Stochastic Parameterisation and the El Nino-Southern OscillationReport as inadecuate




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Reference: Christensen, Hannah, Palmer, Tim N., Berner, Judith et al., (2016). Stochastic Parameterisation and the El Nino-Southern Oscillation. Journal of Climate.Citable link to this page:

 

Stochastic Parameterisation and the El Nino-Southern Oscillation

Abstract: The El Niño-Southern Oscillation (ENSO) is the dominant mode of interannual variability in the tropical Pacific. However, the models in the Coupled Model Intercomparison Project (CMIP) 5 ensemble have large deficiencies in ENSO amplitude, spatial structure and temporal variability. We consider the use of stochastic parameterisations as a technique to address these pervasive errors. We include the multiplicative Stochastically Perturbed Parameterisation Tendencies scheme (SPPT) in coupled integrations of the National Center for Atmospheric Research (NCAR) Community Atmosphere Model, version 4 (CAM4). SPPT results in a significant improvement to the representation of ENSO in CAM4, improving the power spectrum, and reducing the magnitude of ENSO towards that observed. To understand the observed impact, we consider additive and multiplicative noise in a simple Delayed Oscillator (DO) model of ENSO. Additive noise results in an increase in ENSO amplitude, but multiplicative noise can reduce the magnitude of ENSO, as was observed for SPPT in CAM4. In the light of these results, two complementary mechanisms are proposed by which the improvement occurs in CAM. Comparison of the coupled runs with a set of atmosphere only runs indicates that SPPT first improves the variability in the zonal winds through perturbing the convective heating tendencies, which improves the variability of ENSO. In addition, SPPT improves the distribution of westerly wind bursts (WWB) important for initiation of El Niño events, by increasing the stochastic component of WWB and reducing the overly strong dependency on SST compared to the control integration.

Publication status:PublishedPeer Review status:Peer reviewedVersion:Accepted ManuscriptDate of acceptance:22 August 2016Notes:© 2016 American Meteorological Society. The final version is available online from American Meteorological Society at: 10.1175/JCLI-D-16-0122.1

Bibliographic Details

Publisher: American Meteorological Society

Publisher Website: https://www.ametsoc.org/ams/

Journal: Journal of Climatesee more from them

Publication Website: https://www.ametsoc.org/ams/index.cfm/publications/journals/journal-of-climate/

Issue Date: 2016Identifiers

Issn: 0894-8755

Eissn: 1520-0442

Uuid: uuid:c98c20b1-6a35-4eaa-b2e3-53ad6e317b9d

Urn: uri:c98c20b1-6a35-4eaa-b2e3-53ad6e317b9d

Pubs-id: pubs:641073

Doi: https://doi.org/10.1175/JCLI-D-16-0122.1 Item Description

Type: journal-article;

Version: Accepted Manuscript

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Author: Christensen, Hannah - Oxford, MPLS, Physics, Atmos Ocean and Planet Physics fundingEuropean Research Council grantNumber291406 -

Source: https://ora.ox.ac.uk/objects/uuid:c98c20b1-6a35-4eaa-b2e3-53ad6e317b9d



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