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, Brühl et al., 2012, Atmos.Chem.Phys., 12, ; 2013, ACPD 13, Pringle et al. 2010, Geosci.Model Dev. 3, Bardeen et al., 2008, J.Geophys.Res. 113, D17202.

3. Sulphur sources Pinatubo (Jun 91) 17000 kt, up to 27km
Reventador + (Nov,Dec 02)
90 kt, 20km
Manam (Jan 05)
190 kt, 20km
Soufriere Hills (May 06)
280 kt, 20km
Rabaul (Oct 06)
380 kt, 18km
Kasatochi (Aug 08, 52N)
1580 kt (750 kt in strat.)
Sarychev (Jun 09, 48N)
1200 kt (650 kt in strat.)
Soufriere Hills (Feb 10)
70 kt, 19km
Merapi (Oct 10)
230 kt, 17km
Nabro (Jun 11, tropics + midlat)
1500 kt (500 kt in strat.)
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
Manam
Kasatochi 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)
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 rcs>1.6µm
MODIS (Pringle et al, 2010)
rcs>1.6µm

38. Accum mode, number and rwet, 1.6µm and 1.0µm limit to coarse
(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