Ozone Depleting Substances: Key Drivers of Past and Future BDC - PowerPoint PPT Presentation

Ozone Depleting Substances: Key Drivers of Past and Future BDC Trends Marta Abalos 1 Lorenzo Polvani 2 Natalia Calvo 1 Douglas Kinnison 3 Felix Ploeger 4 William Randel 3 Lei Wang 5 CCMI coauthors 1 Universidad Complutense de Madrid, Spain 2 Columbia University, NY, USA 3 National Center for Atmospheric Research, CO, USA 4 Forschungszentrum Jülich, Germany 5 Fudan University, Shanghai, China 20 th AMS Middle Atmosphere Conference – January 2019 Phoenix, AZ

Anthropogenic emissions: the ODS fingerprint ODS 50 hPa CO 2 surface WMO A1 RCP 6.0 Peak in ~2000 Monotonic increase All forcing Fixed ODS Fixed GHG 1960-2100 runs CESM-WACCM1 ODS fixed to GHG fixed to ODS + GHG + CCMVal2 + CCMI models 1960, GHG 1960, ODS varying varying varying 2

Age of air trends PAST FUTURE annual WACCM pre-2000 post-2000 mean All forcing Polvani, Abalos et al. 2018 GRL Fixed ODS Fixed GHG 3

Results are consistent in 20 models (CCMI and CCMVal2) annual FUTURE PAST mean pre-2000 post-2000 Weaker AoA trends in the future (factor of ~2 for the MMM) 4 Polvani, Wang, Abalos et al. under review

Change in past/future annual trends due to ODS in most models All forcing Fixed ODS Fixed GHG 5 Polvani, Wang, Abalos et al. under review

Disentangling the radiative versus chemical effects of ODS All forcing Fixed ODS No (HET) ozone depletion 6 Abalos et al. under review

Impact of Antarctic ozone hole on DJF SH downwelling accelerates tropical upwelling by mass continuity DJF net mass flux SH Tropics NH All forcing Fixed ODS No (HET) ozone depletion 7 Abalos et al. under review

Residual circulation trends DJF 1980-2000 JRA-55 All forcings WACCM Impact of ODS (All forcings minus Fixed ODS) 8 Abalos et al. under review

Isentropic mixing trends (Λ eq ) DJF ~30 km 1980-2000 JRA-55 ~10 km All forcings WACCM Impact of ODS (All forcings minus Fixed ODS) 9 Abalos et al. under review

Mean age of air trends DJF 1980-2000 JRA-55 All forcings WACCM Impact of ODS (All forcings minus Fixed ODS) 10 Abalos et al. under review

DJF SH trends are robust in reanalyses JRA-55 ERA-I DJF 1980-2000 Residual circulation Isentropic mixing 1984-2000 Mean age of air 11 Abalos et al. under review

Conclusions ● Ozone depleting substances (ODS) are key drivers of past and future Brewer-Dobson circulation (BDC) trends. ● This impact is mainly through ozone depletion , the greenhouse effect contribution of ODS to the BDC is negligible. ● The ozone hole is the cause of the most robust BDC trend features in reanalyses over the last decades of 20 th century. 12

Published: - Polvani L., Abalos M. , Garcia R., Kinnison D. and Randel W.: Significant weakening of the Brewer-Dobson circulation trends over the 21 st century as a consequence of the Montreal Protocol. Geophysical Research Letters (2017), doi: 10.1002/2017GL075345. Under Review: - Polvani L., Wang L., Abalos M. , M.P. Chipperfield, M. Deushi, S.S. Dohmse, P. Jöckel, D. Kinnison, M. Michou, O. Morgenstern, L.D. Oman, D.A. Plummer, K.A. Stone: Large impacts, past and future, of ozone depleting substances on Brewer-Dobson circulation trends: A multi-model assessment . Under Review. - Abalos M. , Polvani L., Calvo N., Kinnison D., Ploeger F., Randel W.: New insights on the impact of ozone depleting substances on the Brewer-Dobson circulation. Under Review. Thank you! 13

Residual circulation: ODS signal dominated by austral summer SH polar Tropical NH polar downwelling upwelling downwelling All forcing Polvani, Abalos et al. 2018 GRL Fixed ODS Fixed GHG annual DJF 14

Annual mean trends 1980-2000 JRA-55 ERA-I Residual circulation Isentropic mixing Mean age of air 15

w* w*m w*Q 1980-2000 DJF: Most robust reanalysis trends in residual circulation 16