International Journal of Science and Research (IJSR) ISSN (Online): 2319-7064 Index Copernicus Value (2013): 6.14 | Impact Factor (2013): 4.438 Volume 4 Issue 1, January 2015 www.ijsr.net Licensed Under Creative Commons Attribution CC BY Estimation of Solar UV-B Radiation at Visakhapatnam and its Variability with Columnar Ozone N. V. Krishna Prasad 1 , M.S.S.R.K.N.Sarma 2 , S. Ramesh 3 , K.S.D.L.K.Prasad 4 , N. Madhavi 5 1, 2, 3 Department of Physics (G.S.T), GITAM University-Banglore, India 4 Department of Physics, VITS College (Eng).Visakhapatnam, India 5 Department of Statistics, Govt. College (Aut), Rajhamundry, India Abstract: Measurements of solar UV-B radiation in the biological band (280 nm – 320 nm) with the help of ground based UV-B Photometer at VISAKHAPATNAM (17.7 0 N, 83.3 0 E) have been used to develop a simple regression model. The model was developed with measured values of incoming UV-B radiation obtained by UV-B photometer deployed in the Department of Physics, Andhra University (1989-1993) and satellite measured column ozone as inputs. The model is useful to find unknown values by providing known inputs. Hence satellite measured values of columnar ozone for the period 2005-2013 were provided as one input, solar zenith angle as another input and incoming UV-B radiation for this period was estimated. With the estimated values of incoming solar UV- B radiation an attempt was made to analyze the dependence of incoming solar UV-B radiation on columnar ozone and also its dependence on solar zenith angle and wavelength. Keywords: UV-B, Columnar Ozone, Solar Zenith Angle, Regression Model 1. Introduction Reduction of stratospheric ozone and enhancement in the ground reaching solar UV-B radiation in the biological band (280-320 nm) has gained wide importance due to its adverse impact on the human beings, animals and plants. In the late 70’s it has been reported that a reduction of stratospheric ozone by 1% would lead to 2% increase in UV-B radiation (Cutchis, 1974). This may vary depending on specific wavelength, season and solar zenith angle of the sun (Bias et. al 1994). The effect of increased exposure to UV-B radiation by a human body depends on the physical properties of this radiation. The UV-B radiation does not penetrate far into the body as it is absorbed in the superficial tissue layers of 0.1 mm depth (Longstreth et al., 1998). However it affects skin and eyes. It causes effects like erythema, sunburn and tanning which is due to 0.5 % of the incident radiation. The dependence of these effects on wavelength is given by Everett et al.(1966). It also has effect on the immune system, aging of the skin, eyes and cause skin cancer. Previous studies indicate that these effects do not increase with an increase of incoming UV-B radiation. It is estimated that the number of excess skin cancers (1980 to 2100) due to this radiation increases from 100 to 500 million per year (Longstreth. et al., 1998). In addition to these effects of UV-B radiation on human society, it also shows significant influence on animals, agriculture, forest, plants and crops (Caldwell et al., 1998). Middleton et al., (2001) reported that amphibian declines occur due to the increase in UV-B exposure. It is reported that the physiological and developmental processes of plants are affected by UV-B radiation. Since the first reports of stratospheric ozone reduction over 20 years ago (Johnston 1971), effects of UV- B radiation on higher plants have been the subject of considerable research. Enhanced UV-B radiation can have many direct and indirect effects on plants including inhibition of photosynthesis, DNA damage, changes in morphology, phenology and biomass accumulation. UV-B radiation can alter both the time of flowering as well as the number of flowers in certain species. (Caldwell et al., 1998). In addition to these effects, UV-B radiation has its influence on air quality (Tang et al., 1998), materials (Andrady et al., 1998) and also on biogeochemical cycles (Zepp et al., 1998). To assess the significant changes in the incoming biological ultraviolet radiation with ozone depletion the values of RAF (Radiation Amplification Factor) are calculated for various effects like Erythema, DNA and Skin Cancer etc. It is a known fact that the increase in UV-B radiation strongly depends on wavelength( in addition to its dependence on solar zenith angle, ozone etc) and to assess a particular biological effect an action spectrum that gives the sensitivity of wavelength dependent UV change is to be considered.( Madronich et al., 2003). Even instruments like UV-B meters are developed which can measure some of the biological effects with high sensitivity (Maryn Moris and Daniel Berger 1993. The variation of biologically effective UV-B radiation with respect to ozone is given by RAF which is defined as the percentage increase in the incoming biological UV–B radiation for a given species that would result from a 1 % decrease in the amount of total Columnar ozone. (Madronich et al., 1998). RAF values indicate the sensitivity of a particular biological effect to the corresponding change in ozone. Madronich et al., 1998 reported the values of RAF’s for different biological effects with the help of different action spectra. They also studied the trends in biologically active radiation (Erythema) by using the action spectrum suggested by Mc Kinlay and Diffey and TOMS ozone data (1978-1992) for various latitudes and reported that for latitudes lying between 10 to 20 degrees North where the current station Visakhapatnam (17.7 0 North) lies have zero % change per decade and for Paper ID: SUB1545 870