Aerosol size distribution measurements and modeling in urban environments for rainy atmospheric conditions

2006 ◽  
Author(s):  
S. Bendersky ◽  
N. Kopeika ◽  
N. Blaunstein
Keyword(s):  
Size Distribution ◽  
Urban Environments ◽  
Aerosol Size Distribution ◽  
Atmospheric Conditions

scholarly journals Numerical simulations of homogeneous freezing processes in the aerosol chamber AIDA

2002 ◽  
Vol 2 (5) ◽  
pp. 1467-1508
Author(s):  
W. Haag ◽  
B. Kärcher ◽  
S. Schaefers ◽  
O. Stetzer ◽  
O. Möhler ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Size Distribution ◽  
Time History ◽  
Companion Paper ◽  
Aerosol Size Distribution ◽  
Size Spectrum ◽  
Mixing Ratio ◽  
Atmospheric Conditions ◽  
Aerosol Chamber ◽  
Homogeneous Freezing

Abstract. The homogeneous freezing of supercooled H2SO4/H2O aerosols in an aerosol chamber is investigated with a microphysical box model using the activity parameterization of the nucleation rate by Koop et al (2000). The simulations are constrained by measurements of pressure, temperature, total water mixing ratio, and the initial aerosol size distribution, described in a companion paper Möhler et al. (2002). Model results are compared to measurements conducted in the temperature range between 194 and 235 K, with cooling rates in the range between 0.5 and 2.6 K min-1, and at air pressures between 170 and 1000 hPa. The simulations focus on the time history of relative humidity with respect to ice, aerosol size distribution, partitioning of water between gas and particle phase, onset times of freezing, freezing threshold relative humidities, aerosol chemical composition at the onset of freezing, and the number of nucleated ice crystals. The latter three parameters can directly be inferred from the experiments, the former three aid in interpreting the measurements. Sensitivity studies are carried out to address the relative importance of uncertainties of basic quantities such as temperature, H2O mixing ratio, aerosol size spectrum, and deposition coefficient of H2O molecules on ice. The ability of the numerical simulations to provide detailed explanations of the observations greatly increases confidence in attempts to model this process under real  atmospheric conditions, for instance with regard to the formation of cirrus clouds or type-II polar stratospheric clouds, provided that accurate temperature and humidity measurements are available.

scholarly journals Numerical simulations of homogeneous freezing processes in the aerosol chamber AIDA

2003 ◽  
Vol 3 (1) ◽  
pp. 195-210 ◽  
Author(s):  
W. Haag ◽  
B. Kärcher ◽  
S. Schaefers ◽  
O. Stetzer ◽  
O. Möhler ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Size Distribution ◽  
Time History ◽  
Companion Paper ◽  
Aerosol Size Distribution ◽  
Size Spectrum ◽  
Mixing Ratio ◽  
Atmospheric Conditions ◽  
Aerosol Chamber ◽  
Homogeneous Freezing

Abstract. The homogeneous freezing of supercooled H2SO4/H2O aerosols in an aerosol chamber is investigated with a microphysical box model using the activity parameterization of the nucleation rate by Koop et al. (2000). The simulations are constrained by measurements of pressure, temperature, total water mixing ratio, and the initial aerosol size distribution, described in a companion paper Möhler et al. (2003). Model results are compared to measurements conducted in the temperature range between 194 and 235 K, with cooling rates in the range between 0.5 and 2.6 K min-1, and at air pressures between 170 and 1000 hPa. The simulations focus on the time history of relative humidity with respect to ice, aerosol size distribution, partitioning of water between gas and particle phase, onset times of freezing, freezing threshold relative humidities, aerosol chemical composition at the onset of freezing, and the number of nucleated ice crystals. The latter four parameters can be inferred from the experiments, the former three aid in interpreting the measurements. Sensitivity studies are carried out to address the relative importance of uncertainties of basic quantities such as temperature, total H2O mixing ratio, aerosol size spectrum, and deposition coefficient of H2O molecules on ice. The ability of the numerical simulations to provide detailed explanations of the observations greatly increases confidence in attempts to model this process under real atmospheric conditions, for instance with regard to the formation of cirrus clouds or polar stratospheric ice clouds, provided that accurate temperature and humidity measurements are available.

scholarly journals The evolution of biomass-burning aerosol size distributions due to coagulation: dependence on fire and meteorological details and parameterization

2016 ◽  
Author(s):  
K. M. Sakamoto ◽  
R. G. Stevens ◽  
J. R. Pierce
Keyword(s):  
Wind Speed ◽  
Size Distribution ◽  
Biomass Burning ◽  
Independent Set ◽  
Aerosol Size Distribution ◽  
Size Distributions ◽  
Atmospheric Conditions ◽  
Mixing Depth ◽  
Fire Area ◽  
Biomass Burning Aerosol

