The ALADIN System is a numerical weather prediction (NWP) system developed by the international ALADIN consortium for operational weather forecasting and research purposes. It is based on a code that is shared with the global model IFS of the ECMWF and the ARPEGE model of Météo-France. Today, this system can be used to provide a multitude of high-resolution limited-area model (LAM) configurations. A few configurations are thoroughly validated and prepared to be used for the operational weather forecasting in the 16 partner institutes of this consortium. These configurations are called the ALADIN canonical model configurations (CMCs). There are currently three CMCs: the ALADIN baseline CMC, the AROME CMC and the ALARO CMC. Other configurations are possible for research, such as process studies and climate simulations.
The purpose of this paper is (i) to define the ALADIN System in relation to the global counterparts IFS and ARPEGE, (ii) to explain the notion of the CMCs, (iii) to document their most recent versions, and (iv) to illustrate the process of the validation and the porting of these configurations to the operational forecast suites of the partner institutes of the ALADIN consortium.
This paper is restricted to the forecast model only; data assimilation techniques and postprocessing techniques are part of the ALADIN System but they are not discussed here.
The ALADIN System The ALADIN acronym stands for Aire Limitée
Adaptation Dynamique Développement International (International development
for limited-area dynamical adaptation) See
Currently the partners of
the ALADIN consortium are the (1) Office National de la Météorologie,
Algeria; (2) Zentralanstalt für Meteorologie und Geodynamik, Austria; (3) Royal Meteorological Institute of Belgium, Belgium; (4) Bulgarian National
Institute of Meteorology and Hydrology, Bulgaria, (5) Meteorological and
Hydrological Service, Croatia; (6) Czech Hydrometeorological Institute, Czech
Republic; (7) Météo-France, France; (8) Hungarian Meteorological Service,
Hungary; (9) Direction de la Météorologie Nationale, Morocco; (10) Institute of Meteorology and Water Management – State Research Institute of
Poland, Poland; (11) Instituto Português do Mar e da Atmosfera, Portugal;
(12) National Meteorological Administration of Romania, Romania; (13) Slovak
Hydrometeorological Institute, Slovakia; (14) Slovenian Environment Agency,
Slovenia; (15) Institut National de la Météorologie de Tunisie; and (16) Turkish State Meteorological Service,
Turkey.
The ALADIN consortium carries out an ambitious research program and has delivered a state-of-the-art NWP system that is used by its member states for their operational weather-forecasting applications. This is achieved by the following specific activities. The consortium performs research and development activities with the aim of maintaining the ALADIN System at scientific and technical state-of-the-art level within the NWP community. It carries out the necessary scientific and technical studies to define and maintain the ALADIN System and its canonical model configurations (CMCs). The consortium organizes the general maintenance of the ALADIN System with the aim to create new versions on a regular basis. It organizes coordination and networking activities in order to support the ALADIN consortium members in their ability to run the ALADIN canonical model configurations on the computing platforms of their national institutes. The consortium provides a platform for sharing scientific results, numerical codes, operational environments, related expertise and know-how, as necessary for all ALADIN consortium members to conduct operational and research activities with the same tools.
The collaboration follows the initial objectives of the consortium, as they
were introduced by its founder Jean-François Geleyn:
to have or to gain with the help of other members the capability to define,
build and run local versions of the ALADIN System, but also, to build the capability to conceive, develop, test and ultimately integrate
scientific ideas locally and finally in the new versions of the ALADIN System.
Both objectives lead to the benefit of all through the exchange of expertise
and the improvements of the ALADIN System, and contributes to the steady
progress of the discipline of NWP
While all partner services have the capacity to implement their operational versions of the ALADIN System by themselves, some activities are organized into more formally structured cooperations to develop applications that go beyond the deliverables of the ALADIN consortium.
The ALADIN consortium hosts the geographically localized regional cooperation
for Limited-Area Modelling in Central Europe (RC LACE) consortium, with seven
members: the national (hydro)meteorological services of Austria,
Croatia, Czech, Hungary, Romania, Slovakia and Slovenia. It contributes a lot
to the development of the ALADIN System. It made key contributions to the
ALADIN nonhydrostatic dynamical core and the development of the physics
parameterizations, in particular the ALARO CMC that will be described in
Sect.
