In situ detection of aerosol layers in the middle stratosphere

Abstract

We present here 14 new flights of the aerosol counter STAC, performed in the 2008-2010 period under 3 different geophysical conditions: equator, summer Arctic, and spring Arctic. Measurements were conducted during the balloon ascent, at float altitude, and during the balloon descent. The float altitude was between 14 and 2 hPa (29-42 km), depending on the flights. Aerosol enhancements were detected for altitude levels above 40 hPa, with a stronger variability above 20 hPa. Two of them could be attributed to the fortuitous detection of meteoric debris. Thin layers of strong local enhancements of submicronic aerosols were detected during the other flights. Using simultaneous in situ measurements of the N 2 O tracers by the infra-red SPIRALE balloon-borne spectrometer, it can be concluded that the occurrence of these enhancements is not directly linked to the variability of air mass origins. A process involving atmospheric electric field is proposed to tentatively explain the aerosol containment. © 2010 by the American Geophysical Union.