PNNL

Abstract

Systematic aircraft measurements in a modest operational program can resolve key limitations of satellite aerosol data for climate and air quality applications. Current satellite observations provide frequent, global maps of aerosol amount, but offer only loose constraints on aerosol properties needed for climate and air quality applications. We define an aircraft payload to measure key aerosol optical, microphysical, and chemical properties in situ. The flight program will characterize major aerosol air mass types statistically, at a level-of-detail unobtainable from space. It will: (1) enhance satellite aerosol retrieval products with better climatology assumptions, and (2) improve translation between satellite-retrieved optical properties and species-specific aerosol mass and size simulated in climate models that assess aerosol forcing, its anthropogenic components, and other environmental impacts. As such, the Systematic Aircraft Measurements to Characterize Aerosol Air Masses (SAM-CAAM) project will add value to data records representing several decades of aerosol observations from space, improve aerosol constraints on climate modeling, and contribute to future satellite aerosol missions. We identify 15 Required Variables, and define four Payload Options, of increasing ambition, to constrain these quantities. “Option C” meets all the SAM-CAAM objectives with about 20 instruments, most of which have flown before, but never routinely several times per week, and never as a group. Aircraft integration, and approaches to data handling, payload support, and logistical considerations for a long-term, operational mission are discussed. SAM-CAAM is feasible because, for most aerosol sources and specified seasons, particle properties tend to be repeatable, even if aerosol loading varies.