Revision 713e387867ca7061e1e171ca75097a03fab55f8b authored by Adiv Paradise on 09 January 2019, 02:10:04 UTC, committed by Adiv Paradise on 09 January 2019, 02:10:04 UTC
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preface.tex
For two decades, a comprehensive, three-dimensional global atmospheric
general circulation model (GCM) is being provided by the National
Center for Atmospheric Research (NCAR, Climate and Global Dynamics Division)
to university and other scientists for use in analysing and understanding
the global climate. Designed as a Community Climate Model (CCM)
it has been continuously developed since. Other centres have also
constructed comprehensive climate models of similarly high complexity,
mostly for their research interests.
As the complexity of general circulation models has been and still
is growing considerably, it is not surprising that, for both
education and research, models simpler than those comprehensive
GCMs at the cutting edge of the development, are becoming more
and more attractive. These medium complexity models do not simply
enhance the climate model hierarchy. They support understanding
atmospheric or climate phenomena by simplifying the system
gradually to reveal the key mechanisms. They also provide an
ideal tool kit for students to be educated and to teach themselves,
gaining practice in model building or modeling. Our aim is to
provide such a model of intermediate complexity for the university
environment: the PlanetSimulator. It can be used for training
the next GCM developers, to support scientists to understand
climate processes, and to do fundamental research.
From PUMA to PlanetSimulator: Dynamical core and physical processes
comprise a general circulation model (GCM) of planetary atmospheres.
Stand-alone, the dynamical core is a simplified general circulation
model like our Portable University Model of the Atmosphere or PUMA.
Still, linear processes are introduced to run it, like Newtonian
cooling and Rayleigh friction, which parameterise diabatic heating
and planetary boundary layers. Though simple, PUMA has been enjoying
a wide spectrum of applications and initiating collaborations in
fundamental research, atmospheric dynamics and education alike.
Specific applications, for example, are tests and consequences
of the maximum entropy production principle, synchronisation and
spatio-temporal coherence resonance, large scale dynamics of the
atmospheres on Earth, Mars and Titan. Based on this experience we
combined the leitmotifs behind PUMA and the Community Model, to
applying, building, and coding a 'PlanetSimulator'.
Applying the PlanetSimulator in a university environment has two
aspects: First, the code must be open and freely available as
the software required to run it; it must be user friendly,
inexpensive and equipped with a graphical user interface.
Secondly, it should be suitable for teaching project studies
in classes or lab, where students practice general circulation
modelling, in contrast to technicians running a comprehensive GCM;
that is, science versus engineering.
Building the PlanetSimulator includes, besides an atmospheric
GCM of medium complexity, other compartments of the climate
system, for example, an ocean with sea ice, a land surface with
biosphere. Here these other compartments are reduced to linear
systems. That is, not unlike PUMA as a dynamical core with
linear physics, the PlanetSimulator consists of a GCM with,
for example, a linear ocean/sea-ice module formulated in
terms of a mixed layer energy balance. The soil/biosphere
module is introduced analoguously. Thus, working the PlanetSimulator
is like testing the performance of an atmospheric or oceanic GCM
interacting with various linear processes, which parameterise
the variability of the subsystems in terms of their energy
(and mass) balances.
Coding the PlanetSimulator requires that it is portable to many
platforms ranging from personal computers over workstations
to mainframes; massive parallel computers and clusters of
networked machines are also supported. The system is scalable
with regard to vertical and horizontal resolutions, provides
experiment dependent model configurations, and it has a transparent
and rich documented code.
Acknowledgement: The development of the Planet Simulator
was generously granted by the
German Federal Ministry for Education and Research (BMBF)
during the years 2000 - 2003.
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