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ANNUAL VARIABILITY AND
DISTRIBUTION OF ULTRAVIOLET
INDEX OVER INDIA USING TEMIS
DATA
R. BHATTACHARYA
Department of Environmental Science, University of Kalyani, Kalyani 741235
rinaenv@yahoo.com
S. PAL
Department of Environmental Science, University of Kalyani, Kalyani 741235
sudiptaenv@yahoo.com
A. BHOUMICK
Department of Environmental Science, University of Kalyani, Kalyani 741235
amrita.bhoumick@gmail.com
P. BARMAN
Department of Environmental Science, University of Kalyani, Kalyani 741235
Piyalibarman2912@gmail.com
Abstract
Interlink among surface ultraviolet radiation, climate change, ozone depletion and living creatures make the
necessity of regional based ultraviolet monitoring at ground level for control measures. Annual variation and
seasonal distribution of UVI over Srinagar, New Delhi, Bhopal, Ahmadabad, Kolkata, Mumbai, Pune,
Hyderabad and Chennai in India are examined. Analysis of UVI is performed using TEMIS data from
SCIMACHY for the period July 2002- June 2012. Maximum value 16.73 of UVI is observed at Bhopal during
monsoon season whereas minimum value 2.18 is noted at Srinagar in winter. Seasonal decadal trend are found
to vary from -0.19 to +0.15. UVI is found high in monsoon months for all the observing sites. UVI scale index is
a five graded scale starting from minimal (scale index I) to extreme (scale index V). The analysis shows that
scale index V dominates over Chennai throughout the year.
Key words: Ultraviolet Index, Radiation amplification factor, Attenuation
1. Introduction
Decrease of stratospheric ozone and associated ultraviolet radiation reaching the earth surface has become a
matter of growing concern (Richard and Hudson, 1991; WMO, 2003; Pal, 2010; Prasad et al., 2011;
Bhattacharya and Bhoumick, 2012a). The increase is high in UV-B (280-315) nm and low in UV-A (315-400)
nm. Moreover the changes of environmental ultraviolet index (UVI) vary from place to place depending on
several factors such as incoming solar radiation, sun-earth distance, stratospheric temperature, sky condition,
total column ozone, altitude, latitude and solar zenith angle. UV- C (< 280 nm) is mostly absorbed by ozone,
oxygen and nitrogen molecules before penetrating the earth’s atmosphere where as UV-B are absorbed strongly
by the stratospheric ozone. UV-A is not affected by the atmospheric constituents. The changes UVI with
different physical parameters are represented in Table 1 (Eskes et al., 2003, Grobner et al., 2000, Burrows 1997,
Allart et al., 2004, Lemus-Deschamps et al., 1999, Meloni, et al., 2000). The discovery of ozone hole over
Antarctica in 1985 has knocked the door of the earth to alert about the ground reaching UV radiation which
consists of UV-B and UV-A (Kononakis et al., 2002, Larkin et al, 2000, Bhattacharya et al, 2012). Ultraviolet
photon has both beneficial and detrimental impact on living beings. UV-B photon may damage DNA molecules
and some proteins. On the other hand, it helps to produce vitamin D. Ultraviolet radiation also takes part in
troposphere-stratosphere interaction. The absorption sensitivity of UV radiation by trace gases is particularly
important in polluted environment (Atkinson et al., 1997; Jacobson 1999; Koronakis et al., 2002; Myhre and
Nielsen, 2004; Bias et al., 2005). In highly polluted area, NO2 may attenuate UV-B up to 15% and SO2 upto 8%.
On clear sunny days UV irradiance is about 3% higher over sand than plane. UV radiance is also changed with
soil-vegetation index and surface altitude. It is observed that the increase is about 7-16% per km (Zaratti et al.,
2003; Singh and Singh, 2004).
R. Bhattacharya et al. / International Journal of Engineering Science and Technology (IJEST)
ISSN : 0975-5462
Vol. 4 No.11 November 2012
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Table 1 Change in UVI value with environmental variables
Parameters Change in UVI Parameter Change in UVI
Sun-Earth Distance ± 3% Aerosol Optical Depth ± 5%
Stratospheric Temperature ± 2% Latitude ± 3%
Solar Zenith Angle ± 3% Altitude + 5% per km
Total Column Ozone ± 4% Overcast Cloud − 50%
Ground Albedo (Water, Rock,
Vegetation) +0.04 to +0.09 Scattered Cloud when Solar
Distance is not Occluded upto + 25%
Sulpher dioxide (SO2) -6% to -8% (NO2) Nitrogen dioxide -8% to -15%
Diversity of plant, animal, insect and even human health may be affected by ground ultraviolet radiation for a
minor change of stratospheric ozone. The response of ultraviolet radiation to the depletion of ozone is depicted
in Figure 1. The Figure indicates the radiation amplification factor of the damages of human and plants with 1%
change of total column ozone. The different components of UV also undergo an enhancement of level ranges
from 0.03 to 1.25 unit with 1% decrease of O3 (Setlow 1974; Hader and Worrest, 1991; Kligman and Sayre,
1991; de Gruijl et al., 1993; Anders et al., 1995, Madronich et al., 1998).
