Christoph Brühl, Jos Lelieveld MPI for Chemistry, Mainz

1. Stratospheric sulphur and its implications for radiative forcing as simulated by the CCM EMAC with interactive aerosol Christoph Brühl, Jos Lelieveld MPI for Chemistry, Mainz Holger Tost, J. Gutenberg University, Mainz Michael Höpfner, KIT, Karlsruhe

2. EMAC, ATF-Version (1.9/1.10) • Mecca1 chemistry module, modified for SOx (with enhanced H2SO4 NIR photolysis [966nm] and SOx sink on meteoritic dust) + GMXe aerosol module (4 soluble and 3 insoluble modes with eqsam, snuc,ait=1.59, sacc=1.49, scs=1.7; lower mode boundaries ait 0.006, acc 0.07, cs 1.6µm) + scavenging by clouds • Resolution T42/L90 (to 1Pa with QBO), up to 13 years, spin-up of background sulphate aerosol 3 years, beginning in 1996 • Optical properties of aerosol from lookup-table (Mie based, types H2O, water soluble, OC, BC, dust, sea salt) • Aerosol radiative forcing calculated diagnosticly (multiple calls of radiation routine online, with and without feedback to dynamics) • Aerosol sedimentation of F. Benduhn (JGR 2013) • GMXe-aerosol can be used in heterogeneous chemistry References: Jöckel et al., 2006, Atmos.Chem.Phys. 6, 5067-5104. Brühl et al., 2012, Atmos.Chem.Phys., 12, 1239-1253; 2013, ACPD 13, 11395. Pringle et al. 2010, Geosci.Model Dev. 3, 391-412. Bardeen et al., 2008, J.Geophys.Res. 113, D17202.

3. Sulphur sources • Volcanic SO2 injections into stratosphere estimated from SAGE, MIPAS and OMI/TOMS data (for most tropical volcanoes zonal average used, for midlatitudes peaking at observed longitude with linear decrease to zero at the other side of the globe. Manual input) • Climatology for outgassing volcanoes • COS at surface nudged to observations (Montzka). Typical mixing ratio 0.5ppbv. • DMS contributes a few ppt to stratospheric SO2 locally (East Pacific), often neglected. • Anthropogenic emissions from EDGAR(2000ft or 4.2)

4. COS MIPAS (Adrian Leyser, Diplomathesis, Karlsruhe, 2013) EMAC May 2010 E Sept. 2011 2011 2010 W E E

5. Observed and calculated COS MIPAS EMAC E 26km E 16km

6. Calc and obs SO2, 22km EMAC Höpfner et al, ACPD 13, 12389

7. Calculated and observed SO2 28km E E

8. Calculated and observed SO2 %

9. SO2, 40km

10. SO2, 40km %

11. SO2, tropics, EMAC and MIPAS

12. SO2, tropics, EMAC and MIPAS

13. EMAC, sulphate aerosol and SO2 Contours zonal wind 5S-5N in steps of 10m/s Merapi Soufriere Hills Kasatochi Manam E E E E E Nyiragongo + Reventador S.H. Nabro Rabaul Sarychev

14. Sulphate, COS and QBO E E E

15. Sulphate and SO2 burden above 13km EMAC sulphate, symbols SAGE II 80S-80N EMAC SO2 80S-80N 60S-60N, 13-20km MIPAS SO2, indiv. data

16. Radiative forcing and optical depth Pinatubo Medium size eruptions

17. Global strat. aerosol forcing W/m2 EMAC, 5-day values EMAC, annually smoothed EMAC, annual, x 0.1; 5-day, x 0.1 (Pinatubo) Solomon et al, Science 333, 866

18. Accum. mode, soluble, r and N

19. Stratospheric aerosol total radiative heating midlatitude tropics

20. Enhancement of tropical upwelling by Pinatubo aerosol heating, lofting H2O N2O SO2 Sulphate

21. Pinatubo, Log (1µm extinction), EMAC and SAGE (20Mt scenario) Feedback of aerosol radiative heating to dynamics leads to lofting of the aerosol and a significant increase of extinction in the upper part of the aerosol cloud (20Mt runs)

22. DMS and SO2-change at 100hPa (2004) Volcano, dynamics DMS

23. Effects of anthropogenic emissions in China (5xEDGAR2000ft), 100hpa Annual average (2007) July to October (monsoon)

24. SO2 at 18km, EMAC and MIPAS

25. SO2 at 18km, EMAC and MIPAS Pollution x 5 Volcano?

26. 5 x Chinese pollution, tropics Volcanoes 5 x pollution W/m2 Global forcing

27. Sulfate and organic carbon

28. Conclusions • Transport of COS from the troposphere and volcanic eruptions in the tropics explain most of the observed stratospheric aerosol load • The global radiative forcing of the aerosol from medium size volcanoes of up to -0.3W/m2 is non-negligible and may contribute to the observed slowdown of global warming • The contribution of Chinese SO2 pollution is small against that (about 1%, 5% in case of 5 x pollution) • For major eruptions like Pinatubo the coupling of aerosol radiative heating to model dynamics is essential for the development of sulphur species in the stratosphere and radiative forcing to the troposphere • In case of Pinatubo the 4-mode aerosol scheme is at its limits, because a minor fraction in the coarse mode causes an overestimate of particle sedimentation and too fast aerosol removal. Nevertheless we found a working compromise for a consistent troposphere and stratosphere

29. Aerosol water and black carbon

30. Dust Cl

31. Sulphate mixing ratios, Pinatubo, 20Mt • Too fast sedimentation in 1992 because even with the large mode boundary of 1.6µm there is up to about 1ppbv in the coarse mode (for 1.0µm was up to 8ppb there). • Further increase of mode boundary does not help much but leads to too unrealistic results in troposphere • Introduce further mode?

32. Effects of 5 x anthropogenic emissions in China 11 June 2007 SO2, ppbv level From volcanoes in 2006 Sulphate, ppbv EDGAR 5 x EDGAR

33. Total optical depth at 530 (525) nm Tropics EMAC 20-30km EMAC 15-30km Neely, 2013, satellite Neely, 2013, model Midlatitudes EMAC 15-30km

34. Burdens of OC, BC, dust, sea salt (annual average 2004) BC OC dust SS, mg/m2 Compare Pringle et al 2010 GMD

35. Burdens of sulphate, nitrate, aerosol water (annual average 2004) SO4 to 14km SO4 to 9km H2O to 14km, mg/m2 NO3 to 14km

36. Burdens of sulphate, nitrate, aerosol water (annual average 2006) SO4 to 14km, With volcanoes SO4 to 9km H2O to 14km, mg/m2 NO3 to 14km

37. AOD at 530nm, average 2007 rcs>1.0µm MODIS (Pringle et al, 2010) rcs>1.6µm

38. Accum mode, number and rwet, 1.6µm and 1.0µm limit to coarse 1.6µm 1.0µm (1/cm3) (µm)

39. Pinatubo, rwet (µm), 4 modes, EQ Model year 2000 is 1991

40. Pinatubo, log(number), 4 modes, EQ Model year 2000 is 1991 30km Trop. Tropopause

41. Strat. aerosol radiative heating

42. Radiative heating and change of T, u, and water vapor, tropics Contours zonal wind without feedback to dynamics