Impact of a quasi-stochastic cellular automaton backscatter scheme on the systematic error and seasonal prediction skill of a global climate model

in Stochastic Physics and Climate Modelling, Cambridge University Press (2009) 15

J Berner, FJ Doblas-Reyes, TN Palmer, GJ Shutts, A Weisheimer

Future change in wintertime atmospheric blocking simulated using a 20-km-mesh atmospheric global circulation model

Journal of Geophysical Research: Atmospheres 114 (2009)

M Matsueda, R Mizuta, S Kusunoki

Future change in the frequency of atmospheric blocking is investigated through present-day (1979-2003) and future (2075-2099) simulations using 20-, 60-, 120-, and 180-km-mesh atmospheric general circulation models (AGCMs) under the Intergovernmental Panel on Climate Change Special Reports on Emission Scenarios AlB emission scenario, focusing on the Northern Hemisphere winter (December-February). The results of present-day climate simulations reveal that the AGCM with the highest horizontal resolution is required to accurately simulate Euro-Atlantic blocking, whereas the AGCM with the lowest horizontal resolution is in good agreement with reanalysis data regarding the frequency of Pacific blocking. While the lower-resolution models accurately reproduce long-lived Pacific blocking, they are unable to accurately simulate long-lived Euro-Atlantic blocking. This result suggests that the maintenance mechanism of Euro-Atlantic blocking is different from that of Pacific blocking. In the future climate simulations, both frequencies of Euro-Atlantic and Pacific blockings are predicted to show a significant decrease, mainly in the western part of each peak in present-day blocking frequency, where the westerly jet is predicted to increase in strength; no significant change is predicted in the eastern part of each peak. The number of Euro-Atlantic blocking events is predicted to decrease for almost all blocking durations, whereas the decrease in the number of Pacific blockings is remarkable for long-duration events. It is possible that long-lived (>25 days) Euro-Atlantic and Pacific blockings will disappear altogether in the future. Copyright 2009 by the American Geophysical Union.

A comparative method to evaluate and validate stochastic parametrizations

Quarterly Journal of the Royal Meteorological Society 135 (2009) 1095-1103

L Hermanson, BJ Hoskins, TN Palmer

There is a growing interest in using stochastic parametrizations in numerical weather and climate prediction models. Previously, Palmer (2001) outlined the issues that give rise to the need for a stochastic parametrization and the forms such a parametrization could take. In this article a method is presented that uses a comparison between a standard-resolution version and a high-resolution version of the same model to gain information relevant for a stochastic parametrization in that model. A correction term that could be used in a stochastic parametrization is derived from the thermodynamic equations of both models. The origin of the components of this term is discussed. It is found that the component related to unresolved wave-wave interactions is important and can act to compensate for large parametrized tendencies. The correction term is not proportional to the parametrized tendency. Finally, it is explained how the correction term could be used to give information about the shape of the random distribution to be used in a stochastic parametrization. © 2009 Royal Meteorological Society.

Stochastic parametrization and model uncertainty. ECMWF Tech Memo.

(2009) 598

TN Palmer, R Buizza, FJ Doblas-Reyes, T Jung, M Leutbecher, GJ Shutts, M Steinheimer, A Weisheimer

Monte Carlo approach to turbulence

Proceedings of the XXVII International Symposium on Lattice Field Theory ‘Lattice 2009' (2009)

Dueben, D Homeier, K Jansen, D Mesterhazy, G Muenster

The Invariant Set Postulate: a new geometric framework for the foundations of quantum theory and the role played by gravity


TN Palmer

Introduction. Stochastic physics and climate modelling.

Philos Trans A Math Phys Eng Sci 366 (2008) 2421-2427

TN Palmer, PD Williams

Finite computing resources limit the spatial resolution of state-of-the-art global climate simulations to hundreds of kilometres. In neither the atmosphere nor the ocean are small-scale processes such as convection, clouds and ocean eddies properly represented. Climate simulations are known to depend, sometimes quite strongly, on the resulting bulk-formula representation of unresolved processes. Stochastic physics schemes within weather and climate models have the potential to represent the dynamical effects of unresolved scales in ways which conventional bulk-formula representations are incapable of so doing. The application of stochastic physics to climate modelling is a rapidly advancing, important and innovative topic. The latest research findings are gathered together in the Theme Issue for which this paper serves as the introduction.

Impact of a quasi-stochastic cellular automaton backscatter scheme on the systematic error and seasonal prediction skill of a global climate model.

