DEPENDENCE OF SPECTRAL UV IRRADIANCE ON CLOUD AMOUNT AND TYPE

摘要

Spectral solar UV radiation measurements performed at high mountain Sonnblick observatory (47.03 N, 12.57 E, Austria) at 3106 m altitude are presented and the influences of cloud amount and type examined. By analyzing the scan we have elaborated an algorithm for differentiating between scans taken with and without sun obscuration by clouds. By applying scan classification, we were able to refine the obtained UV-cloud relationship. This algorithm was tested for 200 scans; 9 % of cloudy cases were however classified as "sunny". The algorithm failed especially for very thin clouds or for cloud conditions where change occurred in such a way that two ratios were within the specified intervals. In this case, using the absolute levels of UV may help to improve the accuracy of the algorithm.