On the spectral dependency of UV radiation enhancements due to clouds in Valdivia, Chile (39.8°S)

摘要: [1] Data gathered with a five-channel radiometer are used to analyze the spectral composition of cloud enhancements and attenuations UV (305, 320, 340, 380 nm) photosynthetically active radiation (PAR) (400–700 at Valdivia, Chile (39.8°S), during summer months within 3 hours from solar noon. Variations referred clear-sky days occurring not too distant dates or obtained as polynomial fit cloud-free periods on partially cloudy days. Photographic images sky were taken simultaneously part radiometric data. Frequency occurrence duration estimated. Most associated cumuliform clouds in dissipation stage while fringes crossing over Sun disk. Both present dependence: first decreasing second increasing toward longer wavelengths. Typical magnitude enhancement 1-min averages for PAR is close 20%, highest values exceeding 40%, 6% 305 nm. Cases well-defined side reflections observed. A weak relation between cover was found: Larger higher enhancements.