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33 results on '"Watson, Peter A. G."'

5. Applying machine learning to improve simulations of a chaotic dynamical system using empirical error correction

Author

Watson, Peter A. G.

Subjects
Physics - Atmospheric and Oceanic Physics, Computer Science - Machine Learning, Nonlinear Sciences - Chaotic Dynamics, Statistics - Machine Learning
Abstract

Dynamical weather and climate prediction models underpin many studies of the Earth system and hold the promise of being able to make robust projections of future climate change based on physical laws. However, simulations from these models still show many differences compared with observations. Machine learning has been applied to solve certain prediction problems with great success, and recently it's been proposed that this could replace the role of physically-derived dynamical weather and climate models to give better quality simulations. Here, instead, a framework using machine learning together with physically-derived models is tested, in which it is learnt how to correct the errors of the latter from timestep to timestep. This maintains the physical understanding built into the models, whilst allowing performance improvements, and also requires much simpler algorithms and less training data. This is tested in the context of simulating the chaotic Lorenz '96 system, and it is shown that the approach yields models that are stable and that give both improved skill in initialised predictions and better long-term climate statistics. Improvements in long-term statistics are smaller than for single time-step tendencies, however, indicating that it would be valuable to develop methods that target improvements on longer time scales. Future strategies for the development of this approach and possible applications to making progress on important scientific problems are discussed., Comment: 26p, 7 figures To be published in Journal of Advances in Modeling Earth Systems

Published
2019
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18. Climate SPHINX: evaluating the impact of resolution and stochastic physics parameterisations in the EC-Earth global climate model

Author

Davini, Paolo, von Hardenberg, Jost, Corti, Susanna, Christensen, Hannah M., Juricke, Stephan, Subramanian, Aneesh, Watson, Peter A. G., Weisheimer, Antje, Palmer, Tim N., Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)

Subjects
lcsh:Geology, [SDU]Sciences of the Universe [physics], [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, lcsh:QE1-996.5
Abstract

International audience; The Climate SPHINX (Stochastic Physics HIgh resolutioN eXperiments) project is a comprehensive set of ensemble simulations aimed at evaluating the sensitivity of present and future climate to model resolution and stochastic parameterisation. The EC-Earth Earth system model is used to explore the impact of stochastic physics in a large ensemble of 30-year climate integrations at five different atmospheric horizontal resolutions (from 125 up to 16 km). The project includes more than 120 simulations in both a historical scenario (1979-2008) and a climate change projection (2039-2068), together with coupled transient runs (1850-2100). A total of 20.4 million core hours have been used, made available from a single year grant from PRACE (the Partnership for Advanced Computing in Europe), and close to 1.5 PB of output data have been produced on SuperMUC IBM Petascale System at the Leibniz Supercomputing Centre (LRZ) in Garching, Germany. About 140 TB of post-processed data are stored on the CINECA supercomputing centre archives and are freely accessible to the community thanks to an EUDAT data pilot project. This paper presents the technical and scientific set-up of the experiments, including the details on the forcing used for the simulations performed, defining the SPHINX v1.0 protocol. In addition, an overview of preliminary results is given. An improvement in the simulation of Euro-Atlantic atmospheric blocking following resolution increase is observed. It is also shown that including stochastic parameterisation in the low-resolution runs helps to improve some aspects of the tropical climate - specifically the Madden-Julian Oscillation and the tropical rainfall variability. These findings show the importance of representing the impact of small-scale processes on the large-scale climate variability either explicitly (with high-resolution simulations) or stochastically (in low-resolution simulations).

Published
2017

19. PRIMAVERA: High resolution climate processes. Evaluating the impact of resolution and stochastic physics parameterisations in climate simulations

Author

Davini, Paolo, von Hardenberg, Jost, Corti, Susanna, Subrarmanian, Aneesh, Christensen, Hannah, Jurike, Stephan, Watson, Peter A. G., Weisheimer, Antje, Palmer, Tim, and Yang, Chunxue

Subjects
Stochastic Physics, High resolution, Climate simulations, Climate scenarios
Abstract