Since 2005, the ALADIN consortium also shares its code with the HIRLAM
consortium HIgh-Resolution Limited-Area Model consortium.
The codes of the ALADIN System are common with the codes of the global
Integrated Forecast system (IFS) of the ECMWF European Centre for
Medium-Range Weather Forecasts. Action
de Recherche Petite Echelle Grande Echelle.
The aim of this link between the LAM and global models is threefold. First we
can consider the configurations of the ALADIN System as limited-area
configurations of the global model. Secondly, by sharing parts of the codes,
the maintenance efforts can be reduced, and developments done in either global
or limited-area models become mutually available. Lastly, as mentioned by
A quasiinfinite number of choices can be made in the scientific physics and dynamics options of the configurations of the ALADIN System. This offers a high degree of freedom for the participating partners of the ALADIN consortium to configure their national NWP applications, and even to develop tailor-made applications to address specific requests from their end users. However, it should be stressed that not all combinations of the available dynamics and physics schemes lead to scientifically meaningful model configurations.
Historically the ALADIN model was created as the LAM version of ARPEGE
AROME stands for Application of Research to Operations at
Mesoscale. ALARO stands for
ALadin–AROme.
This paper is organized as follows. In Sect.
A version of the ALADIN System is a release of the ALADIN System. Some versions are distributed at regular times to the ALADIN partners for research and development, as well as for operational purposes. These versions are called export versions. A configuration of the ALADIN System is a subset of ALADIN Codes used by a consortium member for its own implementation. Canonical model configurations are configurations of the ALADIN System for which the ALADIN consortium organizes collective efforts for the scientific and technical validation according to the state of the art of the latest research and development. The consortium also organizes the coordination and networking activities in order to install and run these canonical configurations in the operational NWP suites of the ALADIN consortium members.
Today there are two CMCs in the full sense: the AROME model configuration and the ALARO model configuration. While the ALADIN configuration is not exported to the partners of the consortium anymore, it is considered as the baseline CMC to ensure the link with the global model ARPEGE.
Code updates are done about every 6 months: one common with IFS–ARPEGE, one common only to the ALADIN partners.
A new version build is planned about 1 year in advance, and this original kick-off decision is followed by an “upstream coordination” process with the intention to anticipate as much as possible any potential conflict between expected code commitments. This effort is considered strategic for the NWP system, due to its highly integrated nature, and it involves scientific experts along with system (programming) experts.
The practical understanding of the link between the global IFS–ARPEGE and the
limited-area ALADIN code updates can be seen as a piece of genuine
ARPEGE–ALADIN know-how. Scientific developments performed first in one system
might be of potential interest to the other system, which raises the question
of how to thoroughly analyze the implementation steps for such a transfer of
science. A few fundamental rules are followed.
For spectral space codes, adaptations from spherical harmonics to bi-Fourier
spectral decompositions (or vice versa) are routinely analyzed. This
adaptation will usually result in specific new codes mimicking the call trees
and the general structure of the original development (e.g., horizontal
diffusion). For the grid-point computations involving geometry, adaptation from spherical
definitions to plane projected settings, or vice versa, is done (e.g.,
horizontal interpolations). However, some general available data enable a
common use of information in both codes, like the map factor of the
projection or the direction of the geographical north. The handling of the poles is specific to the global code, and usually occurs
as an optional code. The lateral boundaries are handled where necessary as optional code with
respect to the global version. Likewise, the treatment of lateral boundary
coupling is an optional code within the general time stepping of the whole
system.
Section
The practical steps of the initial build of a new ALADIN version release are mostly taking place at Météo-France: merge of code contributions and early validation process. Progressively, as the early versions become technically stable, some remote installation and further validation can take place, until the new release is declared. This process does not comprise preoperational local implementations in which the meteorological quality of a new release is evaluated, beyond the technical tests.
