. Phys., 18, 6601-6624 ()
DOI Number: 10.5194/acp-18-6601-2018
Author: Fabien Brosse, Maud Leriche, CĂ©line Mari, and Fleur Couvreux
The hydroxyl radical (OH) is a highly reactive specie and plays a key role in the oxidative capacity of the atmosphere.
The total OH reactivity, corresponding to the inverse of OH lifetime, may have a significant fraction non-attributable to
commonly measured compounds. The turbulence-driven segregation of OH and its reactants can cause substantial modification
of averaged reaction rates, and thus of the total OH reactivity, when compared to a perfectly mixed assumption. We study the
impact of turbulent  mixing on the OH reactivity with Large-Eddy Simulations from theMeso-NH model coupled on-line with a
detailed chemistry mechanism in two contrasted regimes. Our findings show that the non-mixing of isoprene (resp. aldehydes)
and OH leads to 30% decrease (resp. 16% increase) of the mean reaction rate at the top of the boundary layer and consequently
to 9% decrease (resp. 5% increase) of the OH total reactivity in a biogenic (resp. anthropogenic) environment. Moreover, the
total OH reactivity is highest inside thermals in both cases.