Spaceborne lidar retrieved composite and speciated aerosol extinction profiles and optical depths over India: A decade of observations

Özet

Despite several independent observational studies, a comprehensive picture on the aerosol vertical distributionand its spatial gradients has not yet evolved over the Indian subcontinent. The present study analyses around 10years (June 2006 to December 2016) of version 3 level 3 CALIPSO (Cloud-Aerosol Lidar and Infrared PathfinderSatellite Observation) spaceborne lidar (light detection and ranging) retrieved night time, cloud free verticalextinction profiles (at 532 nm) of composite aerosol, and its major species (dust, polluted dust and smoke) tounderstand the three-dimensional distribution of aerosols over India. The shape and vertical extent of the ex-tinction profiles varied in space and time. The vertical extent of the aerosol distribution is shallower in the colderseasons compared to that of warmer seasons, which could potentially be due to suppressed convection duringcolder months. Meridional gradients are observed in the near-surface extinction coefficients (increasing towardsnorth of India). Polluted dust (defined as a mixture of dust and smoke) emerged as the dominant aerosol speciesover most parts of the study region. Over the north western and central India, dust aerosols contributed the mostto the aerosol optical depths and extinction profiles during the summer and monsoon months. Smoke aerosolsprevailed over the southern and north eastern parts of India, which are attributed to biomass, agriculturalburning, and long-range transport. Boundary layer aerosol optical depths (AOD) contributed to columnar AODsignificantly during post-monsoon and winter, while the elevated-AOD had almost an equal share in columnarAOD during the summer and monsoon seasons.