volcanoes and the atmosphere
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Pinatubo. Volcanoes and the Atmosphere. Rich Stolarski 22 June 2012. Lessons learned about atmospheric effects from recent volcanoes. Volcanic effects short-lived unless plume reaches stratosphere Large particles (ash) fall out quickly - PowerPoint PPT PresentationTRANSCRIPT
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