Stephan Siemen

Forecast Department


Stephan Siemen is currently seconded as a Policy Officer to the European Commission in Luxembourg. As part of the Open Science and Digital Modelling unit at DG-CNECT he is involved in the work around the European Open Science Cloud (EOSC) and other research infrastructure initiatives across Europe. 

Before his secondment, Stephan was for almost a decade leading the Development Section at ECMWF. The section develops software and services to support core activities at ECMWF. The software enables researchers and analysts in and outside of ECMWF to en/decode, process, access, archive and visualise observations and forecast data. Service developments cover production services to handle forecast and archive data and web services to support users of ECMWF.  

Stephan was also involved in the management of multi-year projects like the pilot of the European Weather Cloud and the technical part of the IFShub project.

Stephan was directly involved in the development of the plotting package Magics and supported in general new developments on visualisations at ECMWF.

Professional interests:
  • Offering of cloud services for Big Data weather and climate data processing
  • Visualisation of meteorological data
  • Providing efficient access to large data sets
  • Software development methodologies and modern programming models & languages
Career background:


  • Policy Officer (SNE), Open Science and Digital Modelling unit, DG-CNECT, European Commission, 2021 - present
  • Head of Development Section, Forecast Department,  ECMWF, 2013 - 2021
  • Head of Graphics / Meteorological Visualisation Section, Operations Department, ECMWF, 2007 - 2013
  • Analyst working on Magics, Graphics Section, Operations Department, ECMWF, 2003 - 2007
  • Senior Research Officer, Propagation Laboratory, Mathematics Department, University of Essex, 2001 - 2003

Peer-reviewed publications

  • S. Siemen and A.R. Holt, A Modified VAD Technique for Analysing Wind Fields with Doppler radar, Physics and Chemistry of the Earth, vol. 25, p. 1201-1204, 2000 (This paper was presented by me as a talk on the 1st European Conference on Radar Meteorology in Bologna, Italy, September 2000)
  • S. Siemen, A.R. Holt, P. Hardaker, Extracting Doppler Radar Wind Information in Weather Prediction, 30th International Conference on Radar Meteorology, AMS, p. 461-462, Munich, 2001
  • S. Siemen and A.R. Holt, Recovering wind field features from VAD signatures for use in numerical forecasting, URSI Commission F Open Symposium, 2002
  • Y.K Goh, S.Siemen and A.R. Holt, Progress in dual Doppler radar wind retrieval from operational radars, Poster, Royal Meteorological Society Conference, Sep. 2003
  • Chris G. Collier, Fay Davies, Karen E. Bozier, Anthony R. Holt, Doug R. Middleton, Guy N. Pearson, Stephan Siemen, Dave V. Willetts, Graham J.G. Upton and Rob I. Young, Dual-Doppler Lidar Measurements for Improving Dispersion Models, p.825-838, Bulletin of the American Meteorological Society, vol. 86, no 6, June 2005

Other publications

ECMWF Newsletter


Articles published in German/UK edition of Linux magazine

  • S. Siemen, Virtuelle Welt, Linux Magazin (DE)  02/2003, S. 100-103
  • S. Siemen, Bewegte Objekte, Linux Magazin (DE)  03/2003 , S.98-101
  • S. Siemen, Coin 3D – Make the programming of 3D worlds easier than with OpenGL, Linux Magazine (UK), Issue 28, March 2003
  • S. Siemen, Räumliche Malerei, Linux Magazin (DE) 04/2003, S.98-102
  • S. Siemen, Moving Objects – Interactive 3D with Coin and Qt, Linux Magazine (UK), Issue 29, April 2003
  • S. Siemen, Drawing in 3D – Interactive 3D Worlds with Coin and Qt, Linux Magazine (UK), Issue 30, May 2003
  • S. Siemen, Software-Doping, Linux Magazin (DE) 06/2003, S.59-62
  • S. Siemen, Speed Compiler, Compiling C and C++ Programs with Intel’s Compiler, Linux Magazine (UK), Issue 32, July 2003
  • S. Siemen, Vier auf einen Streich, Code-Optimierung für SSE2-fähige Prozessoren, Linux Magazin (DE) 08/2003, S.101-105
  • S. Siemen, Go Faster, Optimizing Programs for SSE2-capable Processors, Linux Magazine (UK) Issue 34, September 2003
  • S. Siemen, Top Speed, Programme optimieren mit Profilern und Memory-Debuggern, Linux Magazin (DE) 10/2003, S.88-92
  • O. Frommel, S. Siemen, Glänzende Effekte, 3D-Grafiken verbessern durch Shader, Linux Magazin (DE) 02/2004
  • S. Siemen, Mit Vektoren zeichnen, Das Grafikformat SVGStruktur und Praxis, Linux Magazin (DE) 11/2004, S.90-94
  • S. Siemen, Vektorgrafik in Bewegung, Vektorgrafiken im SVG-Format animieren, Linux Magazin Sonderheft Multitalent (DE) April – Juni 2006, S.78-80