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nasa new
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nasa new
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texts
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texts
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collection:
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nasa_techdocs
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nasa_techdocs
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title:
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Radiative Properties of Cirrus Clouds in the Infrared (8-13 microns) Spectral Region
title
Radiative Properties of Cirrus Clouds in the Infrared (8-13 microns) Spectral Region
title
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description:
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Atmospheric radiation in the infrared (IR) 8-13 microns spectral region contains a wealth of information that is very useful for the retrieval of ice cloud properties from aircraft or space-borne measurements. To provide the scattering and absorption properties of nonspherical ice crystals that are fundamental to the IR retrieval implementation, we use the finite-difference time domain (FDTD) method to solve for the extinction efficiency, single-scattering albedo, and the asymmetry parameter of the phase function for ice crystals smaller than 40 microns. For particles larger than this size, the improved geometric optics method (IGOM) can be employed to calculate the asymmetry parameter with an acceptable accuracy, provided that we properly account for the inhomogeneity of the refracted wave due to strong absorption inside the ice particle. A combination of the results computed from the two methods provides the asymmetry parameter for the entire practical range of particle sizes between 1 micron and 10000 microns over wavelengths ranging from 8 microns to 13 microns. For the extinction and absorption efficiency calculations, several methods including the IGOM, Mie solution for equivalent spheres (MSFES), and the anomalous diffraction theory (ADT) can lead to a substantial discontinuity in comparison with the FDTD solutions for particle sizes on the order of 40 microns. To overcome this difficulty, we have developed a novel approach called the stretched scattering potential method (SSPM). For the IR 8-13 microns spectral region, we show that SSPM is a more accurate approximation than ADT, MSFES, and IGOM. The SSPM solution can be further refined numerically. Through a combination of the FDTD and SSPM, we have computed the extinction and absorption efficiency for hexagonal ice crystals with sizes ranging from 1 to 10000 microns at 12 wavelengths between 8 and 13 microns Calculations of the cirrus bulk scattering and absorption properties are performed for 30 size distributions obtained from various field campaigns for midlatitude and tropical cirrus cloud systems. Parameterization of these bulk scattering properties is carried out by using second-order polynomial functions for the extinction efficiency and the single-scattering albedo and the power law expression for the asymmetry parameter. We note that the volume-normalized extinction coefficient can be separated into two parts: one is inversely proportional to effective size and is independent of wavelength, and the other is the wavelength-dependent effective extinction efficiency. Unlike conventional parameterization efforts, the present parameterization scheme is more accurate because only the latter part of the volume-normalized extinction coefficient is approximated in terms of an analytical expression. After averaging over size distribution, the single-scattering albedo is shown to decrease with an increase in effective size for wavelengths shorter than 10.0 microns whereas the opposite beha
description
Atmospheric radiation in the infrared (IR) 8-13 microns spectral region contains a wealth of information that is very useful for the retrieval of ice cloud properties from aircraft or space-borne measurements. To provide the scattering and absorption properties of nonspherical ice crystals that are fundamental to the IR retrieval implementation, we use the finite-difference time domain (FDTD) method to solve for the extinction efficiency, single-scattering albedo, and the asymmetry parameter of the phase function for ice crystals smaller than 40 microns. For particles larger than this size, the improved geometric optics method (IGOM) can be employed to calculate the asymmetry parameter with an acceptable accuracy, provided that we properly account for the inhomogeneity of the refracted wave due to strong absorption inside the ice particle. A combination of the results computed from the two methods provides the asymmetry parameter for the entire practical range of particle sizes between 1 micron and 10000 microns over wavelengths ranging from 8 microns to 13 microns. For the extinction and absorption efficiency calculations, several methods including the IGOM, Mie solution for equivalent spheres (MSFES), and the anomalous diffraction theory (ADT) can lead to a substantial discontinuity in comparison with the FDTD solutions for particle sizes on the order of 40 microns. To overcome this difficulty, we have developed a novel approach called the stretched scattering potential method (SSPM). For the IR 8-13 microns spectral region, we show that SSPM is a more accurate approximation than ADT, MSFES, and IGOM. The SSPM solution can be further refined numerically. Through a combination of the FDTD and SSPM, we have computed the extinction and absorption efficiency for hexagonal ice crystals with sizes ranging from 1 to 10000 microns at 12 wavelengths between 8 and 13 microns Calculations of the cirrus bulk scattering and absorption properties are performed for 30 size distributions obtained from various field campaigns for midlatitude and tropical cirrus cloud systems. Parameterization of these bulk scattering properties is carried out by using second-order polynomial functions for the extinction efficiency and the single-scattering albedo and the power law expression for the asymmetry parameter. We note that the volume-normalized extinction coefficient can be separated into two parts: one is inversely proportional to effective size and is independent of wavelength, and the other is the wavelength-dependent effective extinction efficiency. Unlike conventional parameterization efforts, the present parameterization scheme is more accurate because only the latter part of the volume-normalized extinction coefficient is approximated in terms of an analytical expression. After averaging over size distribution, the single-scattering albedo is shown to decrease with an increase in effective size for wavelengths shorter than 10.0 microns whereas the opposite beha
description
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description:
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vior is observed for longer wavelengths. The variation of the asymmetry parameter as a function of effective size is substantial when the effective size is smaller than 50 microns. For effective sizes larger than 100 microns, the asymmetry parameter approaches its asymptotic value. The results derived in this study can be useful to remote sensing applications involving IR window bands under cirrus cloud conditions.
