Comparison between urban aerosol products retrieved from collocated Cimel and Prede Sun/sky radiometers at Pune, India

To comprehend the characteristics of heterogeneous aerosols, apart from some thematic multi-institutional, multi-platform and multi-parameter campaigns conducted at several places over the globe, presently two major ground-based networks, involving Cimel (AERONET) and Prede (SKYNET) Sun/sky photometers/radiometers have been in progress. In this paper, we report the results of a study that has been undertaken to compare the performance and data products of Cimel and Prede instruments, which were operated concurrently for a period of about 2 years, at the Indian Institute of Tropical Meteorology, Pune, India. The results show a good agreement in the direct Sun observations (aerosol optical depth). The results are also substantiated by making comparison with surface-level black carbon aerosol mass concentration, apart from comparison of other parameters. With regard to the retrieved products such as aerosol size distribution, Prede shows more or less equal concentration of fine mode and relatively more concentration of coarse mode aerosol as compared to those measured by the Cimel. Moreover, the single scattering albedo values measured by the Prede overestimate those observed by the Cimel. These deviations are found to be primarily due to the nature of aerosol loading (turbidity) in the sensing region which is sensitive to the data retrieval techniques including model assumptions employed in both networks. The results of the present study are found useful for multidimensional mapping of aerosol characteristics by integrating the products from both AERONET and SKYNET monitoring stations and thereby help understanding better the impact of aerosols on climate.