HR: 1330h
AN: A12B-0086    [PDF]
TI: Further Developments in Closure Experiments for Surface Diffuse Irradiance Under Cloud-free Skies at a Continental Site
AU: * Halthore, R N
EM: halthore@nrl.navy.mil
AF: Naval Research Laboratory, Code 7228 4555 Overlook Ave., SW, Washington, DC 20375 United States
AU: Miller, M A
EM: miller@bnl.gov
AF: Brookhaven National Laboratory, Earth System Science Division Bldg. 490D, Upton, NY 11973 United States
AU: Ogren, J A
EM: John.A.Ogren@noaa.gov
AF: NOAA Climate Monitoring and Diagnostic Laboratory,, 325 Broadway R/CMDL1, Boulder, CO 80303 United States
AU: Sheridan, P J
EM: Patrick.Sheridan@noaa.gov
AF: NOAA Climate Monitoring and Diagnostic Laboratory,, 325 Broadway R/CMDL1, Boulder, CO 80303 United States
AU: Stoffel, T L
EM: Stoffel@nrel.gov
AF: National Renewable Energy Laboratory, 1617 Cole Blvd, Golden, CO 80401-3393 United States
AB: Problems with measurements of components of shortwave radiation at the surface using traditional pyranometers ("black" or the single element pyranometer) including zero-offsets, have led to the recommendation of the use of "black and white" pyranometers (B\&W) whose inherent superiority arises from low thermal inertia of the `cold junction'. Here we discuss closure experiments for direct and diffuse surface irradiances measured with the shaded and ventilated B\&W Eppley Model 8-48 pyranometers under cloud-free skies at DOE's ARM site and which are compared with radiative transfer model calculated values. For the measurements in 2002, calculations of irradiance utilizing surface-measured aerosol single scattering albedo (SSA) agree with that measured to within the mutual uncertainties. For the days in 2001 and 2003, the modeled irradiance values agree with that measured only if highly absorbing aerosols of SSA ~0.7, well below surface measured SSA, are used. For measurements in 2002 and 2003 modeled diffuse/direct irradiance ratios continue to exceed those measured using a silicon detector-based radiometer (Multi-Filter Rotating Shadowband Radiometer) for wavelengths in the visible and near-IR, suggesting problems with either (i) measurements and/or (ii) model estimates of atmospheric, specifically, aerosol, absorption. A detailed study is therefore required to establish the role of aerosol absorption in shortwave radiative transfer.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0360 Transmission and scattering of radiation
DE: 0365 Troposphere--composition and chemistry
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting