Laboratory-Measured Optical Properties of Inorganic and Organic Aerosols at Relative Humidities up to 95%

Brem, Benjamin T.; Gonzalez, Francisco C. Mena; Meyers, Scott; Bond, Tami C.; Rood, Mark J.

doi:10.1080/02786826.2011.617794

Cited by 47 publications

(48 citation statements)

References 44 publications

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“…Nessler et al (2005) do not provide absorption enhancements as a function of RH, but Adam et al (2012) suggest absorption enhancements due to hygroscopic growth of less than 1.1 at 80 % humidity. Brem et al (2012) report on laboratory studies that show that aerosol absorption was enhanced by a factor of 2.2 to 2.7 at 95 % relative humidity relative to absorption at 32 % relative humidity, although for RH less than ∼ 80 % (i.e., the RH values observed in this study) they show no absorption enhancement (their Fig. 9).…”

Section: In Situ Uncertaintiesmentioning

confidence: 99%

Comparison of AOD, AAOD and column single scattering albedo from AERONET retrievals and in situ profiling measurements

et al. 2017

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Abstract. Here we present new results comparing aerosol optical depth (AOD), aerosol absorption optical depth (AAOD) and column single scattering albedo (SSA) obtained from in situ vertical profile measurements with AERONET ground-based remote sensing from two rural, continental sites in the US. The profiles are closely matched in time (within ±3 h) and space (within 15 km) with the AERONET retrievals. We have used Level 1.5 inversion retrievals when there was a valid Level 2 almucantar retrieval in order to be able to compare AAOD and column SSA below AERONET's recommended loading constraint (AOD > 0.4 at 440 nm). While there is reasonable agreement for the AOD comparisons, the direct comparisons of in situderived to AERONET-retrieved AAOD (or SSA) reveal that AERONET retrievals yield higher aerosol absorption than obtained from the in situ profiles for the low aerosol optical depth conditions prevalent at the two study sites. However, it should be noted that the majority of SSA comparisons for AOD 440 > 0.2 are, nonetheless, within the reported SSA uncertainty bounds. The observation that, relative to in situ measurements, AERONET inversions exhibit increased absorption potential at low AOD values is generally consistent with other published AERONET-in situ comparisons across a range of locations, atmospheric conditions and AOD values. This systematic difference in the comparisons suggests a bias in one or both of the methods, but we cannot assess whether the AERONET retrievals are biased towards high absorption or the in situ measurements are biased low. Based on the discrepancy between the AERONET and in situ values, we conclude that scaling modeled black carbon concentrations upwards to match AERONET retrievals of AAOD should be approached with caution as it may lead to aerosol absorption overestimates in regions of low AOD. Both AERONET retrievals and in situ measurements suggest there is a systematic relationship between SSA and aerosol amount (AOD or aerosol light scattering) -specifically that SSA decreases at lower aerosol loading. This implies that the fairly common assumption that AERONET SSA values retrieved at high-AOD conditions can be used to obtain AAOD at low-AOD conditions may not be valid.

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Section: In Situ Uncertaintiesmentioning

confidence: 99%

Comparison of AOD, AAOD and column single scattering albedo from AERONET retrievals and in situ profiling measurements

et al. 2017

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“…However, the core-shell model is an ideal representation, and enhancements of 50 % or more in absorption are possible due to the presence of black carbon aggregates as opposed to simple spherical cores (Bond et al, 2013). High RH has been found to amplify absorption by as much as a factor of 2.7 (Brem et al, 2012), but the RH in the sampling lines in Alert is < 40 % and it is unlikely to be a significant influence here.…”

Section: Seasonal Variability Of Macmentioning

confidence: 99%

An evaluation of three methods for measuring black carbon in Alert, Canada

et al. 2017

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Abstract. Absorption of sunlight by black carbon (BC) warms the atmosphere, which may be important for Arctic climate. The measurement of BC is complicated by the lack of a simple definition of BC and the absence of techniques that are uniquely sensitive to BC (e.g., Petzold et al., 2013). At the Global Atmosphere Watch baseline observatory in Alert, Nunavut (82.5 • N), BC mass is estimated in three ways, none of which fully represent BC: conversion of light absorption measured with an Aethalometer to give equivalent black carbon (EBC), thermal desorption of elemental carbon (EC) from weekly integrated filter samples to give EC, and measurement of incandescence from the refractory black carbon (rBC) component of individual particles using a single particle soot photometer (SP2). Based on measurements between March 2011 and December 2013, EBC and EC are 2.7 and 3.1 times higher than rBC, respectively. The EBC and EC measurements are influenced by factors other than just BC, and higher estimates of BC are expected from these techniques. Some bias in the rBC measurement may result from calibration uncertainties that are difficult to estimate here. Considering a number of factors, our best estimate of BC mass in Alert, which may be useful for evaluation of chemical transport models, is an average of the rBC and EC measurements with a range bounded by the rBC and EC combined with the respective measurement uncertainties. Winter-, spring-, summer-, and fall-averaged (± atmospheric variability) estimates of BC mass in Alert for this study period are 49 ± 28, 30 ± 26, 22 ± 13, and 29 ± 9 ng m −3 , respectively. Average coating thicknesses estimated from the SP2 are 25 to 40 % of the 160-180 nm diameter rBC core sizes. For particles of approximately 200-400 nm optical diameter, the fraction containing rBC cores is estimated to be between 10 and 16 %, but the possibility of smaller undetectable rBC cores in some of the particles cannot be excluded. Mass absorption coefficients (MACs) ± uncertainty at 550 nm wavelength, calculated from light absorption measurements divided by the best estimates of the BC mass concentrations, are 8.0 ± 4.0, 8.0 ± 4.0, 5.0 ± 2.5 and 9.0 ± 4.5 m 2 g −1 , for winter, spring, summer, and fall, respectively. Adjusted to better estimate absorption by BC only, the winter and spring values of MACs are 7.6 ± 3.8 and 7.7 ± 3.8 m 2 g −1 . There is evidence that the MAC values increase with coating thickness.