Abstract. Biomass-burning aerosols have a significant effect on global and regional aerosol climate forcings. To model the magnitude of these effects accurately requires knowledge of the size distribution of the emitted and evolving aerosol particles. Current biomass-burning inventories do not include size distributions, and global and regional models generally assume a fixed size distribution from all biomass-burning emissions. However, biomass-burning size distributions evolve in the plume due to coagulation and net organic aerosol (OA) evaporation or formation, and the plume processes occur on spacial scales smaller than global/regional-model grid boxes. The extent of this size-distribution evolution is dependent on a variety of factors relating to the emission source and atmospheric conditions. Therefore, to account for biomass-burning aerosol size in global models accurately requires an effective aerosol size distribution that accounts for this sub-grid evolution and can be derived from available emissions-inventory and meteorological parameters. In this paper, we perform a detailed investigation of the effects of coagulation on the aerosol size distribution in biomass-burning plumes. We compare the effect of coagulation to that of OA evaporation and formation. We develop coagulation-only parameterizations for effective biomass-burning size distributions using the SAM-TOMAS large-eddy simulation plume model. For the most-sophisticated parameterization, we use the Gaussian Emulation Machine for Sensitivity Analysis (GEM-SA) to build a parameterization of the aged size distribution based on the SAM-TOMAS output and seven inputs: emission median dry diameter, emission distribution modal width, mass emissions flux, fire area, mean boundary-layer wind speed, plume mixing depth, and time/distance since emission. This parameterization was tested against an independent set of SAM-TOMAS simulations, and yields R2 values of 0.83 and 0.89 for Dpm and modal width, respectively. The aged size distribution is particularly sensitive to the mass emissions flux, fire area, wind speed, and time, and we provide simplified fits of the aged size distribution to just these input variables. These fits may be used in global and regional aerosol models. Finally, we show that variability in coagulation may lead to greater variability in the particle size distribution than does OA evaporation/formation using estimates of OA production/loss from the literature.

scholarly journals The evolution of biomass-burning aerosol size distributions due to coagulation: dependence on fire and meteorological details and parameterization

2016 ◽  
Vol 16 (12) ◽  
pp. 7709-7724 ◽  
Author(s):  
Kimiko M. Sakamoto ◽  
James R. Laing ◽  
Robin G. Stevens ◽  
Daniel A. Jaffe ◽  
Jeffrey R. Pierce
Keyword(s):  
Wind Speed ◽  
Size Distribution ◽  
Biomass Burning ◽  
Independent Set ◽  
Aerosol Size Distribution ◽  
Size Distributions ◽  
Atmospheric Conditions ◽  
Mixing Depth ◽  
Fire Area ◽  
Biomass Burning Aerosol

Abstract. Biomass-burning aerosols have a significant effect on global and regional aerosol climate forcings. To model the magnitude of these effects accurately requires knowledge of the size distribution of the emitted and evolving aerosol particles. Current biomass-burning inventories do not include size distributions, and global and regional models generally assume a fixed size distribution from all biomass-burning emissions. However, biomass-burning size distributions evolve in the plume due to coagulation and net organic aerosol (OA) evaporation or formation, and the plume processes occur on spacial scales smaller than global/regional-model grid boxes. The extent of this size-distribution evolution is dependent on a variety of factors relating to the emission source and atmospheric conditions. Therefore, accurately accounting for biomass-burning aerosol size in global models requires an effective aerosol size distribution that accounts for this sub-grid evolution and can be derived from available emission-inventory and meteorological parameters. In this paper, we perform a detailed investigation of the effects of coagulation on the aerosol size distribution in biomass-burning plumes. We compare the effect of coagulation to that of OA evaporation and formation. We develop coagulation-only parameterizations for effective biomass-burning size distributions using the SAM-TOMAS large-eddy simulation plume model. For the most-sophisticated parameterization, we use the Gaussian Emulation Machine for Sensitivity Analysis (GEM-SA) to build a parameterization of the aged size distribution based on the SAM-TOMAS output and seven inputs: emission median dry diameter, emission distribution modal width, mass emissions flux, fire area, mean boundary-layer wind speed, plume mixing depth, and time/distance since emission. This parameterization was tested against an independent set of SAM-TOMAS simulations and yields R2 values of 0.83 and 0.89 for Dpm and modal width, respectively. The size distribution is particularly sensitive to the mass emissions flux, fire area, wind speed, and time, and we provide simplified fits of the aged size distribution to just these input variables. The simplified fits were tested against 11 aged biomass-burning size distributions observed at the Mt. Bachelor Observatory in August 2015. The simple fits captured over half of the variability in observed Dpm and modal width even though the freshly emitted Dpm and modal widths were unknown. These fits may be used in global and regional aerosol models. Finally, we show that coagulation generally leads to greater changes in the particle size distribution than OA evaporation/formation does, using estimates of OA production/loss from the literature.

scholarly journals Evaluating model parameterizations of submicron aerosol scattering and absorption with in situ data from ARCTAS 2008

