Diffuse light around cities: New perspectives in satellite remote sensing of nighttime aerosols

Satellite remote sensing of nighttime aerosols in the lower atmosphere poses additional challenges in comparison with daytime sensing, due to the specific features of the available light sources and the different scattering geometries. In this work we develop a detailed quantitative model for the top-of-atmosphere radiance of the halos of diffuse light observed around cities in satellite nighttime imagery. It is shown that these scattered light distributions contain relevant information about the aerosol properties, and that under some basic assumptions they can be used to estimate them. We formalize the basis of a method for retrieving the aerosol particle size number distribution function based on inverting the angular dependence of the radiance detected in near-nadir remote sensing observations. The results stress the convenience of endowing future night Earth observation missions with enhanced angular detection capabilities. • Diffuse halos of light around cities are visible in satellite nighttime imagery. • These diffuse light distributions contain relevant aerosol information. • Nightime aerosol properties can be retrieved from multi-angle satellite data. • Aerosol number size distributions can be estimated by inverting a Fredholm equation. • Satellite remote sensing would benefit from enhanced multi-angle capabilities.