Keywords: radiation, Linke turbidity factors, aerosols, optical depth, transmittance, India, air pollution, air quality, India
Estimation of Linke turbidity factors for different regions of India
This paper analyses the temporal and spatial variation of Linke turbidity factor (TL) at five Indian stations; namely New Delhi, Kolkata, Poona, Jaipur and Mumbai. For computation of turbidity, data spanning eight years (1993–2000) for these stations has been procured from the Indian Meteorological Department (IMD) Poona. It is seen that turbidity values are low in winter, ranging from 4 to 6; and high in summer, ranging from 5 to 9. For the post–monsoon season, turbidity values are intermediate, ranging from 5 to 8. It is also seen that turbidity values highly depend on the pollution level of the station; e.g., Kolkata, being an industrialised city, has the highest value of turbidity - as high as 10.2 in May. For Poona, a relatively pollution–free city, the turbidity value is about 5.5 in May. Diurnal variation is small; it is about 14 % in winter and about 11.5% in summer for Poona. Regarding annual variation, it is seen that turbidity remains almost constant for all the years for two stations: Kolkata (TL = 7.5) and Poona (TL = 4.6). For the other three stations, Jaipur, New Delhi and Mumbai, the turbidity values are almost constant for the first 4 years (1993–1996) and then there is sharp increase in turbidity values during 1997 for Jaipur (TL = 6.4) and for New Delhi (TL = 6.8). Frequency distribution of turbidity values shows that most of the values lie between 3 and 10. For Kolkata maximum frequency, 37%, lies in the range 6.0–7.5; for New Delhi it is 46% and the range is 4.5–6.0.