The technical validation is done in several steps, some of which are
ignored if found to be unnecessary:
a benchmark of base tests – adiabatic model versions, change of model grid
geometry versions, tangent-linear/adjoint model run tests, and specific
forecast tests including physics packages among which those used for defining
the CMCs; comparison with the previous reference version, aiming to trace back changes
that disrupt bit reproducibility, or to put it differently, verifying that
bit reproducibility is broken for understood reasons; computation of statistical scores such as bias and root-mean-square errors
(RMSEs) with respect to observations or reference analyses; specific model output diagnostics used in research mode like averages of model tendencies; one-dimensional model tests to assess profiles of
fields and their tendencies; specific data assimilation test periods are run (the time period is chosen in order to match with a recent context for the throughput of observations).
This process is meant to bring the embedded implementations of the LAM
configurations of the ALADIN System in phase with the cycles of the global
IFS and the ARPEGE models and is called “phasing”. The cycle numbers of the
ALADIN versions are the same as the corresponding cycles of IFS and ARPEGE.
The outcome of the build and validation process is a new version of the
ALADIN System labeled in the Météo-France central source code
repository. Mature versions of the ALADIN System are packages in so-called
“export versions” for installation in the ALADIN partner centers.
The definition of the ALADIN System is rooted in the options of the shared code to configure the LAM model configurations. This section describes the architecture of the code to outline what is common with the global model and what differentiates the LAM configurations from the global model.
One of the main concerns in the developments of these
codes Historically the code had to run in time-critical applications
on a large variety of available computing platforms across the different
partners of the ALADIN consortium – hence the specific care for numerical
efficiency through the use of large time steps.
Schematic overview of the time-step algorithm of the configurations of the ALADIN System and the choices that differentiate them with respect to the global ARPEGE model.
The code of the ALADIN System is shared with the code of the IFS of ECMWF and
the ARPEGE model of Météo-France. The current operational versions use a
spectral dynamical core with a two-time level semiimplicit semi-Lagrangian
(SISL) scheme
The time-step computations are organized in such a way that the same dynamics
formulations can be used for both limited-area and global geometries. The
time-step algorithm is schematically outlined in Table
Note that this algorithm is not the same for IFS as far as the physical
parameterizations calculations are concerned. In the IFS, the physics is
performed on variables at different times depending on the physical process,
whereas in the ARPEGE model and the ALADIN System it is performed entirely on
the
Three features differentiate the ALADIN System configurations from its global
counter part:
the choice of the horizontal bi-Fourier spectral transform instead of the
spherical spectral transforms (steps 1, 2, 9 in Table the lateral-boundary conditions (step 8 in Table the physics packages which are adapted in step 3 in Table
The code can be run with a nonhydrostatic dynamical core
that solves the fully compressible Euler equations
The vertical coordinate system uses a mass-based hybrid pressure
terrain-following coordinate
There are two additional prognostic variables compared to the hydrostatic
model core: the nonhydrostatic pressure departure from the hydrostatic
pressure and a specific expression of the vertical-divergence variable,
denoted as
This choice ensures satisfactory stability properties of the semiimplicit
scheme
The nonhydrostatic equation set can be solved using a separable linear
noniterative semiimplicit problem. However, the parameter domain of
stability is reduced with respect to the hydrostatic case. One way of
improving it is to use two distinct temperatures in the scheme, instead of a
single one. Roughly, one characterizes gravity waves, the other acoustic
waves. To go further,
The dynamical core (both hydrostatic and nonhydrostatic) includes a linear
numerical horizontal diffusion based on a power of the Laplace operator as
proposed by
The code also allows the use of a nonlinear semi-Lagrangian horizontal diffusion
(SLHD) scheme, computed under step 6 of the time-step algorithm in Table
The shared code also allows a digital-filtering initialization
(DFI) on a model state to be performed
Most of the above-described features are embedded in the common code with the global ARPEGE model.
