A More Transparent Infrared Window
Journal Article
·
· Journal of Geophysical Research. Atmospheres
- Atmospheric and Environmental Research, Lexington, MA (United States); Atmospheric and Environmental Research
- Atmospheric and Environmental Research, Lexington, MA (United States)
- NOAA/Global Systems Laboratory, Boulder, CO (United States)
- California Institute of Technology (CalTech), Pasadena, CA (United States)
- University of Oklahoma School of Meteorology, Norman, OK (United States)
- Columbia University, New York, NY (United States)
The infrared window region (780–1,250 cm–1, 12.8 to 8.0 μm) is of great importance to Earth's climate due to its high transparency and thermal energy. We present here a new investigation of the transparency of this spectral region based on observations by interferometers of downwelling surface radiance at two DOE Atmospheric Radiation Measurement program sites. We focus on the dominant source of absorption in this region, the water vapor continuum, and derive updated values of spectral absorption coefficients for both the self and foreign continua. Our results show that the self continuum is too strong in the previous version of Mlawer-Tobin_Clough-Kneizys-Davies (MT_CKD) water vapor continuum model, a result that is consistent with other recent analyses, while the foreign continuum is too weak in MT_CKD. In general, the weaker self continuum derived in this study results in an overall increase in atmospheric transparency in the window, although in atmospheres with low amounts of water vapor the transparency may slightly decrease due to the increase in foreign continuum absorption. These continuum changes lead to a significant decrease in downwelling longwave flux at the surface for moist atmospheres and a modest increase in outgoing longwave radiation. The increased fraction of surface-leaving radiation that escapes to space leads to a notable increase (~5–10%) in climate feedback, implying that climate simulations that use the new infrared window continuum will show somewhat less warming than before. This study also points out the possibly important role that aerosol absorption may play in the longwave radiative budget.
- Research Organization:
- Atmospheric and Environmental Research, Lexington, MA (United States)
- Sponsoring Organization:
- National Aeronautics and Space Administration (NASA); National Oceanic and Atmospheric Administration (NOAA); National Science Foundation (NSF); USDOE Office of Science (SC), Biological and Environmental Research (BER)
- Grant/Contract Number:
- 89243019SSC000034; SC0018296
- OSTI ID:
- 2478012
- Journal Information:
- Journal of Geophysical Research. Atmospheres, Journal Name: Journal of Geophysical Research. Atmospheres Journal Issue: 22 Vol. 129; ISSN 2169-897X
- Publisher:
- American Geophysical Union; WileyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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