A. Aladin model

Operational and research numerical weather
prediction applications in the Meteorological and
Hydrological Service of Croatia
B. Ivančan-Picek*, K. Horvath*, S. Ivatek-Šahdan*, M. Tudor*, A. Bajić*, I. Stiperski* and A. Stanešić*
Meteorological and Hydrlogical Service/Department of research and development, Zagreb, Croatia
e-mail [email protected]
Abstract - The applications being developed and used at
Meteorological and Hydrological Service of Croatia cover
broad areas of meteorology, climatology, renewable energy,
hydrology, air quality modelling, and other. Applications
used for operational weather forecast include the numerical
weather prediction model ALADIN, data pre-processing
and model output post-processing tools as well as
visualization applications. Other meteorological numerical
models (such as WRF, COAMPS, WAsP, MM5, RegCM)
are utilized for research and additional applicative purposes
and tasks. The operational system is automatic and
controlled by a set of scripts that coordinate the model
execution and related modules with the availability of the
input data. The final products are disseminated to the endusers as soon as the module responsible for its generation is
This article will describe the applications developed,
maintained and used in the Research department the
Croatian Meteorological and hydrological service
The operational applications in CMHS are the timecritical jobs controlled by a cron deamon on the
designated computer. If the computer is used for other,
non-operational purposes, that are not time-critical, a job
submission and queueing system controlls the execution
and priority of the jobs. The operational class jobs are
given priority and the non-operational jobs are stopped or
held until the operational job completes.
Slika 1.
The operational model domains.
The operational forecast of the weather conditions for
the two domains shown in Figure 1 is obtained by running
the numerical weather prediction (NWP) model ALADIN
(Aire Limitee Adaptation Dynamique developement
InterNational) [1] from the initial time (analysis) up to 72
hours in advance for the 2 domains shown in Figure 1.
The domains do not cover the whole Earth, so this is a
limited area model (LAM) application. Each operational
forecast run requires the initial data and the lateral
boundary conditions (LBC) forecast data. The LBC data
are obtained from a global NWP forecast model
operational output. Either data from the ARPEGE (Action
de Recherche Petite Echelle Grande Echelle) model run
operationally in Meteo France (MF) or the IFS (Integrated
Forecast System) model run operationally at ECMWF
(European Center for Medium-range Weather Forecast)
can be used for initial and LBC.
The process to get “as best as possible” initial state of
atmosphere is called analysis. A complex analysis that
takes into account the time distribution of observations
and dynamical properties of analyzed system is called data
assimilation (Talagrand, 1967). The data assimilation
procedure is run at MF and ECMWF includes data
measured in Croatia so up to now main operational
forecast suite in CMHS did not utilize additional data
assimilation procedure. The operational forecast is run
twice per day, starting from 00 and 12 UTC analyses, but
two other sets of analyses and LBCs are available each
day, at 06 and 18 UTC.
The operational forecast is a soft time-critical
application. The measured meteorological data are
collected from the measuring stations and disseminated to
the data center. The data assimilation procedure uses only
the data collected up to a certain time. The data pass an
automatic quality check procedure. Then starts the
meteorological model dependent assimilation procedure
that is described in the next section. The final product of
the assimilation procedure is the initial file for the model
forecast run.
The model forecast run is the most demanding task of
the operational suite for the mainframe computer in
CMHS. The forecast run should finish in time so that the
complete set of the forecast products can be created in a
process called postprocessing and disseminated to the endusers. The forecast products are being created during the
model forecast run or upon its completion depending on
the input data set required by the particular postprocessing
The computer system
The mainframe computer in CMHS (violet in Figure
3) is a SGI Altix LSB-3700 BX2 Server with 48 Intel
Itanium2 1.6GHz/6MB CPUs and 96 GB standard system
memory and 2x146 GB/10Krpm SCSI disk drive. It runs
with OS SUSE Linux Enterprise Server 9 for IPF with
SGI Package. The NWP model software is compiled by
Intel Fortran & C++ compilers version 9.0.031. The
execution of the operational suite scripts and other not
time-critical jobs is controlled by queuing system (PBS
Pro). The individual tasks of the operational suite are
submitted to the queueing system by a cron deamon.