The structure of the geographical domain of the LAM configurations is based
on the idea of
The LAM configurations of the ALADIN System use the
The domain of the LAM model is composed of three zones: a physical central zone (C), an intermediate zone (I) where the lateral-boundary conditions are imposed by a relaxation, and the extension zone (E) where artificial periodic extensions of the fields are inserted.
In the ALADIN System the lateral-boundary conditions are imposed in step 8 in
Table
The new biperiodization and LBC scheme proposed by
In practice the configurations of the ALADIN System are coupled to the IFS or
to the ARPEGE model. To this end the dynamical fields are spatially
interpolated to the LAM domain. The periodic extensions are inserted in the E
zone at this stage. To run the system with Boyd's scheme, one needs the
information of the fields of the host model outside the C and the I zone; see
The interpolation software also allows the interpolation of the fields of a LAM
configuration to a LAM subdomain with possibly a new resolution. The telecom
files are created at regular times with 1 h, 3 h or 6 h time
intervals. These files are read during a forecast run of the guest model and
interpolated in time to get the fields at each time step. Note that time
interpolations of the bi-periodic fields yields bi-periodic fields. In
practice the time interpolation is carried out by a linear interpolation or a
quadratic interpolation
The scientific content of the physics schemes that are called under step 3 in
Table
The coupling of the physics to the dynamics (step 4 in Table
For the efficiency of the LAM configurations on modern parallel computing
architectures, the same strategies as for the global IFS–ARPEGE models are
employed, with limited needs of adaptation. Mostly thanks to ECMWF and the
integration concept, this code is characterized by a rather rare fully
parameterized hybrid parallelization (MPI–OpenMP) capability. This means that
the code can use various mixes of distributed memory parallel tasks and shared
memory parallel threads. On the current dominant interconnected multi-CPU
boards, the LAM configurations primarily use the same cache-blocking
mechanism for cache-based computers These are the so-called NPROMA
blocks, named after the dimensioning NPROMA variable. This variable was
initially designed to optimize the vectorization length on vector machines.
The NPROMA blocking was developed first for vector shared memory machines.
Then the code was adapted for vector distributed memory machines by
introducing MPI. Since then OpenMP has been progressively implemented.
Recently, the performance on large computing domains has been significantly improved by introducing an input–output (I/O) server developed by Météo-France. It enables to resume the time integration itself, while the writing to disk is performed in parallel. Reading may also be distributed. Dual parallelization makes it possible to use multicore boards. Dual parallelization combined with parallel I/O together with a much reduced number of time steps to reach a given forecast range makes these codes extremely efficient, even though the transpositions required by the use of spectral transforms are not ideal from a scalability viewpoint.
The main three particularities of the LAM parallelism with respect to the
global model configurations concern the following:
the handling of the coupling data in grid-point space,
for which a specific message passing distribution and parallelism has been
developed; the handling of the limited-area aspects in grid-point space (unlike in the global model, the semi-Lagrangian trajectories have to be
constrained to the physical area C+I and possibly a margin of the extension
zone in the case of the Boyd solution mentioned above. Also, the
semi-Lagrangian trajectories are computed on a plane, which requires, among
other things, to construct the so-called halo for the MPI implementation in a
different way); In spectral space, the distributed Fourier-transform code is shared
with the global model in the zonal direction (while in the other direction a
second distributed Fourier transform code replaces the distributed Legendre
transforms).
The three physics packages ALADIN, AROME and ALARO can be called under step 3
of the time-step organization in Table
The current ALADIN baseline CMC calls the ARPEGE physics that is used at Météo-France between summer 2013 and spring 2017. Here we limit ourselves to a brief description of this version.
The ALADIN CMC.
Its radiation scheme is based for the long-wave on the so-called Rapid Radiative Transfer Model (RRTM) scheme
The different LAM configurations of the ALADIN System and their target resolutions.
The AROME canonical model configuration has been developed to run in the
convection-permitting resolutions starting from 2.5 km resolution. It is a
nonhydrostatic convective-scale limited-area model setup described by
COMAD is active in the ALADIN System code
since CY40T1 and in particular in the current cycle CY41T1 described here.
