Atmos. Chem. Phys. Discuss., 12, 23603-23644, 2012
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Observational constraints on ozone radiative forcing from the Atmospheric Chemistry Climate Model Intercomparison Project (ACCMIP)
K. Bowman1, D. Shindell2, H. Worden3, J. F. Lamarque3, P. J. Young4,5, D. Stevenson7, Z. Qu18, M. de la Torre1, D. Bergmann6, P. Cameron-Smith6, W. J. Collins8, R. Doherty6, S. Dalsøren9, G. Faluvegi2, G. Folberth8, L. W. Horowitz11, B. Josse12, Y. H. Lee2, I. MacKenzie7, G. Myhre9, T. Nagashima13, V. Naik11, D. Plummer14, S. Rumbold8, R. Skeie9, S. Strode15, K. Sudo13, S. Szopa16, A. Voulgarakis19, G. Zeng17, S. Kulawik1, and J. Worden1
1Jet Propulsion Laboratory-California Institute of Technology, Pasadena, CA, USA
2NASA Goddard Institute for Space Studies and Columbia Earth Institute, New York, NY, USA
3National Center for Atmospheric Research,Boulder, Colorado, USA
4Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA
5Chemical Sciences Division, NOAA Earth System Research Laboratory, Boulder, Colorado, USA
6Lawrence Livermore National Laboratory, Livermore, CA, USA
7School of GeoSciences, The University of Edinburgh, Edinburgh, UK
8Met Office Hadley Centre, UK
9Center for International Climate and Environmental Research, Oslo, Norway
11NOAA Geophysical Fluid Dynamics Laboratory, Princeton, NJ, USA
12GAME/CNRM, Météo-France, CNRS – Centre National de Recherches Météorologiques, Toulouse, France
13Nagoya University, Nagoya, Japan
14Environment Canada, Canada
15NASA Goddard Space Flight Center and Universities Space Research Association, Columbia, Maryland, USA
16Laboratoire des Sciences du Climat et l'Environnement, Gif-sur-Yvette, France
17National Institute of Water and Atmospheric Research, Lauder, New Zealand
18Raytheon Intelligence & Information Systems, Pasadena, CA, USA
19Department of Physics, Imperial College London, London, UK

Abstract. We use simultaneous observations of ozone and outgoing longwave radiation (OLR) from the Tropospheric Emission Spectrometer (TES) to evaluate ozone distributions and radiative forcing simulated by a suite of chemistry-climate models that participated in the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP). The ensemble mean of ACCMIP models show a persistent but modest tropospheric ozone low bias (5–20 ppb) in the Southern Hemisphere (SH) and modest high bias (5–10 ppb) in the Northern Hemisphere (NH) relative to TES for 2005–2010. These biases lead to substantial differences in ozone instantaneous radiative forcing between TES and the ACCMIP simulations. Using TES instantaneous radiative kernels (IRK), we show that the ACCMIP ensemble mean has a low bias in the SH tropics of up to 100 m W m−2 locally and a global low bias of 35 ± 44 m W m−2 relative to TES. Combining ACCMIP preindustrial ozone and the TES present-day ozone, we calculate an observationally constrained estimate of tropospheric ozone radiative forcing (RF) of 399 ± 70 m W m−2, which is about 7% higher than using the ACCMIP models alone but with the same standard deviation (Stevenson et al., 2012). In addition, we explore an alternate approach to constraining radiative forcing estimates by choosing a subset of models that best match TES ozone, which leads to an ozone RF of 369 ± 42 m W m−2. This estimate is closer to the ACCMIP ensemble mean RF but about a 40% reduction in standard deviation. These results point towards a profitable direction of combining observations and chemistry-climate model simulations to reduce uncertainty in ozone radiative forcing.

Citation: Bowman, K., Shindell, D., Worden, H., Lamarque, J. F., Young, P. J., Stevenson, D., Qu, Z., de la Torre, M., Bergmann, D., Cameron-Smith, P., Collins, W. J., Doherty, R., Dalsøren, S., Faluvegi, G., Folberth, G., Horowitz, L. W., Josse, B., Lee, Y. H., MacKenzie, I., Myhre, G., Nagashima, T., Naik, V., Plummer, D., Rumbold, S., Skeie, R., Strode, S., Sudo, K., Szopa, S., Voulgarakis, A., Zeng, G., Kulawik, S., and Worden, J.: Observational constraints on ozone radiative forcing from the Atmospheric Chemistry Climate Model Intercomparison Project (ACCMIP), Atmos. Chem. Phys. Discuss., 12, 23603-23644, doi:10.5194/acpd-12-23603-2012, 2012.
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