Absorption of solar radiation by the atmosphere as determined using satellite, aircraft, and surface data during the Atmospheric Radiation Measurement Enhanced Shortwave Experiment (ARESE)

Data sets acquired during the Atmospheric Radiation Measurement Enhanced Sh ortwave Experiment (ARESE) using simultaneous measurements from five indepe ndent platforms (GOES 8 geostationary satellite, ER-2, Egrett and Twin Otte r aircraft, and surface) are analyzed and compared. A consistent data set c an be built for selected days during ARESE on the basis of the observations from these platforms. The GOES 8 albedos agree with the ER 2, Egrett, and Twin Otter measured instantaneous albedos within 0.013 +/- 0.016, 0.018 +/- 0.032, and 0.006 +/- 0.011, respectively. It is found that for heavy overc ast conditions the aircraft measurements yield an absorptance of 0.32 +/- 0 .03 for the layer between the aircraft (0.5-13 km), while the GOES 8 albedo versus surface transmittance analysis gives an absorptance of 0.33 +/- 0.0 4 for the total atmosphere (surface to top). The absorptance of solar radia tion estimated by model calculations for overcast conditions varies between 0.16 and 0.24, depending on the model used and on cloud and aerosol implem entation. These results are in general agreement with recent findings for c loudy skies, but here a data set that brings together independent simultane ous observations (satellite, surface, and aircraft) is used. Previous ARESE results are reexamined in light of the new findings, and it is concluded t hat the overcast absorptance in the 0.224-0.68 mu m spectral region ranges between 0.04 +/- 0.06 and 0.08 +/- 0.06, depending on the particular case a nalyzed. No evidence of excess clear-sky absorption beyond model and experi mental errors is found.