Aircraft-based observation of meteoric material in lower stratospheric
aerosol particles between 15 and 68°N
Abstract
Particles containing meteoric material were observed in the lower
stratosphere during five aircraft research missions in recent years.
Single particle laser ablation technique in a bipolar configuration was
used to measure the chemical composition of particles in a size range of
approximately 150 nm to 3 µm. The five aircraft missions, conducted
between 2014 and 2018, cover a latitude range from 15 to 68°N. In total,
more than 330 000 single particles were analyzed. A prominent fraction
(more than 50 000) of the analyzed particles was characterized by strong
abundances of magnesium, iron, and rare iron oxide compounds, together
with sulfuric acid. This particle type was found almost exclusively in
the stratosphere and is interpreted as meteoric material immersed or
dissolved in stratospheric sulfuric acid particles. Below the tropopause
the fraction of this particle type decreases sharply. However, small
abundances were observed below 3000 m a.s.l. in the Canadian Arctic and
also at the Jungfraujoch high altitude station (3600 m a.s.l.). Thus,
the removal pathway by sedimentation and/or mixing into the troposphere
is confirmed. Our data show that particles containing meteoric material
are present in the lower stratosphere in very similar relative
abundances, regardless of latitude or season. This finding suggests that
the meteoric material is transported from the mesosphere into the
stratosphere in the downward branch of the Brewer-Dobson-Circulation and
efficiently distributed towards low latitudes by isentropic mixing. As a
result, meteoric material is found in particles of the stratospheric
Junge layer at all latitudes.