Generic structure: Leaky water tank A model for atmospheric methyl chloroform C2H3Cl3
Methyl chloroform 1989 to 2004 observations taken from http://cdiac.ornl.gov/trends/otheratg/blake/data.html and 2005 to 2009 data taken from http://www.esrl.noaa.gov/gmd/hats/ . Global mean estimates are show by black squares
Why look at methyl chloroform? • The transient behavior of methyl chloroform over the past 20 years is interesting. • Because of its stratospheric ozone destruction potential, in 1992 the Montreal protocol called for a complete phase out of methyl chloroform emissions. Modeling methyl chloroform provides an estimate of how rapidly countries from around the world complied with this emission reduction policy and how close the world has come towards zero methyl chloroform emissions. • The lifetime of methyl chloroform is very important to understanding atmospheric chemistry related to the OH radical, see Montzka et. al, 2000. The OH radical removes many pollutants from the atmosphere by oxidation.
1. When the atmospheric concentration of methyl chloroform is in equilibrium the slope of the concentration graph vs. time is zero. This means that the removal rate is balanced out by the emissions. Use Eqn. 4 to estimate the emissions of methyl chloroform at equilibrium when the concentration is 130 ppt. Do this calculation twice; first assuming an atmospheric lifetime of 5.0 and then 5.5 years.
Example • http://www.atmosedu.com/WSU/esrp310-550/MethylC/MCFXX.STM • What are the 1989 to 2009 Emissions of XX and the atmospheric lifetime of XX?
Emissions estimated from: Methyl chloroform sales McCulloch (2005), and 5 different model simulations with assumed atmospheric lifetimes of 4.0, 4.5, 5.0, 5.5, and6.0 year simulations. http://www.geiacenter.org/reviews/mcf.html (McCulloch, 2005)
Other References • Prinn, R, , D. Cunnold, R. Rasmussen, P. Simmonds, F. Alyea, A. Crawford, P. Fraser, and R. Rosen, 1987. Atmospheric Trends in Methylchloroform and the Global Average for the Hydroxyl Radical. Science 13 November 1987:Vol. 238. no. 4829, pp. 945 – 950. • Montzka, S. A., C. M. Spivakovsky, J. H. Butler, J. W. Elkins, L. T. Lock, D. J. Mondeel, 2000. New Observational Constraints for Atmospheric Hydroxyl on Global and Hemispheric Scales. Science 21 April 2000: Vol. 288. no. 5465, pp. 500 - 503