2.2 NASA Atmospheric Tomography mission (ATom)

The goal of the NASA Atmospheric Tomography mission (ATom), led by Steve Wofsy (Harvard) and conducted using the NASA DC-8 aircraft, is to identify and quantify human impacts on the chemistry of the remote atmosphere. ACOM scientists provided key data: 1) spectrally resolved down- and up-welling in situ ultraviolet and visible actinic flux measurements from approximately 280-650 nm (Hall and Ullman, CAFS instrument) and 2) speciated measurements of a wide range of VOCs (Apel, Hornbrook, and Hills) using the Trace Organic Gas Analyzer (TOGA). The ATom-1 campaign consisted of eleven research flights covering a wide longitudinal and latitudinal range (Figure 1) and investigated the vertical chemical structure from 0-11 km in both the Atlantic and Pacific.

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Figure 1. DC-8 flight tracks for the 11 ATom-1 research flights.

Among the VOCs measured by TOGA was acetonitrile (CH3CN), a biomass burning (BB) tracer. Figure 2b displays measurements of CH3CN in both the Pacific and the Atlantic clearly showing air that was impacted by Siberian fires in the Pacific and African fires over the equatorial Atlantic. Figure 2a shows O3 measurements over the same regime with strong indications that the fires were responsible for the large enhancements of tropospheric ozone in these regions.

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Figure 2. Interpolated curtain plots obtained during ATom-1 for a) ozone (O3) and b) acetonitrile CH3CN)