Optical properties of absorbing and non-absorbing aerosols retrieved by cavity ring down (CRD) spectroscopy

Riziq, A. Abo; Erlick, Carynelisa; Dinar, E.; Rudich, Yinon

doi:10.5194/acp-7-1523-2007

Cited by 187 publications

(288 citation statements)

References 44 publications

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“…To retrieve the RI from the CRD-AS measurements, the extinction efficiency of the humidified aerosols (Q ext-%RH ) was calculated from the measured GF and the extinction coefficient at every diameter. By knowing the value of Q ext at different diameters for internally mixed aerosols, a refractive index can be retrieved (Lang-Yona et al, 2009;Pettersson et al, 2004;Abo Riziq et al, 2007). Figure 4 shows two examples of the results of the complex RI derivation and comparison performed.…”

Section: Optical Growth Of Humidified Absorbing Aerosolsmentioning

confidence: 99%

“…The time it takes the initial intensity of the light to decay to 1/e is then measured. By measuring the empty cavity (filled only with the carrier gas) decay time (τ o ) and the decay time filled with aerosols (τ ), the extinction coefficient (extinction = scattering + absorption) can be directly measured (Pettersson et al, 2004;Abo Riziq et al, 2007):…”

Section: Aerosol Optical Extinction Measurementsmentioning

confidence: 99%

“…1. A full description of the CRD-AS used in this study can be found in Abo Riziq et al (2007). Briefly, two plano-concave highly reflective mirrors (Los Gatos) are mounted at both ends of a stainless steel tube.…”

Section: Aerosol Optical Extinction Measurementsmentioning

confidence: 99%

“…The most common rule is the volume weighted mixing rule, which is often used in chemical transport models that estimate the aerosol direct forcing (Haywood et al, 1997;Liu et al, 2007b), and in laboratory studies. Abo Riziq et al (2007) measured different organic mixtures to test the validity of this mixing rule for a solution. Garland et al (2007) used the volume weighted mixing rule (assuming complete mixing of the aerosols as they passed through a humidification stage) to test the performance of their system and to parameterize the change in the extinction coefficient when purely scattering substances (inorganic and organic) were exposed to an RH of 80 %.…”

Section: Introductionmentioning

confidence: 99%

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Absorbing aerosols at high relative humidity: linking hygroscopic growth to optical properties

et al. 2012

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Abstract. One of the major uncertainties in the understanding of Earth's climate system is the interaction between solar radiation and aerosols in the atmosphere. Aerosols exposed to high humidity will change their chemical, physical, and optical properties due to their increased water content. To model hydrated aerosols, atmospheric chemistry and climate models often use the volume weighted mixing rule to predict the complex refractive index (RI) of aerosols when they interact with high relative humidity, and, in general, assume homogeneous mixing. This study explores the validity of these assumptions. A humidified cavity ring down aerosol spectrometer (CRD-AS) and a tandem hygroscopic DMA (differential mobility analyzer) are used to measure the extinction coefficient and hygroscopic growth factors of humidified aerosols, respectively. The measurements are performed at 80 % and 90 %RH at wavelengths of 532 nm and 355 nm using size-selected aerosols with different degrees of absorption; from purely scattering to highly absorbing particles. The ratio of the humidified to the dry extinction coefficients (f RH ext (%RH, Dry)) is measured and compared to theoretical calculations based on Mie theory. Using the measured hygroscopic growth factors and assuming homogeneous mixing, the expected RIs using the volume weighted mixing rule are compared to the RIs derived from the extinction measurements.We found a weak linear dependence or no dependence of f RH(%RH, Dry) with size for hydrated absorbing aerosols in contrast to the non-monotonically decreasing behavior with size for purely scattering aerosols. No discernible difference could be made between the two wavelengths used. Less than 7 % differences were found between the real parts of the complex refractive indices derived and those calculated using the volume weighted mixing rule, and the imaginary parts had up to a 20 % difference. However, for substances with growth factor less than 1.15 the volume weighted mixing rule assumption needs to be taken with caution as the imaginary part of the complex RI can be underestimated.

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Section: Optical Growth Of Humidified Absorbing Aerosolsmentioning

confidence: 99%

Section: Aerosol Optical Extinction Measurementsmentioning

confidence: 99%

Section: Aerosol Optical Extinction Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Absorbing aerosols at high relative humidity: linking hygroscopic growth to optical properties

et al. 2012

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“…Several different methods have been used to generate surrogate marine aerosols within enclosed tanks including pressurized atomizers (Svenningsson et al, 2006;Riziq et al, 2007;Saul et al, 2006;McNeill et al, 2006;Braban et al, 2007;Niedermeier et al, 2008;Taketani et al, 2009), forcing air through glass filters or sintered materials (Cloke et al, 1991;Martensson et al, 2003;Sellegri et al, 2006;Keene et al, 2007;Tyree et al, 2007;Wise et al, 2009;Hultin et al, 2010;Fuentes et al, 2010) and by a plunging water jet (Cipriano and Blanchard, 1981;Sellegri et al, 2006;Facchini et al, 2008;Fuentes et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

A Marine Aerosol Reference Tank system as a breaking wave analogue for the production of foam and sea-spray aerosols

et al. 2013

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In order to better understand the processes governing the production of marine aerosols a repeatable, controlled method for their generation is required. The Marine Aerosol Reference Tank (MART) has been designed to closely approximate oceanic conditions by producing an evolving bubble plume and surface foam patch. The tank utilizes an intermittently plunging sheet of water and large volume tank reservoir to simulate turbulence, plume and foam formation, and the water flow is monitored volumetrically and acoustically to ensure the repeatability of conditions

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Optical extinction of highly porous aerosol following atmospheric freeze drying

et al. 2014

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Porous glassy particles are a potentially significant but unexplored component of atmospheric aerosol that can form by aerosol processing through the ice phase of high convective clouds. The optical properties of porous glassy aerosols formed from a freeze-dry cycle simulating freezing and sublimation of ice particles were measured using a cavity ring down aerosol spectrometer (CRD-AS) at 532 nm and 355 nm wavelength. The measured extinction efficiency was significantly reduced for porous organic and mixed organic-ammonium sulfate particles as compared to the extinction efficiency of the homogeneous aerosol of the same composition prior to the freeze-drying process. A number of theoretical approaches for modeling the optical extinction of porous aerosols were explored. These include effective medium approximations, extended effective medium approximations, multilayer concentric sphere models, Rayleigh-Debye-Gans theory, and the discrete dipole approximation. Though such approaches are commonly used to describe porous particles in astrophysical and atmospheric contexts, in the current study, these approaches predicted an even lower extinction than the measured one. Rather, the best representation of the measured extinction was obtained with an effective refractive index retrieved from a fit to Mie scattering theory assuming spherical particles with a fixed void content. The single-scattering albedo of the porous glassy aerosols was derived using this effective refractive index and was found to be lower than that of the corresponding homogeneous aerosol, indicating stronger relative absorption at the wavelengths measured. The reduced extinction and increased absorption may be of significance in assessing direct, indirect, and semidirect forcing in regions where porous aerosols are expected to be prevalent.

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Optical properties of absorbing and non-absorbing aerosols retrieved by cavity ring down (CRD) spectroscopy

Cited by 187 publications

References 44 publications

Absorbing aerosols at high relative humidity: linking hygroscopic growth to optical properties

Absorbing aerosols at high relative humidity: linking hygroscopic growth to optical properties

A Marine Aerosol Reference Tank system as a breaking wave analogue for the production of foam and sea-spray aerosols

Optical extinction of highly porous aerosol following atmospheric freeze drying

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