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| Titel |
The 1-way on-line coupled atmospheric chemistry model system MECO(n) – Part 2: On-line coupling with the Multi-Model-Driver (MMD) |
| VerfasserIn |
A. Kerkweg, P. Jöckel |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1991-959X
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| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 5, no. 1 ; Nr. 5, no. 1 (2012-01-19), S.111-128 |
| Datensatznummer |
250002295
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| Publikation (Nr.) |
 copernicus.org/gmd-5-111-2012.pdf |
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| Zusammenfassung |
A new, highly flexible model system for the seamless dynamical
down-scaling of meteorological and chemical processes from the global
to the meso-γ scale is presented. A global model and a cascade
of an arbitrary number of limited-area model instances run
concurrently in the same parallel environment, in which the coarser
grained instances provide the boundary data for the finer grained
instances. Thus, disk-space intensive and time consuming intermediate
and pre-processing steps are entirely avoided and the time
interpolation errors of common off-line nesting approaches are
minimised. More specifically, the regional model COSMO of the German
Weather Service (DWD) is nested on-line into the atmospheric
general circulation model ECHAM5 within the Modular Earth Submodel
System (MESSy) framework. ECHAM5 and COSMO have previously been
equipped with the MESSy infrastructure, implying that the same process
formulations (MESSy submodels) are available for both models. This
guarantees the highest degree of achievable consistency, between both,
the meteorological and chemical conditions at the domain boundaries of
the nested limited-area model, and between the process formulations on
all scales.
The on-line nesting of the different models is established by
a client-server approach with the newly developed Multi-Model-Driver
(MMD), an additional component of the MESSy infrastructure. With MMD
an arbitrary number of model instances can be run concurrently within
the same message passing interface (MPI) environment, the respective
coarser model (either global or regional) is the server for the nested
finer (regional) client model, i.e. it provides the data required to
calculate the initial and boundary fields to the client model.
On-line nesting means that the coupled (client-server) models exchange
their data via the computer memory, in contrast to the data exchange
via files on disk in common off-line nesting approaches. MMD consists
of a library (Fortran95 and some parts in C) which is based on the MPI
standard and two new MESSy submodels, MMDSERV and MMDCLNT (both
Fortran95) for the server and client models, respectively.
MMDCLNT contains a further sub-submodel, INT2COSMO, for the
interpolation of the coarse grid data provided by the server models
(either ECHAM5/MESSy or COSMO/MESSy) to the grid of the respective
client model (COSMO/MESSy). INT2COSMO is based on the off-line
pre-processing tool INT2LM provided by the DWD.
The new achievements allow the setup of model cascades for zooming
(down-scaling) from the global scale to the lower edge of the
meso-γ scale (≈1 km) with a very high degree of
consistency between the different models and between the chemical and
meteorological boundary conditions. |
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