Project Details
Projekt
Convection and turbulent cross tropopause exchange: ConvEx
Applicant
Professor Dr. Peter Hoor
Subject Area
Atmospheric Science
Term
since 2026
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 564845058
Convection plays a substantial role in shaping the chemical composition of the upper troposphere and lower stratosphere (UTLS). It efficiently transports air masses from the boundary layer to the upper troposphere, carrying constituents such as humidity, aerosols, and aerosol precursors from pristine surface regions over South America. Recent studies suggest these precursors may significantly influence new particle formation in the upper troposphere. Similarly, pollutants originating from biomass burning or densely populated urban centers can be transported to the tropopause, disrupting the natural chemical equilibrium in this region. Upon crossing the tropopause, transported constituents integrate into the so-called extratropical transition layer (ExTL). This layer, located just above the tropopause, exhibits a hybrid chemical composition with characteristics of both the troposphere and the stratosphere. The ExTL is highly sensitive to chemical perturbations, with implications for the atmospheric energy budget and, consequently, surface climate. This project focuses on the mechanisms of tropopause exchange driven by convection and their effects on the tropopause region. Relevant mechanisms include convective gravity waves and horizontal or vertical wind shear, both of which can induce turbulence near the tropopause. However, convection itself significantly perturbs the dynamic tropopause, making its identification using meteorological analysis data highly uncertain. Such data often fail to resolve the small-scale processes critical for analyzing cross-tropopause exchange and tracer fluxes. To address these challenges, we will adopt a tracer-based approach to define the tropopause, leveraging the inert tracer N2O to unambiguously distinguish between tropospheric and stratospheric air. Additionally, we will employ a novel method based on recent measurements of C2H6 (ethane), which allows precise determination of the upper boundary of the ExTL. Finally, we aim to quantify the contribution of gravity-wave-induced turbulence generated by convective cells to the composition of the ExTL. To achieve this, we will utilize high-resolution (100 Hz) wind data to derive irreversible tracer fluxes near and downstream of convective cells at the tropopause. This approach builds on methodologies successfully applied to orographically induced gravity waves and their impact on turbulent tracer transport, with the goal of elucidating their influence on ExTL composition.
DFG Programme
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