The value of initialisation on decadal timescales: state dependent predictability in the CESM Decadal Prediction Large Ensemble
Information in decadal climate prediction arises from a well initialised ocean state and from the predicted response to an external forcing. The length of time over which the initial conditions benefit the decadal forecast depends on the start date of the forecast. We characterise this state-depende...
Published in: | Journal of Climate |
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Format: | Article in Journal/Newspaper |
Language: | English |
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American Meteorological Society
2020
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Online Access: | https://doi.org/10.1175/JCLI-D-19-0571.1 https://ora.ox.ac.uk/objects/uuid:726ae0cc-62bf-4cf3-a599-3a67954db444 |
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ftuloxford:oai:ora.ox.ac.uk:uuid:726ae0cc-62bf-4cf3-a599-3a67954db444 2024-10-06T13:51:13+00:00 The value of initialisation on decadal timescales: state dependent predictability in the CESM Decadal Prediction Large Ensemble Christensen, HM Berner, J Yeager, S 2020-06-19 https://doi.org/10.1175/JCLI-D-19-0571.1 https://ora.ox.ac.uk/objects/uuid:726ae0cc-62bf-4cf3-a599-3a67954db444 eng eng American Meteorological Society doi:10.1175/JCLI-D-19-0571.1 https://ora.ox.ac.uk/objects/uuid:726ae0cc-62bf-4cf3-a599-3a67954db444 https://doi.org/10.1175/JCLI-D-19-0571.1 info:eu-repo/semantics/openAccess Journal article 2020 ftuloxford https://doi.org/10.1175/JCLI-D-19-0571.1 2024-09-06T07:47:36Z Information in decadal climate prediction arises from a well initialised ocean state and from the predicted response to an external forcing. The length of time over which the initial conditions benefit the decadal forecast depends on the start date of the forecast. We characterise this state-dependent predictability for decadal forecasts of upper ocean heat content in the Community Earth System Model. We find regionally dependent initial condition predictability, with extended predictability generally observed in the extra-tropics. We also detect state-dependent predictability, with the year of loss of information from the initialisation varying between start dates. The decadal forecasts in the North Atlantic show substantial information from the initial conditions beyond the ten-year forecast window, and a high degree of state-dependent predictability. We find some evidence for state dependent predictability in the ensemble spread in this region, similar to that seen in weather and subseasonal-to-seasonal forecasts. For some start dates, an increase of information with lead time is observed, for which the initialised forecasts predict a growing phase of the Atlantic Multidecadal Oscillation. Finally we consider the information in the forecast from the initial conditions relative to the forced response, and quantify the crossover timescale after which the forcing provides more information. We demonstrate that the climate change signal projects onto different patterns than the signal from the initial conditions. This means that even after the crossover timescale has been reached in a basin-averaged sense, the benefits of initialisation can be felt locally on longer timescales. Article in Journal/Newspaper North Atlantic ORA - Oxford University Research Archive Journal of Climate 33 17 7353 7370 |
institution |
Open Polar |
collection |
ORA - Oxford University Research Archive |
op_collection_id |
ftuloxford |
language |
English |
description |
Information in decadal climate prediction arises from a well initialised ocean state and from the predicted response to an external forcing. The length of time over which the initial conditions benefit the decadal forecast depends on the start date of the forecast. We characterise this state-dependent predictability for decadal forecasts of upper ocean heat content in the Community Earth System Model. We find regionally dependent initial condition predictability, with extended predictability generally observed in the extra-tropics. We also detect state-dependent predictability, with the year of loss of information from the initialisation varying between start dates. The decadal forecasts in the North Atlantic show substantial information from the initial conditions beyond the ten-year forecast window, and a high degree of state-dependent predictability. We find some evidence for state dependent predictability in the ensemble spread in this region, similar to that seen in weather and subseasonal-to-seasonal forecasts. For some start dates, an increase of information with lead time is observed, for which the initialised forecasts predict a growing phase of the Atlantic Multidecadal Oscillation. Finally we consider the information in the forecast from the initial conditions relative to the forced response, and quantify the crossover timescale after which the forcing provides more information. We demonstrate that the climate change signal projects onto different patterns than the signal from the initial conditions. This means that even after the crossover timescale has been reached in a basin-averaged sense, the benefits of initialisation can be felt locally on longer timescales. |
format |
Article in Journal/Newspaper |
author |
Christensen, HM Berner, J Yeager, S |
spellingShingle |
Christensen, HM Berner, J Yeager, S The value of initialisation on decadal timescales: state dependent predictability in the CESM Decadal Prediction Large Ensemble |
author_facet |
Christensen, HM Berner, J Yeager, S |
author_sort |
Christensen, HM |
title |
The value of initialisation on decadal timescales: state dependent predictability in the CESM Decadal Prediction Large Ensemble |
title_short |
The value of initialisation on decadal timescales: state dependent predictability in the CESM Decadal Prediction Large Ensemble |
title_full |
The value of initialisation on decadal timescales: state dependent predictability in the CESM Decadal Prediction Large Ensemble |
title_fullStr |
The value of initialisation on decadal timescales: state dependent predictability in the CESM Decadal Prediction Large Ensemble |
title_full_unstemmed |
The value of initialisation on decadal timescales: state dependent predictability in the CESM Decadal Prediction Large Ensemble |
title_sort |
value of initialisation on decadal timescales: state dependent predictability in the cesm decadal prediction large ensemble |
publisher |
American Meteorological Society |
publishDate |
2020 |
url |
https://doi.org/10.1175/JCLI-D-19-0571.1 https://ora.ox.ac.uk/objects/uuid:726ae0cc-62bf-4cf3-a599-3a67954db444 |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_relation |
doi:10.1175/JCLI-D-19-0571.1 https://ora.ox.ac.uk/objects/uuid:726ae0cc-62bf-4cf3-a599-3a67954db444 https://doi.org/10.1175/JCLI-D-19-0571.1 |
op_rights |
info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.1175/JCLI-D-19-0571.1 |
container_title |
Journal of Climate |
container_volume |
33 |
container_issue |
17 |
container_start_page |
7353 |
op_container_end_page |
7370 |
_version_ |
1812179413414969344 |