Atmos. Chem. Phys. Discuss., 11, 12487-12518, 2011
© Author(s) 2011. This work is distributed
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Using surface remote sensors to derive mixed-phase cloud radiative forcing: an example from M-PACE
G. de Boer1, W. D. Collins1, S. Menon1, and C. N. Long2
1Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA
2Pacific Northwest National Laboratory, 902 Batelle Boulevard, Richland, WA 99352, USA

Abstract. A suite of ground-based measurements are used in conjunction with a column version of the Rapid Radiative Transfer Model (RRTMG) to derive the cloud radiative forcing of mixed-phase stratiform clouds observed during the United States Department of Energy (US DOE) Atmospheric Radiation Measurement (ARM) Mixed-Phase Arctic Clouds Experiment (M-PACE) between September and November of 2004. In total, sixteen half hour time periods are reviewed due to their coincidence with radiosonde launches. Cloud liquid (ice) water paths are found to range between 11.0–366.4 (0.5–114.1) gm−2, and cloud physical thicknesses fall between 286–2075 m. Combined with temperature and hydrometeor size estimates, this information is used to calculate surface radiative fluxes using RRTMG, which are demonstrated to generally agree with measured fluxes from surface-based radiometric instrumentation. Errors in longwave flux estimates are found to be largest for thin clouds, while shortwave flux errors are generally largest for thicker clouds. Cloud radiative forcing is calculated for all profiles, and illustrates the dominance of the longwave component during this time of year, with net cloud forcing generally between 50 and 90 Wm−2. Finally, sensitivity of calculated surface fluxes to droplet effective radius, surface albedo and surface temperature are tested, with changes in minimum droplet size between 3.5 and 10 μm altering the surface shortwave flux by up to 50 Wm−2, and changes in surface albedo between 0.5 and 0.95 altering surface shortwave fluxes by up to 85 Wm−2.

Citation: de Boer, G., Collins, W. D., Menon, S., and Long, C. N.: Using surface remote sensors to derive mixed-phase cloud radiative forcing: an example from M-PACE, Atmos. Chem. Phys. Discuss., 11, 12487-12518, doi:10.5194/acpd-11-12487-2011, 2011.
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