Publications


The influence of north‐west Atlantic sea surface temperature: An unplanned experiment

Weather 50 (1995) 413-419

TN Palmer


Towards a unified approach to climate and weather prediction

ENVIRONMENT AND QUALITY OF LIFE (1995) 265-280

TN PALMER, PJ WEBSTER


Impact of localized tropical and extratropical SST anomalies in ensembles of seasonal GCM integrations

Quarterly Journal of the Royal Meteorological Society 120 (1994) 1613-1645

L Ferranti, F Molteni, TN Palmer

A series of 120‐day ensemble integrations of a general circulation model, designed to assess the impact of geographically localized sea‐surface‐temperature (SST) anomalies in both the tropics and extratropics, are described. These experiments contribute firstly to an appraisal of the relative roles of tropical and extratropical SST anomalies on interannual variability of the large‐scale circulation in the northern extratropics, and secondly to an assessment of the role of quasi‐stationary diabatic‐heating anomalies on model systematic error, including blocking activity. Overall it is found that SST anomalies associated with El Niño and La Niña have a larger and more reproducible impact on the extratropics than the chosen extratropical SST anomalies. These extratropical anomalies were localized to the north‐west Pacific, and north‐west Atlantic, with realistic amplitude. However, unlike earlier studies, a response to the extratropical North Pacific SST anomalies has been obtained over the North Pacific which is correlated with the sign of the imposed SST anomaly. The response to extratropical SST anomalies in the north‐west Atlantic are similar to the results obtained from an earlier study. The downstream responses to the extratropical Pacific and Atlantic SST anomalies are qualitatively similar to one another. Overall it is concluded that the northern large‐scale flow is influenced by such extratropical SST anomalies. The response to idealized tropical SST anomalies was also studied. In particular, a localized anomaly over Indonesia had a very substantial impact on the Hadley circulation, on zonal flow, and on blocking frequency over the North Pacific and Europe. This response was such as to reduce model systematic error: locally in the vicinity of the SST anomaly, remotely around the tropics, and remotely in the extratropics. A similar, though weaker, impact on Euro‐Atlantic blocking was obtained with an idealized Caribbean SST anomaly. Further statistical and dynamical analyses suggested that the extratropical response to the Indonesian SST anomaly occurs through the creation of two distinct planetary‐scale regimes, in one of which the formation of blocks is much favoured by increased ridges on the north‐eastern side of the oceans. Copyright © 1994 Royal Meteorological Society


Singular vectors and the predictability of weather and climate

Philosophical Transactions - Royal Society of London, A 348 (1994) 459-475

TN Palmer, R Buizza, F Molteni, YQ Chen, S Corti

Singular vector calculations are made using a coupled ocean-atmosphere model of the tropical Pacific region. Results from a multi-decadal integration of a medium-resolution quasi-geostrophic model are shown and the possible relevance of singular vector analysis for the problem of climate change are discussed. -from Authors


The prospects for seasonal forecasting—A review paper

Quarterly Journal of the Royal Meteorological Society 120 (1994) 755-793

TN Palmer, DLT Anderson

The evidence for predictability of interannual fluctuations in the atmosphere and oceans is reviewed. The more linear nature of tropical dynamics is contrasted with the chaotic nature of extratropical circulations. The role of the largest interannual fluctuation, the El Niño Southern Oscillation, which has its origins in the tropical Pacific, but extends to influence half the globe, is the focus of much of the review. It is argued that the statistics of the chaotic regime behaviour of the extratropics are influenced by such forcing from the tropics. Seasonal predictions can be made with empirical or physically based models. The skill of both is reviewed but most consideration is given to the latter. Such models have both atmospheric and oceanic components but there is a wide range in the complexity of these modules. Developments in both atmospheric and oceanic models, needed to improve seasonal forecasts, are discussed. It is shown that predictions are sensitive to initial conditions as well as model formulation, implying the need for ensemble integrations similar to those currently under development for medium‐range weather forecasting. The benefits of developing a seasonal‐climate prediction capability are considered, including connections with weather forecasting on the one hand and climate change on the other. This is not an exhaustive review of extended‐range predictions. Monthly forecasting is not considered and seasonal predictability is only discussed for the tropics and northern extratropics, with some focus on Europe. Copyright © 1994 Royal Meteorological Society


