Effect of relative humidity on light scattering by mineral dust aerosol as measured in the marine boundary layer over the tropical Atlantic Ocean

Li-Jones, Xu; Maring, Hal; Prospero, Joseph M.

doi:10.1029/98jd01800

Cited by 101 publications

(63 citation statements)

References 36 publications

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“…Because the ambient RH was consistently elevated for the Africa flow, γ for this flow fell into the range of the other flow regimes. All of these values are significantly higher than the values for γ reported in the literature (Quinn et al, 2005;Massoli et al, 2009;Clarke et al, 2007;Gasso et al, 2000) as are the values of f (RH) where values of 1.0-3.2 are more common (Li-Jones et al, 1998;Carrico et al, 2003;Lewis and Schwartz, 2004). Calculating f (RH) with Eq.…”

Section: Comparison Of Surface Level Aerosol Scattering Data and Exticontrasting

confidence: 39%

“…Light scattering coefficients of near-surface aerosols at a wavelength of 530 nm were measured continuously with a Radiance Research M903 integrating nephelometer (Li et al, 1996;Li-Jones et al, 1998;Moody et al, 2014). Ambient aerosols were drawn through an omnidirectional inlet (Liu et al, 1983) at the top of the tower and transmitted under laminar flow through a 20 cm diameter polyvinyl chloride plenum to the instrument at the base of the tower.…”

Section: Measured Scattering Characteristics Of Near-surface Aerosolsmentioning

confidence: 99%

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Comparison of surface and column measurements of aerosol scattering properties over the western North Atlantic Ocean at Bermuda

et al. 2014

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Abstract.Light scattering by size-resolved aerosols in nearsurface air at Tudor Hill, Bermuda, was measured between January and June 2009. Vertical distributions of aerosol backscattering and column-averaged aerosol optical properties were characterized in parallel with a micro-pulse lidar (MPL) and an automated sun-sky radiometer. Comparisons were made between extensive aerosol parameters in the column, such as the lidar-retrieved extinction at 400 m and the aerosol optical depth (AOD), and scattering was measured with a surface nephelometer. Comparisons were also made for intensive parameters such as the Ångström exponent and calculations using AERONET(Aerosol Robotic Network)-derived aerosol physical parameters (size distribution, index of refraction) and Mie theory, and the ratio of submicron scattering to total scattering for size-segregated nephelometer measurements. In these comparisons the r 2 was generally around 0.50. Data were also evaluated based on back trajectories. The correlation between surface scattering and lidar extinction was highest for flows when the surface scattering was dominated by smaller particles and the flow had a longer footprint over land then over the ocean. The correlation of AOD with surface scatter was similar for all flow regimes. There was also no clear dependence of the atmospheric lapse rate, as determined from a nearby radiosonde station, on flow regime. The Ångström exponent for most flow regimes was 0.9-1.0, but for the case of air originating from North America, but with significant time over the ocean, the Ångström exponent was 0.57 ± 0.18. The submicron fraction of aerosol near the surface (R sub-surf ) was significantly greater for the flows from land (0.66 ± 0.11) than for the flows which spent more time over the ocean (0.40 ± 0.05). When comparing R sub-surf and the columnintegrated submicron scattering fraction, R sub-col , the correlation was similar, r 2 = 0.50, but R sub-surf was generally less than R sub-col , indicating more large particles contributing to light scattering at the surface, contrary to conditions over continents and for polluted continental transport over the ocean. In general, though, the marginal correlations indicate that the column optical properties are weakly correlated with the surface optical measurements. Thus, if it is desired to associate aerosol chemical/physical properties with their optical properties, it is best to use optical and chemical/physical measurements with both collected at the surface or both collected in the column.

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Section: Comparison Of Surface Level Aerosol Scattering Data and Exticontrasting

confidence: 39%

Section: Measured Scattering Characteristics Of Near-surface Aerosolsmentioning

confidence: 99%

Comparison of surface and column measurements of aerosol scattering properties over the western North Atlantic Ocean at Bermuda

et al. 2014

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“…Hand and Malm (2006) indicated that the scattering coefficients of (NH 4 ) 2 SO 4 and (NH 4 )HSO 4 aerosols could be enhanced by a factor of three when relative humidity is over 85%. Dust particles, dominant in coarse mode, are mostly insoluble with f (RH=80%) smaller than 1.1 (Li-Jones et al, 1998), but they could also be hygroscopic when coated by sulfate or other soluble inorganic aerosols during transportation (Perry et al, 2004;Shi et al, 2007). During the period of Aerosol Characterization Experiment (ACE-Asia), dust particle's hygroscopic factor of f (RH=80%)=1.25 was observed in Ron Brown cruise (Carrico et al, 2003), and even as high as 2.0 in Korea (Kim et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Observational study of influence of aerosol hygroscopic growth on scattering coefficient over rural area near Beijing mega-city