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“…The hygroscopicity of particles alters not only their light scattering properties by changing their size and refractive index (cf. Brem et al, 2012;and references therein), but also greatly increases the light absorption by BC aerosol internally mixed with hygroscopic materials through radiation lensing effects (e.g., Redemann et al, 2001). To a lesser extent, the absorbed water for hygroscopic aerosols could provide a medium for heterogeneous chemical reactions in the atmosphere (Khlystov et al, 2005) and also changes the partitioning of semi-volatile species between the gas and aerosol phase (Ansari and Pandis, 2000).…”

Section: Hygroscopicity and Aerosol-cloud-radiation Interactionmentioning

confidence: 99%

Satellite-Surface Perspectives of Air Quality and Aerosol-Cloud Effects on the Environment: An Overview of 7-SEAS/BASELInE

Tsay

Maring²,

Lin

et al. 2016

Aerosol Air Qual. Res.

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The objectives of 7-SEAS/BASELInE (Seven SouthEast Asian Studies/Biomass-burning Aerosols & Stratocumulus Environment: Lifecycles & Interactions Experiment) campaigns in spring 2013-2015 were to synergize measurements from uniquely distributed ground-based networks (e.g., AERONET, MPLNET) and sophisticated platforms (e.g., SMARTLabs, regional contributing instruments), along with satellite observations/retrievals and regional atmospheric transport/chemical models to establish a critically needed database, and to advance our understanding of biomass-burning aerosols and trace gases in Southeast Asia (SEA). We present a satellite-surface perspective of 7-SEAS/BASELInE and highlight scientific findings concerning: (1) regional meteorology of moisture fields conducive to the production and maintenance of low-level stratiform clouds over land, (2) atmospheric composition in a biomass-burning environment, particularly tracers/markers to serve as important indicators for assessing the state and evolution of atmospheric constituents, (3) applications of remote sensing to air quality and impact on radiative energetics, examining the effect of diurnal variability of boundary-layer height on aerosol loading, (4) aerosol hygroscopicity and ground-based cloud radar measurements in aerosol-cloud processes by advanced cloud ensemble models, and (5) implications of air quality, in terms of toxicity of nanoparticles and trace gases, to human health. This volume is the third 7-SEAS special issue (after Atmospheric Research, vol. 122, 2013; and Atmospheric Environment, vol. 78, 2013) and includes 27 papers published, with emphasis on air quality and aerosol-cloud effects on the environment. BASELInE observations of stratiform clouds over SEA are unique, such clouds are embedded in a heavy aerosol-laden environment and feature characteristically greater stability over land than over ocean, with minimal radar surface clutter at a high vertical spatial resolution. To * Corresponding author.Tel.: +13016146188; Fax: +13016146307 E-mail address: si-chee.tsay@nasa.gov ** Corresponding author.Tel./Fax: +886-3-4254069 E-mail address: nhlin@cc.ncu.edu.tw Tsay et al., Aerosol and Air Quality Research, 16: 2581-2602, 2016 2582 facilitate an improved understanding of regional aerosol-cloud effects, we envision that future BASELInE-like measurement/modeling needs fall into two categories: (1) efficient yet critical in-situ profiling of the boundary layer for validating remote-sensing/retrievals and for initializing regional transport/chemical and cloud ensemble models, and (2) fully utilizing the high observing frequencies of geostationary satellites for resolving the diurnal cycle of the boundarylayer height as it affects the loading of biomass-burning aerosols, air quality and radiative energetics.

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Laboratory-Measured Optical Properties of Inorganic and Organic Aerosols at Relative Humidities up to 95%

Cited by 47 publications

References 44 publications

Comparison of AOD, AAOD and column single scattering albedo from AERONET retrievals and in situ profiling measurements

Comparison of AOD, AAOD and column single scattering albedo from AERONET retrievals and in situ profiling measurements

An evaluation of three methods for measuring black carbon in Alert, Canada

Satellite-Surface Perspectives of Air Quality and Aerosol-Cloud Effects on the Environment: An Overview of 7-SEAS/BASELInE

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