Journal of Atmospheric and Solar-Terrestrial Physics, 2013
We investigate mass transfer during absorption of highly soluble gases such as HNO 3 , H 2 O 2 by... more We investigate mass transfer during absorption of highly soluble gases such as HNO 3 , H 2 O 2 by stagnant cloud droplets in the presence of inert admixtures. Thermophysical properties of the gases and liquids are assumed to be constant. Diffusion interactions between droplets, caused by the overlap of depleted of soluble gas regions around the neighboring droplets, are taken into account in the approximation of a cellular model of a gas-droplet suspension whereby a suspension is viewed as a periodic structure consisting of the identical spherical cells with periodic boundary conditions at the cell boundary. Using this model we determined temporal and spatial dependencies of the concentration of the soluble trace gas in a gaseous phase and in a droplet and calculated the dependence of the scavenging coefficient on time. We found that scavenging coefficient for gas absorption by cloud droplets remains constant and sharply decreases only at the final stage of absorption. In the calculations we employed a Monte Carlo method and assumed gamma size distribution of cloud droplets. It is shown that despite of the comparable values of Henry's law constants for the hydrogen peroxide (H 2 O 2 ) and the nitric acid (HNO 3 ), the nitric acid is scavenged more effectively by cloud droplets than the hydrogen peroxide due to a major affect of the dissociation reaction on HNO 3 scavenging. It is demonstrated that scavenging of highly soluble gases by cloud droplets leads to strong decrease of soluble trace gas concentration in the interstitial air. We obtained also analytical expressions for the ''equilibrium values'' of concentration of the soluble trace gas in a gaseous phase and for concentration of the dissolved gas in a liquid phase for the case of hydrogen peroxide and nitric acid absorption by cloud droplets.
Recent advances in understanding of the surface energy balance of urban areas, based on both expe... more Recent advances in understanding of the surface energy balance of urban areas, based on both experimental investigations andnumerical models, are reviewed. Particular attention is directedto the outcome of a COST-715 Expert Meeting held in April 2000, as well as experiments initiated by that action. In addition, recentcomplete parameterisations of urban effects in meso-scalemodels are reviewed. Given that neither the surface energybalance, nor its components, normally are directly measuredat meteorological stations, nor are ...
This study reviews the top ranked meteorology and chemistry interactions in online coupled 32 mod... more This study reviews the top ranked meteorology and chemistry interactions in online coupled 32 models recommended by an experts' survey conducted in COST Action EuMetChem and 33 examines the sensitivity of those interactions during two pollution episodes: the Russian forest 34 fires 25 Jul -15 Aug 2010 and a Saharan dust transport event from 1 Oct -31 Oct 2010 as a part of 35 the AQMEII phase-2 exercise. Three WRF-Chem model simulations were performed for the 36 forest fire case for a baseline without any aerosol feedback on meteorology, a simulation with 37 aerosol direct effects only and a simulation including both direct and indirect effects. For the dust 38 case study, eight WRF-Chem and one WRF-CMAQ simulations were selected from the set of 39 simulations conducted in the framework of AQMEII. Of these two simulations considered no 40 feedbacks, two included direct effects only and five simulations included both direct and indirect 41 effects. The results from both episodes demonstrate that it is important to include the 42 meteorology and chemistry interactions in online-coupled models. Model evaluations using 43 routine observations collected in AQMEII phase-2 and observations from a station in Moscow 44 show that for the fire case the simulation including only aerosol direct effects has better 45 performance than the simulations with no aerosol feedbacks or including both direct and indirect 46 effects. The normalized mean biases are significantly reduced by 10-20% for PM10 when 47 including aerosol direct effects. The analysis for the dust case confirms that models perform 48 better when including aerosol direct effects, but worse when including both aerosol direct and 49 indirect effects, which suggests that the representation of aerosol indirect effects needs to be 50 improved in the model. 51 52 M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT Key words: aerosol direct effects, feedback, PM10, fire and dust 1 2 Highlights 3 4
