Journal article
Retrieval of Surface Spectral Emissivity in Polar Regions Based on the Optimal Estimation Method
Journal of geophysical research. Atmospheres, Vol.127(5), e2021JD035677
03/16/2022
DOI: 10.1029/2021JD035677
Abstract
Surface spectral emissivity plays an important role in the polar radiation budget. The significance of surface emissivity in the far‐infrared (far‐IR) has been recognized by recent studies, yet there have been no observations to constrain far‐IR surface spectral emissivity over the entire polar regions. In preparation for the Polar Radiant Energy in the Far‐InfraRed Experiment (PREFIRE) mission, this study develops and assesses an optimal estimation‐based retrieval algorithm to estimate both mid‐IR and far‐IR polar surface emissivity from the future PREFIRE measurements. Synthetic PREFIRE spectra are simulated by feeding the ERA5 reanalysis and a global surface emissivity data set to a radiative transfer model. Information content analysis indicates that the far‐IR surface emissivity retrievals can be more influenced by the atmospheric water vapor abundance than the mid‐IR counterparts. When the total column water vapor is above 1 cm, the far‐IR surface emissivity retrievals largely rely on the a priori constraints. Performance of the optimal‐estimation algorithm is assessed using 960 synthetic PREFIRE clear‐sky radiance spectra over the Arctic. The results based on current best estimate of instrument performance show that all retrievals converge within 15 iterations, the retrieved surface spectral emissivity has a mean bias within ±0.01 and a root‐mean‐square error less than 0.024. The far‐IR surface emissivity retrievals are much more affected by the a priori choice than the mid‐IR ones. A properly constructed a priori covariance can also help to improve the computational efficiency. Influences of other factors for future operational retrievals are also discussed.
Key Points
An optimal‐estimation algorithm for surface spectral emissivity retrieval is developed and assessed for the forthcoming PREFIRE mission
Surface spectral emissivity retrievals in the far‐infrared can be significantly influenced by the atmospheric water vapor abundance
Compared to the mid‐infrared, the far‐infrared surface emissivity retrievals are more affected by the choice of a priori constraints
Details
- Title: Subtitle
- Retrieval of Surface Spectral Emissivity in Polar Regions Based on the Optimal Estimation Method
- Creators
- Yan Xie - Department of Climate and Space Sciences and EngineeringUniversity of MichiganAnn ArborMichiganXianglei Huang - Department of Climate and Space Sciences and EngineeringUniversity of MichiganAnn ArborMichiganXiuhong Chen - Department of Climate and Space Sciences and EngineeringUniversity of MichiganAnn ArborMichiganTristan S L’Ecuyer - University of Wisconsin‐MadisonBrian J Drouin - Jet Propulsion LaboratoryJun Wang - University of Iowa
- Resource Type
- Journal article
- Publication Details
- Journal of geophysical research. Atmospheres, Vol.127(5), e2021JD035677
- DOI
- 10.1029/2021JD035677
- ISSN
- 2169-897X
- eISSN
- 2169-8996
- Number of pages
- 17
- Grant note
- NASA (80NSSC18K1485)
- Language
- English
- Date published
- 03/16/2022
- Academic Unit
- Civil and Environmental Engineering; Physics and Astronomy; Chemical and Biochemical Engineering
- Record Identifier
- 9984228899602771
Metrics
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