The AROME configuration uses a turbulence scheme based on a prognostic equation of TKE, a mass flux shallow convection scheme, a one-moment microphysics prognostic scheme, a detailed surface scheme and a radiation scheme described below.
The representation of the turbulence is based on a prognostic TKE equation
A mass flux scheme
A statistical cloud scheme is used in AROME
AROME uses a one-moment microphysics scheme
AROME uses the surface modeling platform SURFEX
The AROME CMC.
AROME uses the same radiation scheme as the ALADIN-baseline CMC. It is a
simplified version of the European Centre for Medium-Range Weather Forecasts
(ECMWF) radiation parameterizations. The shortwave radiation scheme
The choices of the physics parameterizations of the AROME CMC are summarized
in Table
Météo-France is the main center for the developments of the AROME CMC. The French operational implementation, called AROME-France, is the flagship regional forecast system covering mainland France and the neighboring regions. The AROME configuration has been first implemented in operations on 18 December 2008 in Météo-France. The current version has a resolution of 1.3 km and 90 vertical levels. The ensemble version and a number of overseas and commercial applications are based on a 2.5 km resolution, using the same 90 levels, reaching very close to the surface.
Maps of 3 h cumulated precipitations (mm) between 18:00 and
21:00 UTC over the southeast of France, for the case of 3 October 2015.
The AROME configuration is also, by design, a vehicle for the developments of
data assimilation of high-resolution observational data
The performance of the AROME CMC at Météo-France is regularly
statistically assessed with respect to observations or specific analysis
products. The verification encompasses WMO types of scores and more focused
statistical evaluations as illustrated in Fig.
Frequency bias index
The ALARO physics is implemented in the ALADIN System under the same calling
routines as those for the ALADIN configurations in step 3 of Table
The aim of the ALARO configurations of the ALADIN System is to provide a
setup that can also be used in intermediate resolutions between the
mesoscale and the convection-permitting scales; see Fig.
The basis for this is the application of a multiscale parameterization
concept. For moist deep convection, the Modular Multiscale Microphysics and
Transport scheme (3MT) has been developed to overcome problems when
convection gets partly resolved at the so-called gray-zone model resolutions.
The ALARO configuration is built upon this physics parameterizations concept
relying on the governing equations for the moist physics, cast in a flux-form
From the code point of view, new versions of the schemes are developed by taking utmost care of the ascending compatibility with the former versions. This allows easier validations, progressive upgrades and tailoring of the scientific complexity of the local applications. The coding and the numerical solutions strive for economical use of computing resources and are developed to allow for the long time steps allowed by the dynamical core. New schemes are also designed to be modular at the level of processes rather than at the level of full schemes.
The 3MT scheme is based on a mass-flux formulation and is designed to be used
at the so-called convection-permitting model resolutions, i.e., for model grid
lengths going from about 10 km down to a few hundred meters. It is
described in detail in
The 3MT scheme does not rely on any assumption that convective cells cover a negligible fraction of the grid-box area, since this is not valid when increasing the resolution. Diagnostic relationships are therefore replaced by a time integration of the deep convection equations. In particular, the prognostic equations are solved for the updraft velocity, the downdraft velocity and also for the mesh area fractions occupied by the updraft and the downdraft, respectively. The quasiequilibrium hypothesis commonly used in deep convection parameterizations is abandoned. Instead 3MT uses a prognostic closure, relying on the cloud-base updraft area evolution.
