AeroCom

-> Aerosol Comparisons between Observations and Models

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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

AEROCOM
is an international
science initiative
on aerosols and climate

supported by
EU Framework programmes
ACTRIS
MACC-II
EUCAARI
PHOENICS


Norw. Met Office
ESA-cci
Max-Planck Ges.
NASA
French CNES