Volcanic SAI
John Nissen
Hi all,
Aaron Franklin alerted us to the paper about
a submarine volcano [1] suggesting it showed aerosol warming but I don’t think
it does: read the extracts below. Water
and sulphate aerosol separate, and they discuss the cooling from the water
vapour. It is interesting to see that
the aerosol injected at low latitude (20.54°S) from a powerful volcano lingers
for months in the mid-stratosphere, gradually falling out due to gravity.
For polar cooling intervention, injection would be in late spring and early summer into the lower stratosphere at high latitude, such that Brewer-Dobson air circulation plus gravity would ensure a much shorter life-time of a few months, as optimum for albedo cooling and avoiding ozone depletion, a late winter reaction.
Cheers, John
[1] Schieberl et al (AGU, September 2022)
Analysis and Impact of the Hunga Tonga-Hunga Ha'apai Stratospheric Water Vapor Plume
Abstract
On 15 January 2022, the Hunga Tonga-Hunga Ha'apai eruption injected SO2 and H2O into the middle stratosphere. The eruption produced a persistent mid-stratospheric sulfate aerosol and H2O layer mostly confined to Southern Hemisphere (SH) tropics (Eq. to 30°S). These layers are still present in the tropics 5½ months after the eruption. The SH tropical confinement is simulated using a trajectory model. Measurements following the eruption show that the H2O layer is slowly rising while the aerosol layer is descending. The H2O layer's upward movement is consistent with the residual vertical velocity. Gravitationally settling explains the descent of the aerosol layer. A −4 K temperature anomaly coincident with the H2O enhancement is observed and is caused by thermal adjustment to the additional H2O IR cooling. A simple model of volcanic water injection at the time of the eruption simulates the observed vertical distribution H2O.
Key Points
· Hunga Tonga-Hunga Ha'apai eruption produced vertically overlapping but slightly displaced mid-stratospheric enhancements in H2O and aerosols
· IR cooling by enhanced H2O layer explains the observed 4.1 K mid-stratospheric temperature decrease following the eruption
· A simple model of the eruption H2O enhancement combined with spreading of the plume explains the observations