Publications


The past and the future of El Nino

NATURE 390 (1997) 562-564

PJ Webster, TN Palmer


Atmospheric seasonal predictability and estimates of ensemble size

MONTHLY WEATHER REVIEW 125 (1997) 859-874

C Brankovic, TN Palmer


Sensitivity analysis of atmospheric low-frequency variability

QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 123 (1997) 2425-2447

S Corti, TN Palmer


A study of the predictability of tropical pacific SST in a coupled atmosphere-ocean model using singular vector analysis: The role of the annual cycle and the ENSO cycle

Monthly Weather Review 125 (1997) 831-845

Y-Q Chen, DS Battisti, TN Palmer, J Barsugli, ES Sarachik

The authors examine the sensitivity of the Battisti coupled atmosphere-ocean model - considered as a forecast model for the E1 Niño-Southern Oscillation (ENSO) - to perturbations in the sea surface temperature (SST) field applied at the beginning of a model integration. The spatial structures of the fastest growing SST perturbations are determined by singular vector analysis of an approximation to the propagator for the linearized system. Perturbation growth about the following four reference trajectories is considered: (i) the annual cycle, (ii) a freely evolving model ENSO cycle with an annual cycle in the basic state, (iii) the annual mean basic state, and (iv) a freely evolving model ENSO cycle with an annual mean basic state. Singular vectors with optimal growth over periods of 3, 6, and 9 months are computed. The magnitude of maximum perturbation growth is highly dependent on both the phase of the seasonal cycle and the phase of the ENSO cycle at which the perturbation is applied and on the duration over which perturbations are allowed to evolve. However, the spatial structure of the optimal perturbation is remarkably insensitive to these factors. The structure of the optimal perturbation consists of an east-west dipole spanning the entire tropical Pacific basin superimposed on a north-south dipole in the eastern tropical Pacific. A simple physical interpretation for the optimal pattern is provided. In most cases investigated, there is only one structure that exhibits growth. Maximum perturbation growth takes place for integrations that include the period June-August, and the minimum growth for integrations that include the period January-April. Maxima in potential growth also occur for forecasts of ENSO onset and decay, while minima occur for forecasts initialized during the beginning of a warm event, after the transition from a warm to a cold event, and continuing through the cold event. The physical processes responsible for the large variation in the amplitude of the optimal perturbation growth are identified. The implications of these results for the predictability of short-term climate in the tropical Pacific are discussed.


The impact of increased resolution on predictability studies with singular vectors

QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 123 (1997) 1007-1033

R Buizza, R Gelaro, F Molteni, TN Palmer


Finite-time instabilities of lower-stratospheric flow

Journal of the Atmospheric Sciences 53 (1996) 2129-2143

DL Hartmann, TN Palmer, R Buizza

The linear structures that produce the most in situ energy growth in the lower stratosphere for realistic wintertime flows are investigated using T21 and T42 calculations with the ECMWF 19-level forecast model. Significant growth is found for relatively large scale structures that grow by propagating from the outer edges of the vortex into the strong jet features of the lower-stratospheric flow. The growth is greater when the polar vortex is more asymmetric and contains localized jet structures. If the linear structures are properly phased, they can induce strong nonlinear interactions with the polar vortex, both for Northern Hemisphere and Southern Hemisphere flow conditions, even when the initial amplitudes are small. Large extensions from the main polar vortex that are peeled off during wave-breaking events give rise to a separate class of rapidly growing disturbances that may hasten the mixing of these vortex extensions.


Extreme rainfall prediction using the European centre for medium-range weather forecasts ensemble prediction system

JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 101 (1996) 26227-26236

T Petroliagis, R Buizza, A Lanzinger, TN Palmer


Singular vectors and seasonal predictability

EIGHTH CONFERENCE ON AIR-SEA INTERACTION AND CONFERENCE ON THE GLOBAL OCEAN-ATMOSPHERE-LAND SYSTEM (GOALS) (1996) 69-69

TN Palmer, AM SOC


The ECMWF ensemble prediction system: Methodology and validation

QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 122 (1996) 73-119

F Molteni, R Buizza, TN Palmer, T Petroliagis


Intraseasonal oscillations in 15 atmospheric general circulation models: Results from an AMIP diagnostic subproject

CLIMATE DYNAMICS 12 (1996) 325-357

JM Slingo, KR Sperber, JS Boyle, JP Ceron, M Dix, B Dugas, W Ebisuzaki, J Fyfe, D Gregory, JF Gueremy, J Hack, A Harzallah, P Inness, A Kitoh, WKM Lau, B McAvaney, R Madden, A Matthews, TN Palmer, CK Park, D Randall, N Renno


Interannual tropical rainfall variability in general circulation model simulations associated with the atmospheric model intercomparison project

JOURNAL OF CLIMATE 9 (1996) 2727-2750

KR Sperber, TN Palmer


A local deterministic model of quantum spin measurement

PROCEEDINGS OF THE ROYAL SOCIETY-MATHEMATICAL AND PHYSICAL SCIENCES 451 (1995) 585-608

TN Palmer


Non-modal finite-time instabilities in a primitive equation model

TENTH CONFERENCE ON ATMOSPHERIC AND OCEANIC WAVES AND STABILITY (1995) 260-261

R Buizza, F Molteni, TN Palmer, T Petroliagis, AM SOC


THE SINGULAR-VECTOR STRUCTURE OF THE ATMOSPHERIC GLOBAL CIRCULATION

JOURNAL OF THE ATMOSPHERIC SCIENCES 52 (1995) 1434-1456

R BUIZZA, T PALMER


Towards a unified approach to climate and weather prediction

ENVIRONMENT AND QUALITY OF LIFE (1995) 265-280

T PALMER, P WEBSTER


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


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


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


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


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