2016 ◽  
Vol 16 (14) ◽  
pp. 9435-9455 ◽  
Author(s):  
Matthew J. Alvarado ◽  
Chantelle R. Lonsdale ◽  
Helen L. Macintyre ◽  
Huisheng Bian ◽  
Mian Chin ◽  
...  
Keyword(s):  
Optical Properties ◽  
Size Distribution ◽  
Aerosol Size Distribution ◽  
Visible Radiation ◽  
Submicron Aerosol ◽  
In Situ Data ◽  
Aerosol Absorption ◽  
Aerosol Scattering ◽  
The Impact

Abstract. Accurate modeling of the scattering and absorption of ultraviolet and visible radiation by aerosols is essential for accurate simulations of atmospheric chemistry and climate. Closure studies using in situ measurements of aerosol scattering and absorption can be used to evaluate and improve models of aerosol optical properties without interference from model errors in aerosol emissions, transport, chemistry, or deposition rates. Here we evaluate the ability of four externally mixed, fixed size distribution parameterizations used in global models to simulate submicron aerosol scattering and absorption at three wavelengths using in situ data gathered during the 2008 Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) campaign. The four models are the NASA Global Modeling Initiative (GMI) Combo model, GEOS-Chem v9-02, the baseline configuration of a version of GEOS-Chem with online radiative transfer calculations (called GC-RT), and the Optical Properties of Aerosol and Clouds (OPAC v3.1) package. We also use the ARCTAS data to perform the first evaluation of the ability of the Aerosol Simulation Program (ASP v2.1) to simulate submicron aerosol scattering and absorption when in situ data on the aerosol size distribution are used, and examine the impact of different mixing rules for black carbon (BC) on the results. We find that the GMI model tends to overestimate submicron scattering and absorption at shorter wavelengths by 10–23 %, and that GMI has smaller absolute mean biases for submicron absorption than OPAC v3.1, GEOS-Chem v9-02, or GC-RT. However, the changes to the density and refractive index of BC in GC-RT improve the simulation of submicron aerosol absorption at all wavelengths relative to GEOS-Chem v9-02. Adding a variable size distribution, as in ASP v2.1, improves model performance for scattering but not for absorption, likely due to the assumption in ASP v2.1 that BC is present at a constant mass fraction throughout the aerosol size distribution. Using a core-shell mixing rule in ASP overestimates aerosol absorption, especially for the fresh biomass burning aerosol measured in ARCTAS-B, suggesting the need for modeling the time-varying mixing states of aerosols in future versions of ASP.

Faucet aerator design influences aerosol size distribution and microbial contamination level

2021 ◽  
Vol 775 ◽  
pp. 145690
Author(s):  
Marie-Ève Benoit ◽  
Michèle Prévost ◽  
Antonella Succar ◽  
Dominique Charron ◽  
Eric Déziel ◽  
...  
Keyword(s):  
Size Distribution ◽  
Microbial Contamination ◽  
Aerosol Size Distribution ◽  
Contamination Level

scholarly journals Combining airborne in situ and ground-based lidar measurements for attribution of aerosol layers

2018 ◽  
Author(s):  
Anna Nikandrova ◽  
Ksenia Tabakova ◽  
Antti Manninen ◽  
Riikka Väänänen ◽  
Tuukka Petäjä ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Size Distribution ◽  
Aerosol Size Distribution ◽  
Long Range Transport ◽  
Back Trajectories ◽  
Clear Sky ◽  
Temporal And Spatial Variability ◽  
Range Transport ◽  
Temporal And Spatial

Abstract. Understanding the distribution of aerosol layers is important for determining long range transport and aerosol radiative forcing. In this study we combine airborne in situ measurements of aerosol with data obtained by a ground-based High Spectral Resolution Lidar (HSRL) and radiosonde profiles to investigate the temporal and vertical variability of aerosol properties in the lower troposphere. The HSRL was deployed in Hyytiälä, Southern Finland, from January to September 2014 as a part of the US DoE ARM (Atmospheric Radiation Measurement) mobile facility during the BAECC (Biogenic Aerosols – Effects on Cloud and Climate) Campaign. Two flight campaigns took place in April and August 2014 with instruments measuring the aerosol size distribution from 10 nm to 10 µm at altitudes up to 3800 m. Two case studies from the flight campaigns, when several aerosol layers were identified, were selected for further investigation: one clear sky case, and one partly cloudy case. During the clear sky case, turbulent mixing ensured low temporal and spatial variability in the measured aerosol size distribution in the boundary layer whereas mixing was not as homogeneous in the boundary layer during the partly cloudy case. The elevated layers exhibited greater temporal and spatial variability in aerosol size distribution, indicating a lack of mixing. New particle formation was observed in the boundary layer during the clear sky case, and nucleation mode particles were also seen in the elevated layers that were not mixing with the boundary layer. Interpreting local measurements of elevated layers in terms of long-range transport can be achieved using back trajectories from Lagrangian models, but care should be taken in selecting appropriate arrival heights, since the modelled and observed layer heights did not always coincide. We conclude that higher confidence in attributing elevated aerosol layers with their air mass origin is attained when back trajectories are combined with lidar and radiosonde profiles.

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