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Radiative Surface Forcing from CH4 at the North Slope of Alaska and Southern Great Plains Sites

 

Authors

David D. Turner — NOAA- Global Systems Laboratory
Eli Jay Mlawer — Atmospheric and Environmental Research, Inc.
Margaret S. Torn — Lawrence Berkeley National Laboratory
Sebastien Christophe Biraud — Lawrence Berkeley National Laboratory
William D. Collins — Lawrence Berkeley National Laboratory
Jonathan Gero — University of Wisconsin
Daniel Feldman — Lawrence Berkeley National Laboratory

Category

Radiation

Description

Recent increases in atmospheric CH4 have been spatially heterogeneous as indicated by in situ flask measurements and space-borne remote-sensing retrievals from the AIRS instrument, potentially leading to increased radiative forcing. We present an analysis of detailed, specialized measurements at the DOE ARM North Slope of Alaska (NSA) and Southern Great Plains (SGP) sites to derive the time-series of both CH4 atmospheric concentrations and associated radiative implications at highly-contrasting natural and anthropogenic sources. Using a combination of spectroscopic measurements, in situ observations, and ancillary data for the atmospheric thermodynamic state from radiosondes and cloud-clearing from active sounders, we can separate out the contribution of CH4 to clear-sky downwelling radiance spectra and its infrared surface radiative forcing. We find that the trend in the forcing from CH4 since 2005 is of the same magnitude at the trend from rising CO2.