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Building a traceable climate model hierarchy with multi-level emulators

Building a traceable climate model hierarchy with multi-level emulators
Building a traceable climate model hierarchy with multi-level emulators
To study climate change on multi-millennial timescales or to explore a model's parameter space, efficient models with simplified and parameterised processes are required. However, the reduction in explicitly modelled processes can lead to underestimation of some atmospheric responses that are essential to the understanding of the climate system. While more complex general circulations are available and capable of simulating a more realistic climate, they are too computationally intensive for these purposes. In this work, we propose a multi-level Gaussian emulation technique to efficiently estimate the outputs of steady-state simulations of an expensive atmospheric model in response to changes in boundary forcing. The link between a computationally expensive atmospheric model, PLASIM (Planet Simulator), and a cheaper model, EMBM (energy–moisture balance model), is established through the common boundary condition specified by an ocean model, allowing for information to be propagated from one to the other. This technique allows PLASIM emulators to be built at a low cost. The method is first demonstrated by emulating a scalar summary quantity, the global mean surface air temperature. It is then employed to emulate the dimensionally reduced 2-D surface air temperature field. Even though the two atmospheric models chosen are structurally unrelated, Gaussian process emulators of PLASIM atmospheric variables are successfully constructed using EMBM as a fast approximation. With the extra information gained from the cheap model, the multi-level emulator of PLASIM's 2-D surface air temperature field is built using only one-third the amount of expensive data required by the normal single-level technique. The constructed emulator is shown to capture 93.2?% of the variance across the validation ensemble, with the averaged RMSE of 1.33?°C. Using the method proposed, quantities from PLASIM can be constructed and used to study the effects introduced by PLASIM's atmosphere.
17-37
Tran, Giang T.
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Oliver, Kevin I.C.
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Sobester, Andras
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Toal, David J.J.
eeda1d93-b05f-4bde-8f0e-b82c32e156ac
Holden, Philip B.
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Marsh, Robert
702c2e7e-ac19-4019-abd9-a8614ab27717
Challenor, Peter
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Edwards, Neil R.
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Tran, Giang T.
96da2b45-b395-4a27-b328-423f4d31becd
Oliver, Kevin I.C.
588b11c6-4d0c-4c59-94e2-255688474987
Sobester, Andras
096857b0-cad6-45ae-9ae6-e66b8cc5d81b
Toal, David J.J.
eeda1d93-b05f-4bde-8f0e-b82c32e156ac
Holden, Philip B.
007e7f65-7cba-4117-bea8-bcd2caa38459
Marsh, Robert
702c2e7e-ac19-4019-abd9-a8614ab27717
Challenor, Peter
638f34a3-a133-4172-9032-ebfd8735b46b
Edwards, Neil R.
9b7ab7c6-6229-4522-9780-1c24470ee7b4

Tran, Giang T., Oliver, Kevin I.C., Sobester, Andras, Toal, David J.J., Holden, Philip B., Marsh, Robert, Challenor, Peter and Edwards, Neil R. (2016) Building a traceable climate model hierarchy with multi-level emulators. Advances in Statistical Climatology Meteorology and Oceanography, 2 (1), 17-37. (doi:10.5194/ascmo-2-17-2016).

Record type: Article

Abstract

To study climate change on multi-millennial timescales or to explore a model's parameter space, efficient models with simplified and parameterised processes are required. However, the reduction in explicitly modelled processes can lead to underestimation of some atmospheric responses that are essential to the understanding of the climate system. While more complex general circulations are available and capable of simulating a more realistic climate, they are too computationally intensive for these purposes. In this work, we propose a multi-level Gaussian emulation technique to efficiently estimate the outputs of steady-state simulations of an expensive atmospheric model in response to changes in boundary forcing. The link between a computationally expensive atmospheric model, PLASIM (Planet Simulator), and a cheaper model, EMBM (energy–moisture balance model), is established through the common boundary condition specified by an ocean model, allowing for information to be propagated from one to the other. This technique allows PLASIM emulators to be built at a low cost. The method is first demonstrated by emulating a scalar summary quantity, the global mean surface air temperature. It is then employed to emulate the dimensionally reduced 2-D surface air temperature field. Even though the two atmospheric models chosen are structurally unrelated, Gaussian process emulators of PLASIM atmospheric variables are successfully constructed using EMBM as a fast approximation. With the extra information gained from the cheap model, the multi-level emulator of PLASIM's 2-D surface air temperature field is built using only one-third the amount of expensive data required by the normal single-level technique. The constructed emulator is shown to capture 93.2?% of the variance across the validation ensemble, with the averaged RMSE of 1.33?°C. Using the method proposed, quantities from PLASIM can be constructed and used to study the effects introduced by PLASIM's atmosphere.

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Accepted/In Press date: 25 March 2016
e-pub ahead of print date: 18 April 2016
Published date: 18 April 2016
Organisations: Physical Oceanography

Identifiers

Local EPrints ID: 393350
URI: http://eprints.soton.ac.uk/id/eprint/393350
PURE UUID: 1a8054e8-5720-4a64-a809-7a6fe6028313
ORCID for Andras Sobester: ORCID iD orcid.org/0000-0002-8997-4375

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Date deposited: 25 Apr 2016 10:46
Last modified: 17 Jul 2020 00:27

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Contributors

Author: Giang T. Tran
Author: Andras Sobester ORCID iD
Author: David J.J. Toal
Author: Philip B. Holden
Author: Robert Marsh
Author: Peter Challenor
Author: Neil R. Edwards

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