I&CLC 2000 Applications report
DOWNSCALING OF NEAR SURFACE WIND IN THE ALPINE REGION
Domain of the application: Tackling climate change
Policy driver: Alpine Convention (?)
Country/Region: Alpine region
ABSTRACT
In late 2003, the 3-year project “Research for Climate Protection: Model Run Evaluation” (reclip:more)
has been started to evaluate and compare two different regional climate models (RCM) by performing
control and future scenario model runs (Loibl, 2004) to analyse meteorological effects of climate
change in the Alpine regions at mesoscale and microscale resolutions. This project has been
developed due to the high demand in near surface wind pattern information at high resolution by wind
energy companies, insurances, air pollution dispersion assessments, research and management in
biology, hydrology, and agriculture.
The wind-downscaling task of reclip:more aims at providing freely accessible statistics (frequency
distributions) of wind speed and direction as well as density of wind energy and air at a spatial
resolution of 200 m based on sophisticated long term RCM runs. The downscaling of near surface
wind to 200 m target resolution is accomplished by the sequential execution of meso- and microscale
models, using CORINE land cover data to properly set up the lower boundary conditions at high
resolution.
Finally, while the RCMs cover the entire Alpine region, the complete set of reclip’s downscaling
applications (concerning temperature, precipitation, solar radiation, snow cover and wind respectively)
are performed within three study areas (including Lower Austria, South-East Styrian, and Hohe Tauern
regions).
Figure 1:
Thermal driven slope flows
calculated by the microscale
diagnostic model CALMET over
the south-eastern foothills of the
Wölzer Tauern at Sept. 4, 2003,
12:00 UTC. Near surface wind
(streamlines) [m/s] at 10 m above
ground and the elevation model
are shown.
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MORE INFORMATION
Methodology used
The well known Wind Atlas Analysis and Application Program (WAsP) (Mortensen et al., 1993), which
has been used for the preparation of the European Wind Atlas (Troen et al, 1989), unfortunately
delivers satisfying results only in homogenous flat terrain (Dobesch et al., 1997). To overcome this
disadvantage, a combined application of prognostic and diagnostic models is used. This application
consists of two main steps.
A first dynamical downscaling step is applied to the RCM results, using MM5 in order to prepare initial
conditions at higher resolution (5 km) through domain nesting within the study areas. The second step
is carried out by a modified version of the microscale model CALMET (Scire et al., 1999). In this case
CALMET is used to compute a three dimensional divergence-free wind field up to about 1000 m above
ground level (agl) in a diagnostic manner at the final grid resolution and under consideration of
kinematic terrain-effects, slope flows, and thermodynamic blocking-effects. To set up the lower
boundary conditions certain physio-geographic data (external parameters), such as roughness length,
surface albedo, Bowen ratio (ratio between sensible heat flux and latent heat flux) and surface heat
flux parameter (ratio between heat flux into the ground and net incoming radiation), have to be derived
and related to CORINE land cover classes. As a first approach, the external parameters are taken
from literature (Hagemann, 2002; Pineda et al., 2004) and statically linked to the CORINE land cover
classes. An improved version will afford to derive the surface heat fluxes directly from the driving RCM
(Pielke, 2002) to achieve both, more accurate results and a consistent modelling at different scales.
Results obtained and outlook
At the current status of the project reclip:more, the development of the first version of the winddownscaling method has been completed.
Future works will focus on the evaluation of the method using SODAR (sonic detection and ranging)
and surface observations from the Mesoscale Alpine Programme (Bougeault et al., 2001) as well as
on the optimisation of the process to prepare the external parameters. Finally, the downscaling
method will be applied to the two long-term MM5 datasets to accomplish the needed wind
climatologies.
References
BOUGEAULT, P., P. BINDER, A. BUZZI, R. DIRKS, R. HOUZE, J. KUETTNER, R. B. SMITH, R. STEINACKER,
and H. VOLKERT (2001): The MAP Special Observing Period, American Meteorological Society, 83, 3,
433-462.
