Working Group leads:   James Keeble, University of Cambridge, UK (jmk64 @ cam.ac.uk)

                                              Paul Griffiths, University of Cambridge, UK (ptg21 @ cam.ac.uk)

    TOAR-II Steering Committee liaison:  Keding Lu, Peking University, China (k.lu @ pku.edu.cn) 

     Established:  August 20, 2021

The Role of STE in the Earth System (ROSTEES) Focus Working Group has the following objectives:

The transport of ozone from the stratosphere to the troposphere is a key contributor to the tropospheric ozone budget. It is estimated that the stratosphere-to-troposphere flux of ozone (STT) leads to ~500 Tg of ozone transported into the troposphere each year, which is comparable to the net chemical production of ozone within the troposphere. As stratospheric ozone recovers in response to declining levels of ozone depleting substances, and stratospheric circulation accelerates in response to increasing greenhouse gases, it is expected that STT will increase throughout the 21st century, which poses a challenge to climate change mitigation and air quality targets. The WG aims to identify the role of STT in the Earth system through exploitation of model simulations performed as part of the CCMI-2022 activity and observational datasets. Key objectives of the WG include:

1. Improved quantification of present day STT and its role in the tropospheric ozone budget
2. Quantification of the extent to which STT affects surface ozone mixing ratios
3. Identify the impacts of stratospheric ozone recovery and stratospheric circulation changes on STT
4. Examine the sensitivity of stratosphere-to-troposphere transport of ozone to different definitions of the tropopause
5. Quantification of the transport of species from the troposphere to the stratosphere

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