Figure 1 Response of Radiation amplification factor (RAF) with UVI Figure 2 Biologically active UV radiation at earth’s
surface
Association among ground reaching UV radiation, climate changes, living beings on earth and ozone have
pointed out the need of monitoring ground UV level. UVI is a technique to estimate degree of UV exposure that
is important for biological response of living beings. Figure 2 shows the dependence of biologically active
exposure radiation on the wavelength (Madronich et al., 1998). Our aim is to analyze UVI over some Indian
stations having different topographic characteristics. In this paper we have also examined the seasonal and
annual variability of UVI over all the sites.
Table 2 Geographical locations of observing sites
Name/Code
assigned Latitude
(ºN) Longitude
(ºE) Altitude
(m) Av.Temperature
High/Low (in ºC) Annual Rainfall
(mm)
Srinagar/S1 34.09 74.79 1730 19.70/07.30 710.0
New Delhi/S2 29.01 77.38 239 31.40/18.20 797.3
Bhopal/S3 23.25 77.42 501 31.58/18.00 1146
Ahmadabad/S4 23.03 72.61 56 34.26/20.58 780.0
Kolkata/S5 22.57 88.34 6.4 31.70/22.20 1800
Mumbai/S6 18.96 72.82 11 31.66/22.16 2422
Pune/S7 18.52 73.84 559 31.50/17.70 741.0
Hyderabad/S8 17.36 78.46 542 32.00/20.20 804.5
Chennai/S9 13.08 80.27 8 33.30/23.80 1391.5
2. Materials and Method
TEMIS data (www.temis.nl) of UV radiation monitoring products from SCIMACHY over nine locations of
India
(Table 2) from July 2002 to June 2012 are used in this study. India being a tropical country, receives large
amount of solar radiation throughout the year.
R. Bhattacharya et al. / International Journal of Engineering Science and Technology (IJEST)
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Vol. 4 No.11 November 2012
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Figure 3 Solar radiation on India [courtesy: Abraham and Luthra, 2011]
Figure 3 gives the annual average insolation over India. Average insolation over the observing sites S1 to S9
varies from 4.4 to 5.8 kWH/m2. UVI gives the degree of ground level UV radiation exposure at noon and its
value gives the indication of precautions needed for sun burn according to International Commission on
Illumination Reference Action Spectrum, (McKinley and Diffy, 1987). Exposure categories of UV radiation
depending on UVI range along with protective measures are depicted in Table 3. However exposure that
produces sun burn takes about 5 to 6 times longer for brown to dark skin in comparison with pale to white skin
(Frederick et al., 1998). Annual variation and distribution of UVI scale in different seasons such as premonsoon
(March, April, May), monsoon (June, July, August), postmonsoon (September, October, November) and winter
(December, January, February) for all the sites are computed from the daily available data during the
investigating period.
Table 3 Ultraviolet exposure scale and control measures
Exposure
Category Minimal Low Moderate High Extreme
Index Scale I II III IV V
UVI range 0-2 3-5 6-7 8-10 >10
Precautions Hat,
Sunglass Hat, Sunglass,
Sunscreen
(SPF 15+)
Hat, Sunglass,
Sunscreen
(SPF 15+),
Umbrella
Hat, Sunglass,
Sunscreen (SPF
15+), Umbrella,
Stay indoor from
10:00 to16:00 hrs
Minimum
outdoor activity
in addition to all
the previous
precautions
3. Results and Discussion
Mean annual variation of UVI averaged over all stations during July 2002-June 2012 is given in Figure 4. It is
observed that UVI is high from June to August and lowest in December. Low ozone concentration after winter
and high after summer months may explain the overall variation of UVI (Correa et al., 2003). UV exposure
level over India on two solstices June 20 and December 22, 2011 are shown in Figure 5. It is observed that UVI
varies from 12 to 16 in June’12
R. Bhattacharya et al. / International Journal of Engineering Science and Technology (IJEST)
ISSN : 0975-5462
Vol. 4 No.11 November 2012
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Figure 4 Mean annual cycle of UVI
Figure 5 The UVI map in summer and winter solstice over India
Figure 6 Time series UVI anomaly (%) at each site
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Vol. 4 No.11 November 2012
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Figure 7 Frequency distribution of UVI index at each site with overall mean annual frequency in a pie diagram
whereas in winter solstice December’11, the range lies between 2 and 8 over India. Figure 6 shows the time
series of UVI anomaly (%) over the observing sites. UVI anomaly shows periodic cycle with high values in July
and low in January. Besides this periodic variation, some stations show slightly different behavior. Cloud cover
in monsoon months is one of the modulating factors of UVI. Hence the anomaly of UVI is high particularly in
July. The anomaly is also high over Srinagar and low over Chennai. The result is agreed with previous studies
(Prasad et al., 1992; Engelsen et al., 2005 Ganguly, 2011).
