Annular Modes in the Extratropical Circulation. Part I: Month-to-Month Variability*

Thompson, David W. J.; Wallace, John M.

doi:10.1175/1520-0442(2000)013<1000:amitec>2.0.co;2

Cited by 2,708 publications

(2,378 citation statements)

References 47 publications

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“…This result suggests that there is not any preferential SaM phase along the 20 years period used here. however, from figure 1 it is observed that there is a small positive phase tendency from 1993 to 2000 which agrees with some other studies (thompson andWallace 2000b, Marshall 2003). the seasonal SaM phase variability is small where the difference between the season with maximum frequency of negative phase occurrence (winter) and the minimum (spring) is of 5 months.…”

Section: Methodssupporting

confidence: 91%

Relationship between the southern annular mode and southern hemisphere atmospheric systems

Reboita

Ambrizzi

Rocha

2009

Rev. bras. meteorol.

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Seasonal relationship between the Southern annular Mode (SaM) and the spatial distribution of the cyclone systems over Southern hemisphere is investigated for the period 1980 to 1999. in addition, seasonal frontogenesis and rainfall distribution over South america and South atlantic ocean during different SaM phases were also analyzed. it is observed that during negative SaM phases the cyclone trajectories move northward when compared to the positive one, and in the South america and South atlantic sector there is intense frontogenetic activity and positive anomaly precipitation over the Southeast of the South america. in general, SaM positive phase shows opposite signals. Key-words: SaM, cyclones density, frontogenetic function, southeast South america ResuMo: RelaÇÃo entRe o Modo anUlaR SUl e oS SiSteMaS atMoSféRicoS no heMiSféRio SUl a relação sazonal entre o Modo anular Sul (Southern annular Mode -SaM) e a distribuição espacial dos sistemas ciclônicos sobre o hemisfério Sul foi investigada no período de 1980 a 1999. também foram analisados os padrões sazonais de frontogêneses e de distribuição de precipitação, sobre a américa do Sul e oceano atlântico Sul, durante as diferentes fases da SaM. na fase negativa da SaM foi observado que a trajetória dos ciclones em todo o hemisfério Sul move-se para norte, comparada à fase positiva, e que no setor da américa do Sul e atlântico Sul há intensa atividade frontogenética e anomalias positivas de precipitação na costa sudeste da américa do Sul. em geral, na fase positiva da SaM são observadas condições inversas. palavras-chave: SaM, densidade de ciclones, função frontogenética, sudeste da américa do Sul

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Section: Methodssupporting

confidence: 91%

Relationship between the southern annular mode and southern hemisphere atmospheric systems

Reboita

Ambrizzi

Rocha

2009

Rev. bras. meteorol.

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“…The AO index is provided by NOAA/CPC (National Oceanic and Atmospheric Administration/Climate Prediction Center) and is identified as the leading EOF mode of the 1000−700 hPa height anomaly north of 20°N. The definition is a slight variant from the original index proposed by Thompson and Wallace (2000) where a year-round monthly mean SLP is used instead of taking each month separately. The loading pattern is created based on years 1979−2000, and is projected on the following years to create a daily index.…”

Section: Datamentioning

confidence: 99%

Recurrence of Intraseasonal Cold Air Outbreak during the 2009/2010 Winter in Japan and its Ties to the Atmospheric Condition over the Barents-Kara Sea

Hori

Inoue

Kikuchi

et al. 2011

SOLA

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In the winter of 2009/2010, Japan and the East Asian region experienced a frequent occurrence of cold air outbreaks. Although the winter average temperature in the Japan main islands was slightly positive (+0.81°C for DJF average and +0.71°C for NDJFM average), repeated decline in temperature was notable throughout the season. One explanation for this abnormal winter season is the extremely negative condition of the Arctic Oscillation (AO) that persisted from December to mid-January. However, AO alone does not provide sufficient explanation for the cold air outbreak during November or its intraseasonal periodicity. A case study of the cold air outbreak that reached Japan on Dec. 18 reveals an anomalous ridge forming over the Barents-Kara Sea, which leads to the cold air accumulation over western Siberia. The pressure anomaly subsequently shifted westward to mature into a blocking high which created a wave-train pattern downstream, advecting the cold air eastward towards East Asia and Japan. The sequence of events was also apparent in multiple cases throughout the season. This study suggests that there is a strong and systematic linkage in the intraseasonal timescale between the atmospheric condition over the Barents-Kara Sea and the cold air accumulation over the Eurasian continent, leading to the anomalous cold air outbreak over East Asia and Japan. The mechanism may also provide explanation to extreme winter conditions such as those observed during the winter of 2010/2011.

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“…The SAM is the dominant mode of atmospheric variability around Antarctica, essentially describing the north-south pressure gradient and the associated strength of the circumpolar zonal winds (e.g., Thompson and Wallace 2000). However, the SAM is additionally characterized by a significant nonannular component in the ABSL area (Lefebvre et al 2004;Fogt et al 2012a).…”

Section: Introductionmentioning

confidence: 99%

The Influence of the Amundsen–Bellingshausen Seas Low on the Climate of West Antarctica and Its Representation in Coupled Climate Model Simulations

et al. 2013

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In contrast to earlier studies, the authors describe the climatological deep low pressure system that exists over the South Pacific sector of the Southern Ocean, referred to as the Amundsen-Bellingshausen Seas low (ABSL), in terms of its relative (rather than actual) central pressure by removing the background areaaveraged mean sea level pressure (MSLP). Doing so removes much of the influence of large-scale variability across the ABSL sector region (e.g., due to the southern annular mode), allowing a clearer understanding of ABSL variability and its effect on the regional climate of West Antarctica. Using ECMWF Interim ReAnalysis (ERA-Interim) fields, the annual cycle of the relative central pressure of the ABSL for the period from 1979 to 2011 shows a minimum (maximum) during winter (summer), differing considerably from the earlier studies based on actual central pressure, which suggests a semiannual oscillation. The annual cycle of the longitudinal position of the ABSL is insensitive to the background pressure, and shows it shifting westward from ;2508 to ;2208E between summer and winter, in agreement with earlier studies. The authors demonstrate that ABSL variability, and in particular its longitudinal position, play an important role in controlling the surface climate of West Antarctica and the surrounding ocean by quantifying its influence on key meteorological parameters. Examination of the ABSL annual cycle in 17 CMIP5 climate models run with historical forcing shows that the majority of them have definite biases, especially in terms of longitudinal position, and a correspondingly poor representation of West Antarctic climate.

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Annular Modes in the Extratropical Circulation. Part I: Month-to-Month Variability*

Cited by 2,708 publications

References 47 publications

Relationship between the southern annular mode and southern hemisphere atmospheric systems

Relationship between the southern annular mode and southern hemisphere atmospheric systems

Recurrence of Intraseasonal Cold Air Outbreak during the 2009/2010 Winter in Japan and its Ties to the Atmospheric Condition over the Barents-Kara Sea

The Influence of the Amundsen–Bellingshausen Seas Low on the Climate of West Antarctica and Its Representation in Coupled Climate Model Simulations

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