description
vior is observed for longer wavelengths. The variation of the asymmetry parameter as a function of effective size is substantial when the effective size is smaller than 50 microns. For effective sizes larger than 100 microns, the asymmetry parameter approaches its asymptotic value. The results derived in this study can be useful to remote sensing applications involving IR window bands under cirrus cloud conditions.
description
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subject:
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AEROTHERMODYNAMICS
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AEROTHERMODYNAMICS
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subject:
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WIND TUNNEL TESTS
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WIND TUNNEL TESTS
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subject:
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DATA ACQUISITION
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DATA ACQUISITION
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subject:
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TECHNOLOGY UTILIZATION
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TECHNOLOGY UTILIZATION
subject
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subject:
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QUALITY CONTROL
subject
QUALITY CONTROL
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subject:
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EXPERIMENT DESIGN
subject
EXPERIMENT DESIGN
subject
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subject:
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SUPERSONIC WIND TUNNELS
subject
SUPERSONIC WIND TUNNELS
subject
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identifier:
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nasa_techdoc_2001002 5273
identifier
nasa_techdoc_2001002 5273
identifier
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licenseurl:
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uploader:
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gwilliam@archive.org
uploader
gwilliam@archive.org
uploader
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addeddate:
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2011-05-30 03:27:50
addeddate
2011-05-30 03:27:50
addeddate
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publicdate:
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2011-05-30 03:27:50
publicdate
2011-05-30 03:27:50
publicdate
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creator:
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Gao, Bo-Cai
creator
Gao, Bo-Cai
creator
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creator:
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Baum, Bryan A.
creator
Baum, Bryan A.
creator
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creator:
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Yang, Ping
creator
Yang, Ping
creator
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creator:
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Tsay, Si-Chee
creator
Tsay, Si-Chee
creator
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creator:
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Hu, Yong X.
creator
Hu, Yong X.
creator
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creator:
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Wiscombe, Warren J.
creator
Wiscombe, Warren J.
creator
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creator:
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Winker, Dave M
creator
Winker, Dave M
creator
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ImageUID:
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file:/home/lunaadmin /Source_download/201 105/1/nasa_techdoc_2 0010025273/200100252 73.pdf
ImageUID
file:/home/lunaadmin /Source_download/201 105/1/nasa_techdoc_2 0010025273/200100252 73.pdf
ImageUID
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date:
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2000
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rights:
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Public Domain
rights
Public Domain
rights
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ppi:
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300
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year:
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2000
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language:
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eng
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document-source:
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CASI
document_source
CASI
document-source
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documentid:
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20010025273
documentid
20010025273
documentid
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nasa-center:
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Goddard Space Flight Center; Langley Research Center
nasa_center
Goddard Space Flight Center; Langley Research Center
nasa-center
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online-source:
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http://wayback.archi ve-it.org/1792/20100 214205512/http://hdl .handle.net/2060/200 10025273
online_source
http://wayback.archi ve-it.org/1792/20100 214205512/http://hdl .handle.net/2060/200 10025273
online-source
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original-nasa-rights:
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Unclassified; Copyright (Distribution as joint owner in the copyright) ; Unlimited; Publicly available;
original_nasa_rights
Unclassified; Copyright (Distribution as joint owner in the copyright) ; Unlimited; Publicly available;
original-nasa-rights
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report-number:
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AIAA Paper 2001-0456
report_number
AIAA Paper 2001-0456
report-number
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updated-added-to-ntrs:
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2009-07-29
updated_added_to_ntr s
2009-07-29
updated-added-to-ntr s
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contributor:
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NASA
contributor
NASA
contributor
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identifier-access:
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identifier_access
identifier-access
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identifier-ark:
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ark:/13960/t1vd7qc26
identifier_ark
ark:/13960/t1vd7qc26
identifier-ark
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ABBYY FineReader 8.0
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4
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