Slika 2.
Scheme of the access from the member service (MS) to the
Slika 3.
The scheme of the computers and connections involved in
the ALADIN operational suite.
The operational forecast suite starts with the retrieval
of the files containing initial and boundary conditions.
They are retrieved from MF via internet. The copy of
these files is being delivered by MF to ECMWF server for
backup transfer via internet or much slower dedicated
RMDCN (Regional Meteorological Data Communications
Network in Europe) line. Additional files produced at
ECMWF are available too.
Aladin model
The operational forecast is performed using the
hydrostatic version of ALADIN model [1] with 8 km
horizontal resolution on 37 levels in the vertical. It is a
spectral model that uses double Fourier representation of
fields with elliptic truncation [7] and a hybrid pressuretype terrain following coordinate [9]. Operationally, the 8
km resolution run is initialized using digital filter
initialization (DFI) [6]. The model version used
operationally has changed from the one described in [4] as
desribed in [10]. The primitive equation set for the wind
components, temperature, specific humidity, cloud water
and ice, rain and snow as well as surface pressure is
solved using the two-time-level semi-implicit semilagrangian integration scheme.
The 8 km resolution forecast is operationally further
dynamically downscaled to 2 km horizontal resolution on
a single domain of 450x450 points, using the same
procedure as described in Ivatek-Šahdan and Tudor
(2004). Instead of running the full model forecast on 2km
resolution for 72 hours, each output file of 8 km resolution
is used as initial and coupling file and the forecast is run
on only 15 levels using hydrostatic dynamics and vertical
turbulent diffusion parameterization. The model is run for
30 one-minute timesteps which allows wind to adapt
dynamically to the high resolution terrain.
Operational network
The computing and archive facilitiws of ECMWF
(light blue in Figure 3) can be accessed via ECaccess
server through the internet or the dedicated RMDCN line.
Both require usage of the ECaccess software and an
ECaccess gateway installed at CMHS (pluton in Figure 3).
The computing and archive facilities of MF (green in
Figure 3) can be accessed through a similar firewall
system from a registered server (Figure 3).
The operational model output is stored on a massive
storage facility (zemlja, Figure 3) and disseimated to other
serves internal to CMHS (orange in Figure 3), to be
picked up by the users, or disseminated directly to the
servers outside (red in Figure 3).
Aladin model code
The ALADIN NWP model software package is ported
to the mainframe computer using a compiler in
combination with the gmkpack compiling utillity that has
to be ported first. Porting and compilation of the model
source is done only once and separately from the model
execution and the model executable is stored for further
use. The model re-compilation happens only when the
research subject demands the model source code
modification or when a new version of the model becomes
available to be ported.
the research performed on a different computer or when
switching the operational suite from one computer to the
other one.
The postprocessing system
The operational model run produces the output as
model variables stored as spectral coefficients on the
model levels as well as specific meteorological variables
interpolated on the pressure surfaces or 2 and 10 meters
above ground. The output files are in a model specific
format. The users require model output data in either
GRIB or ASCII fromats and on specific sub-domains.
These can be created and disseminated already during the
model forecast run.
Slika 4. The CPU time per timestep during backward forward DFI
and 66 timesteps of the forward model forecast (6 hours) for various
model set-ups (different experiments).
The figures of the meteorological forecast fields are
ploted on a separate server that also hosts the intranet
pages of the operational ALADIN forecast products.
Another set of model output data are pseudo-TEMP
messages and model forecasts for specific points that
require the model output data for the entire 72 hour
forecast period and can be created only after the model
forecast run is finished.