Journal of Atmospheric and Solar-Terrestrial Physics, 2013
We investigate mass transfer during absorption of highly soluble gases such as HNO 3 , H 2 O 2 by... more We investigate mass transfer during absorption of highly soluble gases such as HNO 3 , H 2 O 2 by stagnant cloud droplets in the presence of inert admixtures. Thermophysical properties of the gases and liquids are assumed to be constant. Diffusion interactions between droplets, caused by the overlap of depleted of soluble gas regions around the neighboring droplets, are taken into account in the approximation of a cellular model of a gas-droplet suspension whereby a suspension is viewed as a periodic structure consisting of the identical spherical cells with periodic boundary conditions at the cell boundary. Using this model we determined temporal and spatial dependencies of the concentration of the soluble trace gas in a gaseous phase and in a droplet and calculated the dependence of the scavenging coefficient on time. We found that scavenging coefficient for gas absorption by cloud droplets remains constant and sharply decreases only at the final stage of absorption. In the calculations we employed a Monte Carlo method and assumed gamma size distribution of cloud droplets. It is shown that despite of the comparable values of Henry's law constants for the hydrogen peroxide (H 2 O 2 ) and the nitric acid (HNO 3 ), the nitric acid is scavenged more effectively by cloud droplets than the hydrogen peroxide due to a major affect of the dissociation reaction on HNO 3 scavenging. It is demonstrated that scavenging of highly soluble gases by cloud droplets leads to strong decrease of soluble trace gas concentration in the interstitial air. We obtained also analytical expressions for the ''equilibrium values'' of concentration of the soluble trace gas in a gaseous phase and for concentration of the dissolved gas in a liquid phase for the case of hydrogen peroxide and nitric acid absorption by cloud droplets.
Recent advances in understanding of the surface energy balance of urban areas, based on both expe... more Recent advances in understanding of the surface energy balance of urban areas, based on both experimental investigations andnumerical models, are reviewed. Particular attention is directedto the outcome of a COST-715 Expert Meeting held in April 2000, as well as experiments initiated by that action. In addition, recentcomplete parameterisations of urban effects in meso-scalemodels are reviewed. Given that neither the surface energybalance, nor its components, normally are directly measuredat meteorological stations, nor are ...
This study reviews the top ranked meteorology and chemistry interactions in online coupled 32 mod... more This study reviews the top ranked meteorology and chemistry interactions in online coupled 32 models recommended by an experts' survey conducted in COST Action EuMetChem and 33 examines the sensitivity of those interactions during two pollution episodes: the Russian forest 34 fires 25 Jul -15 Aug 2010 and a Saharan dust transport event from 1 Oct -31 Oct 2010 as a part of 35 the AQMEII phase-2 exercise. Three WRF-Chem model simulations were performed for the 36 forest fire case for a baseline without any aerosol feedback on meteorology, a simulation with 37 aerosol direct effects only and a simulation including both direct and indirect effects. For the dust 38 case study, eight WRF-Chem and one WRF-CMAQ simulations were selected from the set of 39 simulations conducted in the framework of AQMEII. Of these two simulations considered no 40 feedbacks, two included direct effects only and five simulations included both direct and indirect 41 effects. The results from both episodes demonstrate that it is important to include the 42 meteorology and chemistry interactions in online-coupled models. Model evaluations using 43 routine observations collected in AQMEII phase-2 and observations from a station in Moscow 44 show that for the fire case the simulation including only aerosol direct effects has better 45 performance than the simulations with no aerosol feedbacks or including both direct and indirect 46 effects. The normalized mean biases are significantly reduced by 10-20% for PM10 when 47 including aerosol direct effects. The analysis for the dust case confirms that models perform 48 better when including aerosol direct effects, but worse when including both aerosol direct and 49 indirect effects, which suggests that the representation of aerosol indirect effects needs to be 50 improved in the model. 51 52 M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT Key words: aerosol direct effects, feedback, PM10, fire and dust 1 2 Highlights 3 4
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