Far-infrared surface emissivity and climate

Journal Article · Mon Nov 03 00:00:00 EST 2014 · Proceedings of the National Academy of Sciences of the United States of America

DOI:https://doi.org/10.1073/pnas.1413640111· OSTI ID:1221842

Feldman, Daniel R. ^[1]; Collins, William D. ^[2]; Pincus, Robert ^[3]; Huang, Xianglei ^[4]; Chen, Xiuhong ^[4]

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1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States)
3. Univ. of Colorado, Boulder, CO (United States)
4. Univ. of Michigan, Ann Arbor, MI (United States)

Presently, there are no global measurement constraints on the surface emissivity at wavelengths longer than 15 μm, even though this surface property in this far-IR region has a direct impact on the outgoing longwave radiation (OLR) and infrared cooling rates where the column precipitable water vapor (PWV) is less than 1 mm. Such dry conditions are common for high-altitude and high-latitude locations, with the potential for modeled climate to be impacted by uncertain surface characteristics. This paper explores the sensitivity of instantaneous OLR and cooling rates to changes in far-IR surface emissivity and how this unconstrained property impacts climate model projections. At high latitudes and altitudes, a 0.05 change in emissivity due to mineralogy and snow grain size can cause a 1.8–2.0 W m⁻² difference in the instantaneous clear-sky OLR. A variety of radiative transfer techniques have been used to model the far-IR spectral emissivities of surface types defined by the International Geosphere-Biosphere Program. Incorporating these far-IR surface emissivities into the Representative Concentration Pathway (RCP) 8.5 scenario of the Community Earth System Model leads to discernible changes in the spatial patterns of surface temperature, OLR, and frozen surface extent. The model results differ at high latitudes by as much as 2°K, 10 W m⁻², and 15%, respectively, after only 25 y of integration. The calculated difference in far-IR emissivity between ocean and sea ice of between 0.1 and 0.2, suggests the potential for a far-IR positive feedback for polar climate change.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 1221842
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America, Vol. 111, Issue 46; ISSN 0027-8424
• Publisher: National Academy of Sciences, Washington, DC (United States)
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
climate change
positive feedback
emissivity
remote sensing
polar amplification