Publications


The twenty-first century?

Weather 57 (2002) 226-227

T Palmer


Quantifying the risk of extreme seasonal precipitation events in a changing climate.

Nature 415 (2002) 512-514

TN Palmer, J Räisänen

Increasing concentrations of atmospheric carbon dioxide will almost certainly lead to changes in global mean climate. But because--by definition--extreme events are rare, it is significantly more difficult to quantify the risk of extremes. Ensemble-based probabilistic predictions, as used in short- and medium-term forecasts of weather and climate, are more useful than deterministic forecasts using a 'best guess' scenario to address this sort of problem. Here we present a probabilistic analysis of 19 global climate model simulations with a generic binary decision model. We estimate that the probability of total boreal winter precipitation exceeding two standard deviations above normal will increase by a factor of five over parts of the UK over the next 100 years. We find similar increases in probability for the Asian monsoon region in boreal summer, with implications for flooding in Bangladesh. Further practical applications of our techniques would be helped by the use of larger ensembles (for a more complete sampling of model uncertainty) and a wider range of scenarios at a resolution adequate to analyse average-size river basins.


Tropical singular vectors computed with linearized diabatic physics

Quarterly Journal of the Royal Meteorological Society 127 (2001) 685-708

J Barkmeijer, R Buizza, TN Plamer, K Puri, JF Mahfouf

With the introduction of diabatic processes in the forward and adjoint tangent models of the European Centre for Medium-Range Weather Forecasts's model, it is possible to determine singular vectors (SVs) for situations where diabatic physics may be important in producing perturbation growth. In this paper, the linear physical parametrizations are used to compute SVs for the tropical region, or subsets thereof, with an optimization time of 48 h. Perturbation growth is measured in terms of the so-called total energy norm, augmented with a term for specific humidity. Difficulties that may arise in computing tropical SVs, such as associated with spurious upper-tropospheric perturbation growth, are described. Also, the impact on the SV structure by including a specific-humidity term in the defining norm is discussed. Using a term for specific humidity based on background-error statistics in the norm at initial time yields SVs with a more realistic specific-humidity vertical profile. SVs are determined in various configurations for two tropical cyclones. Results show that targeting in the vicinity of the cyclone is required to obtain SVs associated with the cyclone dynamics. The dominant targeted SVs for tropical cyclones show resemblance to fast-growing structures found for idealized vortices.


On the structure and variability of atmospheric circulation regimes in coupled climate models

ATMOSPHERIC SCIENCE LETTERS 2 (2001) 72-80

A Weisheimer, D Handorf, K Dethloff


On the structure and variability of atmospheric circulation regimes in coupled climate models

Atmospheric Science Letters 2 (2001)

A Weisheimer, D Handorf, K Dethloff

In order to investigate whether climate models of different complexity have the potential to simulate natural atmospheric circulation regimes, 1000-year-long integrations with constant external forcing have been analysed. Significant non-Gaussian uni-, bi-, and trimodal probability density functions have been found in 100-year segments. © 2001 Royal Meteorological Society.


Physical Climate Processes and Feedbacks

in Climate Change 2001: The Scientific Basis Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press (2001) 7

T Stocker, RT Pierrehumbert, G Clarke, TN Palmer, K Trenberth, R Lindzen

Climate Change 2001: The Scientific Basis is the most comprehensive and up-to-date scientific assessment of past, present and future climate change.


Dynamical seasonal predictability of the Asian summer monsoon

MONTHLY WEATHER REVIEW 129 (2001) 2226-2248

KR Sperber, C Brankovic, M Deque, CS Frederiksen, R Graham, A Kitoh, C Kobayashi, T Palmer, K Puri, W Tennant, E Volodin


Model error in weather forecasting

Nonlinear Processes in Geophysics 8 (2001) 357-371

D Orrell, L Smith, J Barkmeijer, TN Palmer

Operational forecasting is hampered both by the rapid divergence of nearby initial conditions and by error in the underlying model. Interest in chaos has fuelled much work on the first of these two issues; this paper focuses on the second. A new approach to quantifying state-dependent model error, the local model drift, is derived and deployed both in examples and in operational numerical weather prediction models. A simple law is derived to relate model error to likely shadowing performance (how long the model can stay close to the observations). Imperfect model experiments are used to contrast the performance of truncated models relative to a high resolution run, and the operational model relative to the analysis. In both cases the component of forecast error due to state-dependent model error tends to grow as the square-root of forecast time, and provides a major source of error out to three days. These initial results suggest that model error plays a major role and calls for further research in quantifying both the local model drift and expected shadowing times.


A probability and decision-model analysis of a multimodel ensemble of climate change simulations

JOURNAL OF CLIMATE 14 (2001) 3212-3226

J Raisanen, TN Palmer


A nonlinear dynamical perspective on model error: A proposal for non-local stochastic-dynamic parametrization in weather and climate prediction models

QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 127 (2001) 279-304

TN Palmer


Tropical singular vectors computed with linearized diabatic physics

QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 127 (2001) 685-708

J Barkmeuer, R Buizza, TN Palmer, K Puri, JF Mahfouf


Ensemble prediction of tropical cyclones using targeted diabatic singular vectors

QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 127 (2001) 709-731

K Puri, J Barkmeijer, TN Palmer


Forecasting disease risk with seasonal climate predictions

LANCET 355 (2000) 1559-1560

MC Thomson, T Palmer, AP Morse, M Cresswell, SJ Conner


Dynamical seasonal prediction

BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY 81 (2000) 2593-2606

J Shukla, J Anderson, D Baumhefner, C Brankovic, Y Chang, E Kalnay, L Marx, T Palmer, D Paolino, J Ploshay, S Schubert, D Straus, M Suarez, J Tribbia


A probability and decision-model analysis of PROVOST seasonal multi-model ensemble integrations

QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 126 (2000) 2013-2033

TN Palmer, C Brankovic, DS Richardson


Seasonal skill and predictability of ECMWF PROVOST ensembles

QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 126 (2000) 2035-2067

C Brankovic, TN Palmer


Current status and future developments of the ECMWF Ensemble Prediction System

METEOROLOGICAL APPLICATIONS 7 (2000) 163-175

R Buizza, J Barkmeijer, TN Palmer, DS Richardson


Examination of targeting methods in a simplified setting

TELLUS B 52 (2000) 391-411

CA Reynolds, R Gelaro, TN Palmer


Examination of targeting methods in a simplified setting

TELLUS SERIES A-DYNAMIC METEOROLOGY AND OCEANOGRAPHY 52 (2000) 391-411

CA Reynolds, R Gelaro, TN Palmer


Observational error structures and the value of advanced assimilation techniques

JOURNAL OF THE ATMOSPHERIC SCIENCES 57 (2000) 1327-1340

KL Swanson, TN Palmer, R Vautard

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