Evaluation of EPIC oxygen bands stability with radiative transfer simulations over the South Pole

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dc.contributor.authorZhou, Yaping
dc.contributor.authorZhai, Peng-Wang
dc.contributor.authorYang, Yuekui
dc.date.accessioned2024-03-27T13:26:03Z
dc.date.available2024-03-27T13:26:03Z
dc.date.issued2023-07-30
dc.description.abstractThe Earth Polychromatic Imaging Camera (EPIC) onboard the Deep Space Climate Observatory (DSCOVR) satellite orbiting the Sun at the Lagrange-1 point was launched without onboard calibration systems. Vicarious calibration is conducted for 8 of the 10 UV/VIS/NIR channels using other low earth orbiting satellite instruments, while its two O₂ bands (688 nm and 764 nm) rely on indirect moon-view calibrations because the same narrow-band O₂ bands are not readily available from other in-flight instruments. This study compares EPIC measurements from the four O₂ bands aiming at examining sensor stability over a uniquely suited location, i.e., the permanently snow-covered South Pole. The study utilizes radiative transfer model simulations with in-situ atmospheric soundings taken at South Pole during months of December and January from 2015 to 2022. The absolute discrepancy between the model simulations and observations is less than 1.0% for the two reference bands, but 5.75% and 15.63% for the 688 nm, and 764 nm absorption bands, respectively. The simulated A-band and B-band ratios are 16.09% and 4.74% higher than that from the observations. Various sensitivities are conducted to estimate possible contributions to the discrepancies from input atmospheric profiles, spectral surface albedos and surface BRDF. While none of the input uncertainties is likely to account for the large discrepancies in the oxygen absorption bands, a small shift in the instrument response function could be the main reason for these biases. On the other hand, the model simulations are able to capture systematic variations with observed angular measurements and explain the multi-year trends found in observed O₂ band ratios due to satellite orbit shifting. When model simulated contributions from the angle variations are deducted from the observed O₂ band ratios, the residual O₂ band ratios are found to be stable since 2015.
dc.description.sponsorshipThe authors thank Drs Alexander Marshak, Alexi Lyapustin, Xiaoguang Xu, Omar Torres for helpful discussions and two anonymous reviewers for their constructive coments. The work was supported through grants by the NASA DSCOVR program managed by R. S. Eckman. The authors appreciate the support of the University of Wisconsin-Madison and Madison College AMRDC for the South Pole data set, data display, and information, NSF grant number 1951720 (UW) and 1951603 (MATC). The Ozonesonde data is obtained from NOAA global monitoring laboratory.
dc.description.urihttps://www.sciencedirect.com/science/article/pii/S0022407323002558
dc.format.extent11 pages
dc.genrejournal articles
dc.identifierdoi:10.13016/m2au1q-qqze
dc.identifier.citationZhou, Yaping, Peng-Wang Zhai, and Yuekui Yang. “Evaluation of EPIC Oxygen Bands Stability with Radiative Transfer Simulations over the South Pole.” Journal of Quantitative Spectroscopy and Radiative Transfer 310 (December 1, 2023): 108737. https://doi.org/10.1016/j.jqsrt.2023.108737.
dc.identifier.urihttps://doi.org/10.1016/j.jqsrt.2023.108737
dc.identifier.urihttp://hdl.handle.net/11603/32660
dc.language.isoen_US
dc.publisherElsevier
dc.relation.isAvailableAtThe University of Maryland, Baltimore County (UMBC)
dc.relation.ispartofUMBC Faculty Collection
dc.relation.ispartofUMBC Joint Center for Earth Systems Technology (JCET)
dc.relation.ispartofUMBC Physics Department
dc.relation.ispartofGESTAR II
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.
dc.rightsPublic Domain
dc.rights.urihttps://creativecommons.org/publicdomain/mark/1.0/
dc.subjectRemote sensing
dc.subjectCalibration
dc.subjectDSCOVR
dc.subjectEPIC
dc.subjectRadiative transfer model simulation
dc.subjectSouth Pole
dc.titleEvaluation of EPIC oxygen bands stability with radiative transfer simulations over the South Pole
dc.typeText
dcterms.creatorhttps://orcid.org/0000-0002-7812-851X
dcterms.creatorhttps://orcid.org/0000-0003-4695-5200

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