Future
See infos for the next AeroCom workshop
The following text had been prepared for the 5th AeroCom
workshop.
AeroCom Phase II Planning Docment
To achieve the goals of the AeroCom phase II, work is required
on four areas detailed below:
Goals
The primary goal of the AeroCom initiative is to evaluate
global aerosol models in order to obtain reliable estimates
of the present and future aerosol impact on climate and air
quality. Model output documentation and comparison shall be
facilitated to help upcoming assessments, relevant for policy
decisions related to climate change and air quality. Primary
scientific questions concern the ability to reproduce and
predict aerosol constituent loadings, their optical properties,
the aerosol-cloud interactions and the radiative impact on
different spatial and temporal scales. While more models become
able to study the climate response to anthropogenic aerosol,
it is time to assess the postulated feedback processes in
the framework of a model intercomparison.
Structure
Preface: It is recognised that considerable effort
is underway on national and international levels to better
understand the ambient aerosol. The AeroCom initiative thus
primarily seeks to link and look for synergy with other programs.
Organising committee: To improve the coordination
of the analysis it is proposed to create a broader coordination
committee, comprised of representatives active in the field
of analysing aerosol models and observational data.
A balanced international representation
is seeked. Propositions shall be send to Michael Schulz and
Phil Rash (on behalf of IGAC) before the Virginia Beach meeting.
Task groups: To further analyse the AeroCom model
data assembled it is proposed to form task groups, in which
one member has direct access to the data base and presents
the planned work and the analysis results to the AeroCom participants.
Link to IGAC and WCRP: AeroCom has been solicited
to participate in a new activity being initiated jointly by
WCRP-SPARC and IGBP-IGAC on the issue of "Atmospheric
Chemistry and Climate (AC&C)". At a recent workshop
in Boulder (August 2006) it has been proposed to link the
work on model evaluation in three related fields (1) stratospheric
chemistry, 2) tropospheric chemistry and 3) aerosols) in a
joint "Atmospheric Chemistry and Climate" initiative.
AeroCom and ccmVAL
have been identified as possible major contributing components,
if not subprojects, to such an initiative. The report from
the Boulder workshop and further cooperation shall be discussed
in the forthcoming AeroCom and ccmVAL workshops and in a AC&C
meeting in January 2007.
Link to HTAP: Synergy is proposed by cooperating
with the Task Force on Hemispheric
Transport of Air Pollution. A set of experiments, planned
to analyse long range transport and source receptor relationships,
shall be analysed in connection with previous AeroCom experiments.
An exchange of tools and harmonized formats are being developped.
Aerocom modellers are thus encouraged to participate especially
in experiments SR1 and SR5.
AeroCom workshops: Annual work shops are proposed
to be held in autumn. For 2007 a proposition has been made
to combine a french organised CNES workshop on the work-up
of the A-train data with an AeroCom workshop.
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Joint experiments
The following list is a tentative list of model experiments,
which eventually could be assembled in the framework of AeroCom.
Further discussion, reduction and detailing will be done on
the 5th and forthcoming AeroCom workshop. For each of these
experiments a task group must form to ensure successful analysis.
1) Standard model runs:
To monitor progress and evolution in current multi-component
aerosol models it would be desirable to allow for "any-time
submission" of model results via an automated ftp&cataloging
web based tool (see technical section
below). A simplified protocol is needed, eventually concentrating
on parameters needed for standard benchmark tests and annual
aerosol budget control.
2) HTAP experiments:
Source receptor relationships on a continental level need
to be quantified to characterize long-range transport of air
pollution. This will be better understood based on a multi-model
evaluation. AeroCom modellers are thus encouraged to participate
especially in experiments SR1 and SR5 (see
HTAP experiment description) and if possible others.
3) Climate response due to aerosols:
Several models have done or are about to prepare coupled (chemistry-)aerosol-climate
simulations. At stake are problems of representative aerosol
emission scenarios, the importance of different feedback mechanismns,
the regional impact of an inhomogeneous aerosol forcing, the
potential role of aerosol to explain the evolution of surface
air temperature and global dimming. A set of proposed diagnostics
and storage of output in a new AC&C data center for such
coupled chemistry climate model runs would eventually help
resolving the problems.
