Midwinter Suppression of Baroclinic Wave Activity in the Pacific

Nakamura, Hisashi

doi:10.1175/1520-0469(1992)049<1629:msobwa>2.0.co;2

Cited by 313 publications

(284 citation statements)

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“…Especially, Kageyama et al (1999) suggested an explanation for the LGM North Atlantic storm-track behaviour similar to the midwinter suppression observed by Nakamura (1992) in the North Pacific. Synoptic activity in the North Pacific was reduced during the mid-winter months of the early 1980s compared to the late automn and early spring months whereas mean-flow baroclinicity was at its strongest at this time of the year.…”

Section: Context and Aimssupporting

confidence: 54%

“…Some of the questions we are willing to answer are: Do we expect changes in the amplitude or shifts in the seasonal cycle of northern hemisphere storm-tracks at LGM compared to CTR? Do we get similar behaviours as the midwinter suppression of the North Pacific in the early 1980s first analysed by Nakamura (1992) for the LGM, with weaker synoptic activity during the months of strongest mean-flow baroclinicity? In order to address these questions, we have computed the mean seasonal cycle, i.e.…”

Section: Seasonality Changessupporting

confidence: 54%

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Northern hemisphere storm tracks during the last glacial maximum in the PMIP2 ocean-atmosphere coupled models: energetic study, seasonal cycle, precipitation

et al. 2008

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Mid-latitude eddies are an important component of the climatic system due to their role in transporting heat, moisture and momentum from the tropics to the poles, and also for the precipitation associated with their fronts, especially in winter. We study northern hemisphere stormtracks at the Last Glacial Maximum (LGM) and their influence on precipitation using ocean-atmosphere general circulation model (OAGCM) simulations from the second phase of the Paleoclimate Modelling Intercomparison Project (PMIP2). The difference with PMIP1 results in terms of sea-surface temperature forcing, fundamental for storm-track dynamics, is large, especially in the eastern North Atlantic where sea-ice extends less to the south in OAGCMs compared to atmospheric-only GCMs. Our analyses of the physics of the eddies are based on the equations of eddy energetics. All models simulate a consistent southeastward shift of the North Pacific storm-track in winter, related to a similar displacement of the jet stream, partly forced by the eddies themselves. Precipitation anomalies are consistent with storm-track changes, with a southeastward displacement of the North Pacific precipitation pattern. The common features of North Atlantic changes in the LGM simulations consist of a thinning of the storm-track in its western part and an amplification of synoptic activity to the southeast, in the region between the Azores Islands and the Iberian Peninsula, which reflects on precipitation. This southeastward extension is related to a similar displacement of the jet, partly forced by the eddies. In the western North Atlantic, the synoptic activity anomalies are at first order related to baroclinic generation term anomalies, but the mean-flow baroclinicity increase due to the presence of the Laurentide ice-sheet is partly balanced by a loss of eddy efficiency to convert energy from the mean flow. Moisture availability in this region is greatly reduced due to more advection of dry polar air by stationary waves, leading to less synopticscale latent heat release and hence less precipitation also. In terms of seasonality, the stormy season is shifted later in the year by a few days to a month depending on the season and the model considered. This shift does not directly reflect on the first-order seasonal cycle of precipitation, which also depends on other mechanisms, especially in summer.

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Section: Context and Aimssupporting

confidence: 54%

Section: Seasonality Changessupporting

confidence: 54%

Northern hemisphere storm tracks during the last glacial maximum in the PMIP2 ocean-atmosphere coupled models: energetic study, seasonal cycle, precipitation

et al. 2008

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“…It is of interest to find that the maximum variance appears, for both components PS and PL, over the north Atlantic area, while the variance over the Japan area is rather weak even though the jet is intense there. The suppression of mid-winter wave activity in the Pacific has been pointed out by Nakamura (1992).…”

Section: Mean Wind Fieldmentioning

confidence: 97%

“…There have been some observational and statistical studies on synoptic-scale disturbances in the extratropical tropospheric circulation, ranging from the order of 10 days down to a few days (e.g., Hartmann, 1974;Blackmon, 1976;Nakamura, 1992). Among them, in his Fig.…”

Section: Introductionmentioning

confidence: 99%

Medium-Scale Travelling Waves over the North Atlantic

Hirota

Yamada

Sato

1995

Journal of the Meteorological Society of Japan

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An analysis is made, with the aid of ECMWF operational data, of medium-scale, eastward-traveling waves in the mid-latitude upper troposphere over the north Atlantic area as a counterpart of the similar analysis of Sato et al. (1993) for the medium-scale waves over Japan.It is shown that the waves dominate in wintertime (January and February of 1990) over the north Atlantic centered around 50N, with the typical wavelength of 2400km, a period of 33 hours, and hence an eastward phase velocity of about 20 m s-1.

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“…the review by and the references therein). It has been now realized that there exist different timescale variability in storm track structure and intensity from seasonal (Nakamura, 1992;Christophy et al, 1997) to interannual (Trenberth and Hurrell, 1994;Straus and Shukla, 1997;Zhang and Held, 1999) and to interdecade (Ebisuzaki and Chelliah, 1998;Nakamura and Izumi, 1999;Geng and Sugi, 2001;Chang and Fu, 2002), which is potentially helpful to the medium-and long-term weather prediction.…”

Section: Introductionmentioning

confidence: 99%

Northern hemisphere storm tracks in strong AO anomaly winters

Nie

Wang

Yang

et al. 2008

Atmospheric Science Letters

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Northern Hemisphere winter 300 hPa storm tracks/baroclinic waves and their energetics during strong Arctic Oscillation (AO) anomaly events are investigated. It is shown that during strong positive AO anomaly winters, the Atlantic storm track intensifies significantly and shifts northward and far downstream while Pacific storm track extends westward. Baroclinic waves over the Atlantic propagate along central North Atlantic during strong negative AO anomaly winters while during strong positive AO anomaly winters, waves over the Atlantic split into two branches. Distributions of the kinetic energy and energy conversions of different spatial scale over the storm track regions assume different characteristics for different AO phases.

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Midwinter Suppression of Baroclinic Wave Activity in the Pacific

Cited by 313 publications

References 0 publications

Northern hemisphere storm tracks during the last glacial maximum in the PMIP2 ocean-atmosphere coupled models: energetic study, seasonal cycle, precipitation

Northern hemisphere storm tracks during the last glacial maximum in the PMIP2 ocean-atmosphere coupled models: energetic study, seasonal cycle, precipitation

Medium-Scale Travelling Waves over the North Atlantic

Northern hemisphere storm tracks in strong AO anomaly winters

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