| Summary: | During a cruise on the USCGC POLAR SEA from Hobart, Tasmania to McMurdo, Antarctica, continuous radiation measurements were carried out; the global, UV-A and UV-B are being discussed in this paper. As we were performing the measurements on a moving platform, spot measurements can be incorrect, however, for hourly means the validity was confirmed. It was found that the radiation levels decreased at noon when going South, however, the mean daily flux increased on average, as the reduced radiation at noon was overcompensated by longer day length. For the day-to-day variations, the amount of cloudiness was of greatest importance. The mean value of the clearness index Kt (total transmissivity) was found to be 0.51, a somewhat low value, which was caused by the high mean amount of cloudiness, mostly consisting of stratus. The mean clearness index was 0.74 for clear skies and 0.38 for overcast conditions, while individual values varied even more. The UV radiation can be related to the global radiation. However, correlation coefficients improved substantially when the analyses were done for different cloudiness classes. Clouds produced the largest reduction for the global radiation
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