Air mass origin, transport and mixing associated with dry intrusions (ORIGAMI-DI)

• Applicant: Dr. Daniel Kunkel
• Subject Area: Atmospheric Science
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 552781579

Extratropical cyclones are the dominant meteorological phenomenon at mid-latitudes. They determine our daily weather on the local scale, while contributing significantly to the energy transport from low to high latitudes on the large scale. Within cyclones several coherent air streams exist and some of these air streams can efficiently lift moist and potentially polluted air masses from the near surface altitudes into the middle and upper troposphere. In contrast one of the air streams descends from the upper troposphere into the lower troposphere, eventually reaching the planetary boundary layer. This so called dry intrusion transports momentum and dry air masses and can have significant impacts on the local weather. In our study we aim for a more comprehensive understanding of the dynamical factors which determine the evolution of the air mass composition of the dry intrusion. For this we measure high resolution trace species on-board the research aircraft HALO during the NAWDIC-HALO campaign and study three regions of the dry intrusion. First, we use our tracers of origin (CO, CH4, C2H6, N2O) to identify polluted air masses as well as air masses which had recent contact with the stratosphere. Along with trajectory calculations based on ERA5, we will be able to distinguish between the transport pathways of air masses before they enter the formation region of the dry intrusions. We will thus be able to separate between quasi-horizontal and vertical transport as well as from descend from the stratosphere. Second, in the tropopause region our tracer measurements will allow us to detect whether the air masses have been subject to mixing processes and to stratosphere-troposphere exchange. In particular, we will be able to determine whether stratospheric air masses enter the air masses of the dry intrusion before the air masses start to descend. Our tracer based analysis will be complemented with data from the ERA5 reanalysis and with high resolution ICON model simulations with the goal to shed new light on the dynamics of the small scale mixing processes. Third, we aim to study the downward transport within the dry intrusion. With our tracer measurements we want to analyse how coherent the dry intrusion air stream is and when and where mixing processes occur along the descent. This is of particular interest for a potential downward transport of ozone from the tropopause region into the planetary boundary layer. The stratospheric ozone will be tagged with the help of the N2O measurements and we will further be able to unambiguously distinguish between air masses with enhanced ozone of stratospheric or of pollution origin. Overall, through a combination of high resolution measurement of our origin tracers with Eulerian and Lagrangian model diagnostics, we aim for a more comprehensive understanding of the origin, transport and fate of air masses in dry intrusions and the connection to large- to small-scale dynamical processes.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 1294: Atmospheric and Earth System Research with the "High Altitude and Long Range Research Aircraft" (HALO)
• Co-Investigators: Dr. Heiko Bozem; Professor Dr. Peter Hoor