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Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/196

Title: Ultraviolet (UV) Radiation and its physical Modulating Factors in Africa Based on TOMS and NOAA Polar Orbiting Satellites
Authors: Gemechu, Fanta
Advisors: Abebe Yeshanew (PhD)
Copyright: 2007
Date Added: 11-Oct-2007
Publisher: Addis Ababa University
Abstract: Ultraviolet radiation is the main source of energy for the photochemical reaction and dynamics in the stratosphere and ionosphere. It is also one of the main sources of energy required for the evolution of animals and plants. The method used to make people aware the risks related to UV is using a calculation of the amount of daily irradiance, which is called dose rate. This dose rate then is changed to UV index (UVI). Erythermal UV radiation (UVery) is the integrated solar spectrum over the effective biological response to UV wavelengths on the ground between 295-400 nm. This effective biological response is called action spectrum. The action spectrum is the normalized UV amount, which affects the health of animals and plants or biosphere in general. The value of UVI in Africa is 4 to 9, moderate to high overall. This is due to the tropical nature of most parts of Africa. The trend of UV radiation in Africa shows significant decrease in the year from 1980 to 1992 and a slight increase in recent years from 1997 to 2002. The ozone amount on the other hand is increasing in Africa. The variability of ozone in tropical Africa is relatively stable. The aerosol index in Africa is generally decreasing. UV, aerosols and ozone do not show high seasonal variability in this part of the continent. The study and understanding of UV and its determining factors in Africa hardly exists. Here attempts are made to associate UV with these determining factors. UV and ozone established 41% of the total variability in the surface UV in Africa. Clouds show 31% variability in the surface UV and aerosols established only 7% total surface UV determination.
Description: A Thesis Submitted to Addis Ababa University, Faculty of Science, Physics Department for the partial fulfillment of Master of Science degree for physics
URI: http://hdl.handle.net/123456789/196
Appears in:Thesis - Physics

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