Climate Dynamics

, Volume 30, Issue 2–3, pp 191–202

Internal variability in a regional climate model over West Africa

  • Emilie Vanvyve
  • Nicholas Hall
  • Christophe Messager
  • Stéphanie Leroux
  • Jean-Pascal van Ypersele
Article

Abstract

Sensitivity studies with regional climate models are often performed on the basis of a few simulations for which the difference is analysed and the statistical significance is often taken for granted. In this study we present some simple measures of the confidence limits for these types of experiments by analysing the internal variability of a regional climate model run over West Africa. Two 1-year long simulations, differing only in their initial conditions, are compared. The difference between the two runs gives a measure of the internal variability of the model and an indication of which timescales are reliable for analysis. The results are analysed for a range of timescales and spatial scales, and quantitative measures of the confidence limits for regional model simulations are diagnosed for a selection of study areas for rainfall, low level temperature and wind. As the averaging period or spatial scale is increased, the signal due to internal variability gets smaller and confidence in the simulations increases. This occurs more rapidly for variations in precipitation, which appear essentially random, than for dynamical variables, which show some organisation on larger scales.

Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  • Emilie Vanvyve
    • 1
  • Nicholas Hall
    • 2
  • Christophe Messager
    • 3
  • Stéphanie Leroux
    • 4
  • Jean-Pascal van Ypersele
    • 1
  1. 1.Institut d’astronomie et de géophysique Georges LemaîtreUniversité catholique de LouvainLouvain-la-NeuveBelgium
  2. 2.Laboratoire d’Etudes en Géophysique et Océanographie Spatiales/Centre National d’Etudes SpatialesToulouse Cedex 9France
  3. 3.Institute for Atmospheric Science, Environment, School of Earth and EnvironmentUniversity of LeedsLeedsUK
  4. 4.Laboratoire d’étude des Transferts en Hydrologie et EnvironnementUniversité Joseph FourierGrenoble Cedex 9France

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