The older parameterization concept of scale separation, common to coarser-resolution models, is not retained. Instead, the suggestion of
In coarser-resolution models, the condensation is usually treated by two
separate parameterization schemes, the so-called cloud scheme for
nonconvective (stratiform) clouds and the moist deep convection scheme. In
contrast CSRMs rely on convective drafts that are fully resolved by the model
dynamics and all the condensation is computed by the cloud scheme. To avoid
these two limits, inapplicable within the convection-permitting scales, and
also to allow for a smooth transition to the CSRM limit, the scheme steps are
organized in a cascade. The cloud scheme condensation, derived from
In the convection-permitting scales it is still necessary to account for the
subgrid-scale features of the unresolved updrafts condensation and the
resulting precipitation. In the 3MT scheme this is done at the thermodynamic
adjustment step of the cloud scheme and in the microphysics. Suspended water
droplets and ice crystals of the convective cloud portion of the grid box are
protected against their reevaporation during the adjustment in the next
time step. The microphysics computations take into account the geometry of
clouds and precipitation vertical overlaps to get a more realistic cloud and
precipitation scene within the grid box. The geometry scheme is the
exponential-random scheme from
Microphysics is therefore at the central position of the 3MT scheme in the
organization of the ALARO CMC physics time step, for which a single call ensures a
smooth and implicit transition between grid scale and the unresolved origin of
precipitation. It works with six species – dry air, water vapor, suspended
liquid and ice cloud water, rain, and snow. The thermodynamics obeys the
governing equations of
In order to enhance consistency and unification of parameterizations, the
strategy employed in ALARO is to use prognostic, memory-keeping schemes
One can argue that bulk parameterizations should converge in their behavior to the behavior of CSRMs in the cloud-resolving limiting resolutions. If the prognostic equations of the mesh fraction and the updraft-vertical velocity scale properly, then the equations should converge to the equations of a CSRM. This yields a mechanism to control this convergence and to formulate a scale-aware parameterization of deep convection.
The 3MT scheme was introduced mid-2008 in a predecessor of the ALARO
configuration operations in the application in CHMI (Prague), allowing the resolution to increase to 4.7 km, i.e., to enter the gray zone of moist deep
convection. It was the world first application of the prognostic
microphysics–transport separation concept in NWP. The multiscale properties
of 3MT are demonstrated in Fig.
Recently, good results were found up to a resolution of 1 km, when running the
so-called gray-zone experiment cold air outbreak case
In the same spirit of separating the precipitating and nonprecipitating
processes, shallow convection is part of the turbulence scheme TOUCANS (Third
Order moments Unified Condensation And N-dependent Solver). This
parameterization of turbulence takes the advantage of recent theoretical
proposals, such as the revisited Mellor–Yamada system
Precipitation accumulated between the
Since TOUCANS can emulate Mellor–Yamada type of stability dependency
functions, valid for all stability conditions, as well as the QNSE and EFB
systems; all these models of turbulence are coded. The ALARO CMC retains the
so-called model II of
The closure–discretization method is a “stability dependent adjustment for
turbulent energy modeling”
The introduction of moisture in the turbulence scheme, i.e., accounting for
phase changes, leading to density changes and latent heat release, is based
on the recent formulation of moist Brunt–Väisälä Frequency (BVF)
As an enhancement of the Louis scheme a pseudo-prognostic TKE treatment
Parameterization of radiative transfer is one of the most expensive computations in NWP models, therefore a compromise between the cost and accuracy is required. In the case of ALARO the choice is to keep the cloud-radiation interaction at full spatial and temporal model resolutions, to account for the fast development and the increased variability of cloudiness that manifest themselves with the increasing resolutions of the model applications. To achieve this, the ALARO CMC builds on a broadband approach with single shortwave and single long-wave spectral intervals, where almost linear scalability of long-wave computations (including scattering) with respect to the number of vertical levels is obtained via the so-called net exchanged rate (NER) decomposition with bracketing.
Currently, the ALARO CMC offers two radiative transfer schemes. The original
scheme, denoted as ACRANEB, is best described in chap. 9.3 of
The ALARO CMC.
The second version, called ACRANEB2
The ALARO CMC, in contrast to the AROME one, contains the gravity wave drag
parameterization
The choices of the physics parameterizations of the ALARO CMC are summarized
in Table
The reference versions of the ALARO are maintained in CHMI. Scientifically
sound versions are committed during the phasings to the central repository in
Météo-France. The ALARO CMCs are created once their model configurations
have successfully passed the technical validations mentioned in Sect.
Some physics parameterizations can be shared between the two configurations.
For instance, the ALARO CMC calls the ISBA surface scheme directly, but it is
possible to call the SURFEX scheme from the ALARO configurations. The
performance of such an inclusion has been tested by
The operational domains of ALADIN System within the ALADIN consortium (situation in April 2017).
