Turbulent mixing of reactive gases in the convective boundary layer

Verver, Gé; Dop, H. van; Holtslag, A.A.M.

doi:10.1023/a:1000414710372

Cited by 39 publications

(27 citation statements)

References 26 publications

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Section: Introductionmentioning

confidence: 99%

“…The immediate origins of the model -which we call the Second-Order Model for Conserved and Reactive Unsteady Scalars (SOMCRUS) -go back to Verver et al (1997Verver et al ( , 2000, who developed a secondorder closure model to investigate reactive species in the CBL. This work by Verver et al (1997Verver et al ( , 2000 was subsequently used by Kristensen et al (2010) as a basis for a simple, one-dimensional second-order closure model to obtain continuous equilibrium profiles of turbulent fluxes and mean concentrations of non-conserved scalars (the O 3 -NO-NO 2 triad) in a steady-state convective boundary layer without shear. The development here combines a simple mixed-layer model (Tennekes, 1973) of the diurnally varying CBL from which we obtain the depth h(t), the mean virtual potential temperature , and the virtual potential temperature difference across the assumed infinitesimally thin CBL top with a second-order model of the turbulence and mean CBL structure for both conserved and reactive species with surface sources and sinks, and turbulent entrainment of FT air across the top of the CBL.…”

Section: Introductionmentioning

confidence: 99%

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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%

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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“…1) Do some fluxes of reactive species diverge with height in the surface layer as calculated by the models (Fitzjarrold and Lenschow 1983;Kramm et al 1991;Kristensen et al 1997), and do the flux profiles of reactants depart from the predicted linear profile of inert scalars in a convective boundary layer (Schumann 1989;Gao and Wesely 1994;Verver et al 1997)? 2) Can we apply the relations based on surface layer or mixed layer similarity theory to the reactants (Hamba 1993;Galmarini et al 1997b;Kristensen et al 1997;Petersen et al 1999)?…”

Section: A Field Experiments Designed To Combine Atmospheric Physics Amentioning

confidence: 99%

“…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.…”

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confidence: 99%

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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“…LES consists of explicitly resolving all scales larger than the grid scale (on the order of tens of meters in the ABL), while the smallest (less energetic) scales are parameterized using a subgrid-scale (SGS) model. Since the pioneering paper of Schumann [2] that showed for the first time that segregation of reactants due the inefficient mixing of the convective turbulence plays an important role on moderating the reaction rates, several numerical studies on the effect of turbulence on chemistry in the ABL have been performed using LES [3,4,5,6,7,8,9,10,11,12,13,14,15,16,17]. In particular, Gao et al [3] and Patton et al [14] focused their study on the lowest part of the ABL and on the interplay between chemistry and turbulence in and above canopies.…”

Section: Introductionmentioning

confidence: 99%

Subgrid-Scale Modeling of Reacting Scalar Fluxes in Large-Eddy Simulations of Atmospheric Boundary Layers

et al. 2006

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In large-eddy simulations of atmospheric boundary layer turbulence, the lumped coefficient in the eddy-diffusion subgrid-scale (SGS) model is known to depend on scale for the case of inert scalars. This scale dependence is predominant near the surface. In this paper, a scale-dependent dynamic SGS model for the turbulent transport of reacting scalars is implemented in large-eddy simulations of a neutral boundary layer. Since the model coefficient is computed dynamically from the dynamics of the resolved scales, the simulations are free from any parameter tuning. A set of chemical cases representative of various turbulent reacting flow regimes is examined. The reactants are involved in a first-order reaction and are injected in the atmospheric boundary layer with a constant and uniform surface flux. Emphasis is placed on studying the combined effects of resolution and chemical regime on the performance of the SGS model. Simulations with the scaledependent dynamic model yield the expected trends of the coefficients as function of resolution, position in the flow and chemical regime, leading to resolution-independent turbulent reactant fluxes.

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Turbulent mixing of reactive gases in the convective boundary layer

Cited by 39 publications

References 26 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

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

Subgrid-Scale Modeling of Reacting Scalar Fluxes in Large-Eddy Simulations of Atmospheric Boundary Layers

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