Dynamics-aerosol-chemistry-cloud interactions in West Africa
Research Publications
General
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
Abstract:
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.