Experimental investigation of variability of ultraviolet fluxes at the earth's surface

Abstract

Some results of two years of regular measurements of UV radiation at the earth's surface in Siberia (56.5o N, 85o E) are given. It is shown that the presence of snow cover increases the UV irradiation of the earth by scattered radiation by 9–15%. In cloudless but windy weather, quasi-periodic fluctuations of UV irradiation with periods of 5–15 min and with fluctuation swings of 1–10% are observed. Low-level, heavy cloudiness in summer considerably reduces (by an average of 30–35%) UV irradiation, especially when the sun is low (down to 30o). Mid-and upper-level clouds increase the UV irradiation of the earth by scattered radiation. When the sun is high (30–50o) and there is heavy cloudiness, this increase can reach 28% in the UV-A spectral range.