Aerosol spectral optical depths and typical size distributions at a coastal urban location in India

ABSTRACT The ground‐reaching direct solar flux measurements at 9 different wavelengths in the visible and near infrared region using a ground based multiwavelength radiometer have been used to study the spectral and temporal variation of aerosol optical depths and size distribution over Visakhapatnam (17.7°N, 83.3°E), a coastal industrial location on the east coast of India. The aerosol optical depths exhibit a typical spectral variation with summer maxima at all the 9 wavelengths. The inversion of the spectral optical depths following the constrained linear inversion algorithms yielded a typical bi‐modal aerosol size distribution at Visakhapatnam with the primary mode centered around 0.1 µm and the secondary mode around 0.8 µm. The observed features, when examined along with the mesoscale meteorological data have indicated a strong control of the local sources and sinks on the aerosol populations of different sizes.