Assessment of Erythemal UV Level in Nepal Based on Solar UV Estimates from Total Ozone Mapping Spectrometer |
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Authors: | Binod Kumar BHATTARAI Berit KJELDSTAD and Trond Morten THORSETH |
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Institution: | Department of Engineering Science and Humanities, Pulchowk Campus, Institute of Engineering, Tribhuvan University, Kathmandu, Nepal,Norwegian University of Science and Technology, N~$7491$ Trondheim, Norway,Sor Trondelag University College, N7004 Trondheim, Norway |
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Abstract: | Nepal lies on the southern slope of Himalaya in Asia. In a width ranging
between 150 and 250 km, the altitude varies greatly from about 100 m at its
southern border to a maximum of 8848 min the northern part. Like the
variation in altitude, climatic condition varies quite a lot. Long-term
monthly mean erythemal UV daily dose values for Nepal are evaluated using
Total Ozone Mapping Spectrometer (TOMS) estimation from the time of its
overpass between 1996 and 2003. The results are presented as summer and
winter maps of mean UV levels in each satellite grid. The mean winter
erythemal UV daily dose ranges between 2.1 and 3.6 kJ m-2 whereas
summer values are found to lie between 4.6 and 9.7 kJ m-2. The altitude
variation increases the UV levels by about 0.2 kJ km-1 in winter
months, and 0.9 kJ km-1 in summer. A multiyear monthly average
erythemal daily dose in most of the areas shows that the summer value is
about three times higher than that in winter. Although year-to-year
variation is not pronounced in high- and mid-elevation regions, UV levels
seemed to decrease from 1997 to 2002 in the southern part of the country in
the low elevation region by about 5.35%. Due to the combined effects of
the altitude, low ozone concentration in the troposphere, and thin air,
surface UV radiation at higher altitudes is found to be higher than in the
surrounding regions. |
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Keywords: | UV daily dose TOMS altitude effect UV maps |
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