Attenuation of UV-B radiation in the atmosphere: Clouds effect,at Qena (Egypt) |
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| Institution: | 1. Applied Energy Research Group, Technologie Campus Freyung, Deggendorf Institute of Technology, 94078 Freyung, Germany;2. Institute of Spatial Planning and Rural Development, University of Natural Resources and Life Sciences, Vienna, Austria;1. University of Turkish Aeronautical Association, Ankara, Turkey;2. Ankara Yildirim Beyazit University, Department of Aerospace Engineering, Cankiri Caddesi, Cicek Sokak No:3, Ulus, Ankara, Turkey;1. University of Corsica, CNRS UMR SPE 6134, 20250 Corte, France;2. Castelluccio Hospital, Radiotherapy Unit, BP 85, 20177 Ajaccio, France;3. Centre Thermique de Lyon (CETHIL), UMR CNRS 5008, INSA Lyon, France;4. Galatasaray University, Computer Science Department, Çırağan Cad. No: 36, Ortaköy 34357, Istanbul, Turkey;1. Department of Physics, Informatics and Mathematics, University of Modena and Reggio Emilia, Via Campi 213/A, 41125 Modena, Italy;2. Department of Industrial Engineering, University of Bologna, Viale del Risorgimento 2, 40138 Bologna, Italy;1. School of Aeronautic Science and Engineering, Beihang University, Beijing 100191, China;2. Institute of telecommunication satellite, China academy of spacecraft technology, Beijing 100094, China;3. Science and Technology on Advanced Composites Laboratory, BIAM, AVIC Composite Center, AVIC Composite Corporation LTD, Beijing 100095, China;4. AVIC China Helicopter Research and Development Institute, Jingdezhen 333001, China |
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| Abstract: | The effects of clouds (amount, type and height) on the surface UV-B radiation have been investigated at Qena, Egypt (26°17′, 32°10′, 96 m asl) using 2 years data (2004–2005) carried out by South Valley University (SVU)-meteorological research station. Thus, the characteristics of cloud's statistical property during the study period were employed to evaluate the general feature of the region of this study. However, ≈86% of all the observations were ⩽2 octas and the overcast conditions (8 octas) were very rarely over the study region (only 0.2% of all cases). These observations included 10% low-level clouds, 3.16% mid-level clouds and 7.59% high-level clouds. The dominated types of these clouds are stratocumulus (8.9%) and cirrus (5.8%).The hourly values of cloudless sky UV-B radiation (UV-B0) and consequently the cloud modification factor (CMF) were estimated. An empirical model was developed for CMF as a function of the amount of cloud at low- and mid-level and high-level clouds. The correlation coefficients were equal to 0.985 and 0.987, respectively. In addition, a general expression of the CMF for situations those are considered as the effect of different clouds was found. The efficiency of this model has been tested in combination with a cloudless sky empirical model using independent data set. For this purpose, the hourly values of UV-B at selected cloudless and cloudy days were estimated. A good agreement was observed between the measured and the predicted values of our model. The mean value of the correlation coefficients of these selected days was 0.98.In addition, the attenuation of UV-B radiation could be determined by considering low- and mid-level and high-level clouds. The reduction of UV-B radiation as a function of cloud amount was non-linear for the both cases. At cloud amount of 100%, UV-B radiation was reduced by 83% on average by the high-level clouds. |
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