scholarly journals Characterization of the <sup>222</sup>Rn family turbulent transport in the convective atmospheric boundary layer

2007 ◽  
Vol 7 (3) ◽  
pp. 697-712 ◽  
Author(s):  
J.-F. Vinuesa ◽  
S. Galmarini
Keyword(s):  
Boundary Layer ◽  
Steady State ◽  
Vertical Distribution ◽  
Turbulent Transport ◽  
Radioactive Decay ◽  
Atmospheric Boundary Layers ◽  
Eddy Simulation ◽  
The One ◽  
The Vertical Distribution ◽  
Unsteady Conditions

Abstract. The combined effect of turbulent transport and radioactive decay on the distribution of 222Rn and its progeny in convective atmospheric boundary layers (CBL) is investigated. Large eddy simulation is used to simulate their dispersion in steady state CBL and in unsteady conditions represented by the growth of a CBL within a pre-existing reservoir layer. The exact decomposition of the concentration and flux budget equations under steady state conditions allowed us to determine which processes are responsible for the vertical distribution of 222Rn and its progeny. Their mean concentrations are directly correlated with their half-life, e.g. 222Rn and 210Pb are the most abundant whereas 218Po show the lowest concentrations. 222Rn flux decreases linearly with height and its flux budget is similar to the one of inert emitted scalar, i.e., a balance between on the one hand the gradient and the buoyancy production terms, and on the other hand the pressure and dissipation at smaller scales which tends to destroy the fluxes. While 222Rn exhibits the typical bottom-up behavior, the maximum flux location of the daughters is moving upwards while their rank in the 222Rn progeny is increasing leading to a typical top-down behavior for 210Pb. We also found that the relevant radioactive decaying contributions of 222Rn short-lived daughters (218Po and 214Pb) act as flux sources leading to deviations from the linear flux shape. In addition, while analyzing the vertical distribution of the radioactive decay contributions to the concentrations, e.g. the decaying zone, we found a variation in height of 222Rn daughters' radioactive transformations. Under unsteady conditions, the same behaviors reported under steady state conditions are found: deviation of the fluxes from the linear shape for 218Po, enhanced discrepancy in height of the radioactive transformation contributions for all the daughters. In addition, 222Rn and its progeny concentrations decrease due to the rapid growth of the CBL. The analysis emphasizes the crucial role of turbulent transport in the behavior of 222Rn n morning concentrations, in particular the ventilation at the top of the boundary layer that leads to the dilution of 222Rn by mixing with radon low concentration air.

scholarly journals Characterization of the <sup>222</sup>Rn family turbulent transport in the convective atmospheric boundary layer

2006 ◽  
Vol 6 (5) ◽  
pp. 8917-8960
Author(s):  
J.-F. Vinuesa ◽  
S. Galmarini
Keyword(s):  
Boundary Layer ◽  
Steady State ◽  
Vertical Distribution ◽  
Turbulent Transport ◽  
Radioactive Decay ◽  
Atmospheric Boundary Layers ◽  
Eddy Simulation ◽  
The One ◽  
The Vertical Distribution ◽  
Unsteady Conditions

Abstract. The combined effect of turbulent transport and radioactive decay on the distribution of 222Rn and its progeny in convective atmospheric boundary layers (CBL) is investigated. Large eddy simulation is used to simulate their dispersion in steady state CBL and in unsteady conditions represented by the growth of a CBL within a pre-existing reservoir layer. The exact decomposition of the concentration and flux budget equations under steady state conditions allowed us to determine which processes are responsible for the vertical distribution of 222Rn and its progeny. Their mean concentrations are directly correlated with their half-life, e.g. 222Rn and 210Pb are the most abundant whereas 218Po show the lowest concentrations. 222Rn flux decreases linearly with height and its flux budget is similar to the one of inert emitted scalar, i.e., a balance between on the one hand the gradient and the buoyancy production terms, and on the other hand the pressure and dissipation at smaller scales which tends to destroy the fluxes. While 222Rn exhibits the typical bottom-up behavior, the maximum flux location of the daughters is moving upwards while their rank in the 222Rn progeny is increasing leading to a typical top-down behavior for 210Pb. We also found that 222Rn short-lived daughters, e.g. 218Po and 214Pb, have relevant radioactive decaying contributions acting as flux sources leading to deviations from the linear flux shape. In addition, while analyzing the vertical distribution of the radioactive decay contributions to the concentrations, e.g. the decaying zone, we found a discrepancy in height of 222Rn daughters' radioactive transformations. Under unsteady conditions, the same behaviors reported under steady state conditions are found: deviation of the fluxes from the linear shape for 218Po, enhanced discrepancy in height of the radioactive transformation contributions for all the daughters. In addition, 222Rn and its progeny concentrations collapse due to the rapid growth of the CBL. The analysis emphasizes the crucial role of turbulent transport in the behavior of 222Rn morning concentrations, in particular the ventilation at the top of the boundary layer that leads to the dilution of 222Rn by mixing with radon low concentration air.

