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Ann. Geophys., 22, 1851-1860, 2004
www.ann-geophys.net/22/1851/2004/
© European Geosciences Union 2004
Aerosol spectral optical depths and size characteristics at a coastal industriallocation in India - effect of synoptic and mesoscale weather
K. Niranjan, B. Malleswara Rao, A. Saha, and K. S. R. Murty
Department of Physics, Andhra University, Visakhapatnam 530 003, India
Abstract. The aerosol spectral optical depths at ten discrete channels in the visible and near IR
bands, obtained from a ground-based passive multi-wavelength solar radiometer at a coastal
industrial location, Visakhapatnam, on the east coast of India, are used to study the response of
the aerosol optical properties and size distributions to the changes in atmospheric humidity,
wind speed and direction. It is observed that during high humidity conditions, the spectral
optical depths show about 30% higher growth factors, and the size distributions show the
generation of a typical new mode around 0.4 microns. The surface wind speed and direction
also indicate the formation of new particles when the humid marine air mass interacts with the
industrial air mass. This is interpreted in terms of new particle formation and subsequent
particle growth by condensation and self-coagulation. The results obtained on the
surface-size segregated aerosol mass distribution from a co-located Quartz Crystal Microbalance
during different humidity conditions also show a large mass increase in the sub-micron size
range with an increase in atmospheric humidity, indicating new particle formation at the sub-micron
size range.
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