Vertical Profiling of Aerosol and Aerosol Types Using Space-Borne Lidar

Abstract

Aerosol remote sensing has become a powerful tool to characterize the optical and microphysical properties of aerosols. Several satellite sensors such as MODIS, MISR, OMI, Tropomi and PARASOL utilize the solar electromagnetic radiation for retrieving aerosol properties from space. These instruments have high spatial coverage and can provide aerosol properties globally on a repeated basis. However, these passive sensors mostly lack the information regarding vertical distribution of aerosol and its types. Using active remote sensing technique however, provide valuable information to understand the vertical distribution of aerosols which is very useful to predict the lifetime of atmospheric aerosols, long-range transport and subsequent interaction with cloud droplets. CALIOP is an active sensor flying on board CALIPSO satellite provide height-dependent aerosol extinction repeatedly on a global basis. CALIOP aerosol retrieval algorithm retrieves aerosol information in 5 km horizontal resolution and 30–60 m vertical resolution. The latest updated CALIOP aerosol retrieval algorithm version 4 (V4) has the ability to identify ten aerosol subtypes; six for tropospheric aerosols and four for stratospheric aerosols. In this context, the annual, seasonal and diurnal variation of smoke aerosol have been investigated over central Indo-Gangetic Plain (IGP), South Asia using ten years V4 CALIOP profile data. We noted that for all the seasons, the highest smoke aerosol extinction observed near surface and contributed 40–60% to the total aerosol extinction during winter (DJF) and postmonsoon seasons (ON). In premonsoon (MAM) and monsoon (JJAS) seasons the highest contribution of smoke to the total extinction coefficient found at relatively higher altitude (premonsoon: 60% at 7–9 km, monsoon: 75% at 5–8 km). The day-night occurrence frequency of smoke aerosol found higher during the day time in winter at 4 km, while during monsoon the occurrence of the smoke was found higher at night time.