The configurations of the ALADIN System running in the ALADIN partner countries (as in April 2017), with their nationally used name, horizontal resolution (HRES), domain size, number of vertical levels (NLEV), version of the ALADIN System, coupling model and the used configuration (ALADIN, ALARO, AROME).
By using the canonical configurations the ALADIN partners can be sure that they are running a configuration with physically consistent choices. The installation and upgrade of the ALADIN System is performed by the partners individually, thanks to the high level of expertise gathered in each NHMS during the past course of the ALADIN project. Dedicated and coordinated efforts are made to support the installations of the newest cycle at partners' NHMS in order bring to them at a state-of-the-art level, allowing the partners to implement the newest research and development achievements. The support also comprises the collection and redistribution of information about known problems and their fixes.
The ALADIN System is run operationally at all 16 partners' NHMSs on the
domains depicted in Fig.
Typical configurations are run with horizontal resolutions of 1.3 and 2.5 km for AROME and about 4–5 km for ALARO. Some partners run both configurations in a double-nesting setup: for instance, ALARO (or ALADIN) on a larger domain with a coarser resolution of 4–10 km, driven either by the IFS or ARPEGE global model, and a convection-permitting AROME or ALARO configuration on a smaller domain focusing on the partner's country and close neighborhoods, that is usually coupled to the intermediate ALARO (or the ALADIN) model configuration.
Currently the ALADIN consortium is installing cycles CY40T1 and CY41T1 that
are described in Sect.
It should also be mentioned that CMCs of the ALADIN System are being used
with data assimilation, with ensemble prediction systems (EPSs) and with rapid
update cycles for nowcasting purposes. For instance, the AROME CMC is
operationally implemented in Météo-France's nowcasting system
In terms of local implementation, the operational ALADIN System configurations mostly focus on the need to provide a state-of-the-art forecasting system with convective scale resolution. The goal is to provide forecasters, other production departments in ALADIN national weather services, and eventually stakeholders and users of various types, an added-value forecast of severe weather outbreaks, very local weather patterns and a variety of meteorological output fields and products. A typical example of severe weather of concern is heavy precipitation and strong convection, with their possible associated features like severe wind gusts, heavy hail or flooding.
The progressive increase in resolution led to more realistic forecasts of
convective systems. As an example, Fig.
The new versions of the ALADIN System are also verified for specific past
cases that are of primary interest, demonstrating added value of the
high-resolution forecasts with respect to the global model or with respect to
the previous versions. Figure This version uses a combined
3D-Var for the atmosphere and an optimal interpolation for the surface to
create the initial conditions. The lateral boundary conditions with hourly
resolution are created from the IFS high-resolution (HRES) model.
Distribution of the number of convective cells against their size
represented by an estimate of the cloudy area, as derived from the data of
the French radar network (40 dBz reflectivity detection level, solid black
curve), from the 1.3 km, 90-level AROME version (dashed red curve) and from
the 2.5 km, 60-level AROME (dotted green curve). The statistics have been
aggregated over 48 convective days of 2012. Adapted from
Efforts are made to steadily increase the resolutions of the applications.
For instance, the operational viability of the CY40T1 ALARO CMC is tested at
kilometer-scale resolution over Belgium by the Royal Meteorological Institute of
Belgium (RMI), as represented the lower part of the diagram in Fig.
24 h accumulated area mean and area max values for the region (longitude/latitude: 12.75–13.5/47.65–48.45) for INCA, AROME-aut and IFS-HRES.
Configurations of ALADIN System are used by the partners of the consortium for scientific studies. In many cases, the partners rely on their own expertise to adapt the versions of the ALADIN System to develop tailor-made tools for their national needs.
