Indirect Effect experiments
proposed model intercomparison study to quantify uncertainties
associated with indirect aerosol radiative forcing
July 13, 2004
Participants expressing interest in participating
and/or helping with analysis: Leon Rotstayn (CSIRO, Australia), Ulrike Lohmann (Dalhousie University,
Canada), John Seinfeld, (CalTech, U.S.A.), Michael Prather (U.C.
Irvine, U.S.A.), Mian Chin (GSFC, U.S.A.), Thanos Nenes (Georgia
Tech, U.S.A.), Ralph Kahn (J.P.L., USA), Johannes Quaas (LMD,
France), Peter Adams (Carnegie Mellon, USA), Stefan Kinne (DKRZ,
Germany), Michael Schulz (LSCE, France), Jim Hansen, Surabe
Menon, Sophia Zhang (GISS, USA), Timeline:
This needs to be moved ahead to meet IPCC deadlines for submitted
manuscripts!
August 2004: Submission of experiments
to central facility (U of M website)
February 2005: Workshop
with presentation of first results and initial comparison
to data
May 2005: Draft paper
circulated to participants (this may not have all analyses
completed) and to IPCC authors
July/August 2005:
Submit first paper to journal
The AEROCOM aerosol model intercomparison study has
entrained a fairly large number of people (see list of meeting
attendees), and includes measurements groups as well as modelers.
They have now defined a set of standard sources (representative of approximately
the year 2000) as well as a set of pre-industrial sources
which will be used in the next set of model intercomparisons
(called phase “B”). These sources will be used in experiments
5, 6 and 7 below, and will form the basis of the comparison
of models with both aerosol and cloud data.
Under the auspices of the U. S. CCSP and in coordination with IPCC, we are proposing a model intercomparison
for indirect aerosol effects. Below is the proposed set of
model calculations. All simulations and diagnostics should
be for 5 years (after the model has reach a quasi-steady state)
and should be for present day and pre-industrial conditions.
With these experiments we aim to quantify the range of model
results that are associated with different aspects of modeling
the indirect effect and to derive the reasons for model differences.
For more info see INDIRECT
PROTOCOL WORD DOCUMENT
Proposed experiments:
Experiment
names:
(1a) Present day: Prescribed aerosol mass; no effect of aerosols on
precipitation efficiency; common treatment of precipitation
efficiency; common treatment of cloud droplet number parameterization;
does not include aerosol direct effects on the heating profile
(1b) Preindustrial: Prescribed aerosol mass; no effect of aerosols
on precipitation efficiency; common treatment of precipitation
efficiency; common treatment of cloud droplet number parameterization;
does not include aerosol direct effects on the heating profile
(2a) Present day: Prescribed aerosol
mass and size distribution; no effect on precipitation by
aerosols; common treatment of precipitation efficiency; no
common cloud droplet number parameterization; does not include
aerosol direct effects on the heating profile
(2b) Preindustrial:
Prescribed aerosol mass and size distribution; no effect on
precipitation by aerosols; common treatment of precipitation
efficiency; no common cloud droplet number parameterization;
does not include aerosol direct effects on the heating profile
(3a) Present day: Prescribed
aerosol mass and size distribution; common treatment of effect
of aerosols on precipitation efficiency; no common cloud droplet
number parameterization; does not include aerosol direct effects
on the heating profile
(3a) Preindustrial:
Prescribed aerosol mass and size distribution; common treatment
of effect of aerosols on precipitation efficiency; no common
cloud droplet number parameterization; does not include aerosol
direct effects on the heating profile
(4a) Present day: Prescribed
aerosol mass and size distribution; no common treatment of
effect of aerosols on precipitation efficiency; no common
cloud droplet number parameterization; does not include aerosol
direct effects on the heating profile
(4b) Preindustrial:
Prescribed aerosol mass and size distribution; no common treatment
of effect of aerosols on precipitation efficiency; no common
cloud droplet number parameterization; does not include aerosol
direct effects on the heating profile
(5a)
Present day: Prescribed aerosol sources; no common treatment of
effect of aerosols on precipitation efficiency; no common
cloud droplet number parameterization; does not include aerosol
direct effects on the heating profile
(5b) Preindustrial:
Prescribed aerosol sources; no common treatment of effect
of aerosols on precipitation efficiency; no common cloud droplet
number parameterization; does not include aerosol direct effects
on the heating profile
(6a)
Present day: Prescribed aerosol sources; no common treatment
of effect of aerosols on precipitation efficiency; no common
cloud droplet number parameterization; includes aerosol direct
effects on the heating profile
(6b) Preindustrial:
Prescribed aerosol sources; no common treatment of effect
of aerosols on precipitation efficiency; no common cloud droplet
number parameterization; includes aerosol direct effects on
the heating profile
(7a) Present day: Prescribed
aerosol sources; prescribed aerosol primary emissions and
size; no common treatment of effect of aerosols on precipitation
efficiency; no common cloud droplet number parameterization;
includes aerosol direct effects on the heating profile
(7a) Preindustrial:
Prescribed aerosol sources; prescribed aerosol primary emissions
and size; no common treatment of effect of aerosols on precipitation
efficiency; no common cloud droplet number parameterization;
includes aerosol direct effects on the heating profile
