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Chapter 3 Evaluation of Atmospheric Loss Processes

Published

Author(s)

Vladimir L. Orkin, James B. Burkholder, Wahid Mellouki, Eric L. Fleming, Christian George, Charles H. Jackman, Timothy J. Wallington , Michael J. Kurylo , Dwayne E. Heard, William H. Swartz

Abstract

Hydroxyl radical (OH), electronically excited atomic oxygen (O(1D)), and atomic chlorine (Cl) reaction rate coefficient data were evaluated and the estimated uncertainties in the recommended parameters reduced, in general, from those currently recommended in the NASA/Jet Propulsion Laboratory (JPL) and International Union of Pure and Applied Chemistry (IUPAC) kinetic and photochemical data evaluations. • New studies of several O(1D) reaction rate coefficients, reaction yields, and their temperature dependences provided data needed to reduce uncertainties in calculated lifetimes. • Lyman- (121.567 nm) absorption cross section recommendations are provided and uncertainties estimated. Lyman- photolysis is shown to be a dominant mesospheric loss process, but makes only a minor contribution to the total global atmospheric lifetimes for the molecules included in this report. • Ultraviolet (UV) absorption cross section data were evaluated and new cross section parameterizations recommended for CCl4 (carbon tetrachloride), CF2Br2 (Halon-1202), CF2ClBr (Halon-1211), CF2BrCF2Br (Halon-2402), and NF3 (nitrogen trifluoride). In addition, systematic errors in the UV spectrum parameterizations for CFCl3 (CFC-11), CF2Cl2 (CFC-12), CFCl2CF2Cl (CFC-113), CF2ClCF2Cl (CFC-114), CH3CCl3, CH3Cl, and CHF2Cl (HCFC-22) given in literature and nist-quoted in NASA/JPL (JPL10-6) from the original literature are corrected here. Uncertainties in absorption cross sections and their temperature dependence are estimated for 5 key photolysis wavelength regions. • Two-dimensional (2-D) atmospheric model calculations were used to quantify the fractional contribution of the OH, O(1D), and Cl reactive losses as well as photolytic loss to the global annually averaged local and overall lifetimes for each of the molecules included in this report. For hydrogen containing molecules, loss due to the OH reaction is dominant (>90%). The dominant loss process for the chlorofluorocarbons (CF
Citation
SPARC – Stratospheric Processes And their Role in Climate / World Climate Research Programme (WCRP)

Keywords

atmosferic lifetime, ozone depletion, stratospheric chemistry
Created December 31, 2013, Updated March 16, 2017