Airborne analysis of the Los Angeles aerosol

Collins, D. R.; Jonsson, Haflidi H.; Liao, Hong; Flagan, Richard C.; Seinfeld, John H.; Noone, Kevin J.; Hering, Susanne V.

doi:10.1016/s1352-2310(00)00225-9

Cited by 29 publications

(23 citation statements)

References 44 publications

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“…reported previously for both aethalometer (Bodhaine et al, 1991;Clarke et al, 1997) and Radiance Research particle soot absorption photometer (Sheridan and Ogren, 1999;Collins et al, 2000b) measurements. Pressure induced distortions of the filters within the instruments are suspected to underlie the observed behavior (Hansen, 2002).…”

Section: Black Carbonmentioning

confidence: 61%

“…Examples in the marine environment include NARE-96 (Cowling et al, 1998), ACE-1 (Bates et al, 1998), ACE-2 (Collins et al, 2000a;, and INDOEX (de Reuss et al, 2001). Over coastal and continental locations, following earlier work of Rosen et al (1992), Kim et al (1993a), Gunter et al (1993), Pinnick et al (1993) and Gunter (1994), more elaborate airborne data sets have been acquired in the Arctic (Hegg et al, 1996), in the US mid-Atlantic coastal region (Hegg et al, 1997;Hartley et al, 2000), and over the Los Angeles Basin (Collins et al, 2000b), among others.…”

Section: Introductionmentioning

confidence: 99%

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Airborne measurements of aerosol extinction in the lower and middle troposphere over Wyoming, USA

Han

Montague

Snider

2003

Atmospheric Environment

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Particle size distributions, and scattering and absorption coefficients were measured over the Green River basin of Wyoming during the Southwest Wyoming Visibility Study (SWYVIS) in February and March 1996. Eleven flights were carried out, using the Wyoming King Air research aircraft. In the least polluted regions of the planetary boundary layer, particle number densities detected in the diameter range 0.13-3.0 mm were o100 cm À3 . Aloft, in the stable air of the free troposphere, they were generally even lower, often falling to a few tens of particles per cm 3 . Analyses of bulk aerosol filter samples showed that organic carbonaceous material was the dominant chemical component, with sulfate and refractory species being the largest inorganic components. Combining the filter data with separately measured black carbon mass loading values allowed refractive indices for the aerosol to be calculated, so that PCASP measured size distributions could be revised. Characterizing size parameters were obtained by fitting particle populations to bimodal lognormal distributions. Particle size distributions were somewhat broader at higher altitudes so that larger particles made greater contributions to extinction. Optical closure was attempted by comparing scattering and total extinctions computed by Mie theory with the corresponding values derived from the observations. While the calculated and measured single scattering albedo average values were in reasonably good agreement, even though individual pairs of values sometimes differed significantly, computed scattering coefficients often exceeded those derived from the measurements, by an average of 60%. Reasons for this discrepancy are explored, including the possible modification of the size distribution by partial or total volatilization of particles within the nephelometer and its inlet. r

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Section: Black Carbonmentioning

confidence: 61%

Section: Introductionmentioning

confidence: 99%

Airborne measurements of aerosol extinction in the lower and middle troposphere over Wyoming, USA

Han

Montague

Snider

2003

Atmospheric Environment

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“…The two main eastern outflows, the El Cajon and Banning (San Gorgonio) Passes, and one less prominent northern outflow, the Tejon (Newhall) Pass, are not sufficient to completely drain the Basin of its atmospheric contents each day, leading to some degree of carry‐over from one day to the next [ Harley et al , 2005]. In addition, mountain‐flow circulations coupled to the sea breeze can produce multiple layers of pollution in and above the temperature inversion; such layers may mix down to the surface on subsequent days as the boundary layer deepens during its diurnal cycle [ Blumenthal et al , 1978; Wakimoto and McElroy , 1986; Moore et al , 1991; Lu and Turco , 1994, 1995; Collins et al , 2000] or may be subject to long‐range transport [ Jaffe et al , 1999; Liu et al , 2003; Liang et al , 2004]. Thus, barring a precipitation event, the atmosphere sampled in the LA Basin on any given day contains a mix of fresh and aged material.…”

