Monitoring Surface PM2.5: An International Constellation Approach to Enhancing the Role of Satellite Observations

Abstract

Exposure to particulate pollution is a severe burden to public health worldwide. Information on near-surface concentrations of particulate matter (PM) is needed on a global scale: as input to air quality services for citizens, to support policy makers in evaluating the efficacy of pollution abatement measures, and to help environmental agencies verify compliance with standards on pollution levels and related emissions. Satellite observations do offer valuable information on PM. However, satellite observations alone are not sufficient to provide the needed PM products. A combination of ground-based measurements, satellite observations, and information from atmospheric chemistry and transport models is needed for monitoring and forecasting near-surface PM concentrations. Optimal application of satellite observations for PM estimation has not yet been achieved. A host of space-borne sensors capture different aspects of PM: imagers observe the horizontal distribution of the vertically integrated burden, multi-angle and polarimetric imagers also allow constraining particle size and type, spectrometers provide some information on the vertical distribution as well as spectral absorption and speciation fractions of absorbers in smoke and dust, lidars capture the vertical distribution of the particle load along narrow tracks. Although some products like aerosol optical depth are mature, many products capturing particle properties remain qualitative. A synergetic exploitation of these capabilities is needed to enhance accuracy of the PM distribution globally. The present whitepaper takes stock of the current and planned sensors with strong potential for constraining PM, and of schemes used for generating particulate pollution products and services. Specific and actionable recommendations are made to strengthen the role of satellites in constraining PM levels and to help creating satellite-informed particulate pollution products.