S. Galmarini et al., SCALING THE TURBULENT TRANSPORT OF CHEMICAL-COMPOUNDS IN THE SURFACE-LAYER UNDER NEUTRAL AND STRATIFIED CONDITIONS, Quarterly Journal of the Royal Meteorological Society, 123(537), 1997, pp. 223-242
A model of the vertical transport of chemically reactive species is pr
esented which is applicable to all possible stability conditions in th
e atmospheric surface-layer. The non-dimensional formulation adopted a
llows any chemical scheme to be included. An equation hierarchy is pre
sented for a fully second-order closure description of the process. Th
e model describes comprehensively the turbulence/chemistry process by
calculating the mean concentrations, the turbulent fluxes and concentr
ation covariances of the chemical species. It explicitly takes into ac
count the chemical transformation in first- and second-order variable
equations. The model is applied to the NO-NO2-O-3 cycle and to the so-
called 'night-time' chemical scheme of nitrogen oxides. An analysis of
the flux budget indicates that the relative importance of the chemist
ry term in the flux equation varies with distance from the surface. Fo
r atmospheric neutral conditions, it is suggested that the chemistry t
erm in the flux equation can be used to make an a priori evaluation of
the possible effect of chemistry upon the nux of a chemical species.
The model also shows that under stable conditions, despite the greatly
reduced activity of turbulence, differences can occur between the tur
bulent transport of an inert tracer and that of a chemically reactive
species. Under any stratification and for typical surface-layer fluxes
of nitrogen oxides, the intensity of segregation is very low and can
in general be neglected in model calculations.