Observations Surface Forcing from WMGHGs at the ARM Southern Great Plains and North Slope of Alaska sites

 

Authors

Daniel Feldman — Lawrence Berkeley National Laboratory
Jonathan Gero — University of Wisconsin
David D. Turner — NOAA Earth System Research Laboratory
William D. Collins — Lawrence Berkeley National Laboratory
Margaret S. Torn — Lawrence Berkeley National Laboratory

Category

Radiation

Description

The physics by which well-mixed greenhouse gases (WMGHGs) including CO2 and CH4 influence the infrared energy balance of the surface are understood through spectroscopy and radiative transfer models that ultimately inform surface forcing estimates in climate models. However, given the frequency with which the spectroscopy and radiative transfer models are updated and uncertainties in how clouds affect this forcing, it is important to confront model forcing estimates with observations. We analyze decadal-length records of spectroscopic measurements from the AERI instrument at the ARM Southern Great Plains and North Slope of Alaska sites and control for contributions of temperature and water vapor with radiosondes to derive a time-series of surface radiative forcing from CO2. This time-series shows a secular trend of 0.3 W/m2/decade and significant seasonal and diurnal variability of 0.5 W/m2. We also discuss prospects for determining surface forcing from CH4 and a path forward for using ARM Best Estimates of clouds to formally assess the role of clouds in modulating surface forcing by WMGHGs.

Lead PI

Margaret S. Torn — Lawrence Berkeley National Laboratory