Atmospheric Chemistry Experiment (ACE): Organic Molecules from Orbit Peter Bernath Department of Chemistry, University of York Heslington, York, UK

ACE Satellite Bernath et al. GRL, 32, L15S01 (2005) See

Solar Occultation Advantages: Radiance of sun gives higher S/N than emission Limb view gives longer path length ~500 km (lower detection limits) than nadir “Self-calibrating” so excellent long-term accuracy and precision Disadvantages: Modest global coverage Samples only free troposphere

Optical Layout (ABB-Bomem)

ACE-FTS Species Measured  Baseline species (version 2.2): H 2 O, O 3, N 2 O, CO, CH 4, NO, NO 2, HNO 3, HF, HCl, N 2 O 5, ClONO 2, CCl 2 F 2, CCl 3 F, as well as pressure and temperature from CO 2 lines  Other routine species: COF 2, CHF 2 Cl, CF 4, CH 3 Cl, C 2 H 6, SF 6, OCS, HCN  Research species: CCl 4, HOCl, H 2 O 2, HO 2 NO 2, CCl 2 FCClF 2, CH 3 CClF 2, ClO, C 2 H 2, C 2 H 4, C 2 H 6, COFCl, COCl 2, CH 3 OH, H 2 CO, HCOOH, N 2 and additional isotopologues

VOCs and Air Quality Volatile Organic Compounds (VOCs) lead to the production of tropospheric ozone, a pollutant.

Formic Acid  HCOOH and CH 3 COOH are the most important organic acids in the troposphere.  Has an important role in HO X chemistry  Main sources: Biomass burning, biogenic (growing season) and anthropogenic (e.g., car exhaust) emissions. Indirect sources from numerous VOCs  Most important sinks: OH reaction (slow), dry and wet deposition  Generally poor agreement between observations and chemical transport models. Gonzalo Gonzalez Abad et al., ACPD 9, (2009)

Previous work  Numerous field measurements have been reported, but not many in the upper troposphere.  Models are still struggling to predict HCOOH concentrations  Rinsland et al. & Coheur et al. report ACE retrievals in biomass burning plumes

ACE RETRIEVALS: SPECTROSCOPY  Spectroscopic parameters for HCOOH taken from Perrin and Vander Auwera (2007) and Vander Auwera et al. (2007). HITRAN 2007 update.  ACE retrievals carried out by Chris Boone.

Annual Average and Seasonal Variation

AVERAGE PROFILES: 2005

HCOOH VALIDATION Data from JPL Mark IV balloon FTS (Geoff Toon)

Ethane, Propane and Acetone

ACE C 2 H 6 (Geoff Toon) All hydrocarbons have their strongest bands near 3000 cm -1 ; C 2 H 6 and CH 4 dominate the spectrum and need to be improved C 2 H 6 ν 7 band at 2985 cm -1 PQ3PQ3

Pure Ethane Spectrum - 3 µm (195 K) PQ3PQ3

New Ethane Spectra T=252 K P=100.0, 351.0, and Torr of synthetic air (pure spectra also recorded) Spectra recorded at T=300, 270, 250, 215, 195 K for several air pressures

Propane T=195 K P=40.1 Torr A set of propane spectra have been recorded and acetone is underway.

Ethane Retrievals  – cm -1 microwindow ( P Q 3 ).

Ethane Retrievals  Various microwindows ( P Q branches)

Cometary Emission (8P/Tuttle) Böhnhardt et al. Ap J, 683, L71 (2008)