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| Home > Publications database > Variability in Upper Troposphere – Lower Stratosphere transport from model age of air |
| Home > Publications database > Variability in Upper Troposphere – Lower Stratosphere transport from model age of air |
| Conference Presentation (After Call) | FZJ-2025-03570 |
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2025
Abstract: Understanding transport pathways and timescales in the upper troposphere and lower stratosphere (UTLS) is essential for assessing changes in atmospheric composition, particularly for radiatively active trace gases. These species play a crucial role in the Earth’s radiation budget, yet their variability and trends remain uncertain due to incomplete representation of transport processes in current models.To address this, we analyze the evolution of UTLS transport over the past four decades by determining the Age of Air—the transit time from the troposphere into the stratosphere. We employ the Chemical Lagrangian Model of the Stratosphere (CLaMS), driven by ERA5 reanalysis data from 1979 to 2024, to investigate these research questions: 1. What does the climatology of Age of Air reveal about underlying transport mechanisms? 2. How have transport pathways and timescales changed over the last 40 years? 3. How do interannual drivers such as the Quasi-Biennial Oscillation (QBO) and El Niño-Southern Oscillation (ENSO) influence transport variability? 4. How do composition changes in the UTLS relate to observed and modeled trends in the Brewer-Dobson circulation (BDC), the tropopause, and subtropical transport barriers?We assess trends, seasonal cycles, and interannual variations in high-resolution Age of Air spectra, mean Age of Air and the mass fractions of young air. Our findings demonstrate significant improvements in the representation of fast transport processes, particularly in the tropics, enabled by the higher temporal resolution of the simulated age spectra compared to previous studies. In particular, fine-scale structure and sharp peaks in the age spectra relate to fast transport processes. These insights contribute to a more robust understanding of UTLS transport dynamics and their role in shaping atmospheric composition and climate variability.
Keyword(s): Geosciences (2nd)
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