5. Fachsitzung 2025

Stephan Borrmann (Max-Planck-Institut für Chemie)

Origin and properties of the Asian Tropopause Aerosol Layer – a conundrum resolved by in-situhigh altitude aircraft measurements

The Asian Tropopause Aerosol Layer (ATAL) forms each year during the Asian monsoon at altitudes between 14 and 18 km. For a long time, its physical characteristics and chemical composition remained poorly understood. Several research campaigns investigated the ATAL and its plume spreading in the upper troposphere and lower stratosphere after the dissolution of the Asian Monsoon Anticyclone. For this high-altitude research aircraft were deployed over Nepal, India, Bangladesh, the Bay of Bengal, and the Pacific, including research flights conducted from South Korea and Alaska.

Our novel ERICA aerosol particle mass spectrometer enabled in-situ aerosol analysis up to 20 km altitude, combining laser and thermal desorption techniques for precise compositional measurements. Observations revealed elevated particle number concentrations (size diameters from 10 nm to 3 μm) within the ATAL. The dominant chemical constituents are ammonium nitrate and organics. Most particles originate through homogeneous nucleation from gas-phase precursors transported upward by regional convection. These in-situ measurements, conducted by the University of Mainz, the Max Planck Institute for Chemistry and other European institutions, are the first carried out directly within the ATAL, helping to resolve the long-standing mystery of its formation and composition.

Bitte beachten Sie: diese physische Teil dieser Fachsitzung wird im Senatssaal der Uni Mainz und nicht beim DWD in Offenbach stattfinden! Dieser ist über die Tram-Haltestelle “Universität Mainz” zu erreichen.

Alle Vorträge finden hybrid statt. Online-Teilnahme ist über Webex möglich.