Host model uncertainties in aerosol radiative forcing estimates

Results from the AeroCom Prescribed intercomparison study

P. Stier, N. A.J. Schutgens, N. Bellouin, H. Bian, O. Boucher, M. Chin, S. Ghan, N. Huneeus, S. Kinne, G. Lin, X. Ma, G. Myhre, J. E. Penner, C. A. Randles, B. Samset, M. Schulz, Toshihiko Takemura, F. Yu, H. Yu, C. Zhou

    Research output: Contribution to journalArticle

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    Abstract

    Simulated multi-model "diversity" in aerosol direct radiative forcing estimates is often perceived as a measure of aerosol uncertainty. However, current models used for aerosol radiative forcing calculations vary considerably in model components relevant for forcing calculations and the associated "host-model uncertainties" are generally convoluted with the actual aerosol uncertainty. In this AeroCom Prescribed intercomparison study we systematically isolate and quantify host model uncertainties on aerosol forcing experiments through prescription of identical aerosol radiative properties in twelve participating models. Even with prescribed aerosol radiative properties, simulated clear-sky and all-sky aerosol radiative forcings show significant diversity. For a purely scattering case with globally constant optical depth of 0.2, the global-mean all-sky top-of-atmosphere radiative forcing is -4.47 Wm-2 and the inter-model standard deviation is 0.55 Wm-2, corresponding to a relative standard deviation of 12 %. For a case with partially absorbing aerosol with an aerosol optical depth of 0.2 and single scattering albedo of 0.8, the forcing changes to 1.04 Wm-2, and the standard deviation increases to 1.01 W-2, corresponding to a significant relative standard deviation of 97 %. However, the top-of-atmosphere forcing variability owing to absorption (subtracting the scattering case from the case with scattering and absorption) is low, with absolute (relative) standard deviations of 0.45 Wm-2 (8 %) clear-sky and 0.62 Wm -2 (11 %) all-sky. Scaling the forcing standard deviation for a purely scattering case to match the sulfate radiative forcing in the AeroCom Direct Effect experiment demonstrates that host model uncertainties could explain about 36 % of the overall sulfate forcing diversity of 0.11 Wm -2 in the AeroCom Direct Radiative Effect experiment. Host model errors in aerosol radiative forcing are largest in regions of uncertain host model components, such as stratocumulus cloud decks or areas with poorly constrained surface albedos, such as sea ice. Our results demonstrate that host model uncertainties are an important component of aerosol forcing uncertainty that require further attention.

    Original languageEnglish
    Pages (from-to)3245-3270
    Number of pages26
    JournalAtmospheric Chemistry and Physics
    Volume13
    Issue number6
    DOIs
    Publication statusPublished - Nov 20 2013

    Fingerprint

    radiative forcing
    aerosol
    scattering
    top of atmosphere
    clear sky
    optical depth
    albedo
    sulfate
    stratocumulus
    experiment
    sea ice

    All Science Journal Classification (ASJC) codes

    • Atmospheric Science

    Cite this

    Host model uncertainties in aerosol radiative forcing estimates : Results from the AeroCom Prescribed intercomparison study. / Stier, P.; Schutgens, N. A.J.; Bellouin, N.; Bian, H.; Boucher, O.; Chin, M.; Ghan, S.; Huneeus, N.; Kinne, S.; Lin, G.; Ma, X.; Myhre, G.; Penner, J. E.; Randles, C. A.; Samset, B.; Schulz, M.; Takemura, Toshihiko; Yu, F.; Yu, H.; Zhou, C.

    In: Atmospheric Chemistry and Physics, Vol. 13, No. 6, 20.11.2013, p. 3245-3270.

    Research output: Contribution to journalArticle

    Stier, P, Schutgens, NAJ, Bellouin, N, Bian, H, Boucher, O, Chin, M, Ghan, S, Huneeus, N, Kinne, S, Lin, G, Ma, X, Myhre, G, Penner, JE, Randles, CA, Samset, B, Schulz, M, Takemura, T, Yu, F, Yu, H & Zhou, C 2013, 'Host model uncertainties in aerosol radiative forcing estimates: Results from the AeroCom Prescribed intercomparison study', Atmospheric Chemistry and Physics, vol. 13, no. 6, pp. 3245-3270. https://doi.org/10.5194/acp-13-3245-2013
    Stier, P. ; Schutgens, N. A.J. ; Bellouin, N. ; Bian, H. ; Boucher, O. ; Chin, M. ; Ghan, S. ; Huneeus, N. ; Kinne, S. ; Lin, G. ; Ma, X. ; Myhre, G. ; Penner, J. E. ; Randles, C. A. ; Samset, B. ; Schulz, M. ; Takemura, Toshihiko ; Yu, F. ; Yu, H. ; Zhou, C. / Host model uncertainties in aerosol radiative forcing estimates : Results from the AeroCom Prescribed intercomparison study. In: Atmospheric Chemistry and Physics. 2013 ; Vol. 13, No. 6. pp. 3245-3270.
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    AU - Stier, P.

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    AU - Bellouin, N.

    AU - Bian, H.

    AU - Boucher, O.

    AU - Chin, M.

    AU - Ghan, S.

    AU - Huneeus, N.

    AU - Kinne, S.

    AU - Lin, G.

    AU - Ma, X.

    AU - Myhre, G.

    AU - Penner, J. E.

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    AU - Samset, B.

    AU - Schulz, M.

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