Calculation Solar Radiation Transmission in Clear Sky between 0.45 and 0.95 Microns

摘要

In this paper, the spectral characteristic of solar radiation, which reaches earth surface through atmosphere, and the spectral characteristic of sky background, which is formed by molecular scattering, all of them are detailed discussed at different solar zenith angles and observation azimuth angle. The atmosphere is considered clear, that is says no clouds and aerosols. All computations base on the Rayleigh scattering law, Hitran2000 and its database. The atmosphere is divided into 32 layers extending to an altitude of 100km height as Standard Atmosphere Model. The total brightness of scattering is summation of brightness in each layer. The wavelength varies from 0.45 μm to 0.95 μm in the calculation. The primary reasons for choosing this band are listed followed: (1) solar radiation in this band is stronger than other band, (2) molecular scattering is more stronger in this band, (3) A few absorption regions of water vapor, such as 0.59 μm, 65 μm, 0.73 μm, 0.81 μm, and 0.94 μm, are included in this band. The method for calculating in this band is representative and fit for all spectra regions. The paper got figures of brightness varies by observation azimuth angles at wavelength 0.6 μm, solar zenith angle 45°. The calculation limits the solar azimuth angle at 0°. The result is analyzed and compared with the result acquired by Bell and his co-workers at Cocoa Beach, Florida, in 1960. The result shows brightness varied by solar zenith angles and observation azimuth angles is according with the actual observation data. The result has bright future in getting optical characteristic of target in atmosphere.