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

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.

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)

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

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

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

Calculated and observed SO2 28km E E

Calculated and observed SO2 %

SO2, 40km

SO2, 40km %

SO2, tropics, EMAC and MIPAS

SO2, tropics, EMAC and MIPAS

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

Sulphate, COS and QBO E E E

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

Radiative forcing and optical depth Pinatubo Medium size eruptions

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

Accum. mode, soluble, r and N

Stratospheric aerosol total radiative heating midlatitude tropics

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

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)

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

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

SO2 at 18km, EMAC and MIPAS

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

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

Sulfate and organic carbon

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

Aerosol water and black carbon

Dust Cl

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?

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

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

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

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

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

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

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

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

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

Strat. aerosol radiative heating

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