Reduction in 317–780 nm radiance reflected from the sunlit Earth during the eclipse of 21 August 2017

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dc.contributor.authorHerman, Jay
dc.contributor.authorWen, Guoyong
dc.contributor.authorMarshak, Alexander
dc.contributor.authorBlank, Karin
dc.contributor.authorHuang, Liang
dc.contributor.authorCede, Alexander
dc.contributor.authorAbuhassan, Nader
dc.contributor.authorKowalewski, Matthew
dc.date.accessioned2023-01-19T17:52:31Z
dc.date.available2023-01-19T17:52:31Z
dc.date.issued2018-07-25
dc.description.abstractTen wavelength channels of calibrated radiance image data from the sunlit Earth are obtained every 65 min during Northern Hemisphere summer from the EPIC (Earth Polychromatic Imaging Camera) instrument on the DSCOVR (Deep Space Climate Observatory) satellite located near the Earth–Sun Lagrange 1 point (L ₁), about 1.5 million km from the Earth. The L ₁ location permitted seven observations of the Moon’s shadow on the Earth for about 3 h during the 21 August 2017 eclipse. Two of the observations were timed to coincide with totality over Casper, Wyoming, and Columbia, Missouri. Since the solar irradiances within five channels (λi = 388, 443, 551, 680, and 780 nm) are not strongly absorbed in the atmosphere, they can be used for characterizing the eclipse reduction in reflected radiances for the Earth’s sunlit face containing the eclipse shadow. Five channels (λi = 317.5, 325, 340, 688, and 764 nm) that are partially absorbed in the atmosphere give consistent reductions compared to the non-absorbed channels. This indicates that cloud reflectivities dominate the 317.5–780 nm radiances reflected back to space from the sunlit Earth’s disk with a significant contribution from Rayleigh scattering for the shorter wavelengths. An estimated reduction of 10 % was obtained for spectrally integrated radiance (387 to 781 nm) reflected from the sunlit Earth towards L ₁ for two sets of observations on 21 August 2017, while the shadow was in the vicinity of Casper, Wyoming (42.8666◦ N, 106.3131◦ W; centered on 17:44:50 UTC), and Columbia, Missouri (38.9517◦ N, 92.3341◦ W; centered on 18:14:50 UTC). In contrast, when non-eclipse days (20 and 23 August) are compared for each wavelength channel, the change in reflected light is much smaller (less than 1 % for 443 nm compared to 9 % (Casper) and 8 % (Columbia) during the eclipse). Also measured was the ratio Rₑₙ (λi) of reflected radiance on adjacent non-eclipse days divided by radiances centered in the eclipse totality region with the same geometry for all 10 wavelength channels. The measured Rₑₙ(443 nm) was smaller for Columbia (169) than for Casper (935), because Columbia had more cloud cover than Casper. Rₑₙ (λi) forms a useful test of a 3-D radiative transfer models for an eclipse in the presence of optically thin clouds. Specific values measured at Casper with thin clouds are Rₑₙ(340 nm) = 475, Rₑₙ(388 nm) = 3500, Rₑₙ(443 nm) = 935, Rₑₙ(551 nm) = 5455, Rₑₙ(680 nm) = 220, and Rₑₙ(780 nm) = 395. Some of the variability is caused by changing cloud amounts within the moving region of totality during the 2.7 min needed to measure all 10 wavelength channels.en_US
dc.description.sponsorshipThe author would like to thank the DSCOVR project for support in completing this study as well as financial support from an accepted NASA-ROSES proposal in response to NNH16ZDA001N-ISE.en_US
dc.description.urihttps://amt.copernicus.org/articles/11/4373/2018/en_US
dc.format.extent16 pagesen_US
dc.genrejournal articlesen_US
dc.genrepreprintsen_US
dc.identifierdoi:10.13016/m2jc1f-jxfe
dc.identifier.citationHerman, J., et al. “Reduction in 317–780 nm radiance reflected from the sunlit Earth during the eclipse of 21 August 2017” Atmos. Meas. Tech. 11(25 July 2018): 4373–4388. https://doi.org/10.5194/amt-11-4373-2018.en_US
dc.identifier.urihttps://doi.org/10.5194/amt-11-4373-2018
dc.identifier.urihttp://hdl.handle.net/11603/26674
dc.language.isoen_USen_US
dc.publisherEGUen_US
dc.relation.isAvailableAtThe University of Maryland, Baltimore County (UMBC)
dc.relation.ispartofUMBC Joint Center for Earth Systems Technology
dc.relation.ispartofUMBC Faculty Collection
dc.rightsThis work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.en_US
dc.rightsPublic Domain Mark 1.0*
dc.rights.urihttp://creativecommons.org/publicdomain/mark/1.0/*
dc.titleReduction in 317–780 nm radiance reflected from the sunlit Earth during the eclipse of 21 August 2017en_US
dc.title.alternativeReduction in Earth Reflected Radiance during the Eclipse of 21 August 2017en_US
dc.typeTexten_US
dcterms.creatorhttps://orcid.org/0000-0002-9146-1632en_US
dcterms.creatorhttps://orcid.org/0000-0002-3865-657Xen_US

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