How is the stratosphere-troposphere coupling affected by climate change, and how strong is the climate feedback? (SHARP-STC)

• Antragstellerinnen / Antragsteller: Professor Dr. Martin Dameris; Professorin Dr. Ulrike Langematz; Dr. Hauke Schmidt
• Fachliche Zuordnung: Physik und Chemie der Atmosphäre
• Förderung: Förderung von 2009 bis 2017
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 68851489

• Erstellungsjahr: 2017

Zusammenfassung der Projektergebnisse

In Phase II, the SHARP-STC project continued to address advanced aspects of stratospheretroposphere coupling (STC). In addition to the dynamical coupling, which had been the focus of SHARP- STC in Phase I, new emphasis was put on the effects of the radiative and chemical coupling between the layers. Moreover, additional climate feedback associated with atmosphere-ocean-cryosphere coupling was investigated. The relevance of the model configuration for STC, such as the vertical resolution, the representation of the stratosphere, and the coupling to the ocean, was addressed. The overall interest was on the effects of climate change on STC as well as on the feedback of changes in STC on climate. New simulations with the ECHAM/MESSy Atmospheric chemistry (EMAC) chemistry climate model (CCM) were performed and analysed by the partners in the different SHARP projects. A new version was EMAC coupled to the MPI ocean model was applied, hence allowing us to take feedback processes between atmospheric chemistry and ocean into account. In addition, CMIP5 simulations with the MPI-ESM-LR (Max Planck Institute Earth System Model) were analysed. The following major results have been achieved: About 80 % of stratospheric weak or strong polar vortex events show no significant tropospheric response. A tropospheric response is found after persistent stratospheric perturbation, while the strength of the stratospheric perturbation determines the tropospheric response only to a small degree. ₋ No statistically significant variation is found in the decadal-mean frequency of MSWs in the future, however a shift of their timing toward midwinter is detected. The strengthening of the polar vortex in early winter is due to ozone recovery. In midwinter, stratospheric dynamical variability will increase due to higher tropical sea surface temperatures. ₋ While the Arctic stratosphere is projected to be colder in early winter, the stronger planetary wave activity in late winter is likely to prevent large chemical Arctic spring ozone losses, as observed in March 2011. ₋ The radiative cooling of the stratosphere will be dominated by the increase of CO2 and increase throughout the 21st century according to the RCP8.5 greenhouse gas scenario. The projected changes of stratospheric ozone will lead to temperature changes of opposite sign in the upper stratosphere (positive) and lower stratosphere and mesosphere (negative). ₋ Between 2000 and 2100 the ozone mass flux into the troposphere will increase by 53 % under the RCP8.5 scenario. 46 % of the increase is due to rising GHGs, 7 % is due to ozone recovery. ₋ Significant effects of reduced future Arctic sea ice were found in the stratosphere in November. ₋ Past Antarctic sea ice changes are linked to intensified meridional winds caused by a lowering of the high-latitude surface pressure due to both stratospheric ozone depletion and GHG increase. ₋ The stratospheric decline in water vapor in 2000 was triggered by tropical sea surface temperature anomalies associated with ENSO and anomalously low tropopause temperatures. ₋ Longer projections under extreme climate change (scenario RCP8.5 after 2100) show a reduced frequency of sudden stratospheric warmings, a seasonal shift towards late winter with a strong impact on tropospheric circulation.

Projektbezogene Publikationen (Auswahl)

• (2012), Implications of all season Arctic sea-ice anomalies on the stratosphere, Atmos. Chem. Phys., 12, 11819-11831
  Cai, D., M. Dameris, H. Garny, and T. Runde
  
• (2013), The role of climate change and ozone recovery for the future timing of major stratospheric warmings, Geophys. Res. Lett., 40, 2460–2465
  Ayarzagüena, B., U. Langematz, S. Meul, S. Oberländer, J. Abalichin, and A. Kubin
  
• (2013). The response of the middle atmosphere to anthropogenic and natural forcing in the CMIP5 simulations with the MPI-ESM. Journal of Advances in Modeling Earth Systems, 5, 98-116
  Schmidt, H., Rast, S., Bunzel, F., Esch, M., Giorgetta, M., Kinne, S., Krismer, T., Stenchikov, G., Timmreck, C., Tomassini, L. & Walz, M.
  
• (2014), Anthropogenic influence on recent circulation-driven Antarctic sea-ice changes. Geophys. Res. Lett., 41, 8429-8437
  Haumann, F., D. Notz, and H. Schmidt
  
• (2014), Future Arctic temperature and ozone: The role of stratospheric composition changes, J. Geophys. Res. Atmos., 119, 2092–2112
  Langematz, U., S. Meul, K. Grunow, E. Romanowsky, S. Oberländer, J. Abalichin, and A. Kubin
  
• (2015), The Relevance of the Location of Blocking Highs for Stratospheric Variability in a Changing Climate. J. Climate, 28, 531–549
  Ayarzagüena, B., Y. J. Orsolini, U. Langematz, J. Abalichin, and A. Kubin
  
• (2016), Classification of stratospheric extreme events according to their downward propagation to the troposphere, Geophys. Res. Lett., 43, 6665–6672
  Runde, T., M. Dameris, H. Garny, and D. E. Kinnison
  
• (2016), The millennium water vapour drop in chemistry-climate model simulations, Atmos. Chem. Phys., 16, 8125 – 8140
  Brinkop, S., M. Dameris, P. Jöckel, H. Garny, S. Lossow and G. P. Stiller
  
• A new radiation infrastructure for the Modular Earth Submodel System (MESSy, based on version 2.51), Geosci. Model Dev., 9, 2209-2222, 2016
  Dietmüller, S., Jöckel, P., Tost, H., Kunze, M., Gellhorn, C., Brinkop, S., Frömming, C., Ponater, M., Steil, B., Lauer, A., and Hendricks, J.