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    Estimation of Surface and Top-of-Atmosphere Shortwave Irradiance in Biomass-Burning Regions during SCAR-B

    Source: Journal of Applied Meteorology:;2000:;volume( 039 ):;issue: 010::page 1742
    Author:
    Christopher, Sundar A.
    ,
    Li, Xiang
    ,
    Welch, Ronald M.
    ,
    Reid, Jeffrey S.
    ,
    Hobbs, Peter V.
    ,
    Eck, Thomas F.
    ,
    Holben, Brent
    DOI: 10.1175/1520-0450-39.10.1742
    Publisher: American Meteorological Society
    Abstract: Using in situ measurements of aerosol optical properties and ground-based measurements of aerosol optical thickness (τs) during the Smoke, Clouds and Radiation?Brazil (SCAR-B) experiment, a four-stream broadband radiative transfer model is used to estimate the downward shortwave irradiance (DSWI) and top-of-atmosphere (TOA) shortwave aerosol radiative forcing (SWARF) in cloud-free regions dominated by smoke from biomass burning in Brazil. The calculated DSWI values are compared with broadband pyranometer measurements made at the surface. The results show that, for two days when near-coincident measurements of single-scattering albedo ?0 and τs are available, the root-mean-square errors between the measured and calculated DSWI for daytime data are within 30 W m?2. For five days during SCAR-B, however, when assumptions about ?0 have to be made and also when τs was significantly higher, the differences can be as large as 100 W m?2. At TOA, the SWARF per unit optical thickness ranges from ?20 to ?60 W m?2 over four major ecosystems in South America. The results show that τs and ?0 are the two most important parameters that affect DSWI calculations. For SWARF values, surface albedos also play an important role. It is shown that ?0 must be known within 0.05 and τs at 0.55 ?m must be known to within 0.1 to estimate DSWI to within 20 W m?2. The methodology described in this paper could serve as a potential strategy for determining DSWI values in the presence of aerosols. The wavelength dependence of τs and ?0 over the entire shortwave spectrum is needed to improve radiative transfer calculations. If global retrievals of DSWI and SWARF from satellite measurements are to be performed in the presence of biomass-burning aerosols on a routine basis, a concerted effort should be made to develop methodologies for estimating ?0 and τs from satellite and ground-based measurements.
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      Estimation of Surface and Top-of-Atmosphere Shortwave Irradiance in Biomass-Burning Regions during SCAR-B

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    contributor authorChristopher, Sundar A.
    contributor authorLi, Xiang
    contributor authorWelch, Ronald M.
    contributor authorReid, Jeffrey S.
    contributor authorHobbs, Peter V.
    contributor authorEck, Thomas F.
    contributor authorHolben, Brent
    date accessioned2017-06-09T14:09:32Z
    date available2017-06-09T14:09:32Z
    date copyright2000/10/01
    date issued2000
    identifier issn0894-8763
    identifier otherams-13501.pdf
    identifier urihttp://onlinelibrary.yabesh.ir/handle/yetl/4148959
    description abstractUsing in situ measurements of aerosol optical properties and ground-based measurements of aerosol optical thickness (τs) during the Smoke, Clouds and Radiation?Brazil (SCAR-B) experiment, a four-stream broadband radiative transfer model is used to estimate the downward shortwave irradiance (DSWI) and top-of-atmosphere (TOA) shortwave aerosol radiative forcing (SWARF) in cloud-free regions dominated by smoke from biomass burning in Brazil. The calculated DSWI values are compared with broadband pyranometer measurements made at the surface. The results show that, for two days when near-coincident measurements of single-scattering albedo ?0 and τs are available, the root-mean-square errors between the measured and calculated DSWI for daytime data are within 30 W m?2. For five days during SCAR-B, however, when assumptions about ?0 have to be made and also when τs was significantly higher, the differences can be as large as 100 W m?2. At TOA, the SWARF per unit optical thickness ranges from ?20 to ?60 W m?2 over four major ecosystems in South America. The results show that τs and ?0 are the two most important parameters that affect DSWI calculations. For SWARF values, surface albedos also play an important role. It is shown that ?0 must be known within 0.05 and τs at 0.55 ?m must be known to within 0.1 to estimate DSWI to within 20 W m?2. The methodology described in this paper could serve as a potential strategy for determining DSWI values in the presence of aerosols. The wavelength dependence of τs and ?0 over the entire shortwave spectrum is needed to improve radiative transfer calculations. If global retrievals of DSWI and SWARF from satellite measurements are to be performed in the presence of biomass-burning aerosols on a routine basis, a concerted effort should be made to develop methodologies for estimating ?0 and τs from satellite and ground-based measurements.
    publisherAmerican Meteorological Society
    titleEstimation of Surface and Top-of-Atmosphere Shortwave Irradiance in Biomass-Burning Regions during SCAR-B
    typeJournal Paper
    journal volume39
    journal issue10
    journal titleJournal of Applied Meteorology
    identifier doi10.1175/1520-0450-39.10.1742
    journal fristpage1742
    journal lastpage1753
    treeJournal of Applied Meteorology:;2000:;volume( 039 ):;issue: 010
    contenttypeFulltext
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    DSpace software copyright © 2002-2015  DuraSpace
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