Philos Trans A Math Phys Eng Sci 366 (2008) 2561-2579

J Berner, FJ Doblas-Reyes, TN Palmer, G Shutts, A Weisheimer

The impact of a nonlinear dynamic cellular automaton (CA) model, as a representation of the partially stochastic aspects of unresolved scales in global climate models, is studied in the European Centre for Medium Range Weather Forecasts coupled ocean-atmosphere model. Two separate aspects are discussed: impact on the systematic error of the model, and impact on the skill of seasonal forecasts. Significant reductions of systematic error are found both in the tropics and in the extratropics. Such reductions can be understood in terms of the inherently nonlinear nature of climate, in particular how energy injected by the CA at the near-grid scale can backscatter nonlinearly to larger scales. In addition, significant improvements in the probabilistic skill of seasonal forecasts are found in terms of a number of different variables such as temperature, precipitation and sea-level pressure. Such increases in skill can be understood both in terms of the reduction of systematic error as mentioned above, and in terms of the impact on ensemble spread of the CA's representation of inherent model uncertainty.

Ensemble forecasting


M Leutbecher, TN Palmer

Monte Carlo simulations of the randomly forced Burgers equation

Europhysics Letters: a letters journal exploring the frontiers of physics 84 (2008)

Dueben, D Homeier, K Jansen, D Mesterhazy, G Muenster, C Urbach

Toward seamless prediction: Calibration of climate change projections using seasonal forecasts

Bulletin of the American Meteorological Society 89 (2008) 459-470

TN Palmer, FJ Doblas-Reyes, A Weisheimer, MJ Rodwell

Trustworthy probabilistic projections of regional climate are essential for society to plan for future climate change, and yet, by the nonlinear nature of climate, finite computational models of climate are inherently deficient in their ability to simulate regional climatic variability with complete accuracy. How can we determine whether specific regional climate projections may be untrustworthy in the light of such generic deficiencies? A calibration method is proposed whose basis lies in the emerging notion of seamless prediction. Specifically, calibrations of ensemble-based climate change probabilities are derived from analyses of the statistical reliability of ensemble-based forecast probabilities on seasonal time scales. The method is demonstrated by calibrating probabilistic projections from the multimodel ensembles used in the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC), based on reliability analyses from the seasonal forecast Development of a European Multimodel Ensemble System for Seasonal-to-Interannual Prediction (DEMETER) dataset. The focus in this paper is on climate change projections of regional precipitation, though the method is more general. © 2008 American Meteorological Society.

Edward Norton Lorenz - Obituaries

PHYSICS TODAY 61 (2008) 81-82

T Palmer

Can MCGE Outperform the ECMWF Ensemble?

SOLA 4 (2008) 77-80

M Matsueda, HL Tanaka

The new VarEPS-monthly forecasting system: A first step towards seamless prediction


F Vitart, R Buizza, MA Balmaseda, G Balsamo, J-R Bidlot, A Bonet, M Fuentes, A Hofstadler, F Molteni, TN Palmer

Convective forcing fluctuations in a cloud-resolving model: Relevance to the stochastic parameterization problem

JOURNAL OF CLIMATE 20 (2007) 187-202

GJ Shutts, TN Palmer

Seasonal Forecast Datasets - A resource for Calibrating Regional Climate Change Projections?

CLIVAR Exchanges 43 (2007) 6-7

TN Palmer, FJ Doblas-Reyes, A Weisheimer, M Rodwell

Initialisation strategies for decadal hindcasts for the 1960-2005 period within the ENSEMBLES project. ECMWF Tech Memo.

(2007) 521

A Weisheimer, FJ Doblas-Reyes, P Rogel, N Keenlyside, MA Balmaseda, J Murphy, D Smith, M Collins, B Bhaskaran, TN Palmer

Recent Advances in Radiation Transfer Parametrizations. ECMWF Tech Memo.

(2007) 539

J-J Morcrette, P Bechtold, A Beljaars, A Weisheimer

Historical Overview of Climate Change Science

in Intergovernmental Panel on Climate Change (IPCC), 4th Assessment Report, Working Group 1: The Physical Basis of Climate Change, (2007) 1

H Le Treut, R Somerville, A Weisheimer

Historical reconstruction of the Atlantic Meridional Overturning Circulation from the ECMWF operational ocean reanalysis

Geophysical Research Letters 34 (2007)

MA Balmaseda, GC Smith, K Haines, DLT Anderson, TN Palmer, A Vidard

A reconstruction of the Atlantic Meridional Overturning Circulation (MOC) for the period 1959-2006 has been derived from the ECMWF operational ocean reanalysis. The reconstruction shows a wide range of time-variability, including a downward trend. At 26N, both the MOC intensity and changes in its vertical structure are in good agreement with previous estimates based on trans-Atlantic surveys. At 50N, the MOC and strength of the subpolar gyre are correlated at interannual time scales, but show opposite secular trends. Heat transport variability is highly correlated with the MOC but shows a smaller trend due to the warming of the upper ocean, which partially compensates for the weakening of the circulation. Results from sensitivity experiments show that although the time-varying upper boundary forcing provides useful MOC information, the sequential assimilation of ocean data further improves the MOC estimation by increasing both the mean and the time variability. Copyright 2007 by the American Geophysical Union.