Aladin data assimilation system
A description of setup of the local assimilation system
for a LAM ALADIN HR is given. Assimilation system at
CMHS consists of two parts; the surface assimilation
which is used to change the state of a model soil variables
and the upper air assimilation which changes an upper air
model fields. Surface assimilation is done by the optimal
interpolation (OI) technique while upper air assimilation is
done using the 3D variational technique (3DVAR). To get
better initial conditions data assimilation can be used. To
implement data assimilation, first an assimilation cycle
needs to be set up. Assimilation cycle is sequence of
analysis and 6 hour forecasts that is run on regularly basis.
Slika 5. The surface temperature difference obtained with data
assimilation using the same model code and same input data on two
different mainframe computers in Meteo France.
Aladin model code is being developed by a number of
scientists from 16 countires. It also includes the IFS
software that is developed in ECMWF, the ARPEGE
global model as well as the physics part of the MesoNH
research model of MF. All the model developments done
in different countires and on different computer platforms
are collected in a process called phasing and a new
version of the model software is released.
During porting, the model performance is evaluated
for the different optimization levels and various model
parametrization schemes. One of the important issues is to
keep the CPU time per model time-step small and
constant in order to have the operational model forecast
run finished on time. This can depend on the model
configuration for some optimization levels (Figure 3),
which is not good for the operational forecast tasks.
The same model code can give slightly different
forecast on different computer platforms (Figure 5). It is
important to keep this in mind when testing the results of
Observation type
surface pressure, 2m temperature
and relative humidity
wind components
Atmospheric Motion Winds
wind components
pressure, wind components,
temperature and humidity
Wind profiler
wind components
Satellite radiances
In the assimilation cycle, the information coming from
observations (Table I) is accumulated into the model state.
The assimilation cycle is even more important for the
surface analysis, because surface vairables need more time
to be updated.
CMHS is a member of Regional Cooperation for
Limited Area modeling in Central Europe (RC LACE;
http://www.rclace.eu/) that supports the LACE common
observation preprocessing unit (OPLACE). The
observation data is collected, preprocessed and dissipated
to LACE member services. The geographical selection of
data and quality control can be done locally through
LACE observation monitoring tool. The assimilation
cycle and production are run in quasi-operational mode
i.e. observational data is taken at operational time but
analysis and model integration is done with some time
delay (after the operational model run is finished). Scheme
p at DHMZ, as described in previous chapter, is running
in quasi operational mode from end of February 2010.
Approximately at same time storage capacities were
enhanced. This enabled archiving 72 hour forecasts
initialized from the assimilation cycle. This data was used
to evaluate quality of forecast initialized with assimilation
system (ASSIM) against operational forecast (OPER)
Slika 6.
Scheme of assimilation cycle implemented on DHMZ.
Verification is preformed in few steps. First quality
control of data is done using surface optimal interpolation.
The ARPEGE long cut off analysis is taken as background
in order to do “neutral” observation selection. Then, the
same observations are used for computation of model
departures from observations for both OPER and ASSIM.
Departures are used for calculating some basic statistics
like bias, Root Mean Square Error (RMSE) and standard
deviation (STD).
Slika 7. Seasonal verification scores for screen level parameters:
temperature, humidity, wind direction and wind speed versus prognostic
hour. BIAS-dashed lines, RMSE-full line, STD-dotted line. Red is
ASSIM and Black OPER.
of local setup of assimilation cycle at CMHS is shown on
Figure 6.
Model results were interpolated to location of
observation and compared with synoptic and radio
sounding observations. This was over time period of 10
months and over the whole model domain from
02.03.2010. to 04.12.2010. with 6 hour interval. Statistic
are computed for screen level parameters (2 meter
temperature and relative humidity, 10 m wind) and for
upper air parameters (temperature, realtive humidity, wind
components and geopotential). Verification results for
whole period (Figure 7) for 2m parameters show that both
bias and root mean square error are better for temperature
and relative humidity. The results are mostly neutral for
wind speed and direction (not shown).
