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Research Area C - TPChange TRR 301 - Wolken
TPChange 5 Projects 5 Research Area C 5 Project C03

Project C03:
Variability in UTLS transport from model age of air and impacts on composition

Brief Summary

Long-term trends in the composition of the UTLS with radiatively active trace gas species like water vapour and ozone may cause substantial effects on the Earth’s radiation budget and on surface climate and need to be correctly represented in models for reliable predictions. A robust knowledge of the variability of UTLS transport on inter-annual to decadal time scales is a prerequisite for a reliable estimation and attribution of long-term anthropogenically forced trends. However, the representation of such variability, as related to the QBO, ENSO, volcanic aerosol, SSWs, solar cycle, and ODS is often incomplete in current climate model simulations, casting comparisons with measurements into doubt. The proposed project aims at investigating variability and long-term changes of transport pathways and time scales in the UTLS from a Lagrangian model perspective. The comprehensive research strategy combines reanalysis-driven simulations with the Lagrangian CLaMS model and free-running simulations with CLaMS coupled to the climate model EMAC, together with satellite and in-situ observations. Different powerful diagnostics will be used to evaluate transport pathways and time scales in the UTLS. In addition to simulating chemical species we will use a novel age spectrum analysis method, with the age of air spectrum being the distribution of transit times through the stratosphere. The model simulations will be compared to trace gas measurements from satellite instruments (e.g., MLS, ACE-FTS, MIPAS), and to airborne in-situ tracer measurements (e.g., from recent HALO- and G5-missions) provided by the other project partners. Combination of the tracer measurement data with the full model age spectrum, and related mass fractions of young and old air masses, will allow quantifying the effect of changing transport pathways and mixing time scales on the UTLS composition. Furthermore, analysis of the tracer and mean age budgets based on the tracer continuity equation will allow further insights into the roles of different processes (e.g., residual circulation and eddy mixing) in driving transport in the UTLS. Finally, consistent EMAC climate model simulations with both Eulerian and Lagrangian CLaMS tracer transport included will be investigated for effects of Lagrangian transport with reduced numerical diffusion on the model representation of the UTLS. The research questions focus on: (i) Variability and trends in UTLS transport time scales, (ii) the related impacts on trace gas composition, and (ii) the representation of UTLS pathways and time scales in different reanalysis and models.


Jun.-Prof. Dr. Plöger - TPChange

Jun.-Prof. Dr. Felix Plöger

Principal Investigator

Forschungszentrum Jülich, Institut für Energie- und Klimaforschung


Prof. Dr. Peter Hoor - Speaker of TRR 301 TPChange

Prof. Dr. Peter Hoor

Principal Investigator

Johannes Gutenberg-Universität Mainz, Institut für Physik der Atmosphäre


Turhal, Katharina, Doctoral Candidate - TPChange

Katharina Turhal

Doctoral Candidate

Forschungszentrum Jülich, Institut für Energie- und Klimaforschung