A Relationship Between Blue and Near-IR Global Spectral Reflectance and the Response of Global Average Reflectance to Change in Cloud Cover Observed From EPIC

Guoyong Wen (Corresponding Author), Alexander Marshak, Wanjuan Song, Yuri Knyazikhin, Matti Mõttus, Dong Wu

Research output: Contribution to journalArticleScientificpeer-review

Abstract

We performed a detailed analysis of Earth Polychromatic Imaging Camera (EPIC) spectral data. We found that the vector composed of blue and near-infrared (NIR) reflectance follows a counterclockwise closed-loop trajectory from 0 to 24 UTC as Earth rotates. This nonlinear relationship was not observed by any other satellites due to limited spatial or temporal coverage of either low Earth orbit or geostationary satellites. We found that clouds play an important role in determining the nonlinear relationship in addition to the well-known cloud-free land-ocean reflectance contrast in the two bands. The nonlinear relationship is the result of three factors: (1) a much larger cloud-free land-ocean contrast in the NIR band compared to the blue band, (2) significantly larger difference between cloudy land and cloudy ocean reflectance in the NIR band compared to the blue band, and (3) the periodic variation of fractions of clear land, clear ocean, cloudy land, and cloudy ocean in the sunlit hemisphere as Earth rotates. We found that the green vegetation contributes significantly to the NIR global average reflectance when the South and North Americas appear and disappear in the EPIC's field of view. The blue and NIR relationship can be useful for exoplanet research. Clouds impose a strong impact on global spectral reflectance, and the reflectance response to a change in cloud cover depends on whether the change is over land or over the ocean. On average, an increase of 0.1 in cloud coverage will lead to a 7% increase in spectrally integrated global average reflectance.
Original languageEnglish
Pages (from-to)1416-1429
Number of pages14
JournalEarth and Space Science
Volume6
Issue number8
DOIs
Publication statusPublished - 18 Jul 2019
MoE publication typeA1 Journal article-refereed

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spectral reflectance
cloud cover
reflectance
near infrared
ocean
geostationary satellite
field of view
land
trajectory
vegetation

Keywords

  • cloud
  • DSCOVR
  • EPIC
  • reflectance
  • spectral

Cite this

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title = "A Relationship Between Blue and Near-IR Global Spectral Reflectance and the Response of Global Average Reflectance to Change in Cloud Cover Observed From EPIC",
abstract = "We performed a detailed analysis of Earth Polychromatic Imaging Camera (EPIC) spectral data. We found that the vector composed of blue and near-infrared (NIR) reflectance follows a counterclockwise closed-loop trajectory from 0 to 24 UTC as Earth rotates. This nonlinear relationship was not observed by any other satellites due to limited spatial or temporal coverage of either low Earth orbit or geostationary satellites. We found that clouds play an important role in determining the nonlinear relationship in addition to the well-known cloud-free land-ocean reflectance contrast in the two bands. The nonlinear relationship is the result of three factors: (1) a much larger cloud-free land-ocean contrast in the NIR band compared to the blue band, (2) significantly larger difference between cloudy land and cloudy ocean reflectance in the NIR band compared to the blue band, and (3) the periodic variation of fractions of clear land, clear ocean, cloudy land, and cloudy ocean in the sunlit hemisphere as Earth rotates. We found that the green vegetation contributes significantly to the NIR global average reflectance when the South and North Americas appear and disappear in the EPIC's field of view. The blue and NIR relationship can be useful for exoplanet research. Clouds impose a strong impact on global spectral reflectance, and the reflectance response to a change in cloud cover depends on whether the change is over land or over the ocean. On average, an increase of 0.1 in cloud coverage will lead to a 7{\%} increase in spectrally integrated global average reflectance.",
keywords = "cloud, DSCOVR, EPIC, reflectance, spectral",
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A Relationship Between Blue and Near-IR Global Spectral Reflectance and the Response of Global Average Reflectance to Change in Cloud Cover Observed From EPIC. / Wen, Guoyong (Corresponding Author); Marshak, Alexander; Song, Wanjuan; Knyazikhin, Yuri; Mõttus, Matti; Wu, Dong.

In: Earth and Space Science, Vol. 6, No. 8, 18.07.2019, p. 1416-1429.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - A Relationship Between Blue and Near-IR Global Spectral Reflectance and the Response of Global Average Reflectance to Change in Cloud Cover Observed From EPIC

AU - Wen, Guoyong

AU - Marshak, Alexander

AU - Song, Wanjuan

AU - Knyazikhin, Yuri

AU - Mõttus, Matti

AU - Wu, Dong

PY - 2019/7/18

Y1 - 2019/7/18

N2 - We performed a detailed analysis of Earth Polychromatic Imaging Camera (EPIC) spectral data. We found that the vector composed of blue and near-infrared (NIR) reflectance follows a counterclockwise closed-loop trajectory from 0 to 24 UTC as Earth rotates. This nonlinear relationship was not observed by any other satellites due to limited spatial or temporal coverage of either low Earth orbit or geostationary satellites. We found that clouds play an important role in determining the nonlinear relationship in addition to the well-known cloud-free land-ocean reflectance contrast in the two bands. The nonlinear relationship is the result of three factors: (1) a much larger cloud-free land-ocean contrast in the NIR band compared to the blue band, (2) significantly larger difference between cloudy land and cloudy ocean reflectance in the NIR band compared to the blue band, and (3) the periodic variation of fractions of clear land, clear ocean, cloudy land, and cloudy ocean in the sunlit hemisphere as Earth rotates. We found that the green vegetation contributes significantly to the NIR global average reflectance when the South and North Americas appear and disappear in the EPIC's field of view. The blue and NIR relationship can be useful for exoplanet research. Clouds impose a strong impact on global spectral reflectance, and the reflectance response to a change in cloud cover depends on whether the change is over land or over the ocean. On average, an increase of 0.1 in cloud coverage will lead to a 7% increase in spectrally integrated global average reflectance.

AB - We performed a detailed analysis of Earth Polychromatic Imaging Camera (EPIC) spectral data. We found that the vector composed of blue and near-infrared (NIR) reflectance follows a counterclockwise closed-loop trajectory from 0 to 24 UTC as Earth rotates. This nonlinear relationship was not observed by any other satellites due to limited spatial or temporal coverage of either low Earth orbit or geostationary satellites. We found that clouds play an important role in determining the nonlinear relationship in addition to the well-known cloud-free land-ocean reflectance contrast in the two bands. The nonlinear relationship is the result of three factors: (1) a much larger cloud-free land-ocean contrast in the NIR band compared to the blue band, (2) significantly larger difference between cloudy land and cloudy ocean reflectance in the NIR band compared to the blue band, and (3) the periodic variation of fractions of clear land, clear ocean, cloudy land, and cloudy ocean in the sunlit hemisphere as Earth rotates. We found that the green vegetation contributes significantly to the NIR global average reflectance when the South and North Americas appear and disappear in the EPIC's field of view. The blue and NIR relationship can be useful for exoplanet research. Clouds impose a strong impact on global spectral reflectance, and the reflectance response to a change in cloud cover depends on whether the change is over land or over the ocean. On average, an increase of 0.1 in cloud coverage will lead to a 7% increase in spectrally integrated global average reflectance.

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KW - EPIC

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SN - 2333-5084

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