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Dynamical processes in the tropopause region and their impact on the distribution of atmospheric trace gases (PROTRO)
Start date: Jan 1, 2013, End date: Dec 31, 2014 PROJECT  FINISHED 

"This proposal outlines a research project in atmospheric sciences that addresses tropopause related processes, which contribute to chemistry-climate coupling. The tropopause region is characterized by frequent air mass exchange between the upper troposphere (UT) and lower stratosphere (LS). It is a region of significant coupling between atmospheric dynamics, chemistry, and radiation. It is therefore particularly relevant to climate. The aim of this project is to improve our ability to quantify the interaction of dynamical and chemical processes controlling the UT/LS in a changing climate.The study will make use of a novel concept of the dynamical tropopause recently developed by the applicant. This tropopause is identified by maximized potential vorticity (PV) gradients on isentropes. There is a close consistency of this PV gradient-based tropopause and the chemical discontinuity in trace gas concentrations near the jet streams suggesting that the novel tropopause concept well identifies the barrier for cross-tropopause transport. Further, preferred transport pathways in the UT/LS are revealed by studying regions where strong trace gas gradients and the PV gradient-based tropopause decouple. Using the novel tropopause concept, this project will in particular investigate stratosphere-troposphere exchange (STE) on higher altitudes than hitherto common and will aim at an improved quantification of trace gas fluxes across the tropopause. Feature-based climatologies of tropopause structures will be produced using 20 years of ERA-Interim data. UT/LS trace gas constituents associated with these tropopause structures will be investigated using state-of-the-art numerical models, the chemistry-climate model WACCM and the Lagrangian model CLaMS. High quality observational trace gas data based on the SPURT and START08 aircraft campaigns will be employed for model evaluation. In summary, this study will provide new insight into fundamental and climate relevant UT/LS processes."
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