Table 4 Seasonal distribution of UVI
Name Premonsoon Monsoon Postmonsoon Winter
Srinagar 9.75 ± 2.12 12.14 ± 0.95 6.49 ± 2.32 3.55 ± 1.00
New Delhi 9.91 ± 1.47 11.67 ± 0.71 7.33 ± 1.99 4.65 ± 1.03
Bhopal 11.51 ± 1.10 12.60 ± 6.75 9.00 ± 1.91 6.70 ± 1.21
Ahmadabad 11.36 ± 1.07 12.36 ± 0.72 8.89 ± 1.86 6.61 ± 1.18
Kolkata 11.30 ± 1.04 12.32 ± 0.65 9.12 ± 1.87 6.90 ± 1.19
Mumbai 12.15 ± 0.88 12.71 ± 0.67 9.90 ± 1.65 8.11 ± 1.22
Pune 12.62 ± 0.92 13.06 ± 0.69 10.32 ± 1.69 8.51 ± 1.30
Hyderabad 12.87 ± 0.96 12.72 ± 0.63 10.51 ± 1.57 8.93 ± 1.35
Chennai 12.91 ± 0.87 12.24 ± 0.68 11.15 ± 1.32 10.06 ± 1.35
Distribution of UVI according to different exposure category is shown in Figure 7. Long term trend of ground
level UV-B is a difficult task because of the lack of measurement of absolute intensity. Cloud cover, aerosol
optical depth and surface albedo induce error in the real value. Negetive trends during 1974-85 were found over
United States whereas a positive trend was observed during 1989-93 with same amount of ozone depletion
(DeLuisi and Barnett, 1992, Kerr and McElory, 1993). It is found from the figure that index scale V prevails on
monsoon months for all the sites. Exposure category I and II are the dominating factors only in winter for the
sites S1 and S2 respectively. Average UV level over all the sites is extremely high in monsoon months (Table 4).
Hence precautions to prevent harmful effect of UV-B are required throughout the year. Decadal trend as
obtained from the TEMIS data of UVI is shown in Table 5. It is noted that the trend ranges from -0.19 to +0.15.
R. Bhattacharya et al. / International Journal of Engineering Science and Technology (IJEST)
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Vol. 4 No.11 November 2012
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Table 5 Trend analysis of UVI
Station Premonsoon Monsoon Postmonsoon Winter
S1 -0.01 -0.05 0.01 0.02
S2 -0.04 -0.04 0.00 0.02
S3 -0.08 -0.04 -0.01 0.00
S4 -0.10 0.01 -0.19 0.15
S5 0.02 -0.08 -0.25 0.15
S6 -0.09 -0.03 -0.03 -0.03
S7 -0.10 -0.04 -0.03 -0.03
S8 -0.09 -0.03 -0.05 -0.04
S9 -0.10 0.01 -0.19 0.15
4. Conclusions
This investigation gives a view of UV exposure level over India. Analysis of UVI during July 2002 to June 2012
has revealed that the overall trends ranges from -0.01 to -0.05 for all sites. However seasonal enhancements are
both positive and negative for all the sites. Intermonth anomaly is found high from September to March. Timing
of enhanced UVI has a practical importance. We observed that UVI is high in monsoon and post monsoon
seasons. Hence outdoor activity should be minimum during this time. Though less protection is usually taken in
these seasons by the agriculture workers. Use of tree shade can reduce the exposure level from 80% to 98%
depending on the tree species and canopy parameters (Parisi et al., 1999; Yang et al 1995, Gies et al 2007,
Bhattacharya et al 2011, Bhattacharya and Bhoumick 2012b). The UV exposure has been constantly high in all
sites except Srinagar and Delhi. Therefore social programs are needed regularly for campaigning the precautions
need to be taken for tanning, skin cancer, cataract and other problems resulted from UV exposure (Emmons and
Colditz, 1999, Dixon 1999).
Acknowledgement
We would like to thank DST PURSE program of University of Kalyani for financial support.
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