Can you extrapolate to greater altitudes? On Sun, 15 Dec 2019, 05:38 Govindasamy Bala, <[email protected]> wrote:
> Dear Andrew, > Thanks for the posting. The heights studied were 16, 19 and 22 km, height > that are relevant to solar radiation modification problem.. The final > paragraph in the paper is worth reading to get more quantitative > information from this modeling study. > > "To summarize, for the same mass, the efficiency (defined > as changes in surface temperature per Tg S) of volcanic > aerosol is less when it is prescribed at lower altitudes in the > stratosphere (Fig. 9). For example, in our simulations, there is > a surface cooling of 0.44K for each teragram of sulfur placed > in the stratosphere at about 16 km altitude (100 hPa). There > is an additional surface cooling of 0.15K per Tg S when the > prescribed altitude is increased from about 16 km to about > 22 km (37 hPa)." > > On Sat, Dec 14, 2019 at 12:55 AM Andrew Lockley <[email protected]> > wrote: > >> Poster's note : this has significant implications for the engineering of >> delivery systems. I can't do the pressure altitude conversion in my head, >> but it's a lot higher than what's generally been planned for. We're gonna >> need a bigger boat. >> >> >> https://www.earth-syst-dynam.net/10/885/2019/ >> >> Climate system response to stratospheric sulfate aerosols: sensitivity to >> altitude of aerosol layer >> Krishna-Pillai Sukumara-Pillai Krishnamohan et al. Received: 01 May >> 2019 – Discussion started: 23 May 2019 – Revised: 24 Oct 2019 – Accepted: >> 08 Nov 2019 – Published: 13 Dec 2019 >> Abstract >> top <https://www.earth-syst-dynam.net/10/885/2019/#top> >> >> Reduction of surface temperatures of the planet by injecting sulfate >> aerosols in the stratosphere has been suggested as an option to reduce the >> amount of human-induced climate warming. Several previous studies have >> shown that for a specified amount of injection, aerosols injected at a >> higher altitude in the stratosphere would produce more cooling because >> aerosol sedimentation would take longer. In this study, we isolate and >> assess the sensitivity of stratospheric aerosol radiative forcing and the >> resulting climate change to the altitude of the aerosol layer. We study >> this by prescribing a specified amount of sulfate aerosols, of a size >> typical of what is produced by volcanoes, distributed uniformly at >> different levels in the stratosphere. We find that stratospheric sulfate >> aerosols are more effective in cooling climate when they reside higher in >> the stratosphere. We explain this sensitivity in terms of effective >> radiative forcing: volcanic aerosols heat the stratospheric layers where >> they reside, altering stratospheric water vapor content, tropospheric >> stability, and clouds, and consequently the effective radiative forcing. We >> show that the magnitude of the effective radiative forcing is larger when >> aerosols are prescribed at higher altitudes and the differences in >> radiative forcing due to fast adjustment processes can account for a >> substantial part of the dependence of the amount of cooling on aerosol >> altitude. These altitude effects would be additional to dependences on >> aerosol microphysics, transport, and sedimentation, which are outside the >> scope of this study. The cooling effectiveness of stratospheric sulfate >> aerosols likely increases with the altitude of the aerosol layer both >> because aerosols higher in the stratosphere have larger effective radiative >> forcing and because they have higher stratospheric residence time; these >> two effects are likely to be of comparable importance. >> >> -- >> You received this message because you are subscribed to the Google Groups >> "geoengineering" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/geoengineering/CAJ3C-04wbNfg0E3q_8GtwXay88n_2r%2BhzYfVfrNPjq9SpJd9pg%40mail.gmail.com >> <https://groups.google.com/d/msgid/geoengineering/CAJ3C-04wbNfg0E3q_8GtwXay88n_2r%2BhzYfVfrNPjq9SpJd9pg%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> > > > -- > With Best Wishes, > > ------------------------------------------------------------------- > G. Bala > Professor > Center for Atmospheric and Oceanic Sciences > Indian Institute of Science > Bangalore - 560 012 > India > > Tel: +91 80 2293 3428; +91 80 2293 2505 > Fax: +91 80 2360 0865; +91 80 2293 3425 > Email: [email protected]; [email protected] > Web:http://dccc.iisc.ac.in/dr_govindasamy_bala_profile.html > ------------------------------------------------------------------- > > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/geoengineering/CAJ3C-049%3DoFfgn11X-%2B%3Dr2OHJT4QWBKm-M_SzAvH%3DPdmG3H5og%40mail.gmail.com.
