PROTRO

Dynamical processes in the tropopause region and their impact on the distribution of atmospheric trace gases

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 Obiettivo del progetto (Objective)

'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.'

Introduzione (Teaser)

Researchers have developed and tested a new method to identify and quantify processes taking place at the boundary between the troposphere and the stratosphere.

Descrizione progetto (Article)

The boundary between the troposphere and the stratosphere, called the tropopause, plays an important role in the climate system because of the complex interaction of atmospheric dynamics, solar radiation and chemical processes in this region. The tropopause is also a region where vigorous air transfer between the troposphere and stratosphere can occur in both directions.

The EU-funded PROTRO (Dynamical processes in the tropopause region and their impact on the distribution of atmospheric trace gases) project was established to quantify atmospheric processes occurring at the tropopause, based on a newly developed definition of the dynamical tropopause. The researchers studied air mass exchange between the upper troposphere and lower stratosphere for the present climate conditions.

Lastly, researchers analysed water vapour differences across the tropopause, both in models and observations. This information will be very useful to further improve global weather prediction and climate models.

PROTRO has confirmed the relevance of the dynamical tropopause concept, and improved understanding of climate processes at the tropopause. These findings will contribute to the worldwide effort to better understand climate processes and eventually climate change.