Researchers studying the aerosol burden after the Hunga Tonga Ha'apai eruption on the 15th of January 2022 found that the aerosols coagulated and fell out of the stratosphere faster than after the Pinotubo eruption. It is a submarine volcano in the Tongan archipelago in the southern Pacific Ocean. The eruption at its height produced a series of four underwater thrusts, displaced
10 cubic kilometres (2.4 cu mi) of rock, ash and sediment, and generated
the largest atmospheric explosion recorded by modern instrumentation.
The researchers suggested that the faster rate of coagulation and sedimentation in the Hunga Tonga plume was due to the amount of seawater ejected.
The consensus seems to be that fixed-wing jet aircraft are the way forward (or up) for SAI, so we need to take into acount the number of flights crossing the tropopause, which increases mixing across the tropopause, and the amount of CO2 and H2O added and O2 removed from the stratosphere in bulk terms, due to the combustion of jet fuel..
As the aircraft exhaust and the aerosol will be mixed into the plume together at high temperature in the early moments when coagulation can happen rapidly, the amount of water added to the plume may have a significant effect on coagulation and sedimentation rates. Therefore accurately modelling the amount of fuel burnt while deploying the aerosol could be important, as at may affect the atmospheric lifetime of the injected aerosol.
Best Regards, Colin Forrest