Aerosol spectral optical depths and size characteristics at a coastal industriallocation in India - effect of synoptic and mesoscale weather

摘要

The aerosol spectral optical depths at ten discrete channels in the visible and near IRbands, obtained from a ground-based passive multi-wavelength solar radiometer at a coastalindustrial location, Visakhapatnam, on the east coast of India, are used to study the response ofthe 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 spectraloptical depths show about 30% higher growth factors, and the size distributions show thegeneration of a typical new mode around 0.4 microns. The surface wind speed and directionalso indicate the formation of new particles when the humid marine air mass interacts with theindustrial air mass. This is interpreted in terms of new particle formation and subsequentparticle growth by condensation and self-coagulation. The results obtained on thesurface-size segregated aerosol mass distribution from a co-located Quartz Crystal Microbalanceduring different humidity conditions also show a large mass increase in the sub-micron sizerange with an increase in atmospheric humidity, indicating new particle formation at the sub-micronsize range.