Measurements of solar u.v., visible and near i.r. irradiance at 78° N

Spectral measurements of solar radiation in the Arctic during the summer of 1987 were carried out with a double monochromator calibrated in absolute units. Integrated irradiances for parts of the UVB (2900Å-3150Å), UVA (3150Å-4000Å) and the whole measured spectral range (2900Å-8000Å) are tabulated. No irradiance is detected below 3050 Å. The measurements show that the diurnal variation in the UVB is a factor 7 stronger than in the UVA and a factor 6 stronger than for the total measured spectral range. We also find that in the ultraviolet part of the spectrum the diffuse radiation is the dominant component of global irradiance. Under clear sky conditions the measured spectral irradiances are closely reproduced by radiative transfer calculations.