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Long-term trends and variability in measured multi-spectral aerosol optical depth over a tropical urban station in India

Dani, KK and Ernest Raj, P and Devara, PCS and Pandithurai, G and Sonbawne, SM and Maheskumar, RS and Saha, SK and Jaya Rao, Y (2012) Long-term trends and variability in measured multi-spectral aerosol optical depth over a tropical urban station in India. International Journal of Climatology, 32 (1). pp. 153-160.

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Sun photometer-derived multi-spectral aerosol optical depth (AOD) measurements made at Pune (18°32'N, 73°51'E), India, during the period May 1998-December 2007 have been used to examine possible long-term trends and variability. Long-term mean AOD in the spectral range 380-1020 nm ranged between 0.593 ± 0.11 and 0.220 ± 0.04 with a coefficient of variation (COV) of 34-49. Day-to-day variations in AOD at all the wavelengths in the range 380-870 nm showed significant long-term increasing trends; the increasing trend at 380 nm being 45 per decade. AODs are higher at shorter wavelengths in winter (December-February) and at longer wavelengths in the pre-monsoon months (March-May) which implies that relatively smaller-sized particles are more in winter and larger sized particles of soil dust origin are more during the pre-monsoon season. Overall mean value of Angstrom-size exponent (α) at this urban location is 0.55, and the mean turbidity coefficient (β) is 0.76. Value of α is higher in winter season compared to the pre-monsoon season. Both α and β show long-term increasing trends of 25.3 and 8.4 per decade, respectively, which points out that with increasing urbanisation and human activity, more and more smaller-sized aerosols are being added to the atmosphere over the urban regions.

Item Type: Article
Additional Information: Copyright of this article belongs to Royal Meteorological Society.
Uncontrolled Keywords: A-coefficient; Aerosol optical depths; Human activities; Long-term trend; Long-term trends; Mean values; Multi-spectral; Pre-monsoon; Shorter wavelength; Soil dust; Spectral range; Sun photometer; Urban locations; Urban regions; Urban stations; Winter seasons, Atmospheric thermodynamics; Photometers; Photometry; Turbidity, Atmospheric aerosols, aerosol property; dust; long-term change; optical depth; particle size; photometer; trend analysis; turbidity; wavelength, India; Maharashtra; Pune
Subjects: Meteorology and Climatology
Depositing User: IITM Library
Date Deposited: 06 Dec 2013 18:33
Last Modified: 06 Dec 2013 18:33

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