Measurements of ultraviolet solar- and sky-radiation intensities in high latitudes

Abstract

Data are given on t he intensity of the b iologically effe ctive ultraviolet radiation, of wavelengths 3200 A and shorter, from t h e sun and t he entire sky, incident on a horizontal plane, under various meteorological condit ions, in high latitudes. These data were secured by means of a photoelectric cell and automatic recording app aratus, whereby a continuous record of ultraviolet intensities, in absolute value, was obtained during the voyage of t he Louise A. Boyd Ar ctic Expedition, up the west coast of Greenland to Etah (lat. 78.3° N) and down the coast of Baffin Land and Labrador.The ou tstanding results of this survey are, t hat, for the same solar h eights, in the highest latitudes visited (78° N) the ultraviolet intensit ies appear to b e somewhat higher than in latitude 62° N , but somewhat lower than in latit ude 39° N (Washington), in agreement with expectat ion, taking into consideration the distribution of ozone in the stratosphere with lat it ude and t he season . I n the highest latitudes, at the noon hour, on the clear est days, in mid-summer, th e intensity of the ultraviolet solar and sky radiat ion ranged from 30 to 40

Measurements of ultraviolet solar radiation in Washington, 1936 to 1942

“…1 of r ef. [4]). Correcting for solar distance, the ultraviolet intensities in March, relative to September, would b e reduced by about 2 percent.…”

“…1 of ref. [4]), also must be considered. Since the time of making the hereindescribed measurements, from season to season, could not be selected (for example, there were but few clear days during the summer of 1940-see fig.…”

“…This was repeatedly observed in the measurements of 1942 ( fig. 10), the most of which were made in connection with the calibration of a photoelectric cell used for measuring ultraviolet solar and sky radiation incident on a horizontal plane (4,11]. In the course of these measurements of solar and sky radiation it was repeatedly observed (by shadowing the receiver from the direct solar rays) that it was only during the noon hours of the clearest days in early summer that the ultraviolet radiation from the whole sky incident on a horizontal surface was slightly less than the directly incident solar rays, and that when the sky was slightly turbid, the ultraviolet radiation from the whole sky was at least 2.5 times greater than the directly incident solar rays [3,4].…”

“…In these illustrations the scale on the right-hand side is to the nearest rounded numbers. Based upon some preliminary trials [4], it is believed that when satisfactory photoelectric cells are obtainable for use as primary standards, the calibration of meters for measuring ultraviolet solar and sky radiation incident on a horizontal plane will be greatly simplified.…”

“…(b) to secure data required in working out methods of evaluating the biologically effective component of ultraviolet solar radiation [I)-required particularly in one method of standardizing ultraviolet dosage-intensity meters [4,11]; and (c) to determine whether, with the accuracy attainable in the radiometric measurements, the reduction factors (F, G) used in the calculations of ultraviolet intensities, will require modifications with changes in the spectral quality of the biologically effective ultraviolet radiation, which varies with the ozone concentration in the stratosphere, which, in turn, varies with the latitude, the season, the barometric pressure (movements of masses of polar air) and, less systematically, with the sunspot cycle [5,6,18].…”