89th American Meteorological Society Annual Meeting

Wednesday, 14 January 2009: 11:00 AM
A Simple Model for Vertical Transport of Reactive Species in the Convective Atmospheric Boundary Layer
Room 127A (Phoenix Convention Center)
Leif Kristensen, Risoe DTU National Laboratory for Sustainable Energy; and D. H. Lenschow and D. Gurarie
Poster PDF (166.3 kB)
We have developed a simple one-dimensional model that parameterizes vertical turbulence transport throughout the convective planetary boundary layer (CBL), from the surface to the free atmosphere. We apply it here to a set of fast chemical reactants in the CBL that involves the odd nitrogen species NO and NO2 (=NOx ), as well as O3. Similar models have been developed previously, but instead of solving the set of nine or more differential equations by finite difference techniques at a specified set of levels throughout the CBL, we first reduce the set of equations to two equations for NO2 flux and concentration by using mass conservation of the radicals involved in the NO-NO2-O3 triad. We then obtain a numerical solution of these differential equations, and subsequently the entire set of concentration and flux profiles are easily obtained by substituting this solution into the equations for NO and O3 fluxes and concentrations. Thus, we can easily specify whatever vertical resolution we wish over any interval of the CBL, including using very fine resolution to resolve detailed structure in the surface layer. We present examples of flux and concentration profiles of these species to demonstrate the impact of chemical reactivity on the profiles. The eventual goal is to extend the model to volatile organic compounds (VOCs), particularly those emitted by vegetation, that react on time scales comparable to CBL turbulent mixing times, to provide a simple tool for rapid estimation of surface emission rates, and possibly reaction rates, given measurements of VOC fluxes or profiles (or both) at one or more levels in the CBL.

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