THE ATMOSPHERIC CHEMISTRY EXPERIMENT (ACE): CO, CH4 AND N2O ISOTOPOLOGUES Peter Bernath1,2, Eric Buzan1, Chris Beale1, Mahdi Yousefi1 and Chris Boone2 1Old Dominion University, Norfolk, VA 2University of Waterloo, Waterloo, ON

Satellite Remote Sensing Special Issue (JQSRT) 19 papers in total including a substantial number on spectroscopy; HITRAN Special Issue will be open for submissions from Oct. 1, 2016 to Jan. 15, 2017 The Reference Forward Model (RFM) Anu Dudhia OH Meinel band quenching coefficients derived from satellite observations Patrick Sheese LEVEL: A Computer Program for Solving the Radial Schroedinger Equation for Bound and Quasibound Levels Robert Le Roy Tropospheric Emissions: Monitoring of Pollution (TEMPO) Peter Zoogman Global climatology based on the ACE-FTS version 3.5 dataset: Addition of mesospheric levels and carbon-containing species in the UTLS Kaley Walker New and improved infrared absorption cross sections and ACE-FTS retrievals of carbon tetrachloride (CCl4) Jeremy Harrison Optimized approach to retrieve information on atmospheric carbonyl sulfide (OCS) above the Jungfraujoch station and change in its abundance since 1995 Bernard Lejeune Retrieval of HCFC-142b (CH3CClF2) from ground-based high-resolution infrared solar spectra: atmospheric increase since 1989 and comparison with surface and satellite measurements Manu Mahieu ACE-FTS ozone, water vapour, nitrous oxide, nitric acid, and carbon monoxide profile intercomparisons with MIPAS and MLS The Atmospheric Chemistry Experiment (ACE) Peter Bernath PGOPHER: A Program for Simulating Rotational, Vibrational and Electronic Spectra. Colin Western Fast radiative transfer using monochromatic look-up tables Robert Vincent dParFit: A Computer Program for Fitting Diatomic Molecule Spectral Data to Parameterized Level Energy Expressions Robert Le Roy A Computer Program to Fit Pointwise Potentials to Selected Analytic Function Multispectrum analysis of the Oxygen A-band Brian Drouin A Computer Program Implementing the First-Order RKR Method for Determining Diatomic Molecule Potential Energy Functions Spectroscopic line parameters of 12CH4 for atmospheric composition retrievals in the 4300-4500 cm^-1 region Robab Hashemi WINDII on UARS in the context of SCISAT and Odin Gordon Shepherd A Computer Program to Fit Diatomic Molecule Spectral Data to Potential Energy Functions Temperature-dependent absorption cross-sections of 2,2,3,3,3-pentafluoropropanol Paul Godin

MOLLIST Website http://bernath.uwaterloo.ca/mollist

ACE Satellite (Limb View) http://www.ace.uwaterloo.ca/ Bernath et al., GRL, 32, L15S01 (2005)

ACE-FTS Version 3.5 Species Tracers: H2O, O3, N2O, NO, NO2, HNO3, N2O5, H2O2, HO2NO2, N2 Halogen-containing gases: HCl, HF, ClONO2, CFC-11, CFC-12, CFC-113, COF2, COCl2, COFCl, CF4, SF6, CH3Cl, CCl4, HCFC-22, HCFC-141b, HCFC-142b Carbon-containing gases: CO, CH4, CH3OH, H2CO, HCOOH, C2H2, C2H4, C2H6, OCS, HCN as well as pressure and temperature from CO2 lines Isotopologues: H218O, H217O, HDO, O13CO, OC18O, OC17O, O13C18O, 18OO2, O18OO, O17OO, N15NO, 15NNO, N218O, N217O, 13CO, C18O, C17O, 13CH4, CH3D, OC34S, O13CS Research species: ClO, acetone, PAN, HFC-23, acetonitrile, etc. Isotopic fractionation of CO, CH4 and N2O: Chris Beale, Eric Buzan and Mahdi Yousefi (Old Dominion University)

ACE WACCM δD CH4 is an important greenhouse gas; isotopologues give new information on atmospheric chemistry and dynamics δ13C

323, 59-66 (2016) ACE WACCM

N2O Isotopologues N2O is an important greenhouse gas with GWP of 300 (3rd in terms of radiative forcing after CO2 and CH4) Most significant ozone-depleting substance not controlled by the Montreal Protocol Inert in the troposphere but is photolyzed in the stratosphere and reacts with O(1D) to make NO Main sources are from soil and oceans (byproduct of microbial nitrification and denitrification processes) ACE-FTS discovered a new upper atmospheric source from energetic particle precipitation (N + NO2 and N2* + O2 reactions) Semeniuk et al. 2008 & Sheese et al. 2016 ACE-FTS measures N2O, 15NNO, N15NO and NN18O Isotopologues provide information on atmospheric chemistry and dynamics

ACE N2O spectra at 15.5 km tangent altitude, 2ν3 mode 2563 cm-1

Upper Atmospheric N2O Destruction N2O + hν → N2 + O(1D) 90% N2O + O(1D) → N2 + O2 4% N2O + O(1D) → 2NO 6%

Isotopologues: Isotopic Molecules 15Rref = 0.00367666 (N2, air) 18Rref =0.002005 (Vienna standard mean ocean water) 325 ppb 2013 IPCC report

Isotopic Fractionation (Blake et al. 2003) Within the Born-Oppenheimer approximation, the potentials are the same. Heavier isotopologue has a lower ZPE, narrower wavefunction and a shorter r0 bond length for an anharmonic potential; this leads to a change in the absorption cross section.

N2O Isotopic Fractionation J 14N15N16O fractionation observed and calculated N2O + hν → N2 + O(1D) εi = (σi/σ – 1) x 1000 T=284 K T=233 K d[N2O]/dt = - J[N2O] J = ∫σφFdλ σ, absorption cross section φ=1, quantum efficiency F, actinic flux Schmidt et al. 2011

ACE N15NO and 15NNO δ-values Older air over the poles shows more fractionation and an increase in the heavier isotopologues.

N2O Isotopologue Validation Kaiser et al. 2006, ACP 6, 3535: balloon data over France

Whole Atmosphere Climate Community Model (WACCM) Atmosphere component of Community Earth System Model (CESM) Simulates physics and chemistry for 0-140 km 4x5 degree resolution for all ACE comparison runs Each isotopologue treated as a separate species 13CO, 13CH4, CH3D, 15NNO, N15NO, NN18O added with lower boundary conditions; for CO fractionation reactions with OH and photochemistry included; for CH4 fractionation by reaction with OH, Cl and O(1D) added; for N2O fractionation by photolysis and O(1D) added (in progress) LBC calculated by isotope ratios from Röckmann et al. (2011) Chemical kinetics constants from JPL publication, 2010

N2O Isotopologue Modelling Ishijima et al. 2015, ACPD 15, 19947 Model δ-values for 15NNO Observed ACE δ-values for 15NNO ACE Data Model

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