Optical properties of Titan and early Earth haze laboratory analogs in the mid-visible

Hasenkopf, C. A.; Beaver, M. R.; Trainer, M. G.; DeWitt, H. Langley; Freedman, Miriam Arak; Toon, O. B.; McKay, Christopher P.; Tolbert, Margaret A.

doi:10.1016/j.icarus.2009.12.015

Cited by 66 publications

(98 citation statements)

References 45 publications

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“…As the above discussion clearly shows, any uncertainty in the length of the cavity occupied by aerosol has a large impact on the values of the extinction efficiency retrieved by experiment and consequently on the refractive index returned by the fitting process. As the ratios of cavity length to aerosol sample length published in the literature to date vary from 1.13 (Lang-Yona et al 2009;Hasenkopf et al 2010) to 1.67 Xue et al 2009), the uncertainty introduced by this parameter will vary between instruments.…”

Section: Uncertainty In the Length Of The Aerosol Sample Within The Cmentioning

confidence: 99%

“…In the majority of papers published to date, as in the work presented here, particle number density is measured using a CPC (Strawa et al 2003;Pettersson et al 2004;Baynard et al 2006Baynard et al , 2007Garland et al 2007;Riziq et al 2007Riziq et al , 2008Beaver et al 2008Beaver et al , 2010Dinar et al 2008;Freedman et al 2009;Khalizov et al 2009;Lang-Yona et al 2009Radney et al 2009;Xue et al 2009;Adler et al 2010;Hasenkopf et al 2010;Nakayama et al 2010). This device uses light scattering to count the number of particles in a controlled gas flow that pass through a known volume in a given time interval.…”

Section: Absolute Value Of the Particle Number Density Measured By Thmentioning

confidence: 99%

“…By measuring the extinction coefficient b ext as a function of particle number density N for size-selected particles of known diameter, the size-dependent values of the particle extinction efficiency can be extracted from the experimental data. Measuring the value of Q ext at a range of particle radii, r, or size parameter (x = 2π r/λ) allows the complex refractive index of the aerosol to be determined through comparison with theoretical Q ext values calculated from Mie theory Dinar et al 2008;Riziq et al 2008;Butler et al 2009;Freedman et al 2009;Lang-Yona et al 2009Adler et al 2010;Hasenkopf et al 2010;Miles et al 2010aMiles et al , 2010b. This approach relies critically on knowing the size distribution of particles within the cavity, their morphology, and their number density.…”

Section: Introductionmentioning

confidence: 99%

“…A-CRDS is now routinely used in laboratory (Sappey et al 1998;Vander Wal and Ticich 1999;Smith and Atkinson 2001;Bulatov et al 2002Bulatov et al , 2003Bulatov et al , 2006Strawa et al 2003;Pettersson et al 2004;Baynard et al 2006;Garland et al 2007;Riziq et al 2007;Rudić et al 2007;Dinar et al 2008;Riziq et al 2008;Butler et al 2009;Freedman et al 2009;Khalizov et al 2009;Lang-Yona et al 2009Radney et al 2009;Xue et al 2009;Adler et al 2010;Hasenkopf et al 2010;Miles et al 2010aMiles et al , 2010b and field studies (Thompson et al 2002(Thompson et al , 2003Strawa et al 2006;Garland et al 2008;Nakayama et al 2010) to measure extinction by both aerosol ensembles (Vander Wal and Ticich 1999;Thompson et al 2002Thompson et al , 2003Thompson et al , 2008Strawa et al 2003;Pettersson et al 2004;Baynard et al 2006Baynard et al , 2007Garland et al 2007;Riziq et al 2007;Beaver et al 2008;…”

Section: Introductionmentioning

confidence: 99%

“…To our knowledge, there has so far been no study which explicitly considers the effect of these and other instrumental limitations, such as the particle counting efficiency, on the accuracy with which complex refractive index values can be retrieved. Where uncertainties in experimentally retrieved complex refractive indices have been given, these are generally on the order of ±1% for the real part (Dinar et al 2008;Freedman et al 2009;Lack et al 2009;Lang-Yona et al 2009Adler et al 2010;Hasenkopf et al 2010) and range from a few to several hundred percent for the imaginary term (Dinar et al 2008;Lack et al 2009;LangYona et al 2009LangYona et al , 2010bAdler et al 2010;Hasenkopf et al 2010).…”

Section: Introductionmentioning

confidence: 99%

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Sources of Error and Uncertainty in the Use of Cavity Ring Down Spectroscopy to Measure Aerosol Optical Properties

