Volcanoes and the Atmosphere

Rich Stolarski 22 June 2012

Pinatubo

Lessons learned about atmospheric effects from recent volcanoes

• Volcanic effects short-lived unless plume reaches stratosphere

• Large particles (ash) fall out quickly• Sulfur content is what counts (particles < 1μ)

– SO2 converted to H2SO4; reaction initiated by OH– For Pinatubo/El Chichon-sized volcanoes, OH is regenerated– Sulfur content (in %) of larger eruptions less than smaller eruptions– But absolute sulfur amount still increases with larger eruptions– For Toba, hydrogen required for sulfate conversion is > H2O available– Toba calculated to increase tropopause temperature and let much

more H2O into stratosphere

Stratospheric Circulation

• Tropical volcanoes inject gases into upward part of Brewer-Dobson circulation

• High-latitude volcanoes inject gases into downward part of Brewer-Dobson Circulation– Heating within plume

may still cause significant rise

Terminal fall velocities for spherical particles

1 micron

1 km

/mon

th

Upward vertical velocities in tropical lower stratosphere: ~ 1 km/month

Velocities in Pinatubo plume due to sulfate heating ~10 km/month

0.3

km/m

onth

0.5 micron

@ 20 km

Sulfate heating causes significant plume rise for Pinatubo-sized eruption

Pinatubo Injection at 16-18 km

Aquila, V., L. D. Oman, R. S. Stolarski, P. R. Colarco, and P. A. Newman (2012), Dispersion of the volcanic sulfate cloud from a Mount Pinatubo–like eruption, J. Geophys. Res., 117(D6), 1–14, doi:10.1029/2011JD016968.

Spread of Volcanic aerosol now measured in detail from satellites

Aquila, V., L. D. Oman, R. S. Stolarski, P. R. Colarco, and P. A. Newman (2012), Dispersion of the volcanic sulfate cloud from a Mount Pinatubo–like eruption, J. Geophys. Res., 117(D6), 1–14, doi:10.1029/2011JD016968.

Rampino, M. R., and S. Self (1982), Historic eruptions of Tambora (1815), Krakatau (1883), and Agung (1963), their stratospheric aerosols, and climatic impact, Quaternary Research, 18(2), 127–143.

Volcano Ratio Silicate Dust Ratio SulfateTambora 150 7.5

Krakatau 20 3

Agung 1 1

Rampino, M. R., and S. Self (1982), Historic eruptions of Tambora (1815), Krakatau (1883), and Agung (1963), their stratospheric aerosols, and climatic impact, Quaternary Research, 18(2), 127–143.

Highest explosivity volcanic eruptions are less sulfur (and chlorine) rich

Self, S. (2006), The effects and consequences of very large explosive volcanic eruptions, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 364(1845), 2073–2097, doi:10.1098/rsta.2006.1814.

Reaction Mechanism for SO2 to sulfate

SO2 + OH + M HSO3 + MHSO3 + O2 SO3 + HO2

SO3 + H2O H2SO4

HO2 + O3 OH + 2O2

-------------------------------------net: SO2 + H2O + O3 H2SO4 + O2

Self-limiting effects for large volcanic eruptions-------------------------------------------- More sulfur larger particles faster fallout

***************************But lifetime of SO2 can be increased by SO2 absorption-------------------------------------------- SO2 absorption of radiation less O(1D) production less OH production slower conversion to particles

Does available water limit sulfate formation for large volcanoes like Toba?

Rampino, M. R., and S. Self (1993), Climate-volcanism feedback and the Toba eruption of 74,000 years ago, ∼Quaternary Research, 40(3), 269–280.

Warming of tropical tropopause adds significant water to stratosphere after Toba eruption

Robock, A., C. M. Ammann, L. Oman, D. Shindell, S. Levis, and G. Stenchikov (2009), Did the Toba volcanic eruption of 74 ka B.P. produce widespread glaciation? ∼ J. Geophys. Res., 114(D10), doi:10.1029/2008JD011652.

Volcanic Impacts on Stratospheric Ozone

• Sulfur sulfate destroys one ozone, but it is not catalytic• Chlorine/Bromine are obvious candidates

– But are soluble and rainout– Does it all rainout?

• Impacts of Pinatubo/El Chichón/Agung-sized eruptions in present or recent past atmosphere depend on background chlorine concentration– Initial chemical impact is conversion of NOx to HNO3 on surfaces; this

reduces NOx catalytic loss of ozone

– Secondary chemical impact is reduction of NOx interference with HOx and ClOx catalytic cycles; this increases loss of ozone

– Secondary impact significantly larger at high chlorine content ca 2000 (Pinatubo) compared to 1963 (Agung) or 1982 (El Chichón)

Chlorine (HCl) measurements in the El Chichón and Pinatubo

volcanic clouds

Mankin, W. G., M. Coffey, and A. Goldman (1992), Airborne observations of SO2, HCl, and O3 in the stratospheric plume of the Pinatubo volcano in July 1991, Geophys. Res. Lett., 19(2), 179–182.

MANKIN, W., and M. Coffey (1984), Increased Stratospheric Hydrogen-Chloride in the El-Chichon Cloud, Science, 226(4671), 170–172.

El Chichón

Pinatubo

Sensitivity of ozone to volcanic perturbations as a function of background chlorine amount

Tie, X. X., and G. Brasseur (1995), The response of stratospheric ozone to volcanic eruptions: Sensitivity to atmospheric chlorine loading, Geophys. Res. Lett., 22(22), 3035–3038.

Chemical Transport Model of Pinatubo Effect on Ozone

1991 Eruption1975 Eruption

Ozone perturbations due to volcanic eruptions deduced from Ground-Based Total Ozone Data

Angell, J. K. (1997), Estimated impact of Agung, El Chichón and Pinatubo volcanic eruptions on global and regional total ozone after adjustment for the QBO, Geophys. Res. Lett., 24(6), 647–650.

Rampino, M. R., and S. Self (1982), Historic eruptions of Tambora (1815), Krakatau (1883), and Agung (1963), their stratospheric aerosols, and climatic impact, Quaternary Research, 18(2), 127–143.

Nabro Volcano, Eritrea, 2011

o High sulfur contento Penetrated to 14 km (still in tropical troposphere)o Plume captured into Indian monsoon and transported into

stratosphere