DOBESCH, H., G. KURY (1997): Wind Atlas for the Central European Countries – Austria, Croatia, Czech
Republic, Hungary, Slovak Republic and Slovenia, Österreichische Beiträge zu Meteorologie und
Geophysik, 16, Vienna.
DOBESCH, H., H.V. TRAN (1999): The Diagnostic Wind Field Model ZAWIMOD2, Österreichische Beiträge zu
Meteorologie und Geophysik, 22, Vienna.
DUDHIA, J., D. GILL, K. MANNING, W. WANG, C. BRUYERE (2004): PSU/NCAR Mesoscale Modeling System
Tutorial Class Notes and User’s Guide: MM5 Modeling System Version 3, Mesoscale and Microscale
Meteorology Division of the National Center for Atmospheric Research, Boulder.
EEA (1995): CORINE Land Cover, European Environmental Agency Report, Commission of the European
Communities OPOCE (Office for official publications of the European Communities).
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HAGEMANN, S. (2002): An Improved Land Surface Parameter Dataset for Global and Regional Climate Models,
Max Planck Institute for Meteorology (MPI), Report 336, Hamburg.
LOIBL, W. (2004): Kwiss-Programm reclip: Research for Climate Protection, 1. Zwischenbericht, ARC–sys-0009,
Seibersdorf.
MORTENSEN, N.G., I. LANDBERG, I. TROEN, E.L. PETERSEN (1993): Wind Atlas Analysis and Application
Program. WAsP, Version 4.0, Risoe Nat. Lab., Roskilde.
MÉTÉO-FRANCE, (2004): Numerical Weather Prediction Project - Aire Limitée Adaptation dynamique
Développement InterNational (ALADIN), homepage: http://www.cnrm.meteo.fr/aladin
PIELKE, R.A. Sr. (2002): Mesoscale Meteorological Modeling, Second Edition, International Geophysics Series,
Vol. 78, Academic Press, London.
PINEDA, N., O. JORBA, J. JORGE, J.M. BALDASANO (2004): Using NOAA AVHRR and SPOT VGT data to
estimate surface parameters: application to a mesocale meteorological model, International Journal of
Remote Sensing, 25, 1, 129-143.
RABUS, B., M. EINEDER, A. ROTH, R. BAMLER (2003): The shuttle radar topography mission - a new class of
digital elevation models acquired by spaceborne radar, Journal of Photogrammetry & Remote Sensing,
57, 241-262.
ROECKNER, E., G. BAEUML, L. BONAVENTURA, R. BROKOPF, M. ESCH, M. GIORGETTA, S. HAGEMANN,
I. KIRCHNER, L. KORNBLUEH, E. MANZINI, A. RHODIN, U. SCHLESE, U. SCHULZWEIDA, A.
TOMPKINS (2003): The Atmospheric General Circulation Model ECHAM5. Part 1: Model Description,
Max Planck Institute for Meteorology (MPI), Report 349, Hamburg.
SCIRE, J.S., F.R. ROBE, M.E. FERNAU, R.J. YAMARTINO (2000): A User’s Guide for the CALMET
Meteorological Model (Version 5), Earth Tech Inc., Concorde.
SIMMONS, A.J., J.K. Gibson (2000): The ERA-40 Project Plan, ERA-40 Project Report Series No. 1, European
Centre for Medium-Range Weather Forecasts (ECMWF), 63pp, Reading.
TROEN, I., E.L. PETERSEN (1989): European Wind Atlas. Commission of the European Community, Published
by Risoe Nat. Lab., Roskilde.
If you wish to obtain more information about this application, please contact with
Institute of Geophysics, Astrophysics and Meteorology (IGAM), University of Graz
Austria
Heimo Truhetz
heimo.truhetz@uni-graz.at
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