Defining sudden stratospheric warming in climate models

Accounting for biases in model climatologies

Junsu Kim, Seok Woo Son, Edwin Gerber, Hyo Seok Park

Research output: Contribution to journalArticle

Abstract

A sudden stratospheric warming (SSW) is often defined as zonal-mean zonal wind reversal at 10 hPa and 60°N. This simple definition has been applied not only to the reanalysis data but also to climate model output. In the present study, it is shown that the application of this definition to models can be significantly influenced by model mean biases (i.e., more frequent SSWs appear to occur in models with a weaker climatological polar vortex). To overcome this deficiency, a tendency-based definition is proposed and applied to the multimodel datasets archived for phase 5 of the Coupled Model Intercomparison Project (CMIP5). In this definition, SSW-like events are defined by sufficiently strong vortex deceleration. This approach removes a linear relationship between SSW frequency and intensity of the climatological polar vortex in the CMIP5 models. The models' SSW frequency instead becomes significantly correlated with the climatological upward wave flux at 100 hPa, a measure of interaction between the troposphere and stratosphere. Lower stratospheric wave activity and downward propagation of stratospheric anomalies to the troposphere are also reasonably well captured. However, in both definitions, the high-top models generally exhibit more frequent SSWs than the low-top models. Moreover, a hint of more frequent SSWs in a warm climate is found in both definitions.

Original languageEnglish (US)
Pages (from-to)5529-5546
Number of pages18
JournalJournal of Climate
Volume30
Issue number14
DOIs
StatePublished - Jul 1 2017

Fingerprint

climate modeling
polar vortex
troposphere
zonal wind
sudden stratospheric warming
stratosphere
vortex
anomaly
climate
CMIP

Keywords

  • Stratosphere
  • Stratosphere-troposphere coupling

ASJC Scopus subject areas

  • Atmospheric Science

Cite this

Defining sudden stratospheric warming in climate models : Accounting for biases in model climatologies. / Kim, Junsu; Son, Seok Woo; Gerber, Edwin; Park, Hyo Seok.

In: Journal of Climate, Vol. 30, No. 14, 01.07.2017, p. 5529-5546.

Research output: Contribution to journalArticle

Kim, Junsu ; Son, Seok Woo ; Gerber, Edwin ; Park, Hyo Seok. / Defining sudden stratospheric warming in climate models : Accounting for biases in model climatologies. In: Journal of Climate. 2017 ; Vol. 30, No. 14. pp. 5529-5546.
@article{face733e1a0244439ca618293844081d,
title = "Defining sudden stratospheric warming in climate models: Accounting for biases in model climatologies",
abstract = "A sudden stratospheric warming (SSW) is often defined as zonal-mean zonal wind reversal at 10 hPa and 60°N. This simple definition has been applied not only to the reanalysis data but also to climate model output. In the present study, it is shown that the application of this definition to models can be significantly influenced by model mean biases (i.e., more frequent SSWs appear to occur in models with a weaker climatological polar vortex). To overcome this deficiency, a tendency-based definition is proposed and applied to the multimodel datasets archived for phase 5 of the Coupled Model Intercomparison Project (CMIP5). In this definition, SSW-like events are defined by sufficiently strong vortex deceleration. This approach removes a linear relationship between SSW frequency and intensity of the climatological polar vortex in the CMIP5 models. The models' SSW frequency instead becomes significantly correlated with the climatological upward wave flux at 100 hPa, a measure of interaction between the troposphere and stratosphere. Lower stratospheric wave activity and downward propagation of stratospheric anomalies to the troposphere are also reasonably well captured. However, in both definitions, the high-top models generally exhibit more frequent SSWs than the low-top models. Moreover, a hint of more frequent SSWs in a warm climate is found in both definitions.",
keywords = "Stratosphere, Stratosphere-troposphere coupling",
author = "Junsu Kim and Son, {Seok Woo} and Edwin Gerber and Park, {Hyo Seok}",
year = "2017",
month = "7",
day = "1",
doi = "10.1175/JCLI-D-16-0465.1",
language = "English (US)",
volume = "30",
pages = "5529--5546",
journal = "Journal of Climate",
issn = "0894-8755",
publisher = "American Meteorological Society",
number = "14",

}

TY - JOUR

T1 - Defining sudden stratospheric warming in climate models

T2 - Accounting for biases in model climatologies

AU - Kim, Junsu

AU - Son, Seok Woo

AU - Gerber, Edwin

AU - Park, Hyo Seok

PY - 2017/7/1

Y1 - 2017/7/1

N2 - A sudden stratospheric warming (SSW) is often defined as zonal-mean zonal wind reversal at 10 hPa and 60°N. This simple definition has been applied not only to the reanalysis data but also to climate model output. In the present study, it is shown that the application of this definition to models can be significantly influenced by model mean biases (i.e., more frequent SSWs appear to occur in models with a weaker climatological polar vortex). To overcome this deficiency, a tendency-based definition is proposed and applied to the multimodel datasets archived for phase 5 of the Coupled Model Intercomparison Project (CMIP5). In this definition, SSW-like events are defined by sufficiently strong vortex deceleration. This approach removes a linear relationship between SSW frequency and intensity of the climatological polar vortex in the CMIP5 models. The models' SSW frequency instead becomes significantly correlated with the climatological upward wave flux at 100 hPa, a measure of interaction between the troposphere and stratosphere. Lower stratospheric wave activity and downward propagation of stratospheric anomalies to the troposphere are also reasonably well captured. However, in both definitions, the high-top models generally exhibit more frequent SSWs than the low-top models. Moreover, a hint of more frequent SSWs in a warm climate is found in both definitions.

AB - A sudden stratospheric warming (SSW) is often defined as zonal-mean zonal wind reversal at 10 hPa and 60°N. This simple definition has been applied not only to the reanalysis data but also to climate model output. In the present study, it is shown that the application of this definition to models can be significantly influenced by model mean biases (i.e., more frequent SSWs appear to occur in models with a weaker climatological polar vortex). To overcome this deficiency, a tendency-based definition is proposed and applied to the multimodel datasets archived for phase 5 of the Coupled Model Intercomparison Project (CMIP5). In this definition, SSW-like events are defined by sufficiently strong vortex deceleration. This approach removes a linear relationship between SSW frequency and intensity of the climatological polar vortex in the CMIP5 models. The models' SSW frequency instead becomes significantly correlated with the climatological upward wave flux at 100 hPa, a measure of interaction between the troposphere and stratosphere. Lower stratospheric wave activity and downward propagation of stratospheric anomalies to the troposphere are also reasonably well captured. However, in both definitions, the high-top models generally exhibit more frequent SSWs than the low-top models. Moreover, a hint of more frequent SSWs in a warm climate is found in both definitions.

KW - Stratosphere

KW - Stratosphere-troposphere coupling

UR - http://www.scopus.com/inward/record.url?scp=85021084870&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85021084870&partnerID=8YFLogxK

U2 - 10.1175/JCLI-D-16-0465.1

DO - 10.1175/JCLI-D-16-0465.1

M3 - Article

VL - 30

SP - 5529

EP - 5546

JO - Journal of Climate

JF - Journal of Climate

SN - 0894-8755

IS - 14

ER -