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Quantifying the transport of subcloud layer reactants by shallow cumulus clouds over the Amazon
Author(s) -
Ouwersloot H. G.,
Arellano J. Vilà‒Guerau,
H. van Stratum B. J.,
Krol M. C.,
Lelieveld J.
Publication year - 2013
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2013jd020431
Subject(s) - atmospheric sciences , parametrization (atmospheric modeling) , boundary layer , mesoscale meteorology , convective boundary layer , mass flux , planetary boundary layer , flux (metallurgy) , isoprene , environmental science , convection , physics , meteorology , chemistry , mechanics , radiative transfer , organic chemistry , nuclear magnetic resonance , quantum mechanics , copolymer , polymer
We investigate the vertical transport of atmospheric chemical reactants from the subcloud layer to the cumulus cloud layer driven by shallow convection over the Amazon during the dry season. The dynamical and chemical assumptions needed for mesoscale and global chemistry transport model parametrizations are systematically analyzed using a Large Eddy Simulation model. We quantify the mass flux transport contribution to the temporal evolution of reactants. Isoprene, a key atmospheric compound over the tropical rain forest, decreases by 8.5% h −1 on average and 15% h −1 at maximum due to mass‒flux‒induced removal. We apply mass flux parametrizations for the transport of chemical reactants and obtain satisfactory agreement with numerically resolved transport, except for some reactants like O 3 , NO, and NO 2 . The latter is caused by the local partitioning of reactants, influenced by UV radiation extinction by clouds and small‒scale variability of ambient atmospheric compounds. By considering the longer‒lived NO x (NO + NO 2 ), the transport is well represented by the parametrization. Finally, by considering heterogeneous surface exchange conditions, it is demonstrated that the parametrizations are sensitive to boundary conditions due to changes in the boundary layer dynamics.