et al. 2009

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Abstract. We investigated aerosol hygroscopic growth property and its influence on scattering coefficient using M9003 nephelometers in coupling with humidity controlled inlet system at a rural site near Beijing mega-city from 24 April to 15 May 2006. Inlet relative humidity was controlled in an increasing range of 40%-90% while aerosol hygroscopic growth factor of scattering coefficient, f (RH=80%) as ratio of scattering coefficient at RH=80% to "dry" scattering coefficient (RH<40%) varied in a range of 1.07-2.35 during the measurement. Further analysis indicated that under dust episode, measured f (RH=80%) is 1.2±0.02, and estimated periodic mean value of f (RH=80%) was 1.31±0.03 under clean periods; during urban pollution periods, the aerosol displayed relative strong water absorbing properties with f (RH=80%) of about 1.57±0.02. An examination of chemical composition of daily filter samples highlighted that aerosol hygroscopicity was generally depressed with the increasing ratio of organic matter (OMC)/ammonium sulfate (AS) in particle mass, similar with the results of many previous studies. However, a special case with high value of f (RH=80%)=2.21 and high OMC/AS ratio was also observed, this exception reflected physico-chemical particularities of organic matter and its complex interaction with other compounds during this episode.

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“…Assuming that water and acids accumulate on aging atmospheric dust (probably as aqueous surface films) (e.g. Dentener et al, 1996;Li-Jones et al, 1998), bromine activation reactions analogous to those in sea salt aerosol should proceed. Such reactions could have important implications for the chemical evolution of dust plumes.…”

Section: Mineral Aerosolmentioning

confidence: 99%

Inorganic bromine in the marine boundary layer: a critical review

et al. 2003

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Abstract. The cycling of inorganic bromine in the marine boundary layer (mbl) has received increased attention in recent years. Bromide, a constituent of sea water, is injected into the atmosphere in association with sea-salt aerosol by breaking waves on the ocean surface. Measurements reveal that supermicrometer sea-salt aerosol is substantially depleted in bromine (often exceeding 50%) relative to conservative tracers, whereas marine submicrometer aerosol is often enriched in bromine. Model calculations, laboratory studies, and field observations strongly suggest that the supermicrometer depletions reflect the chemical transformation of particulate bromide to reactive inorganic gases that influence the processing of ozone and other important constituents of marine air. Mechanisms for the submicrometer enrichments are not well understood. Currently available techniques cannot reliably quantify many Br-containing compounds at ambient concentrations and, consequently, our understanding of inorganic Br cycling over the oceans and its global significance are uncertain. To provide a more coherCorrespondence to: R. Sander (sander@mpch-mainz.mpg.de) ent framework for future research, we have reviewed measurements in marine aerosol, the gas phase, and in rain. We also summarize sources and sinks, as well as model and laboratory studies of chemical transformations. The focus is on inorganic bromine over the open oceans outside the polar regions. The generation of sea-salt aerosol at the ocean surface is the major tropospheric source producing about 6.2 Tg/a of bromide. The transport of Br from continents (as mineral aerosol, and as products from biomass-burning and fossil-fuel combustion) can be of local importance. Transport of degradation products of long-lived Br-containing compounds from the stratosphere and other sources contribute lesser amounts. Available evidence suggests that, following aerosol acidification, sea-salt bromide reacts to form Br 2 and BrCl that volatilize to the gas phase and photolyze in daylight to produce atomic Br and Cl. Subsequent transformations can destroy tropospheric ozone, oxidize dimethylsulfide (DMS) and hydrocarbons in the gas phase and S(IV) in aerosol solutions, and thereby potentially influence climate. Inorganic bromine in the mbl gas phase during daytime are consistent with expectations based on photochemistry. We expect that the importance of inorganic Br cycling will vary in the future as a function of both increasing acidification of the atmosphere (through anthropogenic emissions) and climate changes. The latter affects bromine cycling via meteorological factors including global wind fields (and the associated production of sea-salt aerosol), temperature, and relative humidity.

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Effect of relative humidity on light scattering by mineral dust aerosol as measured in the marine boundary layer over the tropical Atlantic Ocean

Cited by 101 publications

References 36 publications

Comparison of surface and column measurements of aerosol scattering properties over the western North Atlantic Ocean at Bermuda

Comparison of surface and column measurements of aerosol scattering properties over the western North Atlantic Ocean at Bermuda

Observational study of influence of aerosol hygroscopic growth on scattering coefficient over rural area near Beijing mega-city

Inorganic bromine in the marine boundary layer: a critical review

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