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, T., Yu, F., Yu, H. and Zhou, C.
Host model uncertainties in aerosol radiative forcing estimates: results from the AeroCom Prescribed intercomparison study.
Atmospheric Chemistry and Physics, 13 (6).
To link to this article DOI: 10.5194/acp-13-3245-2013
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 −4.47Wm−2 and the
inter-model standard deviation is 0.55Wm−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 1.04Wm−2, and the standard deviation increases
to 1.01W−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 0.45Wm−2
(8 %) clear-sky and 0.62Wm−2 (11 %) all-sky.
Scaling the forcing standard deviation for a purely scattering
case to match the sulfate radiative forcing in the Aero-
Com Direct Effect experiment demonstrates that host model
uncertainties could explain about 36% of the overall sulfate
forcing diversity of 0.11Wm−2 in the AeroCom Direct Radiative
|Date Deposited:||31 Oct 2013 15:28|
|Last Modified:||08 Jun 2015 08:01|
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