Publications


Representing model uncertainty in weather and climate prediction

ANNUAL REVIEW OF EARTH AND PLANETARY SCIENCES 33 (2005) 163-193

TN Palmer, GJ Shutts, R Hagedorn, E Doblas-Reyes, T Jung, M Leutbecher


More power needed to probe cloud systems

NATURE 434 (2005) 271-271

TN Palmer


Transverse waves in a post-flare supra-arcade

Astronomy and Astrophysics 430 (2005) L65-L68

E Verwichte, VM Nakariakov, FC Cooper


A granular permutation-based representation of complex numbers and quaternions: elements of a possible realistic quantum theory

PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES 460 (2004) 1039-1055

TN Palmer


Nonlinear dynamics of the climate system

CLIMATE IN HISTORICAL TIMES: TOWARDS A SYNTHESIS OF HOLOCENCE PROXY DATA AND CLIMATE MODELS (2004) 13-41

K Dethloff, A Rinke, D Handorf, A Weisheimer, W Dorn,


Internal climate variability in global and regional climate models

CLIMATE IN HISTORICAL TIMES: TOWARDS A SYNTHESIS OF HOLOCENCE PROXY DATA AND CLIMATE MODELS (2004) 365-382

D Handorf, W Dorn, K Dethloff, A Rinke, A Weisheimer,


Gradient free descent: Shadowing, and state estimation using limited derivative information

Physica D: Nonlinear Phenomena 190 (2004) 153-166

K Judd, L Smith, A Weisheimer

Shadowing trajectories can play an important role in assessing the reliability of forecasting models, they can also play an important role in providing state estimates for ensemble forecasts. Gradient descent methods provide one approach for obtaining shadowing trajectories, which have been shown to have many useful properties. There remains the important question whether shadowing trajectories can be found in very high-dimensional systems, like weather and climate models. The principle impediment is the need to compute the derivative (or adjoint) of the system dynamics. In this paper we investigate gradient descent methods that use limited derivative information. We demonstrate the methods with an application to a moderately high-dimensional system using no derivative information at all. © 2003 Elsevier B.V. All rights rserved.


Improved radio occultation sounding of the Arctic atmosphere using simulations with a high resolution atmospheric model

Physics and Chemistry of the Earth 29 (2004) 277-286

V Kunitsyn, V Zakharov, K Dethloff, A Weisheimer, M Gerding, R Neuber, A Rinke, I Hebestadt

Radio occultation experiments have been simulated for the Arctic region on the basis of the regional atmospheric model HIRHAM4. Irregular structures in the atmosphere produce a violation of the quasi-sphericity in the radio signal propagation and exert a strong influence on the accuracy of atmospheric profiles retrieved by the radio occultation technique. Errors in radio occultation data are spatially localised and associated with gradients in atmospheric structures. Local errors reach 2% in retrieved profiles of refractivity corresponding to an error of 6 K in temperature. Therefore mesoscale variations in atmospheric parameter gradients in a specified region must be taken into account when interpreting radio occultation data. We show, that a correction functional can be developed using the refractivity index field calculated from the regional model in order to improve the radio occultation retrieval of atmospheric parameters. This functional is constructed from instantaneous model outputs, as well as from temporally averaged fields of refractivity using data of the HIRHAM4 model for the Arctic atmosphere. The correction functional derived from monthly averaged data reduced the retrieval errors of refractivity, temperature, and pressure in the troposphere, in particular, temperature retrieval errors are reduced up to 1 K. Application of this kind of functional depends on whether the model used for the construction of the functional is able to simulate the real mesoscale atmospheric structures. © 2004 Elsevier Ltd. All rights reserved.


Development of a European multimodel ensemble system for seasonal-to-interannual prediction (DEMETER)

BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY 85 (2004) 853-+

TN Palmer, A Alessandri, U Andersen, P Cantelaube, M Davey, P Delecluse, M Deque, E Diez, FJ Doblas-Reyes, H Feddersen, R Graham, S Gualdi, JF Gueremy, R Hagedorn, M Hoshen, N Keenlyside, M Latif, A Lazar, E Maisonnave, V Marletto, AP Morse, B Orfila, P Rogel, JM Terres, MC Thomson


Forcing singular vectors and other sensitive model structures

QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 129 (2003) 2401-2423

J Barkmeijer, T Iversen, TN Palmer


Short period fast waves in solar coronal loops

Astronomy and Astrophysics 409 (2003) 325-330

FC Cooper, VM Nakariakov, DR Williams


Extratropical low-frequency variability in a three-level quasi-geostrophic atmospheric model with different spectral resolution

Journal of Geophysical Research D: Atmospheres 108 (2003)

A Weisheimer, MV Kurgansky, K Dethloff, D Handorf

Apart from variations of external forcing components and interactions between climate subsystems, natural atmospheric fluctuations with periods of years, decades and centuries can also be generated by inherent atmospheric dynamical instabilities of the flow. The objective of this study is to investigate the spatial and temporal structure of internal low-frequency atmospheric variability of the Northern Hemisphere using a minimum-complexity model of the extratropical circulation. Here, the main focus is the influence of varying spectral horizontal resolution on the formation of dominant patterns of variability. For this purpose, a three-level quasi-geostrophic atmospheric model with idealized thermal and orographic forcing has been integrated over 1,000 years under perpetual winter conditions with T5, T10, T15, and T21 resolutions. It has been shown that for the crude resolution T5 a rather strong bias occurs, whereas starting with T1O resolution, the nonlinear feedback between large- and small-scale features is reasonably well described. At this resolution a sort of plateau in the model performance has been reached, in respect to both the model climatology and the spatiotemporal structure of variability. Ultralow-frequency variability is most pronounced in the model's stratosphere and is associated with changes in the polar vortex strength and shape caused by vertically propagating planetary waves. Rossby wave trains in the lee of the model large-scale orography are the most dominant structures of long-period fluctuations in the middle troposphere. The results show that interannual- and decadal-scale variations can, in substantial part, be considered as a manifestation of the natural variability of the extratropical atmosphere. The inclusion of a seasonal cycle of the model's diabatic heating increases the interannual and interdecadal variability.


Benefits of increased resolution in the ECMWF ensemble system and comparison with poor-man's ensembles

QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 129 (2003) 1269-1288

R Buizza, DS Richardson, TN Palmer


Predictability of weather and climate: From theory to practice - From days to decades

REALIZING TERACOMPUTING (2003) 1-18

TN Palmer


Validation of water vapour profiles from GPS radio occultations in the Arctic

FIRST CHAMP MISSION RESULTS FOR GRAVITY, MAGNETIC AND ATMOSPHERIC STUDIES (2003) 441-446

M Gerding, A Weisheimer


Line-of-sight effects on observability of kink and sausage modes in coronal structures with imaging telescopes

Astronomy and Astrophysics 397 (2003) 765-770

FC Cooper, VM Nakariakov, D Tsiklauri


Potential improvement to forecasts of two severe storms using targeted observations

QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 128 (2002) 1641-1670

M Leutbecher, J Barkmeijer, TN Palmer, AJ Thorpe


The economic value of ensemble forecasts as a tool for risk assessment: From days to decades

QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 128 (2002) 747-774

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