In situ detection of electrified aerosols in the upper troposphere and stratosphere
- 1LPC2E-CNRS/University of Orléans, 3A avenue de la recherche scientifique, UMR7328, 45071 Orléans cedex 2, France
- 2Indian Institute of Technology, Kanpur, Center for Environmental Science and Engineering, Kanpur, India
- 3University of Bath, Department of Electronic and Electrical Engineering, Claverton Down, Bath, BA2 7AY, UK
- 4University of Reading, Department of Meteorology, Reading RG6 6BB, UK
Abstract. Electrified aerosols have been observed in the lower troposphere and in the mesosphere, but have never been detected in the stratosphere and upper troposphere. We present measurements of aerosols obtained during a balloon flight to an altitude of ~ 24 km. The measurements were performed with an improved version of the Stratospheric and Tropospheric Aerosol Counter (STAC) aerosol counter dedicated to the search for charged aerosols. It is found that most of the aerosols are charged in the upper troposphere for altitudes below 10 km and in the stratosphere for altitudes above 20 km. Conversely, the aerosols seem to be uncharged between 10 km and 20 km. Model calculations are used to quantify the electrification of the aerosols with a stratospheric aerosol-ion model. The percentages of charged aerosols obtained with model calculations are in excellent agreement with the observations below 10 km and above 20 km. However, the model cannot reproduce the absence of electrification found in the lower stratosphere, as the processes leading to neutralisation in this altitude range are unknown. The presence of sporadic transient layers of electrified aerosol in the upper troposphere and in the stratosphere could have significant implications for sprite formation.