4) Aerosol loadings in the recent
past (1980-2005): Reconstructions of the
aerosol emissions and reanalysis of the synoptic
meteorolgy become now available. It would be desirable
to analyse the recent past in a concerted manner,
especially because aerosol observations provide
important constraints after 1980.
5) Ensemble prediction of global
PM air quality: Prediction of PM levels is
currently done with regional air quality models. While global
models use higher resolutions and eventually can provide border
conditions for regional models, it becomes of interest to
review work in this area and eventually prepare an ensemble
prediction of PM levels on a global level.
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Process analysis and evalution
with observational data
Model development will benefit from improved analysis of
currenct concepts and a broader testing of the model output.
Standard benchmark tests and in depth analysis are both needed
to make progress. Use and understanding of observational data
is crucial. It would be desirable to construct a table of
identified standard diagnostics to document model quality.
See the ccmVAL
evaluation table as an example. Major fields expected
to be worked upon by an AeroCom task group:
1) Indirect effect:
The importance of the indirect effect is well recognised.
The diagnostics and data driven evaluations are nervtheless
in its infancy. A set of diagnostic parameters should be drawn
from recent work such as that of Penner
et al 2006 and others. Such diagnostics should
develop into standard tests and documentation.
2) Aerosol dynamics:
Aerosol size distribution is expected to play a big role in
aerosol-cloud interaction, determining aerosol life time and
radiative impact. Diagnostics in the original AeroCom protocol
were not sufficient to understand eg the impact of different
size assumptions on aerosol life time. New satellite retrievals
and ground based observations are currently underexploited
with respect to the validation of modelled aerosol size distribution.
3) Dust: Mineral dust
is a major natural and possibly anthropogenic aerosol component with potentially
large impact on radiation and regional climate. Considerable
diversity has been diagnosed among AeroCom models with
respect to simulating the dust cycle (<Textor
et al. 2006). More targeted evaluation is expected to
help constrain the dust cycle and radiative impact.
4) Carbonaceous aerosol:
The role of the carbonaceous aerosol for radiative forcing
has been shown to be a large source of diversity among models
(eg Schulz
et al. 2006). The analysis must be reinforced. Observations
of aerosol absorption, single scattering albedo and black
carbon need to be linked more closely to modelled distributions.
5) Vertical profile of the aerosol:
<Initial
comparison to lidar observations from EARLINET and the
ARM site have shown considerable differences to the modelled
vertical profile of the aerosol. The differences in the vertical
profile of the aerosol are suspected to be responsible for
a major part of the diversity in lifetime in AeroCom models
(<Textor
et al. 2006). With the upcoming Calipso data set and an
improved compilation of aircraft and mountain stations it
should be possible to further constrain the modelled vertical
profile of the aerosol.
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Technical implementation
Joint AC&C data center: The storage and analysis
of an extended AeroCom data set, as outlined above, would
require a large scale data centre with the commitment to maintain
long-term maintenance and support. A joint storage of coupled
chemistry-aerosol-climate simulations together with standard
AeroCom model simulations and those from other atmospheric
tracer comparisons is needed.
Automated model submission and diagnostics: AeroCom
seeks to implement the AutoMod system developed by Charles
Doutriaux (with OCMIP participants) at the LSCE and PCMDI.
Such a system would allow via a web based interface any user
to launch an ftp upload of a new model run. Diagnostic tools
can be selected to be launched after such submissions. Analysis
groups, model experiments, access and model output charcteristics
are stored in a meta-database. (see also recommendations in
report
of intercomparison IT-workshop in Ispra 2006 ).
Aerosol emission scenarios: The next IPCC runs are
expected to be build on multi-component aerosol emission scenarios.
It is proposed to prepare in cooperation with other initiatives
and individuals three consistent 1860-2100 aerosol emission
scenarios, reflecting low, mean and high emission estimates.
As for the AeroCom B and PRE experiments this is expected
to be a public data set.
New standards and rules for model submission: AeroCom
proposes that model output complies to the CF convention. An extension
of standard names is currently prepared via the standard
name discussion website. Utimately we propose that modellers
use CMOR
fortran tools to reformat their output with the help of specific
tables designed to fit each AeroCom experiment. (see IPCC
example for illustration). A full set of tools will be
prepared in autumn to facilitate this transition. This would
allow rapid processing and stability needed for future diagnostic
tools such as AeroCom tools and AutoMod.
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