DIAGNOSIS OF EXTRATROPICAL VARIABILITY IN SEASONAL INTEGRATIONS OF THE ECMWF MODEL

JOURNAL OF CLIMATE 7 (1994) 849-868

L FERRANTI, F MOLTENI, C BRANKOVIC, TN PALMER


PREDICTABILITY OF SEASONAL ATMOSPHERIC VARIATIONS

JOURNAL OF CLIMATE 7 (1994) 217-237

C BRANKOVIC, TN PALMER, L FERRANTI


PREDICTABILITY AND FINITE-TIME INSTABILITY OF THE NORTHERN WINTER CIRCULATION

QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 119 (1993) 269-298

F MOLTENI, TN PALMER


ENSEMBLE PREDICTION USING DYNAMICALLY CONDITIONED PERTURBATIONS

QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 119 (1993) 299-323

R MUREAU, F MOLTENI, TN PALMER


EXTENDED-RANGE ATMOSPHERIC PREDICTION AND THE LORENZ MODEL

BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY 74 (1993) 49-65

TN PALMER


Computation of optimal unstable structures for a numerical weather prediction model

Tellus, Series A 45 A (1993) 388-407

R Buizza, J Tribbia, F Molteni, T Palmer

Numerical experiments have been performed to compute the fastest growing perturbations in a finite time interval for a complex numerical weather prediction model. The models used are the tangent forward and adjoint versions of the adiabatic primitive-equation model of the Integrated Forecasting System developed at the European Centre for Medium-Range Weather Forecasts and Meteo France. These have been run with a horizontal truncation T21, and 19 vertical levels. The fastest growing perturbations are the singular vectors of the propagator of the forward tangent model with the largest singular values. -from Authors


A nonlinear dynamical perspective on climate change

Weather 48 (1993) 314-326

TN Palmer


A DYNAMIC INTERPRETATION OF THE GLOBAL RESPONSE TO EQUATORIAL PACIFIC SST ANOMALIES

JOURNAL OF CLIMATE 6 (1993) 777-795

F MOLTENI, L FERRANTI, TN PALMER, P VITERBO


MODELING INTERANNUAL VARIATIONS OF SUMMER MONSOONS

JOURNAL OF CLIMATE 5 (1992) 399-417

TN PALMER, C BRANKOVIC, P VITERBO, MJ MILLER


THE SENSITIVITY OF THE ECMWF MODEL TO THE PARAMETERIZATION OF EVAPORATION FROM THE TROPICAL OCEANS

JOURNAL OF CLIMATE 5 (1992) 418-434

MJ MILLER, ACM BELJAARS, TN PALMER


A real-time scheme for the prediction of forecast skill

Monthly Weather Review 119 (1991) 1088-1097

F Molteni, TN Palmer

During the winter of 1988/89, a real-time experimental scheme to predict skill of the ECMWF operational forecast was devised. The scheme was based on statistical relations between skill scores (the predictands) and a number of predictors including consistency between consecutive forecasts, amplitude of very short-range forecast errors, and indices of large-scale regime transitions. The results of the experiment are assessed with particular attention to a period with large variations in the skill of the operational forecast. -Authors


EXTENDED-RANGE PREDICTIONS WITH ECMWF MODELS - INTERANNUAL VARIABILITY IN OPERATIONAL MODEL INTEGRATIONS

QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 116 (1990) 799-834

TN PALMER, C BRANKOVIC, F MOLTENI, S TIBALDI


EXTENDED-RANGE PREDICTIONS WITH ECMWF MODELS - INFLUENCE OF HORIZONTAL RESOLUTION ON SYSTEMATIC-ERROR AND FORECAST SKILL

QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 116 (1990) 835-866

S TIBALDI, TN PALMER, C BRANKOVIC, U CUBASCH


EXTENDED-RANGE PREDICTIONS WITH ECMWF MODELS - TIME-LAGGED ENSEMBLE FORECASTING

QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 116 (1990) 867-912

C BRANKOVIC, TN PALMER, F MOLTENI, S TIBALDI, U CUBASCH


The European Centre for Medium-Range Weather Forecasts (ECMWF) program on extended-range prediction

Bulletin - American Meteorological Society 71 (1990) 1317-1330

TN Palmer

The topics discussed include 1) The evolution of extended-range systematic error and skill in forecasting large-scale weather regime transitions; 2) The dependence of extended-range systematic error and skill on model horizontal resolution; 3) Monthly mean forecasts of tropical rainfall; 4) Tropical/extratropical interaction, and the influence of tropical low-frequency variability on extratropical forecast skill; 5) Ensemble forecasting, including the impact of ensemble averaging on forecast skill, and ensemble dispersion as a measure of forecast reliability; and 6) Probabilistic forecasting using phase-space cluster analysis. 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. -from Authors

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