Miles

Rudić

Orr-Ewing

et al. 2011

Aerosol Science and Technology

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The use of cavity ring down spectroscopy to retrieve aerosol complex refractive index from optical property measurements has seen increasing popularity over the past few years. However, few studies have looked at the limit which sources of error and uncertainty inherent in the cavity ring down method place on the accuracy with which the refractive index can be retrieved. In this paper, we consider both experimental sources of error and those which compromise the theoretical models against which measurements are compared, both reviewing previously published work and presenting new data. Our results show that for absolute measurements made using single-cavity instruments, factors such as uncertainty in the length of the ring down cavity occupied by aerosol and the counting efficiency of the CPC can introduce an error of ∼2.5% into the real part of the refractive index retrieved from experiment. This is significantly higher than the typical 1% error quoted in previously published work. We note that due to the dependence of particle extinction efficiency on diameter, the effect of a given error on measurements for different particle sizes is not constant.

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Section: Uncertainty In the Length Of The Aerosol Sample Within The Cmentioning

confidence: 99%

Section: Absolute Value Of the Particle Number Density Measured By Thmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Sources of Error and Uncertainty in the Use of Cavity Ring Down Spectroscopy to Measure Aerosol Optical Properties

Miles

Rudić

Orr-Ewing

et al. 2011

Aerosol Science and Technology

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Influence of shape on the optical properties of hematite aerosol

et al. 2015

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Mineral dust particles are the second highest emitted aerosol type by mass. Due to changes in particle size, composition, and shape that are caused by physical processes and reactive chemistry, optical properties vary during transport, contributing uncertainty in the calculation of radiative forcing. Hematite is the major absorbing species of mineral dust. In this study, we analyzed the extinction cross sections of nigrosin and hematite particles using cavity ring-down aerosol extinction spectroscopy (CRD-AES) and have measured particle shape and size distributions using transmission electron microscopy. Nigrosin was also used in this study as a spherical standard for absorbing particles. The size-selected nigrosin particles have a narrow size distribution, with extinction cross sections that are described by Mie theory. In contrast, the size distribution of size-selected hematite particles is more polydisperse. The extinction cross sections were modeled using Mie theory and the discrete dipole approximation (DDA). The DDA was used to model more complex shapes that account for the surface roughness and particle geometry. Of the four models used, Mie theory was the simplest to implement, but had significant error with a 26.1% difference from the CRD-AES results. By increasing the complexity of the models using the DDA, we determined that spheroids had a 14.7% difference, roughened spheres a 12.8% difference, and roughened spheroids a 11.2% difference from the experimental results. Using additional parameters that account for particle shape is necessary to model the optical properties of hematite particles and leads to improved extinction cross sections for modeling aerosol optical properties.

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Titan's atmosphere and climate

2017

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Titan is the only moon with a substantial atmosphere, the only other thick N2 atmosphere besides Earth's, the site of extraordinarily complex atmospheric chemistry that far surpasses any other solar system atmosphere, and the only other solar system body with stable liquid currently on its surface. The connection between Titan's surface and atmosphere is also unique in our solar system; atmospheric chemistry produces materials that are deposited on the surface and subsequently altered by surface‐atmosphere interactions such as aeolian and fluvial processes resulting in the formation of extensive dune fields and expansive lakes and seas. Titan's atmosphere is favorable for organic haze formation, which combined with the presence of some oxygen‐bearing molecules indicates that Titan's atmosphere may produce molecules of prebiotic interest. The combination of organics and liquid, in the form of water in a subsurface ocean and methane/ethane in the surface lakes and seas, means that Titan may be the ideal place in the solar system to test ideas about habitability, prebiotic chemistry, and the ubiquity and diversity of life in the universe. The Cassini‐Huygens mission to the Saturn system has provided a wealth of new information allowing for study of Titan as a complex system. Here I review our current understanding of Titan's atmosphere and climate forged from the powerful combination of Earth‐based observations, remote sensing and in situ spacecraft measurements, laboratory experiments, and models. I conclude with some of our remaining unanswered questions as the incredible era of exploration with Cassini‐Huygens comes to an end.

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Optical properties of Titan and early Earth haze laboratory analogs in the mid-visible

Cited by 66 publications

References 45 publications

Sources of Error and Uncertainty in the Use of Cavity Ring Down Spectroscopy to Measure Aerosol Optical Properties

Sources of Error and Uncertainty in the Use of Cavity Ring Down Spectroscopy to Measure Aerosol Optical Properties

Influence of shape on the optical properties of hematite aerosol

Titan's atmosphere and climate

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