Two Inversion Layers and Their Impacts on PM2.5 Concentration over the Yangtze River Delta, China

2019 ◽  
Vol 58 (11) ◽  
pp. 2349-2362 ◽  
Author(s):  
Yiwen Xu ◽  
Bin Zhu ◽  
Shuangshuang Shi ◽  
Yong Huang
Keyword(s):  
Boundary Layer ◽  
Vertical Distribution ◽  
Rural Area ◽  
Yangtze River ◽  
Layer Structure ◽  
Yangtze River Delta ◽  
Emission Sources ◽  
The Yangtze River ◽  
The Vertical Distribution ◽  
The Yangtze River Delta

AbstractAn integrated winter field campaign was conducted to investigate the atmospheric boundary layer structure and PM2.5 concentration at three sites over the Yangtze River delta (YRD) in China: Shouxian (a rural area), a site in a northern suburb of Nanjing, and Dongshan (a residential area). Two temperature inversion layers and air pollution events occurred simultaneously from 30 to 31 December 2016, local time, over the YRD. It was found that the two inversion layers were related to the presence of a high pressure system, resulting in divergence in the upper boundary layer and radiative cooling near the ground at night. Dominated by agricultural and residential biomass burning, the surface emission sources from the Shouxian rural area were moderately strong. After the formation of the two inversions, the vertical distribution of PM2.5 concentration below the upper inversion layer was uniform as a result of thorough boundary layer mixing in the earlier hours. During nighttime at the Nanjing site, air pollutant plumes from nearby elevated point sources could not easily diffuse downward/upward between the two inversion layers, which led to a distinct peak in the PM2.5 concentration. At the Dongshan site, the emission sources were weak and the nighttime PM2.5 concentration above 100 m was high. The surface PM2.5 concentration gradually increased from early morning to noon, which was attributed to emissions related to the local residents. The results indicated that the vertical distribution of pollutants was affected by a combination of local emissions, vertical boundary layer structure, and horizontal and vertical transports.

Analysis of the Sutton Model for Aero-Optical Properties of Compressible Boundary Layers

2005 ◽  
Vol 128 (2) ◽  
pp. 239-246 ◽  
Author(s):  
Eric Tromeur ◽  
Eric Garnier ◽  
Pierre Sagaut
Keyword(s):  
Boundary Layer ◽  
Density Field ◽  
The Other ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
Compressible Boundary Layers ◽  
Optical Effects ◽  
Large Eddy ◽  
The One ◽  
Reference Tool

In order to assess the capability of the Sutton model to evaluate aero-optical effects in a turbulent boundary layer, large-eddy simulation (LES) evolving spatially and Reynolds averaged Navier-Stokes (RANS) computations are carried out at Mach number equal to 0.9. First aerodynamic fields are proved to compare favorably with theoretical and experimental results. Once validated, the characteristics of the boundary layer allow us to obtain information concerning optical beam degradation. On the one hand, the density field is used to compute phase distortion directly and, on the other hand, by means of the Sutton model. Therefore, LES and RANS simulations allow us to study optical models and the validity of their assumptions. Finally, LES is proved to be considered as a reference tool to evaluate aero-optical effects.

scholarly journals Linking Meteorology, Turbulence, and Air Chemistry in the Amazon Rain Forest

2016 ◽  
Vol 97 (12) ◽  
pp. 2329-2342 ◽  
Author(s):  
Jose D. Fuentes ◽  
Marcelo Chamecki ◽  
Rosa Maria Nascimento dos Santos ◽  
Celso Von Randow ◽  
Paul C. Stoy ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Surface Layer ◽  
Vertical Distribution ◽  
Rain Forest ◽  
Forest Canopy ◽  
Cloud Condensation Nuclei ◽  
Chemical Species ◽  
Chemical Transformations ◽  
Condensation Nuclei ◽  
The Vertical Distribution

Abstract We describe the salient features of a field study whose goals are to quantify the vertical distribution of plant-emitted hydrocarbons and their contribution to aerosol and cloud condensation nuclei production above a central Amazonian rain forest. Using observing systems deployed on a 50-m meteorological tower, complemented with tethered balloon deployments, the vertical distribution of hydrocarbons and aerosols was determined under different boundary layer thermodynamic states. The rain forest emits sufficient reactive hydrocarbons, such as isoprene and monoterpenes, to provide precursors of secondary organic aerosols and cloud condensation nuclei. Mesoscale convective systems transport ozone from the middle troposphere, enriching the atmospheric boundary layer as well as the forest canopy and surface layer. Through multiple chemical transformations, the ozone-enriched atmospheric surface layer can oxidize rain forest–emitted hydrocarbons. One conclusion derived from the field studies is that the rain forest produces the necessary chemical species and in sufficient amounts to undergo oxidation and generate aerosols that subsequently activate into cloud condensation nuclei.

scholarly journals Atmospheric Stability Influences on Coupled Boundary Layer and Canopy Turbulence

2016 ◽  
Vol 73 (4) ◽  
pp. 1621-1647 ◽  
Author(s):  
Edward G. Patton ◽  
Peter P. Sullivan ◽  
Roger H. Shaw ◽  
John J. Finnigan ◽  
Jeffrey C. Weil
Keyword(s):  
Boundary Layer ◽  
Atmospheric Stability ◽  
Canopy Turbulence ◽  
Vertical Shear ◽  
Horizontal Wind ◽  
Atmospheric Boundary Layers ◽  
Eddy Simulation ◽  
Scalar Fluxes ◽  
Large Eddy ◽  
Scale Structures

Abstract Large-eddy simulation of atmospheric boundary layers interacting with a coupled and resolved plant canopy reveals the influence of atmospheric stability variations from neutral to free convection on canopy turbulence. The design and implementation of a new multilevel canopy model is presented. Instantaneous fields from the simulations show that organized motions on the scale of the atmospheric boundary layer (ABL) depth bring high momentum down to canopy top, locally modulating the vertical shear of the horizontal wind. The evolution of these ABL-scale structures with increasing instability and their impact on vertical profiles of turbulence moments and integral length scales within and above the canopy are discussed. Linkages between atmospheric turbulence and biological control impact horizontal scalar source distributions. Decreasing spatial correlation between momentum and scalar fluxes with increasing instability results from ABL-scale structures spatially segregating momentum and scalar exchange at canopy top. In combination, these results suggest the need for roughness sublayer parameterizations to incorporate an additional length or time scale reflecting the influence of ABL-scale organized motions.

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