Assessing changes in risk of amplified planetary waves in a warming world

Chris Huntingford, Dann Mitchell, Kai Kornhuber, Dim Coumou, Scott Osprey, Myles Allen

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

Summer weather extremes are often associated with high-amplitude atmospheric planetary waves (Petoukhov et al., 2013). Such conditions lead to stationary weather patterns, triggering heat waves and sometimes prolonged intense rainfall. These wave events, referred to as periods of Quasi-Resonant Amplification (QRA), are relatively rare though and hence provide only a few data points in the meteorological record to analyse. Here, we use atmospheric models coupled to boundary conditions that have evolved slowly (i.e., climate), to supplement measurements. Specifically we assess altered probabilities of resonant episodes by employing a unique massive ensemble of atmosphere-only climate simulations to populate statistical distributions of event occurrence. We focus on amplified waves during the two most extreme European heat waves on record, in years 2003 and 2015 (Russo et al., 2015). These years are compared with other modelled recent years (1987–2011), and critically against a modelled world without climate change. We find that there are differences in the statistical characteristics of wave event likelihood between years, suggesting a strong dependence on the known and prescribed Sea Surface Temperature (SST) patterns. The differences are larger than those projected to have occurred under climate change since the pre-industrial period. However, this feature of small differences since pre-industrial is based on single large ensembles, with members consisting of a range of estimates of SST adjustment from pre-industrial to present. Such SST changes are from projections by a set of coupled atmosphere–ocean (AOGCM) climate models. When instead an ensemble for pre-industrial estimates is subdivided into simulations according to which AOGCM the SST changes are based on, we find differences in QRA occurrence. These differences suggest that to reliably estimate changes to extremes associated with altered amplification of planetary waves, and under future raised greenhouse gas concentrations, likely requires reductions in any spread of future modelled SST patterns.

Original languageEnglish
Article numbere929
JournalAtmospheric Science Letters
Volume20
Issue number8
DOIs
Publication statusE-pub ahead of print - 3 Jul 2019

Fingerprint

planetary wave
sea surface temperature
warming
amplification
weather
climate change
atmospheric wave
statistical distribution
climate
simulation
climate modeling
greenhouse gas
boundary condition
world
rainfall
atmosphere
summer
heat wave

Keywords

  • atmospheric models
  • climate change
  • heat waves
  • large ensembles
  • mid-latitude extremes
  • quasi-resonant amplification
  • Rossby waves

Cite this

Huntingford, C., Mitchell, D., Kornhuber, K., Coumou, D., Osprey, S., & Allen, M. (2019). Assessing changes in risk of amplified planetary waves in a warming world. Atmospheric Science Letters, 20(8), [e929]. https://doi.org/10.1002/asl.929
Huntingford, Chris ; Mitchell, Dann ; Kornhuber, Kai ; Coumou, Dim ; Osprey, Scott ; Allen, Myles. / Assessing changes in risk of amplified planetary waves in a warming world. In: Atmospheric Science Letters. 2019 ; Vol. 20, No. 8.
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Huntingford, C, Mitchell, D, Kornhuber, K, Coumou, D, Osprey, S & Allen, M 2019, 'Assessing changes in risk of amplified planetary waves in a warming world' Atmospheric Science Letters, vol. 20, no. 8, e929. https://doi.org/10.1002/asl.929

Assessing changes in risk of amplified planetary waves in a warming world. / Huntingford, Chris; Mitchell, Dann; Kornhuber, Kai; Coumou, Dim; Osprey, Scott; Allen, Myles.

In: Atmospheric Science Letters, Vol. 20, No. 8, e929, 03.07.2019.

Research output: Contribution to JournalArticleAcademicpeer-review

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AB - Summer weather extremes are often associated with high-amplitude atmospheric planetary waves (Petoukhov et al., 2013). Such conditions lead to stationary weather patterns, triggering heat waves and sometimes prolonged intense rainfall. These wave events, referred to as periods of Quasi-Resonant Amplification (QRA), are relatively rare though and hence provide only a few data points in the meteorological record to analyse. Here, we use atmospheric models coupled to boundary conditions that have evolved slowly (i.e., climate), to supplement measurements. Specifically we assess altered probabilities of resonant episodes by employing a unique massive ensemble of atmosphere-only climate simulations to populate statistical distributions of event occurrence. We focus on amplified waves during the two most extreme European heat waves on record, in years 2003 and 2015 (Russo et al., 2015). These years are compared with other modelled recent years (1987–2011), and critically against a modelled world without climate change. We find that there are differences in the statistical characteristics of wave event likelihood between years, suggesting a strong dependence on the known and prescribed Sea Surface Temperature (SST) patterns. The differences are larger than those projected to have occurred under climate change since the pre-industrial period. However, this feature of small differences since pre-industrial is based on single large ensembles, with members consisting of a range of estimates of SST adjustment from pre-industrial to present. Such SST changes are from projections by a set of coupled atmosphere–ocean (AOGCM) climate models. When instead an ensemble for pre-industrial estimates is subdivided into simulations according to which AOGCM the SST changes are based on, we find differences in QRA occurrence. These differences suggest that to reliably estimate changes to extremes associated with altered amplification of planetary waves, and under future raised greenhouse gas concentrations, likely requires reductions in any spread of future modelled SST patterns.

KW - atmospheric models

KW - climate change

KW - heat waves

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KW - mid-latitude extremes

KW - quasi-resonant amplification

KW - Rossby waves

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