Section: Calnex 2010mentioning

confidence: 99%

Black carbon aerosol over the Los Angeles Basin during CalNex

Metcalf¹,

Craven²,

Ensberg³

et al. 2012

J. Geophys. Res.

120

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, with an average of 0.172 mg m À3 . Lower concentrations were measured in the Basin outflow regions and above the inversion layer. The SP2 afforded a quantification of the mixing state of rBC aerosols through modeling the scattering cross-section with a core-and-shell Mie model to determine coating thickness. The rBC particles above the inversion layer were more thickly coated by a light-scattering substance than those below, indicating a more aged aerosol in the free troposphere. Near the surface, as the LA plume is advected from west to east with the sea breeze, a coating of scattering material grows on rBC particles, coincident with a clear growth of ammonium nitrate within the LA Basin and the persistence of water-soluble organic compounds as the plume travels through the outflow regions. Detailed analysis of the rBC mixing state reveals two modes of coated rBC particles; a mode with smaller rBC core diameters ($90 nm) but thick (>200 nm) coating diameters and a mode with larger rBC cores ($145 nm) with a thin (<75 nm) coating. The "weekend effect" in the LA Basin results in more thickly coated rBC particles, coinciding with more secondary formation of aerosol.

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“…The timescales of secondary nitrate and, to a lesser extent, organic aerosol production are thought to be much less than the boundary layer mixing timescale, which result in horizontal and vertical aerosol concentration gradients in the Los Angeles basin and Central Valley [ Duong et al , 2011; Neuman et al , 2003; Collins et al , 2000]. Consequently, using measurements at one or several locations to represent an entire global model grid cell (∼100 km by 100 km) can lead to substantial uncertainties [ Collins et al , 2000].…”

Section: Introductionmentioning

confidence: 99%

Hygroscopicity and composition of California CCN during summer 2010

Moore¹,

Cerully²,

Bahreini³

et al. 2012

J. Geophys. Res.

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We present an overview and analysis of cloud condensation nuclei (CCN) sampled in California by a NOAA WP‐3D aircraft during the 2010 CalNex project. Four distinct geographical regions are characterized, including the Los Angeles basin, the San Joaquin and Sacramento Valleys, and the eastern Pacific Ocean west of southern California. Median size distributions in the Central Valley were unimodal (Dg ∼ 25 nm) with a larger fraction of organic species and smaller fraction of nitrate species in the Sacramento Valley aerosol than in the San Joaquin Valley aerosol. Size distributions in the Los Angeles basin and marine outflow were bimodal (geometric mean diameter, Dg ∼ 30, 90–100 nm) with similar organic fractions and some replacement of nitrate with sulfate in the marine outflow. Both fine particle and CCN concentrations were found to decrease rapidly above the planetary boundary layer (∼2 km altitude), with CCN concentrations in the boundary layer ranging from ∼102–104 cm−3 STP, while fine particle concentrations (0.004–1 μm diameters) ranged from ∼103–105 cm−3STP. The CCN‐active number fraction varied between 0–100% in the Los Angeles Basin and Marine Outflow, but was substantially lower (0–40%) in the San Joaquin and Sacramento Valleys. Values of the hygroscopicity parameter,κ, inferred from the CCN measurements varied from 0.1–0.25, with the highest values in the marine outflow and the lowest values in the Sacramento Valley. The κvalues agreed well with the predictions based on size‐resolved aerosol composition, but were overpredicted by almost twofold when size‐averaged composition was used. CCN closure was assessed for simplified compositional and mixing state assumptions, and it was found that assuming the aerosol to be internally mixed overpredicted CCN concentrations by 30–75% for all air mass types except within the Sacramento Valley, where good closure (overprediction < 10%) was achieved by assuming insoluble organics. Assuming an externally‐mixed aerosol fraction or incorporating size‐resolved composition data improved closure in the other three regions, consistent with the bimodal nature of the aerosol size distribution.

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Airborne analysis of the Los Angeles aerosol

Cited by 29 publications

References 44 publications

Airborne measurements of aerosol extinction in the lower and middle troposphere over Wyoming, USA

Airborne measurements of aerosol extinction in the lower and middle troposphere over Wyoming, USA

Black carbon aerosol over the Los Angeles Basin during CalNex

Hygroscopicity and composition of California CCN during summer 2010

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