We present here the first results of the Climate SPHINX (Stochastic Physics HIgh resolutioN eXperiments) project, which was conducted in preparation of PRIMAVERA. Climate SPHINX (http://sansone.to.isac.cnr.it/sphinx/) is a comprehensive set of ensemble AGCM simulations aimed at evaluating the sensitivity of present and future climate to both model resolution and stochastic parameterization. The atmospheric component of the EC-Earth Earth-System Model is used to explore the impact of stochastic physics in a large ensemble of 30-year climate integrations at five different horizontal resolutions (from 125km up to 16km for the atmosphere). The project includes more than 110 simulations in both a historical scenario (1979-2008) and a climate change projection (2039-2068), together with coupled transient runs (1850-2100). This paper presents the technical and scientific setup of the experiments and an overview of preliminary results. An improvement in the simulation of Euro-Atlantic atmospheric blocking following resolution increases is observed. It is also shown that including stochastic parameterization in the low resolution runs helps to improve some aspects of the tropical climate - specifically the Madden-Julian Oscillation and the tropical rainfall variability. These findings show the importance of representing the impact of small-scale processes on the large scale climate variability either explicitly (with high resolution simulations) or stochastically (in low resolution simulations). A sub-set of similar experiments with the EC-Earth couple system in which high resolution and stochastic physics will be tested in the ocean component as well are in preparation in the framework of the PRIMAVERA European Union-funded Horizon H2020 project.

Published
2016

27. Climate SPHINX: evaluating the impact of resolution and stochastic physics parameterisations in climate simulations.

Author

Davini, Paolo, von Hardenberg, Jost, Corti, Susanna, Christensen, Hannah M., Juricke, Stephan, Subramanian, Aneesh, Watson, Peter A. G., Weisheimer, Antje, and Palmer, Tim N.

Subjects
COMPUTER simulation of climatology, STOCHASTIC analysis, MADDEN-Julian oscillation
Abstract

The Climate SPHINX (Stochastic Physics HIgh resolutioN eXperiments) project is a comprehensive set of ensemble simulations aimed at evaluating the sensitivity of present and future climate to model resolution and stochastic parameterisation. The EC-Earth Earth-System Model is used to explore the impact of stochastic physics in a large ensemble of 30-year climate integrations at five different atmospheric horizontal resolutions (from 125 km up to 16 km). The project includes more than 120 simulations in both a historical scenario (1979-2008) and a climate change projection (2039-2068), together with coupled transient runs (1850-2100). A total of 20.4 million core hours have been used, made available from a single year grant from PRACE (the Partnership for Advanced Computing in Europe), and close to 1.5 PBytes of output data have been produced on SuperMUC IBM Petascale System at the Leibniz Supercomputing Center (LRZ) in Garching, Germany. About 140 TBytes of post-processed data are stored on the CINECA supercomputing center archives and are freely accessible to the community thanks to an EUDAT Data Pilot project. This paper presents the technical and scientific setup of the experiments, including the details on the forcing used for the simulations performed, defining the SPHINX v1.0 protocol. In addition, an overview of preliminary results is given: an improvement in the simulation of Euro-Atlantic atmospheric blocking following resolution increases is observed. It is also shown that including stochastic parameterisation in the low resolution runs helps to improve some aspects of the tropical climate - specifically the Madden-Julian Oscillation and the tropical rainfall variability. These findings show the importance of representing the impact of small scale processes on the large scale climate variability either explicitly (with high resolution simulations) or stochastically (in low resolution simulations). [ABSTRACT FROM AUTHOR]

Published
2016
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31. How Does the Quasi-Biennial Oscillation Affect the Stratospheric Polar Vortex?

Author

Watson, Peter A. G. and Gray, Lesley J.

Subjects
*STRATOSPHERE, *STRATOSPHERIC circulation, *QUASI-biennial oscillation (Meteorology), *ORTHOGONAL functions, *TRANSIENTS (Dynamics)
Abstract

The stratospheric polar vortex is weaker in the easterly phase of the quasi-biennial oscillation (QBO-E) than in the westerly phase (QBO-W), but the mechanism behind the QBO's influence is not well understood. The composite difference of the atmospheric state between QBO-E and QBO-W is found to closely resemble the structure of the northern annular mode, the leading empirical orthogonal function of stratospheric variability, including its wave components. Studies of dynamical systems indicate that many different forcings could give rise to this response, and therefore this composite difference does not provide much information about the forcing mechanism. It is argued that the full transient response of a system to an applied forcing is likely to be much more informative about the dynamics of the forcing mechanism, especially the response on time scales shorter than the dynamical time scale, which is about a week for vortex variability. It is shown that the transient response of the vortex to forcing by the QBO in a general circulation model is consistent with the proposed mechanism of Holton and Tan, indicating that this mechanism has a role in the QBO modulation of vortex strength, in contrast to the conclusions of several recent studies. This novel approach of examining the transient response to a forcing on short time scales may be useful in various other outstanding problems. [ABSTRACT FROM AUTHOR]

Published
2014
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