Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 411301
Title On the segregation of chemical species in a clear boundary layer over heterogeneous land surfaces
Author(s) Ouwersloot, H.G.; Vilà-Guerau de Arellano, J.; Heerwaarden, C.C. van; Ganzeveld, L.N.; Krol, M.C.; Lelieveld, J.
Source Atmospheric Chemistry and Physics 11 (2011). - ISSN 1680-7316 - p. 10681 - 10704.
DOI http://dx.doi.org/10.5194/acp-11-10681-2011
Department(s) Meteorology and Air Quality
Earth System Science
WIMEK
Publication type Refereed Article in a scientific journal
Publication year 2011
Keyword(s) large-eddy simulation - volatile organic-compounds - tropical rain-forest - atmospheric chemistry - deciduous forest - heat-flux - emission - campaign - scale - turbulence
Abstract Using a Large-Eddy Simulation model, we have systematically studied the inability of boundary layer turbulence to efficiently mix reactive species. This creates regions where the species are accumulated in a correlated or anti-correlated way, thereby modifying the mean reactivity. We quantify this modification by the intensity of segregation, IS, and analyse the driving mechanisms: heterogeneity of the surface moisture and heat fluxes, various background wind patterns and non-uniform isoprene emissions. The heterogeneous surface conditions are characterized by cool and wet forested patches with high isoprene emissions, alternated with warm and dry patches that represents pasture with relatively low isoprene emissions. For typical conditions in the Amazon rain forest, applying homogeneous surface forcings and in the absence of free tropospheric NOx, the isoprene- OH reaction rate is altered by less than 10 %. This is substantially smaller than the previously assumed IS of 50% in recent large-scale model analyses of tropical rain forest chemistry. Spatial heterogeneous surface emissions enhance the segregation of species, leading to alterations of the chemical reaction rates up to 20 %. The intensities of segregation are enhanced when the background wind direction is parallel to the borders between the patches and reduced in the case of a perpendicular wind direction. The effects of segregation on trace gas concentrations vary per species. For the highly reactive OH, the differences in concentration averaged over the boundary layer are less than 2% compared to homogeneous surface conditions, while the isoprene concentration is increased by as much as 12% due to the reduced chemical reaction rates. These processes take place at the sub-grid scale of chemistry transport models and therefore need to be parameterized.
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