The geography and climatology of aerosols

Aerosols affect climate by scattering and absorbing radiation and by modifying the physical and radiative properties of clouds. Despite their importance in the climate system, the temporal and spatial variability of aerosols is not well understood. This paper briefly describes the nature of aerosols, their influence on the climate system and methods for quantifying atmospheric turbidity, which is the total column amount of aerosol. The main focus of the paper is a review of turbidity research that serves to document how and why aerosols vary over time and space. This analysis reveals that temporal and spatial variability in aerosol emissions is superimposed by temporal and/or spatial variability in meteorological and climatic factors. These factors include variability in wind speed, humidity, stability, insolation, frontal and cyclonic activity, the position of the Intertropical Convergence Zone and the polar front, rates of precipitation and convection, and the source regions of air masses. This interaction between aerosol emission characteristics and atmospheric processes is manifested in distinct trends in total column aerosol -described herein by geographic region - at a variety of spatial and temporal scales.