Abstract
The broad band spectral measurements of the incident and reflected shortwave radiation were carried out on the snow cover at Mizuho Station, East Antarctica under the POLEX-South program during 1979 and 1981. Diurnal, daily and seasonal variations of both the global solar radiation and albedo were analyzed against two spectral regions, solar zenith angle and cloud cover, with a special intention to the interaction between the global radiation and albedo.
The global radiation was large compared to that at the normal mid-latitude station. The atmospheric transmittance was high about 0.75 to 0.80 in the average in summer months because of small amount of atmospheric molecules, aerosols and water vapor. The diffuse radiation from a clear sky, which was similar to the Rayleigh scattering, was about twice as large as that for the place of 0% albedo owing to the high surface albedo through the multiple reflection between the snow surface and atmospheric layer. The effect of clouds to reduce the global radiation was small also on account of the multiple reflection, especially in the visible spectral region. The effect of drifting snow was also examined.
The snow albedo for the clear sky was about 0.8 on the daily average in the total wavelength region of the solar radiation. The albedo was higher than 0.95 in the visible region and about 0.66 in the near infrared under the clear sky. The cloudy sky albedo was higher than the clear sky albedo on account of the variation of spectral distribution of the incident solar flux. The solar zenith angle dependence of the albedo was various owing to the micro and macroscale snow surface conditions, however, mostly the albedo became high when the solar elevation became low. The measured albedo was compared to the theoretical albedo calculated from a radiative transfer model, and a good accordance was found on the average.
