Effect of inhomogeneous mixing on atmospheric photochemical reactions

Donaldson, Coleman duP.; Hilst, Glenn R.

doi:10.1021/es60068a004

Cited by 81 publications

(30 citation statements)

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“…Galmarini et al (1997a) also used a one-dimensional second-order closure model to study nitrogen oxide chemistry in the nocturnal boundary layer. Donaldson and Hilst (1972) pointed out that locally inhomogeneous mixing of species involved in second-order reactions, as measured by the intensity of segregation (the ratio of the species-species covariance to the product of their means), can change (generally decrease) their reaction rates. Schumann (1989) extended consideration of chemical reactivity effects for two reacting species -one emitted at the surface and the other entrained across the CBL top -to the entire CBL using large-eddy simulation (LES) as a tool and quantified the relationship between the effective reaction rate and intensity of segregation.…”

Section: Introductionmentioning

confidence: 99%

Modeling the diurnal cycle of conserved and reactive species in the convective boundary layer using SOMCRUS

2016

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Abstract.We have developed a one-dimensional secondorder closure numerical model to study the vertical turbulent transport of trace reactive species in the convective (daytime) planetary boundary layer (CBL), which we call the SecondOrder Model for Conserved and Reactive Unsteady Scalars (SOMCRUS). The temporal variation of the CBL depth is calculated using a simple mixed-layer model with a constant entrainment coefficient and zero-order discontinuity at the CBL top. We then calculate time-varying continuous profiles of mean concentrations and vertical turbulent fluxes, variances, and covariances of both conserved and chemically reactive scalars in a diurnally varying CBL. The set of reactive species is the O 3 -NO-NO 2 triad. The results for both conserved and reactive species are compared with large-eddy simulations (LES) for the same free-convection case using the same boundary and initial conditions. For the conserved species, we compare three cases with different combinations of surface fluxes, and CBL and free-troposphere concentrations. We find good agreement of SOMCRUS with LES for the mean concentrations and fluxes of both conserved and reactive species except near the CBL top, where SOMCRUS predicts a somewhat shallower depth, and has sharp transitions in both the mean and turbulence variables, in contrast to more smeared-out variations in the LES due to horizontal averaging. Furthermore, SOMCRUS generally underestimates the variances and species-species covariances. SOM-CRUS predicts temperature-species covariances similar to LES near the surface, but much smaller magnitude peak values near the CBL top, and a change in sign of the covariances very near the CBL top, while the LES predicts a change in sign of the covariances in the lower half of the CBL. SOM-CRUS is also able to estimate the intensity of segregation (the ratio of the species-species covariance to the product of their means), which can alter the rates of second-order chemical reactions; however, for the case considered here, this effect is small. The simplicity and extensibility of SOMCRUS means that it can be utilized for a broad range of turbulencemixing scenarios and sets of chemical reactions in the planetary boundary layer; it therefore holds great promise as a tool to incorporate these processes within air quality and climate models.

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Section: Introductionmentioning

confidence: 99%

Modeling the diurnal cycle of conserved and reactive species in the convective boundary layer using SOMCRUS

2016

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“…A number of authors [1,2,4,7,13,14,15] have pointed out the importance and control of concentration fluctuations, due to inhomogenous mixing, on photochemical reactions. To investigate this effect we assume that at each point in the reaction zone there is always an instantaneous photostationary equilibrium, i.e.…”

Section: The Effect Of Concentration Fluctuations On Photochemical Rementioning

confidence: 99%

Power plant plume NO x reactions and the reaction zone concept

Sinclair

1984

Arch. Met. Geoph. Biocl., Ser. B

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SummaryPower plant plume measurements with instrumented aircraft indicate that the plumeenvironment reactant species (NO and Oa) appear to be spatially segregated with reactions occurring primarily within a relatively narrow zone between the plume core and the environment. Within this reaction zone, the NO2/NO ratios reach a maximum and increas e with plume travel time. Inhomogeneous mixing in the reaction zone appears to provide (net) positive correlations of the photostationary equilibrium (E) fluctuation term [NO]

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“…Since the seminal papers by Donaldson and Hilst (1972) and Fitzjarrald and Lenschow (1983), the role that certain physical pro-…”

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confidence: 99%

“…Since the seminal papers by Donaldson and Hilst (1972) and Fitzjarrald and Lenschow (1983), the role that certain physical pro-cesses, and in particular turbulence, plays in the transformation of reactants has become clearer. Atmospheric turbulence is the process that brings together the reactants and it is the main mixing mechanism in clear and cloudy boundary layers.…”

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Bridging the Gap Between Atmospheric Physics and Chemistry in Studies of Small-Scale Turbulence

Arellano¹

2003

Bull. Amer. Meteor. Soc.

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Experimental evidence for the role played by small-scale atmospheric processes in chemical reactions is necessary to verify the theoretical and numerical findings. questions still need to be addressed if we are to gain a better understanding of reactive scalars in the atmospheric boundary layer (ABL). My intention is to extend the debate initiated during these two workshops to the study of reactive species in the ABL. In this research essay, I explain that it should be possible to gain greater insight into the role played by the atmospheric processes in the turbulent reacting flows by combining observations with simulation studies. Investigation in this area is necessary because, by omitting the effect of small-scale atmospheric processes on the chemical transformations, we are likely to reduce the accuracy of predictions of reactant concentrations like ozone and hydroxyl radical. Furthermore, I attempt to summarize briefly the current state of our knowledge and propose a comprehensive field experiment that will complement the experiments proposed by Muschinski and Lenschow (2001). My aim is to find observational evidence that will corroborate the theoretical findings and the results of the numerical simulations.THEORETICAL BASIS. Since the seminal papers by Donaldson and Hilst (1972) and Fitzjarrald and Lenschow (1983), the role that certain physical pro-cesses, and in particular turbulence, plays in the transformation of reactants has become clearer. Atmospheric turbulence is the process that brings together the reactants and it is the main mixing mechanism in clear and cloudy boundary layers. Following these pioneering studies, other authors Kramm et al. 1991; Hamba 1993;Gao and Wesely 1994; Galmarini et al. 1997a,b;Verver et al. 1997;Petersen et al. 1999) have investigated various ABL reacting flows in order to find out under which conditions and for which parameters chemistry is limited by turbulence. In their research, they studied the influence of turbulence on chemistry by including the chemical terms in the governing equations. Their main conclusions are that under specific turbulent mixing and chemical conditions, the distribution and evolution of the average concentration (first-order moment) and the fluxes and covariances (secondorder moments) can be modified by chemical transformation. As a consequence, the behavior of reactants can differ from the behavior observed and modeled for inert scalars. More specifically, turbulence limits the reactivity of species that are transported, mixed, and transformed at similar timescales. A well-studied example of this limitation is the decrease that occurs in the reaction rate of the depletion of ozone as a result of the reaction with nitric oxide in an atmospheric convective boundary layer. Another physical process that changes the reactivity is the disturbance of the transfer of ultraviolet radiation by aerosols and cloud droplets, leading to variations in the photostationary rate. Similarly, the discontinuous emission and removal of species by nonuniform sour...

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Effect of inhomogeneous mixing on atmospheric photochemical reactions

Cited by 81 publications

References 4 publications

Modeling the diurnal cycle of conserved and reactive species in the convective boundary layer using SOMCRUS

Modeling the diurnal cycle of conserved and reactive species in the convective boundary layer using SOMCRUS

Power plant plume NO x reactions and the reaction zone concept

Bridging the Gap Between Atmospheric Physics and Chemistry in Studies of Small-Scale Turbulence

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