Effects of Aircraft on Aerosol Abundance in the Upper Troposphere

 

Research Staff: Rudolf F. Pueschel, Guy V. Ferry, Anthony W. Strawa, T. Paul Bui

A significant increase in sulfuric acid (H2SO4) aerosol concentration coincidental with an enhancement in nitrogen oxides was detected in commercial flight corridors above 10 km pressure altitude over the northeastern Atlantic Ocean on October 23, 1997 during SONEX (SASS [Subsonic Assessment] Ozone-Nitrogen Oxide Experiment). The source of this aerosol is ascribed to commercial aircraft operations because 1) a stable atmosphere prevented vertical air mass exchanges and thus eliminated surface sources, 2) air mass back trajectories documented the absence of remote continental sources, and 3) temperature profiler data showed the tropopause at least one kilometer above flight altitude throughout the flight, thereby eliminating stratospheric sources. Particle volatility identified 60-80% H2SO4, about 20% (NH4)2SO4 and about 10% non-volatile particles in the proximity of flight corridors, and 10-30% H2SO4, up to 50% (NH4)2SO4 and 40-60% non-volatile aerosols in air that was not affected by aircraft operations below 10 km. The emission index was determined as EI(H2SO4) = 8e17 particles per kg of fuel burned. The newly formed particles were too small to measurably affect surface area and volume of the background aerosol. Hence a direct radiative effect of this aircraft-produced aerosol is not to be expected. However, indirect effects on cloudiness are a possibility since up to 50% of the condensation nuclei that we measured have been determined in previous studies to serve as active cloud condensation nuclei.

 

Collaborators: Y. Kondo, Nagoya University, Japan; Steve Howard, Symtech; Sunita Verma, SSAI; M. Mahoney, JPL, Pasadena, CA; J. Hannan and H. Fuelberg, Florida State University, Tallahassee, FL

Point of Contact: Rudolf F. Pueschel, 650/604-5254, rpueschel@mail.arc.nasa.gov