Regional climate model
Regional climate model RegCM3 (Pal et al, 2007) is
run on local machine viking. Typical simulation includes
European domain with 35 km grid spacing, 142 x 93 mesh
and 23 vertical levels. In recent experiments, 2 years of
simulation per day were run on 16 CPU-s. Installation of
new RegCM4.1 is planned in a near future.
European monitoring and evaluation
The Unified EMEP (European Monitoring and
Evaluation Programme) model is coupled to ALADIN
meteorological output and run on 10km resolution. This
model setup called EMEP4HR is used for air quality
studies in DHMZ. Figure 8. shows monthly maximum
surface ozone fields (in PPBV) for May 2006. This is a
part of a study made to determine the influence of
industrial and traffic emissions on this important pollutant.
The relative effects of 15% increase and 15% decrease
respectively of traffic based NOx and VOC emissions are
also evaluated. In the first case maximum ozone is
increased while in the other it is decreased by
approximately 1% in the area with very high traffic
emissions. This study is made for the purposes of the
Ministry of construction and environment of Croatia.
Slika 8.
Maximum ozone concentrations in PPB for May 2006
Other NWP models
A number of meteorological models is used purely for
research purposes since they are too demanding on the
computer time and memory to be used in the time critical
operational forecast applications on the mainframe
computer used in CMHS. The COAMPS (Hodur, 1997)
model has been used in research of the sea surface
temperature effects on the bura flow (Kraljević and
Grisogono, 2005). The PSU/NCAR MM5 model (Grell et
al, 1995) has been used in a study of the model resolution
impact on the simulated bura (Špoler Čanić and Kraljević,
2005). These models are nevertheless an important tool
used in various case studies and phenomenological
The numerical weather prediction applications related
to the operational forecast are presented with a short
description of other non-operational models used in
particular research studies.
ALADIN International Team, 1997: The ALADIN project:
Mesoscale modelling seen as a basic tool for weather forecasting
and atmospheric research. WMO Bull., 46, 317-324.
[2] Grell, G. A., Dudhia, J. and D.R. Stauffer, 1995: A description of
the fifth-generation Penn State/NCAR mesostale model (MM5).
NCAR Technical Note, NCAR/TN-398+STR, 122 pp.
[3] Hodur, R. M. 1997: The naval research laboratorys coupled
ocean/atmosphere mesoscale prediction system (COAMPS). Mon.
Wea. Rev., 125 (7), pp. 1414-1430.
[4] Ivatek-Šahdan, S., M. Tudor, 2004: Use of highresolution
dynamical adaptation in operational suite and research impact
studies. – Meteorol. Z. 13, 99–108.
[5] Kraljević and Grisogono
[6] Lynch, P., X.-Y. Huang, 1994: Diabatic Initialization using
recursive filters. – Tellus 46A, 583–597.
[7] Machenhauer, B., J.E. Haugen, 1987: Test of a spectral limited
area shallow water model with timedependent lateral boundary
conditions and combined normal mode/semi-lagrangian time
integration schemes. – In: Proceedings from the ECMWF
Workshop on Techniques for HorizontalDiscretization in
NumericalWeather Prediction Models, 2–4 November 1987,
ECMWF, 361–377.
[8] Pal J and 19 coauthors (2007) Regional climate modeling for the
developing world. The ICTP RegCM3 and RegCNET. Bull Amer
Meteorol Soc 88: 1395-1409
[9] Simmons, A.J., D.M. Burridge, 1981: An Energy and AngularMomentumConservingVertical Finite-Difference Scheme and
Hybrid Vertical Coordinates. – Mon. Wea. Rev. 109, 758–766.
[10] Špoler Čanić, K and L. Kraljević.
[11] Talagrand, O., 1997: Assimilation of observations, an
introduction.. J. Met. Soc. Japan, Special Issue 75, 1B, 191-209.
[12] Tudor, M. and S. Ivatek-Šahdan, 2010: The case study of bura of
1st and 3rd February 2007, Meteorologische Zeitschrift, 19, 5;
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