Journal article
A pilot study of shortwave spectral fingerprints of smoke aerosols above liquid clouds
Journal of quantitative spectroscopy & radiative transfer, Vol.221, pp.38-50
12/2018
DOI: 10.1016/j.jqsrt.2018.09.024
Abstract
•Capability of hyperspectral measurements for retrieving properties of aerosols above water cloud is analyzed.•Analytical calculation of measured radiance with respect to the principal components of smoke particle index of refraction is developed.•Comparing with MODIS, hyperspectral data doubles the information for retrieving 5 additional variables•Hyperspectral data provides strong constraints for qualifying radiative heating of aerosols above cloud
Absorbing aerosols like smoke heat the atmosphere by absorbing solar radiation, and such heating is enhanced when aerosols are above liquid clouds. To reduce uncertainty in estimates of the aerosol radiative forcing, it is desirable to characterize the size, index of refraction, optical depth, and altitude of smoke aerosols and underlying cloud droplets. While past work with remotely sensed multi-spectral data have made progress toward such characterization, it remains unclear if those radiatively important parameters can be fully and simultaneously retrieved from shortwave hyperspectral measurements. This issue is studied here first by examining the spectral fingerprints of above-cloud aerosols in the shortwave region (wavelength from 330 nm to 4000 nm) using hyperspectral radiative transfer simulations. These simulations are further explored to analyze the information content for hyperspectral inversion of aerosol and cloud optical depths as well as their microphysical properties over an ocean surface. The analysis shows that the Moderate Resolution Imaging Spectroradiometer (MODIS), with limited spectral bands in the solar spectrum, has partial information required for retrieving the optical depth and the effective radius of smoke and cloud. In contrast, hyperspectral measurements have about 5 extra pieces of information (double the degrees of freedom for signals of MODIS), allowing for the retrieval of additional aerosol and cloud microphysical parameters, including the smoke layer height above cloud, the imaginary part of smoke refractive index, and partially the effective variance of cloud droplet size. Thus, hyperspectral measurements can provide valuable constraints on heating rate estimates of absorbing aerosols above clouds.
Details
- Title: Subtitle
- A pilot study of shortwave spectral fingerprints of smoke aerosols above liquid clouds
- Creators
- Xiaoguang Xu - Department of Chemical and Biochemical Engineering, Center of Global and Regional Environmental Studies, and Informatics Initiative, University of Iowa, Iowa City, IA, USAJun Wang - Department of Chemical and Biochemical Engineering, Center of Global and Regional Environmental Studies, and Informatics Initiative, University of Iowa, Iowa City, IA, USAJing Zeng - Department of Chemical and Biochemical Engineering, Center of Global and Regional Environmental Studies, and Informatics Initiative, University of Iowa, Iowa City, IA, USAWeizhen Hou - Department of Chemical and Biochemical Engineering, Center of Global and Regional Environmental Studies, and Informatics Initiative, University of Iowa, Iowa City, IA, USAKerry G Meyer - Climate and Radiation Lab, NASA Goddard Space Flight Center, Greenbelt, USASteven E Platnick - Climate and Radiation Lab, NASA Goddard Space Flight Center, Greenbelt, USAEric M Wilcox - Desert Research Institute, Reno, NV, USA
- Resource Type
- Journal article
- Publication Details
- Journal of quantitative spectroscopy & radiative transfer, Vol.221, pp.38-50
- Publisher
- Elsevier Ltd
- DOI
- 10.1016/j.jqsrt.2018.09.024
- ISSN
- 0022-4073
- eISSN
- 1879-1352
- Grant note
- DOI: 10.13039/100000104, name: National Aeronautics and Space Administration, award: NNX17AF78G; name: Atmospheric Composition Spectral Climate Signal Program, award: NNX17AF77G; DOI: 10.13039/100000006, name: Office of Naval Research, award: N00014-16-1-2040
- Language
- English
- Date published
- 12/2018
- Academic Unit
- Physics and Astronomy; Chemical and Biochemical Engineering; Iowa Technology Institute; Civil and Environmental Engineering
- Record Identifier
- 9984104812202771
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