As an illustration, the configurations of the ALADIN System of Croatia (shown
in Table
The accumulated precipitation between
ALARO-HRDA has had a large success in forecasting spatial and temporal
variability of local windstorm Bura (
There are episodes of severe Bura associated to local dynamical phenomena
that require high-resolution forecasts using nonhydrostatic dynamics and
complete ALARO physics package
Configurations of the ALADIN System are still used for applications where
mesoscale applications are required: for instance, there are adapted
regional-climate model versions of ALADIN See its project web
site
The aim of this paper was to describe the current state of the forecast model configurations of the ALADIN System and review the rationale behind the scientific options made in the past developments of the ALADIN System. Given the increase in choices in the model configurations, the ALADIN consortium introduced the notion of canonical model configurations. These are privileged, physically consistent configurations that are intensively validated and for which support from the consortium is provided to implement them as operational applications in the ALADIN partner countries. The status of the current two CMCs AROME and ALARO was described and a status report on their validation and implementation in the ALADIN partners' NWP applications was given. While doing so this paper clarified the meaning of the acronyms used within the ALADIN consortium.
Wind speed in Makarska (43.28
The scope of the present paper was limited to the forecast model configurations, excluding data assimilation, EPS perturbation methods, post-processing software, scripting systems and so forth, but relevant references to these systems were given throughout the paper without aiming to be exhaustive.
The ALADIN consortium provides a platform for the ALADIN members for
organizing optional Optional activities mean that the ALADIN
consortium does not per se, today, provides coordination for these activities
among its members, but facilitates them through the management and the
delivery of the codes of the ALADIN System.
Codes developed within the context of the cooperation agreement with the
HIRLAM consortium have been colloquially called HARMONIE HARMONIE
stands for HIRLAM ALADIN Research on Meso-scale Operational NWP in Euromed.
The shared codes are undergoing a number of code modernizations driven by the strong will to keep them fit both for optimal use of upcoming high-performance computing architectures and for further scientific and meteorological evolutions. This is a significant investment, performed together with ECMWF. It involves the use of object-oriented software layers to provide a further abstraction level in data assimilation on the one hand, and in compute grids on the other hand, accompanied by disentangling and modularization, optimization and portability issues (including reliability on massively parallel HPC). Extra work on the development of scripts for data assimilation is planned. There are no short-term reasons to abandon the spectral numerical techniques of the dynamical core of the ALADIN System as long as the inherent scalability weakness is more than balanced by the advantage of being able to run with large Courant numbers. Nonetheless, the ALADIN consortium carries out research on scalability and efficiency issues including the study of local discretization methods with research studies ranging from adapting the semiimplicit problem formulation and solution to try and keep the large Courant number time-stepping, to being able to solve the same equations using a HEVI (horizontally explicit, vertically implicit) scheme, the latter being a kind of fall-back solution.
The ALADIN Codes, along with all their related intellectual property rights, are owned by the members of the ALADIN consortium and are shared with the members of the HIRLAM consortium in the frame of a cooperation agreement. This agreement allows each member of either consortium to license the shared ALADIN-HIRLAM codes to academic institutions of their home country for noncommercial research.
Access to the codes of the ALADIN System
can be obtained by contacting one of the member institutes mentioned in the
introduction of this paper or by submitting a request in the Contact link
below the page of the ALADIN website (
The authors declare that they have no conflict of interest.
The present paper was substantially improved by taking into account many pertinent comments from Philippe Bougeault, Per Unden and the anonymous reviewer.
The activities of the ALADIN consortium started in 1991 after an initiative taken by Météo-France. The current system is the result of the contributions of many experts from the ALADIN, the ARPEGE and the IFS communities. The merits of the authors in the developments of the ALADIN System are small compared to this. The present paper is meant to give a status review of the current system according to our best efforts. While the list of contributors is too long to be acknowledged here, we point out the unique contributions of the late Jean-François Geleyn. He was the driving force behind the creation of the ALADIN consortium and he was the leading scientist of the developments of the ALADIN System. His vision further enabled the training of many young scientists throughout Europe and northern Africa in state-of-the-art numerical weather prediction. When he passed away in 2015 the consortium lost an exceptional mind. We dedicate this paper to his memory. Edited by: Paul Ullrich Reviewed by: Per Unden and one anonymous referee