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Abstract
The Indian subcontinent occupies 2.4% of the world land mass and is home to ∼17% of the world population. It is characterized by a wide range of population density (P), significant population growth and high levels of air pollution. The quantification of the effect of urbanization on aerosol optical thickness (AOT) trends was carried out by analysing 8-year (March 2000 to February 2008) Moderate Resolution Imaging Spectroradiometer (MODIS) and Multiangle Imaging SpectroRadiometer (MISR) satellite data. Here we show that over extensive areas with differing population densities, which are significant parts of the Indian subcontinent, (1) the higher the averaged population density the bigger the averaged AOT and (2) the larger the population growth the stronger the increasing trends in AOT. Over the regions with P > 100 persons km−2 (more than 70% of the territory), a population growth of ∼1.5% year−1 was accompanied by increasing AOT trends of over 2% year−1. The presence of the aforementioned AOT trends is evidence of air quality deterioration, in particular in highly populated areas with P > 500 persons km−2. This situation could worsen with the continued growth of the Indian population.
Acknowledgements
We gratefully acknowledge the GES-DISC Interactive Online Visualization and Analysis Infrastructure (Giovanni) for providing MODIS and GPCP data and the NASA Langley Research Center Atmospheric Sciences Data Center for providing MISR data. This study was supported by the GLOWA (Global Change and the Hydrological Cycle) Jordan River BMBF-MOST (German Ministry of Science and Technology – Israeli Ministry of Science and Technology) project, the BMBF–MOST grant number 1946 on global change. O. Kalashnikova's contribution to this study was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA, and is supported by a grant from the NASA Earth Sciences Division, Climate and Radiation Program, under H. Maring.