Comparison of total column CO and H 2 CO FTIR measurements at Wollongong with a chemical transport model (GEOS-Chem) and an earth-system model (ACCESS) R.R. Buchholz 1 , C. Paton-Walsh 1 , P. Hurley 2 , N. Jones 1 and D. Griffith 1 1 Centre for Atmospheric Chemistry, University of Wollongong, Australia 2 Commonwealth Scientific and Industrial Research Organisation (CSIRO), Australia Introduction In this study, carbon monoxide (CO) and formaldehyde (H 2 CO) over Wollongong in Southeast Australia are investigated with measurements and model simulations. Remote sensing retrievals from ground based Fourier Transform Infrared measurements have been compared with simulations from two computational models, in particular the global Chemical Transport Model, GEOS-Chem, for 2004–2009, as well as initial results from the Australian Community Climate Earth-System Simulator (ACCESS) for 1996–2001. Total Column Measurements ◮ Fourier Transform Infrared Spectrophotometer (FTS) was commissioned at the University of Wollongong (-34.406, 150.879) in 1996. ◮ Molecules absorb solar radiation in the infrared region. ◮ Total column values are retrieved from infrared spectra via inverse methods using the programs GFIT[2] and SFIT[1]. Computational Models ACCESS GEOS-Chem (UKCA v7.3) (v8-03-01) http://www.accessimulator.org.au http://www.geos-chem.org Earth-System Model Global Chemical Transport Model Resolution 1.25 ◦ x 1.875 ◦ , 38 levels (∼35 km) 2.0 ◦ x 2.5 ◦ , 47 levels (∼80 km) Years Run 1980 – 2000 2004 – 2009 Meteorology MetUM simulated, driven by SST NASA GEOS5 reanalysis product Emissions Climatological mode: constant at year 2000, based on UKCA emis- sion dataset for IPCC Assess- ment Report 4. Biomass Burning, Anthropogenic, Biogenic etc. based on inven- tories and scaled for appropriate years. Chemistry 26 standard tropospheric tracers as output (excluding isoprene), 46 species 80 chemical species, 150 reac- tions: Tropospheric chemistry Surface Layer approx. 20 m approx. 130 m Wollongong Carbon Monoxide 0 1e+18 2e+18 3e+18 4e+18 5e+18 1996 1998 2000 2002 2004 2006 2008 CO total column (molec/cm 2 ) Year ACCESS GEOS-Chem FTS Figure 1: Monthly averaged total column values for CO over Wollongong. 0 5e+17 1e+18 1.5e+18 2e+18 2.5e+18 3e+18 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec CO total column (molec/cm 2 ) Month ACCESS 1996-2000 GEOS-Chem 2004-2009 FTS 1996-2000 FTS 2004-2009 Figure 2: CO annual cycle averages for the overlap periods shown in Figure 1. ◮ GEOS-Chem results in Figure 1 match well with FTS measurements; ACCESS results show an offset of ∼ 0.5 × 10 18 molecules/cm 2 . ◮ Annual cycles for both overlap periods for measurement are within one standard deviation of each other (Figure 2). GEOS-Chem annual cycle results are within one standard deviation of the measurements, while ACCESS results are outside one standard deviation and ∼ 0.5 × 10 18 molecules/cm 2 below measurements, apart from Jul, Aug and Sep. ACCESS annual cycle peaks in September as opposed to the annual cycle peak in October for ACCESS and GEOS-Chem. Wollongong Formaldehyde 0 5e+15 1e+16 1.5e+16 2e+16 2.5e+16 1996 1998 2000 2002 2004 2006 2008 HCHO total column (molec/cm 2 ) Year ACCESS GEOS-Chem FTS Figure 3: Monthly averaged total column values for H 2 CO over Wollongong. 0 5e+15 1e+16 1.5e+16 2e+16 2.5e+16 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec HCHO total column (molec/cm 2 ) Month ACCESS 1996-2000 GEOS-Chem 2004-2009 FTS 1996-2000 FTS 2004-2009 Figure 4: H 2 CO annual cycle averages for the overlap periods shown in Figure 3. ◮ GEOS-Chem results in Figure 3 match acceptably with FTS measurements, although show higher results Nov - Feb. ACCESS results show an offset of ∼0.5 to 1 × 10 16 molecules/cm 2 . ◮ GEOS-Chem annual cycle results (Figure 4) are comparable with measurements Mar - Oct, but reveal an overestimation Nov-Feb. For the ACCESS annual cycle, all months underestimate H 2 CO by ∼0.5 to 1 × 10 16 molecules/cm 2 , with a greater underestimation Oct-Mar. Model Grid Comparison ◮ GEOS-Chem and ACCESS grids are mis-aligned (Figure 6). ◮ Partial ACCESS grid boxes shall be included in future comparison. ◮ Surrounding grid box analysis is required to determine if results are statistically representative. Figure 5: GEOS-Chem CO, Average tropospheric mole fraction, October 2006. Figure 6: Model grids overlayed on a satellite image of the Wollongong area. Discussion and Further Research Results indicate areas for improvement in ACCESS: ◮ Emissions: Low estimation for both trace gases and early annual peak for CO in ACCESS may indicate emission inventory inconsistency. Future simulations will include an emission inventory based on IPCC Assessment Report 5. ◮ Chemistry: Lack of isoprene and related chemistry may affect H 2 CO and CO. Future simulations will implement a new isoprene scheme. ◮ Meteorology: Implementation of a meteorological nudging scheme is necessary to confirm areas for improvement in chemistry or emissions. Overall, this study has analysed model validity and also helps to improve our understanding of seasonal variability and background concentrations of the target trace gases in the Australian region. Acknowledgements ◮ Australian Postgraduate Award, awarded by the Australian Government ◮ CSIRO OCE top-up scholarship ◮ National Computing Infrastructure, Australian National University References [1] Pougatchev, N. S., Connor, B. J. and Rinsland, C. P. (1995), J Geophys Res-Atmos, 100(D8), 16689-16697. [2] Washenfelder, R. A., Toon, G. C., Blavier, J. F., Yang, Z., Allen, N. T., Wennberg, P. O., Vay, S. A., Matross, D. M. and Daube, B. C. (2006), J Geophys Res-Atmos, 111(D22), D22305. Mail: rb864@uowmail.edu.au