SASS (Subsonic Assessment) Ozone and NOx Experiment

The SASS (Subsonics Assessment) Ozone and NOx Experiment (SONEX) was an international, multi-organizational mission that took place in October-November 1997. NASA was the US sponsor of SONEX that partnered with POLINAT-2 (Pollution from Aircraft Emissions in the North Atlantic Flight Corridor) funded by the German DLR (Deutsches Zentrum für Luft- und Raumfahrt) or German Aerospace Agency. NASA flew the DC-8 aircraft out of NASA/Ames Research Center. DLR operated an instrumented Falcon 20 aircraft. The staging locations for NAFC sampling were primarily Bangor, Maine (US), and Shannon, Ireland. Subsonic aircraft emissions impact several aspects of atmospheric composition: nitrogen oxides (NOx), CO, and hydrocarbons from emissions can perturb upper tropospheric/lower stratospheric (UT/LS) ozone; water vapor, soot, and sulfur oxides (SOx) emitted by aircraft may perturb clouds and aerosols, changing UT/LS radiative forcing and global temperature.

In SONEX and POLINAT, flights were conducted in the vicinity of the North Atlantic Flight Coordinator (NAFC) to observe the impact of aircraft emissions on NOx and ozone (O3). The DC-8 aircraft payload (Singh et al., 1999) primarily measured in-situ CO, CO2, hydrocarbons/halocarbons, O3, aerosols (Dibb et al., 2000), OH/HO2, water vapor, nitric acid (Talbot et al., 1999), photolysis rates, temperature, pressure, winds, NOx, and NOy.

Three sampling approaches were implemented during SONEX. First, special meteorological (Fuelberg et al., 2000) were developed to allow targeted sampling for air parcels affected by aircraft emissions and various meteorological events, e.g., convection, lightning (Jeker et al., 2000), stratospheric intrusions (Cho et al., 2000). Second, because the NAFC had not been extensively sampled in the past, it was important for SONEX to characterize the climatology of trace species like CN (Wang et al., 2000), NOx and NOy (Koike et al., 2000). Third, tracers (Simpson et al., 2000; Thompson et al., 1999) and model sensitivity studies (Meijer et al., 2000) were employed for Air Mass Identification. This sampling strategy answered the following questions: Where and when are air masses found with the greatest aircraft influence? When and where was stratospheric air sampled? SONEX showed a substantial impact of aircraft emissions on UT/LS NOx and CN in the vicinity of fresh aircraft emissions. However, during October-November 1997 over the NAFC, UT/LS NOx was dominated by surface emissions redistributed by convection and augmented by lightning.

Disciplines:   Field Campaigns

SONEX Citations

Jeker D P, Pfister L, Thompson A M, Brunner D, Boccippio D J, Pickering K E, Wernli H, Kondo Y and Staehelin J (2000). Measurements of nitrogen oxides at the tropopause: Attribution to convection and correlation with lightning. Journal of Geophysical Research: Atmospheres, 105 (D3), 3679. https://doi.org/10.1029/1999JD901053


Wang Y, Liu S-C, Anderson B E, Kondo Y, Gregory G L, Sachse G W, Vay S A, Blake D, Singh B, and Thompson A M (2000). Evidence of convection as a major source of condensation nuclei in the northern midlatitude upper troposphere. Geophysical Research Letters, 27 (3), 369. https://doi.org/10.1029/1999GL010930


Koike M, Kondo Y, Gregory G L, Anderson B E, Sachse G W, Blake D, Singh H B, Thompson A M, Kita K, Zhao Y, Sugita T, Shetter R, Ikeda H, Liu S-C, Jaeglé L, and Toriyama N (2000). Impact of aircraft emissions on reactive nitrogen over the North Atlantic Flight Corridor region. Journal of Geophysical Research: Atmospheres, 105 (D3), 3665. https://doi.org/10.1029/1999JD9010


Thompson A M, Singh H B, and Schlager H (2000). Introduction to special section: SONEX (Subsonic Assessment Ozone and Nitrogen Oxides Experiment) and POLINAT (Pollution in North Atlantic Tracks. Journal of Geophysical Research: Atmospheres, 105 (D3), 3595. https://doi.org/10.1029/2000JD900012


Dibb J E, Talbot R W, and Scheuer E M (2000). Composition and distribution of aerosols over the North Atlantic during the Subsonic Assessment Ozone and Nitrogen Oxide Experiment (SONEX). Journal of Geophysical Research: Atmospheres, 105 (D3), 3709. https://doi.org/10.1029/1999JD900424


Meijer E W, van Velthoven P F J, Thompson A M, Pfister L, Schlager H, Schulte P and Kelder H (2000). Model calculations of the impact of NOx from air traffic, lightning, and surface emissions, compared with measurements. Journal of Geophysical Research: Atmospheres, 105 (D3), 3833. https://doi.org/10.1029/1999JD901052


Fuelberg H E, Hannah J R, van Velthoven P F J, Browell E V, Bieberbach Jr. G, Knabb R D, Gregory G L, Pickering K E, and Selkirk H B (2000). A meteorological overview of the Subsonic Assessment Ozone and Nitrogen Oxide Experiment (SONEX) period. Journal of Geophysical Research: Atmospheres, 105 (D3), 3633. https://doi.org/10.1029/1999JD900917


Simpson I J, Sive B C, Blake D R, Blake N J, Chen T Y, Lopez J F, Anderson B E, Sachse G W, Vay S A, Fuelberg H E, Kondo Y, Thompson A M, and Rowland F S (2000). Nonmethane hydrocarbon measurements on the North Atlantic Flight Corridor during SONEX. Journal of Geophysical Research: Atmospheres, 105 (D3), 3785. https://doi.org/10.1029/1999JD900750


Singh H B, Thompson A M, and Schlager H (1999). SONEX airborne mission and coordinated POLINAT-2 activity: Overview and accomplishments. Geophysical Research Letters, 26 (20), 3053. https://doi.org/10.1029/1999GL900588


Thompson A M, Sparling L C, Kondo Y, Anderson B E, Gregory G L, Sachse G W (1999). Perspectives on NO, NOy and fine aerosol sources and variability during SONEX. Geophysical Research Letters, 26 (20), 3073. https://doi.org/10.1029/1999GL900581


Talbot R W, Dibb J E, Scheuer E M, Kondo Y, Koike M, Singh H B, Salas L B, Fukui Y, Ballenthin J O, Meads R F, Miller T M, Hunton D E, Viggiano A A, Blake D R, Bake N J, Atlas E, Flocke F, Jacob D J, and Jaegle L (1999). Reactive nitrogen budget during the NASA SONEX Mission. Geophysical Research Letters, 26 (20), 3057. https://doi.org/10.1029/1999GL900589


Cho J Y N, Newell R E, Bui T P, Browell E V, Fenn M A, Gary B L, Mahoney M J, Gregory G L, Sachse G W, Vay S A, Kucsera T L, and Thompson A M (1999). Observations of convective and dynamical instabilities in tropopause folds and their contribution to stratosphere-troposphere exchange. Journal of Geophysical Research: Atmospheres, 104 (D17), 21549. https://doi.org/10.1029/1999JD900430


Liu S-C, Yu H, Wang Y, Davis D D, Kondo Y, Anderson B E, Sachse G W, Gregory G L, Ridley B, Fuelberg H E, Thompson A M, and Singh H B (1999). Sources of reactive nitrogen in the upper troposphere during SONEX. Geophysical Research Letters, 26 (16), 2441. https://doi.org/10.1029/1999GL900532