Met Office decadal prediction system: DePreSys

DePreSys is the decadal prediction system developed and run at the Met Office.

DePreSys is the Met Office decadal climate prediction system (Smith et al., 2007).

Although climate is expected to warm over the next century in response to increasing levels of greenhouse gases, regional changes over the coming seasons to a decade or more are likely to be dominated by unforced natural variability of the climate system. Some of this natural variability is potentially predictable months or even years in advance because it is related to relatively slow processes in the ocean, such as El Niño, fluctuations in the thermohaline circulation, and large-scale anomalies of ocean heat content. Decadal forecasts therefore attempt to predict natural variability in addition to externally forced changes. This is achieved by starting a climate model from the current observed state of the climate system, as well as specifying changes in anthropogenic sources of greenhouse gases and aerosol concentrations and projected changes in solar irradiance and volcanic aerosol.

DePreSys now uses the latest version of the Met Office coupled climate model, the Hadley Centre Global Environment Model version 3, HadGEM3. Initialisation is achieved by relaxing to full-depth analyses of ocean temperature and salinity (Smith and Murphy, 2007), and atmosphere analyses of winds, temperature and surface pressure. Until 2012, DePreSys used the earlier Hadley Centre Coupled Model version 3, HadCM3.  Tests for past cases using this model show that initialisation improves the forecast skill of globally-averaged surface temperature throughout the decade (Smith et al., 2007). Updated decadal forecasts, along with verification of previous forecasts, are available from the experimental long-range predictions web page.


References:

  • Smith, D. M., S. Cusack, A. W. Colman, C. K. Folland, G. R. Harris and J. M. Murphy, 2007, Improved surface temperature prediction for the coming decade from a global climate model, Science, 317, 796-799, doi:10.1126/science.1139540
  • Smith, D. M. and J. M. Murphy, 2007, An objective ocean temperature and salinity analysis using covariances from a global climate model, Journal of Geophysical Research, 112, C02022, doi:10.1029/2005JC003172

Last updated: 5 August 2013