GROUND-LEVEL SPECTRAL DISTRIBUTION OF SOLAR DIRECT-NORMAL IRRADIANCE AND MARINE AEROSOL ATTENUATION COEFFICIENTS AT REUNION ISLAND

The ground-level spectral distribution of direct solar irradiance at Reunion Island was measured for six bands covering the spectrum of solar radiation. The measurements, distributed over one year, were made under clear sky conditions with a pyrheliometer (Eppley, NIP) and six large pass-band flat filters. Good stability of spectral irradiances as a function of solar height allows us to propose approximate relationships which significantly characterize the irradiance into each spectral band. Measurements at Reunion vary significantly from data obtained with the same apparatus in a northern hemisphere continental area (Lyon). The determination of aerosol attenuation coefficients, for different spectral bands, allows the establishment of a mean curve, for these coefficients as a function of wavelength, characteristic of marine aerosols.