Can we modify stratospheric water vapor by deliberate cloud seeding? Chen, JGR Atmospheres, Wiley

[Andrew Lockley]

Poster's note : This technique could be useful for tweaking the side effects of SRM. It's useful it works both ways.

http://onlinelibrary.wiley.com/doi/10.1002/2013JD020707/abstract

Keywords:

stratospheric water vapor;overshooting deep convection;vertical transport;cloud seeding;geoengineering

Abstract

Stratospheric water vapor has an important effect on Earth's climate. Considering the significance of overshooting deep convection in modulating the water vapor content (WVC) of the lower stratosphere (LS), we use a three-dimensional convective cloud model to simulate the effects of various silver iodide (AgI) seeding scenarios on tropical overshooting deep convection that occurred on 30 November 2005 in Darwin, Australia. The primary motivation for this study is to investigate whether the WVC in the LS can be artificially modified by deliberate cloud seeding. It is found that AgI seeding done at the early stages of clouds produces significant effects on cloud microphysical and dynamical properties, and that further affects the WVC in the LS, while seeding at the mature stages of clouds has only a slight impact. The response of stratospheric water vapor to changes in the amount of seeding agent is nonlinear. The seeding with a small (large) amount of AgI increases (decreases) the WVC in the LS, due to enhanced (reduced) production and vertical transport of cloud ice from the troposphere and subsequent sublimation in the stratosphere. The results show that stratospheric water vapor can be artificially altered by deliberate cloud seeding with proper amount of seeding agent. This study also shows an important role of graupel in regulating cloud microphysics and dynamics and in modifying the WVC in the LS.

[Dr. Adrian Tuck]

It would be a mistake to believe that model calculations can offer reliable simulations of the factors affecting the stratospheric water vapour content. The requisite scales are not there, and there is still debate about the detailed physical and chemical mechanisms at work.

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'ATMOSPHERIC TURBULENCE: A Molecular Dynamics Perspective'.

Oxford University Press, 2008. ISBN 978-0-19-923653-4.

http://www.oup.com/uk/catalogue/?ci=9780199236534

 

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[Oliver Wingenter]

Here are two interesting papers regarding the impact of reduced water vapor in the stratosphere.  One is attached.

Published Online July 26 2012
Science 17 August 2012:
Vol. 337 no. 6096 pp. 835-839
DOI: 10.1126/science.1222978

UV Dosage Levels in Summer: Increased Risk of Ozone Loss from Convectively Injected Water Vapor

1. James G. Anderson*, David M. Wilmouth, Jessica B. Smith, David S. Sayres

+ Author Affiliations

1. Department of Chemistry and Chemical Biology, Department of Earth and Planetary Sciences and School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
2. *To whom correspondence should be addressed. E-mail: ande...@huarp.harvard.edu

• Abstract

The observed presence of water vapor convectively injected deep into the stratosphere over the United States can fundamentally change the catalytic chlorine/bromine free-radical chemistry of the lower stratosphere by shifting total available inorganic chlorine into the catalytically active free-radical form, ClO. This chemical shift markedly affects total ozone loss rates and makes the catalytic system extraordinarily sensitive to convective injection into the mid-latitude lower stratosphere in summer. Were the intensity and frequency of convective injection to increase as a result of climate forcing by the continued addition of CO₂ and CH₄ to the atmosphere, increased risk of ozone loss and associated increases in ultraviolet dosage would follow.

Oliver Wingenter

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Oliver Wingenter
Assoc. Professor Department of Chemistry
Research Scientist Geophysical Research Center
New Mexico Tech

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