Eastward Propagation of 30–60 Day Perturbations as Revealed from Outgoing Longwave Radiation Data

Murakami, Takio; Longxun, Chen; An, Xin; Shrestha, Madan L.

doi:10.1175/1520-0469(1986)043<0961:epodpa>2.0.co;2

Cited by 64 publications

(38 citation statements)

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“…The existence of eastward-moving convective disturbances over this area was confirmed by making use of outgoing longwave radiation (OLR) data (e.g., see Lau and Chan, 1985;Murakami et al, 1986;Nakazawa, 1986). The eastward-moving speed of the convective disturbances associated with the intraseasonal oscillations is about 4*6ms-1 (Murakami et al, 1984;Lau and Chan, 1985;Knutson et al, 1986). After moving east of the dateline, the convective disturbance begins to decay rapidly, and another eastward-moving convective disturbance can be observed in the Indian Ocean.…”

mentioning

confidence: 82%

“…Their interpretation was that the oscillation consisted of a pair of convection cells having a planetary scale in the zonal direction (a planetary-scale Walker cell) that propagates eastward over the Indian Ocean through the central Pacific Ocean (Madden and Julian, 1972). The existence of eastward-moving convective disturbances over this area was confirmed by making use of outgoing longwave radiation (OLR) data (e.g., see Lau and Chan, 1985;Murakami et al, 1986;Nakazawa, 1986). The eastward-moving speed of the convective disturbances associated with the intraseasonal oscillations is about 4*6ms-1 (Murakami et al, 1984;Lau and Chan, 1985;Knutson et al, 1986).…”

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confidence: 99%

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An Attempt at Obtaining the Local Structure of the Tropical Intraseasonal Oscillation

Miyahara

Morooka

1988

Journal of the Meteorological Society of Japan

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mentioning

confidence: 82%

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confidence: 99%

An Attempt at Obtaining the Local Structure of the Tropical Intraseasonal Oscillation

Miyahara

Morooka

1988

Journal of the Meteorological Society of Japan

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“…2) Madden (1994), Weickmann et al (1985), Vincent et al (1991), and Murakami et al (1986) the intra-seasonal oscillation has a broad spectral character. Subdividing the cycle periods into >10, > 20 and > 30 d for the summers of 1979 to 1994, spectral peaks of 10 to 20 d period occurred 21% of the time, intermediate periods occurred 33% of the time, and > 30 d (the MJO) were most prevalent at 46%, as summarised in Table 1.…”

Section: Convection Oscillationsmentioning

confidence: 99%

Intra-seasonal convective structure and evolution over tropical East Africa

Mpeta¹,

Jury²

2001

Clim. Res.

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Intra-seasonal convection oscillations over southwestern Tanzania during the December to February season are examined using 15 yr (1979 to 1994) of pentad Outgoing Longwave Radiation (OLR) data and kinematic/thermodynamic parameters from ECMWF data. Most significant spectral energy for an area-averaged OLR index is concentrated in periods of 16 to 33 d. Time-longitude diagrams of filtered OLR, and zonal wind anomalies at 850 hPa averaged over the 7.5 to 10°S latitude band for the period November to May reveal eastward (62%), westward (11%) and quasi-stationary convective (27%) features. Phase speeds for transient cases are in the range of 2 to 8 m s -1 . In the eastward propagating case study, 1 to 15 January 1993, map sequences reveal that deep convection shifts northeastward as a southern mid-latitude trough couples with the ITCZ. Convective events over tropical east Africa are associated with an influx of northeasterly Indian monsoon flow followed by increased westerlies from the Guinea/Congo region. Eastward propagating OLR anomalies couple with zonal circulations, suggesting that a transient Walker cell emerges periodically from East Africa. KEY WORDS: Intra-seasonal climate · East AfricaResale or republication not permitted without written consent of the publisher

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“…The tropical 30−60 day oscillation is a result of eastward-propagating low-frequency circulation anomalies and associated large-scale convection. Many studies have noted that the tropical 30−60 day oscillation was suppressed over Indonesia (e.g., Murakami et al 1986;Rui and Wang 1990;Zhu and Wang 1993). Nitta et al (1992) showed that cloud disturbances moving eastward from the Indian Ocean to the western Pacific were weakened or modified in the western part of Indonesia, possibly because of the blocking effects of Sumateran topography.…”

Section: Introductionmentioning

confidence: 99%

Differences of Rainfall Characteristics between Coastal and Interior Areas of Central Western Sumatera, Indonesia

Hamada

Yamanaka

Mori

et al. 2008

Journal of the Meteorological Society of Japan

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Pentad rainfall data from 46 stations in West Sumatera Province, Indonesia in 1992 reveal temporal and spatial variations of rainfall in coastal and inland regions. Distinct contrasts in rainfall amounts and variations are evident between the coastal and inland mountainous regions. Locality index is defined by pentad rainfall time series in coastal and inland regions to classify characteristic rainfall distribution patterns into four types: coastal-, inland-, active-, and inactive-type. In 1992 the coastal-or active-type rainfall patterns tend to appear throughout the year, whereas the inland-type rainfall pattern tends to appear during the Southern Hemisphere summer. The inactive-type tends to appear during the Southern Hemisphere winter.Correlation and composite analyses suggest that lower tropospheric zonal wind variations over central western Sumatera tend to intensify the contrast between coastal and inland rainfall distribution. The correlation coefficient between locality index and zonal wind of 850 hPa NCEP/NCAR reanalysis is 0.77 (99% confidence level) for characteristic rainfall distribution patterns during 1992−1993. This implies that rainfall in the windward side of steep mountain is relatively greater than that of leeward side with increasing wind speed. The occurrence of coastal-type pattern is relatively well related with lower tropospheric westerly wind. Furthermore, although the number is limited, diurnal variations of convective activity are clear when active-type rainfall appears.

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Eastward Propagation of 30–60 Day Perturbations as Revealed from Outgoing Longwave Radiation Data

Cited by 64 publications

References 0 publications

An Attempt at Obtaining the Local Structure of the Tropical Intraseasonal Oscillation

An Attempt at Obtaining the Local Structure of the Tropical Intraseasonal Oscillation

Intra-seasonal convective structure and evolution over tropical East Africa

Differences of Rainfall Characteristics between Coastal and Interior Areas of Central Western Sumatera, Indonesia

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