A 4-channel spectral pyranometer was developed and applied to the estimation of the aerosol absorption index in the vertical air column. Ground-based observations were carried out from June 1984 to May 1985 in the suburbs of Sendai, Japan with this instrument and the spectral pyrheliometer (sunphotometer). A newly developed algorithm was applied to the data of these observations to determine the aerosol absorption index. Numerical simulations showed that our algorithm can retrieve the aerosol single scattering albedo and the ground surface albedo separately from the data of the aerosol optical thickness and downward flux without detailed information on the aerosol size distribution. The obtained values of the aerosol absorption index were within the range from 0.01 to 0.03.Several aircraft observations were also performed over Nagoya, Japan, with two spectral pyranometers and a scanning radiometer (aureolemeter) on a Cessna 206 aircraft. Vertical profiles of the aerosol scattering optical thickness, aerosol size distribution, and upward and downward fluxes were obtained from these observations. Comprehensive radiative transfer calculations showed that the data were quite consistent with each other and the aerosol absorption index can be determined in order to fit the calculated downward fluxes with observed values. The values of the index of absorption in the ranges of 0.003–0.017 and 0.008–0.023 were obtained for the visible and the near infrared spectral regions, respectively.
Weitere Kapitel dieses Buchs durch Wischen aufrufen
- Estimation of the Aerosol Absorption Index from Spectral Measurements of the Solar Radiation Flux
- American Meteorological Society