Aerosol Science: Technology and Applications

Chapter 6

Remote Sensing of Atmospheric Aerosols

Sagnik Dey¹ and Sachchida Nand Tripathi²

¹Centre for Atmospheric Sciences, IIT Delhi, India

²Department of Civil Engineering, IIT Kanpur, India

6.1 Introduction

Atmospheric aerosols are liquid or solid particles suspended in the atmosphere, with radii varying from a few nanometers to tens of micrometers. These particles can be directly emitted by anthropogenic (e.g. fossil-fuel burning) and natural (e.g. dust, maritime aerosol, volcanic ash) sources or can form from precursor gases (e.g. secondary organic aerosol, sulfates, etc.). Interest in the study of atmospheric aerosols can be dated back to the 1920s (Brav, 1929). Since then, significant improvement has occurred in our understanding of the role of aerosols in air quality (Lelieveld et al., 2002; Chow and Watson, 2007) and the earth's energy budget (Haywood and Boucher, 2000; Yu et al., 2006). Geographically localized sources/sinks and transformations within their short lifetimes (e.g. the mixing of various aerosol species, the hygroscopic growth of particles) lead to extreme spatial and temporal heterogeneity in aerosol optical and microphysical properties.

Aerosols influence the earth's radiative budget through three different mechanisms: first, they directly scatter and absorb solar and terrestrial radiation (Charlson and Pilat, 1969; Charlson et al., 1992; Chylek and Wong, 1995; Haywood and Boucher, 2000; Ramanathan et al., 2001; Boucher and Pham, 2002; Bellouin et al., ...