Simulation of the passive infrared spectral signatures of bioaerosol and natural fog clouds immersed in the background atmosphere

Ligon, David; Wetmore, Alan; Gillespie, Patti

doi:10.1364/oe.10.000909

Cited by 9 publications

(7 citation statements)

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“…Aerosol particles, emitted from various natural or anthropogenic sources [1,2], are ubiquitous in the atmosphere of the Earth, and affect the human health [3] and climate system [4]. Atmospheric aerosols influence the earth's radiation budget directly by scattering and absorbing solar radiation [5,6], and indirectly by acting as condensation nuclei in cloud formation, thus affecting the radiative properties and lifetimes of clouds [7].…”

Section: Introductionmentioning

confidence: 99%

Retrieval of effective complex refractive index from intensive measurements of characteristics of ambient aerosols in the boundary layer

Zhang¹,

Huang²,

Rao³

et al. 2013

Opt. Express

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Aerosol complex refractive index (ACRI) has attracted intensive attentions due to its significance in modeling aerosol radiative effects. Determinations of ACRI from surface measurements of aerosol scattering and absorption coefficients as well as number size distributions during June, 2008 based on an iterative Mie algorithm were performed. The aim of our study was to introduce an inversion approach with the merits of high time-resolutions to retrieve the optically effective ACRI, especially its imaginary part. Based on simultaneous measurements of aerosol characteristics, mean ACRI value of 1.50 ( ± 0.34)-i0.025 ( ± 0.015) at 550 nm in Hefei in summer was deducted. The lower imaginary parts with higher single scattering albedos and lower scattering Angstrom exponents were obtained for haze periods compared with nonhaze conditions with similar air-mass back-trajectories, indicating more large and scattering particles contributing to the formation of haze episodes. The derived imaginary parts of ACRI related to agricultural biomass burning were in the range from 0.013 to 0.029 at 550 nm. Significant negative correlations between retrieved imaginary parts of ACRI and measured single scattering albedos indicate that our retrieval approach is a reasonable method for determining the imaginary parts of complex refractive indices of aerosol particles.

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Section: Introductionmentioning

confidence: 99%

Retrieval of effective complex refractive index from intensive measurements of characteristics of ambient aerosols in the boundary layer

Zhang¹,

Huang²,

Rao³

et al. 2013

Opt. Express

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show abstract

“…As mentioned previously, lognormal assumptions are often used to describe the particle size distribution of single-source aerosols, 65 and are regularly made in a variety of applications including remote sensing retrievals, 66,67 climate modeling, 68,69 backscatter calculations, 70 and the simulation of bioaerosol spectral signatures. 71 There is, however, no particular reason why the size distribution of any aerosol should be log-normal. Indeed, several other types of functions have been employed to characterize particle size distributions, but they are often relegated to specific aerosol types.…”

Section: ∆K(ν ˜) )mentioning

confidence: 99%

Infrared Optical Constants for Carvone from the Mie Inversion of Aerosol Extinction Spectra

2004

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Frequency-dependent, complex refractive indices for carvone in the mid-infrared from 750 to 5000 cm-1 have been inverted from the Fourier transform extinction spectra of laboratory-generated aerosols recorded at room temperature. The refractive indices obtained in this analysis are in good qualitative agreement with the results of a previous thin-film study of carvone. However, a full quantitative assessment of this agreement cannot be made as tabulated data for the previous study are no longer available. The refractive indices, or optical constants, reported here add to the small number of frequency-dependent refractive index data sets for other organic compounds that are available in the literature. Such data can be used to elucidate the optical properties of a substance, which are of critical importance in the interpretation of remote sensing data and in the evaluation of how atmospheric particulate matter consisting of organic compounds may affect climate change.

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“…The magnitude of this change and its variation with wavelength provides quantitative information on the amount and type of chemical agent present. In the infrared, radiative-transfer theory has been successfully applied to the modeling of the infrared signatures of chemical agents [17][18][19], as well as biological-agents [20]. The present section applies a similar radiative-transfer model to microwave and millimeterwave chemical signatures to assess the potential of these techniques for the detection of chemical agents.…”

Section: Radiative Transfer Modelingmentioning

confidence: 99%

An assessment of passive microwave and millimeterwave sensors for the standoff detection of chemical agents

Fraser¹,

Walker²

2004

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A radiative-transfer model is used to assess the potential of ground-based, upwardlooking, passive microwave and millimeterwave radiometry from 5 GHz to 300 GHz for the standoff detection of chemical agents. The microwave and millimeterwave spectra of the agents and simulants were modeled using published ab initio quantum-mechanical predictions of the spectroscopic constants validated by laboratory spectroscopic measurements. The pressure-broadened microwave-to-millimeterwave rotational band contours vary in intensity, shape, and peak frequency with agent or simulant, providing the potential for both identification and quantification. The radiative-transfer calculations show that the detection sensitivity is greatest for zenith angles near vertical (θ zenith ≈ 0°), with changes in brightness temperature upon introduction of a 1 km thick, 1 µmol/mol concentration chemical agent cloud of a much as 12 K for soman for a water-vapor column of 1 cm (relative humidity ≈ 38 %). The detection sensitivity as measured by the magnitude of the change in brightness temperature decreases with increasing water-vapor column and with increasing zenith angle till it effectively vanishes at horizontal viewing angles (θ zenith ≈ 90°). The analysis determines that the performance of a realistic sensor will be limited by the atmosphere opacity near horizontal viewing angles of greatest interest for standoff detection and by background brightness temperature fluctuations due to water-column variations driven by atmospheric turbulence of short and long-term duration. It is concluded that ground-based, passive, microwave and millimeterwave radiometry is not a viable technology for the sensitive standoff detection and identification of chemical agents.

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Simulation of the passive infrared spectral signatures of bioaerosol and natural fog clouds immersed in the background atmosphere

Cited by 9 publications

References 0 publications

Retrieval of effective complex refractive index from intensive measurements of characteristics of ambient aerosols in the boundary layer

Retrieval of effective complex refractive index from intensive measurements of characteristics of ambient aerosols in the boundary layer

Infrared Optical Constants for Carvone from the Mie Inversion of Aerosol Extinction Spectra

An assessment of passive microwave and millimeterwave sensors for the standoff detection of chemical agents

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