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T. N. Palmer

The physical basis for extended-range prediction is explored using the famous three-component Lorenz convection model, taken as a conceptual representation of the chaotic extratropical circulation, and extended by coupling to a linear oscillator to represent large-scale tropical–extratropical interactions. The model is used to analyze the roles of time averaging and ensemble forecasting, and, in extended form, the impact of both anomalous tropical sea surface temperature and anomalous extratropical sea surface temperature. The conceptual paradigms and analytic calculations presented are used to interpret results from numerical weather prediction and general circulation model experiments. Some remarks on the relevance of predictability studies for the climate change problem are given.

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T. N. Palmer

Meteorology is a wonderfully interdisciplinary subject. But can nonlinear thinking about predictability of weather and climate contribute usefully to issues in fundamental physics? Although this might seem extremely unlikely at first sight, an attempt is made to answer the question positively. The long-standing conceptual problems of quantum theory are outlined, focusing on indeterminacy and nonlocal causality, problems that led Einstein to reject quantum mechanics as a fundamental theory of physics (a glossary of some of the key terms used in this paper is given in the sidebar). These conceptual problems are considered in the light of both low-order chaos and the more radical (and less well known) paradigm of the finite-time predictability horizon associated with the self-similar upscale cascade of uncertainty in a turbulent fluid. The analysis of these dynamical systems calls into doubt one of the key pieces of logic used in quantum nonlocality theorems: that of counterfactual reasoning. By considering an idealization of the upscale cascade (which provides a novel representation of complex numbers and quaternions), a case is made for reinterpreting the quantum wave function as a set of intricately encoded binary sequences. In this reinterpretation, it is argued that the quantum world has no need for dice-playing deities, undead cats, multiple universes, or “spooky action at a distance.”

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T. N. Palmer

Carl-Gustaf Rossby's work leading to the dispersion equation for his eponymous atmospheric wave form was motivated by his quest to understand interrelationships between fluctuations in the zonal mean wind and the quasi-stationary waves. Rossby believed that climate variability on almost all timescales could be understood in terms of changes in the frequency of occurrence of states of high and low zonal index. Using modern-day terminology and ideas, Rossby's perception of climate variability can be viewed in terms of low-frequency changes to the probability distribution of the nonlinear weather regimes that characterize our chaotic climate attractor.

A perspective on possible future climate change is outlined, based on these ideas. One of the most basic notions to emerge is that even if such change is predominantly anthropogenically induced, its manifestation may be predominantly onto the natural “modes” of variability of the climate system.

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T. N. Palmer
and
A. Weisheimer

Abstract

Although the development of seamless prediction systems is becoming increasingly common, there is still confusion regarding the relevance of information from initial-value forecasts for assessing the trustworthiness of the climate system’s response to forcing. A simple system that mimics the real climate system through its regime structure is used to illustrate this potential relevance. The more complex version of this model defines “reality” and a simplified version of the system represents the “model.” The model’s response to forcing is profoundly incorrect. However, the untrustworthiness of the model’s response to forcing can be deduced from the model’s initial-value unreliability. The nonlinearity of the system is crucial in accounting for this result.

Open access
F. Tennie
and
T. N. Palmer

Abstract

Over the past few years, quantum computers and quantum algorithms have attracted considerable interest and attention from numerous scientific disciplines. In this article, we aim to provide a nontechnical yet informative introduction to key aspects of quantum computing. We discuss whether quantum computers one day might become useful tools for numerical weather and climate prediction. Using a recently developed quantum algorithm for solving nonlinear differential equations, we integrate a simple nonlinear model. In addition to considering the advantages that quantum computers have to offer, we shall also discuss the challenges one faces when trying to use quantum computers for real-world problems involving “big data,” such as weather prediction.

Open access
T. N. Palmer
,
F. J. Doblas-Reyes
,
A. Weisheimer
, and
M. J. Rodwell

Abstract

No Abstract available.

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T. N. Palmer
,
F. J. Doblas-Reyes
,
A. Weisheimer
, and
M. J. 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 ensemblebased climate change probabilities are derived from analyses of the statistical reliability of ensemblebased 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.

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T.N. Palmer
,
C. Brankovic
,
F. Molteni
,
S. Tibaldi
,
L. Ferranti
,
A. Hollingsworth
,
U. Cubasch
, and
E. Klinker

Results from a 3 1/2-yr experimental program of extended-range integrations of the European Centre for Medium-Range Weather Forecasts (ECMWF) numerical weather prediction model are summarized. The topics discussed include

Our results are broadly consistent with those from other major centers evaluating the feasibility of dynamical extended-range prediction. We believe that operational extended-range forecasting using the ECMWF model may be viable to day 20—and possibly beyond—following further research on techniques for Monte Carlo forecasting, and when model systematic error in the tropics has been reduced significantly.

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J. Shukla
,
R. Hagedorn
,
M. Miller
,
T. N. Palmer
,
B. Hoskins
,
J. Kinter
,
J. Marotzke
, and
J. Slingo

Abstract

No Abstract available.

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J. Shukla
,
T. N. Palmer
,
R. Hagedorn
,
B. Hoskins
,
J. Kinter
,
J. Marotzke
,
M. Miller
, and
J. Slingo

The impending threat of global climate change and its regional manifestations is among the most important and urgent problems facing humanity. Society needs accurate and reliable estimates of changes in the probability of regional weather variations to develop science-based adaptation and mitigation strategies. Recent advances in weather prediction and in our understanding and ability to model the climate system suggest that it is both necessary and possible to revolutionize climate prediction to meet these societal needs. However, the scientific workforce and the computational capability required to bring about such a revolution is not available in any single nation. Motivated by the success of internationally funded infrastructure in other areas of science, this paper argues that, because of the complexity of the climate system, and because the regional manifestations of climate change are mainly through changes in the statistics of regional weather variations, the scientific and computational requirements to predict its behavior reliably are so enormous that the nations of the world should create a small number of multinational high-performance computing facilities dedicated to the grand challenges of developing the capabilities to predict climate variability and change on both global and regional scales over the coming decades. Such facilities will play a key role in the development of next-generation climate models, build global capacity in climate research, nurture a highly trained workforce, and engage the global user community, policymakers, and stakeholders. We recommend the creation of a small number of multinational facilities with computer capability at each facility of about 20 petaflops in the near term, about 200 petaflops within five years, and 1 exaflop by the end of the next decade. Each facility should have sufficient scientific workforce to develop and maintain the software and data analysis infrastructure. Such facilities will enable questions of what resolution, both horizontal and vertical, in atmospheric and ocean models, is necessary for more confident predictions at the regional and local level. Current limitations in computing power have placed severe limitations on such an investigation, which is now badly needed. These facilities will also provide the world's scientists with the computational laboratories for fundamental research on weather–climate interactions using 1-km resolution models and on atmospheric, terrestrial, cryospheric, and oceanic processes at even finer scales. Each facility should have enabling infrastructure including hardware, software, and data analysis support, and scientific capacity to interact with the national centers and other visitors. This will accelerate our understanding of how the climate system works and how to model it. It will ultimately enable the climate community to provide society with climate predictions, which are based on our best knowledge of science and the most advanced technology.

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