M. Blumthaler et al., SIMULTANEOUS SPECTRORADIOMETRY - A STUDY OF SOLAR UV IRRADIANCE AT 2 ALTITUDES, Geophysical research letters, 21(25), 1994, pp. 2805-2808
Spectrally resolved measurements of solar ultraviolet (UV) radiation w
ere made at adjacent mountain top and valley sites, vertically separat
ed by 1 km. Data was collected over a period of 4 days in August 1993
providing simultaneously measured spectra for a range of zenith angles
with both sites in direct sunlight and less than 2 octas of cloud cov
er. As there was no snow cover the local albedo was similar at both si
tes. Irradiances at the mountain site were 9% higher than the valley a
t 370 nm, increasing gradually to 11% at 320 nm. Across the UVB waveba
nd the altitude effect increased dramatically to 24% at 300 nm. The ma
gnitude of the altitude effect was independent of zenith angle, within
the measurement accuracy, for the range z = 30 degrees-70 degrees. Th
ese measured differences between the mountain and valley station can b
e interpreted by model calculations using the corresponding difference
s in air pressure, column ozone and aerosol content.