High- and Low-Frequency Intraseasonal Variance of OLR on Annual and ENSO Timescales

Vincent, Dayton G.; Fink, Andreas H.; Schrage, Jon M.; Speth, P.

doi:10.1175/1520-0442(1998)011<0968:halfiv>2.0.co;2

Cited by 42 publications

(44 citation statements)

References 46 publications

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“…Using OLR data, Anyamba and Weare (1995) reported that during two out of the three warm ENSO events considered, there was more eastward penetration of intraseasonal activity or the MJO envelope over the central Pacific, and the propagation speed is slower. Later studies using OLR data with a longer base period (Fink and Speth 1997;Vincent et al 1998;Hendon et al 1999;Kessler 2001) came to similar conclusions. This east-west dipole-like perturbation of activity is reversed during cold ENSO events.…”

Section: Introductionmentioning

confidence: 84%

Modulation of the Madden-Julian Oscillation by ENSO: Inferences from Observations and GCM Simulations

Tam

Lau

2005

Journal of the Meteorological Society of Japan

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The impact of the El Niñ o-Southern Oscillation (ENSO) on the Madden-Julian Oscillation (MJO) is studied, based on reanalysis data and output from an ensemble general circulation model (GCM) experiment. Observed monthly sea surface temperature variations over the period of 1950-99 are imposed in the deep tropical eastern/central Pacific in the course of the SST experiment. Both GCM, and reanalysis data, indicate that intraseasonal activity of the low-level zonal wind is enhanced (reduced) over the central (western) Pacific during El Niñ o events. The propagation and growth/decay characterisitcis of the MJO in different phases of ENSO is also examined, based on a lag correlation technique. During warm events there is an eastward shift in the locations of strong growth and decay, and the propagation of the MJO becomes slower in the warm ENSO phase. These changes are reversed during La Niñ a epsiodes.Using output from the GCM experiment, the effects of ENSO on the circulation and convection during the MJO lifecycle are studied in detail. Further eastward penetration of MJO-related convection is simulated during warm events over the central Pacific. An instability index related to the vertical gradient of the moist static energy is found to be useful for depicting the onset of MJO convection along the equator. During warm events, the stronger magnitudes of this index over the central Pacific are conducive to more eastward penetration of convective anomalies in the region. These changes are mainly due to the intensified moisture accumulation at low levels. Analysis of the moisture budget suggests that the stronger moisture accumulation can be related to the increased low-level humidity over the central Pacific during warm events.

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Section: Introductionmentioning

confidence: 84%

Modulation of the Madden-Julian Oscillation by ENSO: Inferences from Observations and GCM Simulations

Tam

Lau

2005

Journal of the Meteorological Society of Japan

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“…1b) shows maximum convective activity on the 10-25-day timescale over the South China Sea and Bay of Bengal, in agreement with FY99. Past studies have shown that the peak OLR variance for the 10-25-day timescale occurs over these regions during the summer (JJA) (e.g., Kiladis and Weickmann 1997;Vincent et al 1998). Here, mean fields for JuneJuly (Fig.…”

Section: Differences In Transient Disturbancementioning

confidence: 99%

“…Intraseasonal oscillations on so-called submonthly (about 6-30-day) timescales (e.g., Meehl et al 1996) are recognized as an important component of the subseasonal atmospheric variability as same as the Madden-Julian Oscillation (MJO: about 30-60 days) (e.g., Madden andJulian 1972, 1994). Vincent et al (1998) presented a comprehensive review of observational work on submonthly scale variability. After Kiladis and Weickmann (1992a, b) identified significant linkages between tropical deep convection and large-scale circulation, a series of studies clarified the nature of tropical convective disturbances and the associated tropical-extratropical interactions on submonthly timescales.…”

Section: Introductionmentioning

confidence: 99%

“…In particular, Mo (2000) examined the teleconnection between the Pacific intraseasonal mode and North American rainfall during the NH summer. Relationships between extratropical circulations on submonthly timescales and tropical and subtropical convection in the South Pacific convergence zone (SPCZ) (e.g., Kiladis and Weickmann 1992b;Schrage and Vincent 1996;Vincent et al 1997) and the South Atlantic convergence zone (SACZ) (e.g., Weickmann 1992a, 1997;Liebmann et al 1999) have also been studied.…”

Section: Introductionmentioning

confidence: 99%

“…Tropical-extratropical interactions on submonthly timescales and the roles of the interactions in tropical and subtropical variability during the NH summer over the Pacific basin have not been studied in depth. A summertime extreme of convective activity in this frequency range occurs over the western tropical Pacific region including the South China Sea (e.g., Chen and Chen 1995;Vincent et al 1998;Kiladis 1998). Our study examines how this convection is triggered and the impact that it has on large-scale circulation.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Tropical-Extratropical Interaction Associated with the 10-25-day Oscillation over the Western Pacific during the Northern Summer.

Fukutomi

Yasunari

2002

Journal of the Meteorological Society of Japan

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Extratropical forcing of tropical wave disturbances along the Indian Ocean ITCZ

Fukutomi

Yasunari

2014

JGR Atmospheres

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The role of extratropical waves in the excitation of tropical waves on submonthly timescales is explored along the Indian Ocean Intertropical Convergence Zone (ITCZ) during the austral summer using Japanese Reanalysis products and NOAA outgoing longwave radiation data. The analysis period is December-February of 1979/1980to 2008. The submonthly tropical waves are regarded as a type of Rossby wave propagating along the mean monsoon westerly flow. They play an important role in modulating the Indian Ocean ITCZ convection. The linkage between the tropical and extratropical waves, which is responsible for the formation and strengthening of tropical waves, is examined. Composite analysis results linked to the tropical wave train development show that the midlatitude Rossby wave train progresses eastward and northeastward from the South Atlantic into the subtropical Indian Ocean. As a trough and ridge that form part of the midlatitude wave train approach the southern Africa-southwest Indian Ocean (SWIO) region, a southwest-northeast-oriented wave train is subsequently established, originating from this feature, and is strengthened across the tropical Indian Ocean. The midlatitude wave propagation toward the subtropics induces the growth of the trough and ridge over the SWIO. Wave activity flux diagnostics indicate that the amplified trough and ridge over the SWIO act as an energy source for northeastward amplification of the tropical waves through the wave energy dispersion process. The results suggest that the propagation of the midlatitude wave toward the SWIO is the fundamental mechanism behind the development of the tropical waves along the Indian Ocean ITCZ.

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High- and Low-Frequency Intraseasonal Variance of OLR on Annual and ENSO Timescales

Cited by 42 publications

References 46 publications

Modulation of the Madden-Julian Oscillation by ENSO: Inferences from Observations and GCM Simulations

Modulation of the Madden-Julian Oscillation by ENSO: Inferences from Observations and GCM Simulations

Tropical-Extratropical Interaction Associated with the 10-25-day Oscillation over the Western Pacific during the Northern Summer.

Extratropical forcing of tropical wave disturbances along the Indian Ocean ITCZ

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