Opinion: Aerosol Remote Sensing Over The Next Twenty Years

Abstract

Twenty years ago, aerosol remote sensing underwent a revolution with the launch of the Terra and Aqua satellites, followed by additional launches carrying new passive and active sensors. Capable of retrieving information about aerosol loading, rudimentary particle properties and in some cases aerosol layer height, the satellite view of Earth’s aerosol system came into focus. Today we see trends developing in the aerosol remote sensing and modeling communities that allow us to speculate about the future and how the community will approach aerosol remote sensing twenty years from now. We anticipate technology that will replace today’s standard multi-wavelength radiometers with hyperspectral and/or polarimetry all viewing in multiple angles. These will be supported by advanced active sensors with the ability to measure profiles of aerosol extinction in addition to backscatter. The result will be greater insight into aerosol particle properties. Algorithms will move from being primarily physically-based to include an increasing degree of Machine Learning methods, but physically-based techniques will not go extinct. However, the concept of applying algorithms to a single sensor will no longer exist. Retrieval algorithms will encompass multiple sensors and all available ground measurements into a unifying framework, and these inverted products will be ingested directly into assimilation systems, becoming “cyborgs”: half observations, half model. In twenty years we will see a true democratization in space with nations large and small, private organizations and commercial entities of all sizes launching space sensors. With this increasing amount of data and aerosol products available, there will be a lot of bad data. User communities will organize to set standards and the large national space agencies will lead the effort to maintain quality by deploying and maintaining validation ground networks and focused field experiments. Through it all, interest will remain high in the global aerosol system and how that systems affects climate, clouds, precipitation and dynamics, air quality, transport of pathogens and fertilization of ecosystems, and how these processes are adapting to a changing climate.