Publications


SINGULAR VECTORS - THE EFFECT OF SPATIAL SCALE ON LINEAR GROWTH OF DISTURBANCES

JOURNAL OF THE ATMOSPHERIC SCIENCES 52 (1995) 3885-3894

D HARTMANN, R BUIZZA, T PALMER


The prospects for seasonal forecasting - a review paper

Quarterly Journal - 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 Nino 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. 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. -from Authors


DIAGNOSIS OF EXTRATROPICAL VARIABILITY IN SEASONAL INTEGRATIONS OF THE ECMWF MODEL

JOURNAL OF CLIMATE 7 (1994) 849-868

L FERRANTI, F MOLTENI, C BRANKOVIC, T PALMER


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, Y-Q 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


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

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

L Ferranti, F Molteni, TN Palmer

A series of 120-day ensemble intergrations 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. Overall it is found that SST anomalies associated with El Nino and La Nina 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. 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. -Authors


PREDICTABILITY OF SEASONAL ATMOSPHERIC VARIATIONS

JOURNAL OF CLIMATE 7 (1994) 217-237

C BRANKOVIC, T PALMER, L FERRANTI


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

JOURNAL OF CLIMATE 6 (1993) 777-795

F MOLTENI, L FERRANTI, T PALMER, P VITERBO


EXTENDED-RANGE ATMOSPHERIC PREDICTION AND THE LORENZ MODEL

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

T PALMER


PREDICTABILITY AND FINITE-TIME INSTABILITY OF THE NORTHERN WINTER CIRCULATION

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

F MOLTENI, T PALMER


ENSEMBLE PREDICTION USING DYNAMICALLY CONDITIONED PERTURBATIONS

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

R MUREAU, F MOLTENI, T 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


MODELING INTERANNUAL VARIATIONS OF SUMMER MONSOONS

JOURNAL OF CLIMATE 5 (1992) 399-417

T PALMER, C BRANKOVIC, P VITERBO, M MILLER


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

JOURNAL OF CLIMATE 5 (1992) 418-434

M MILLER, A BELJAARS, T 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

T PALMER, C BRANKOVIC, F MOLTENI, S TIBALDI


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

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

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


Regimes in the wintertime circulation over northern extratropics. I: Observational evidence

Quarterly Journal - Royal Meteorological Society 116 (1990) 31-67

F Molteni, S Tibaldi, TN Palmer

Regimes of the northern extratropical circulation in winter are identified in this paper as clusters of atmospheric states in a low-dimensional phase space generated by the leading EOFs of eddy geopotential fields. Our algorithm seeks points corresponding to local maxima for the density of atmospheric states; subsequently, a cluster is defined around each density maximum as that portion of the phase space in which the observed density can be locally approximated by a unimodal function. Six clusters were found. The largest cluster includes 40% of the field in our sample; but it possesses a positive projection on the Pacific-North American (PNA) pattern. The other five clusters represent anomalous flow regimes and include 52% of the fields. One of them shows a low amplitude of the planetary waves; the remaining four represent states with large wave amplitude but different phases. -from Authors


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, T PALMER, C BRANKOVIC, 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


Tropical-extratropical interaction associated with the 30-60 day oscillation and its impact on medium and extended range prediction

Journal of the Atmospheric Sciences 47 (1990) 2177-2199

L Ferranti, TN Palmer, F Molteni, E Klinker

First, an empirical orthogonal function (EOF) analysis is made of outgoing longwave radiation (OLR) in the tropics over seven winters. Having removed the seasonal cycle and interannual variability, the two leading EOFs describe the 30-60 day oscillation. A composite of extratopical 500 mb geopotential height correlated simultaneously with this mode of tropical variability is constructed. The 500 mb height composite is compared succesfully, with the Simmons, Wallace and Branstator (SWB) mode of barotropic instability, which has similar periodicity and similar spatial structure in both its phase-quadrature components. In the final phase of this study, the ECMWF model has been integrated over four wintertime 20-day periods. -from Authors