Westerly Bursts during the 1982/83 ENSO

Murakami, Takio; Sumathipala, W. L.

doi:10.1175/1520-0442(1989)002<0071:wbdte>2.0.co;2

Cited by 30 publications

(14 citation statements)

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“…Utilizing gridded winds at 850 mb, Murakami and Sumathipala (1989) studied westerly bursts. They filtered daily winds into short (1-6 day), medium (7-20) day, and long (30-60 day) modes.…”

Section: Introductionmentioning

confidence: 99%

Westerly Wind Bursts and Surface Heat Fluxes in the Equatorial Western Pacific in May 1982

Chu

Frederick

1990

Journal of the Meteorological Society of Japan

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This paper presents a case study of westerly wind bursts in the equatorial western Pacific (EWP) during May 1982. Using 12-hourly island, atoll, and ship observations, the latitudinal extent of the 11-day long burst was determined to be within about five degrees from the equator, whereas its longitudinal domain varied considerably, raging from 1000 km when the burst was first recognized to more than 3500 km when the burst was fully developed. Consequently, Rossby numbers changed appreciably throughout the burst period, and the acceleration term, as expected, dominate the Coriolis force term at the initial stage of the burst.A pressure increase in the far western equatorial Pacific appeared to follow midlatitude forcing. The imposed zonal pressure distribution there greatly enhanced the otherwise slack background pressure gradient in the EWP and thus favored westerly wind bursts. Westerly winds averaged in the box bounded by 5*N-5*S and 135*-155*E peaked at 12-h and 2 days after the establishment of the equatorial zonal pressure gradient. In addition to the pressure rise in the extreme western Pacific, a pressure plunge in the core of the EWP (*150-160*E) resulted in a strong eastward-directed pressure gradient that acted to prolong the burst.Hovmoller diagrams of the meridionally averaged zonal wind and horizontal divergence in the equatorial waveguide indicate that the major axis of the surface divergence was located on the west of maximum westerlies throughout the burst period. The region of maximum surface convergence was on the eastern terminus of the burst, where convection and ascending motion were strong. Deep convective clouds were sometimes found east of strong westerlies. During the burst period, the zonal circulation in the EWP was marked by two cells, linked by strong convection on the eastern extreme of the burst. While the eastern cell resembled a local Walker circulation, the western cell resembled a reverse one.The mean SST in the aforementioned box fell by 1* during the burst period. The equatorial atmosphere in the same area gained a small amount of heat and a relatively large amount of moisture from the warm ocean during the burst period. These conditions were favorable for the enhancement of moist convection over the equatorial ocean.

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“…Utilizing gridded winds at 850 mb, Murakami and Sumathipala (1989) studied westerly bursts. They filtered daily winds into short (1-6 day), medium (7-20) day, and long (30-60 day) modes.…”

Section: Introductionmentioning

confidence: 99%

Westerly Wind Bursts and Surface Heat Fluxes in the Equatorial Western Pacific in May 1982

Chu

Frederick

1990

Journal of the Meteorological Society of Japan

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“…7) it can be clearly seen that during TOGA-COARE TOP period three episodes of signif organized. The 30-60 day low-frequency oscillations are considered to be associated with the triggering of the ENSO event while they propagate into the western and central Pacific, thus causing a relaxation of the trades and the enhancement of the westerly wind (Lau et al, 1989;Murakami and Sumathipala, 1989). The tonal wind at 200 hPa assumed a similar, slow eastward propagation with a 30-60 day period, but with an anomalous east wind overlying over the low-level anomalous westerly wind.…”

Section: Low-frequency Oscillation During Toga-coare Top Periodmentioning

confidence: 99%

Large-Scale Atmospheric Circulation Features during TOGA-COARE IOP

Sumi

1995

Journal of the Meteorological Society of Japan

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The present paper analyzed the large-scale aspects of the atmospheric circulation features during the TOGA-COARE IOP period (November 1, 1992-February 28, 1993. Atmospheric conditions were in many ways similar to those typical of a developing warm episode over the equatorial eastern Pacific, including the frequent occurrence of the low-level westerly wind or westerly wind bursts and the upper-level easterly wind in the western and central Pacific, a moderate eastward shift of the major atmospheric heat source in winter and the Walker circulation, and continuous eastward propagation of 30-60 day low-frequency oscillation into the central and eastern Pacific.

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“…The 1982 El Niño was the most significant event of its type in recent climatic history (Rasmusson and Wallace, 1983). Conse quently, considerable effort has been directed towards an examination of circula- tion features associated with the El Niño-Southern Oscillation (ENSO) phe nomenon (e.g., Murakami and Sumathipala, 1989;Karoly, 1989;Chu et al, 1991). However, very few studies (e.g., Stephens, 1990;Prabhakara, Short, and Vollmer, 1985) have examined the impact on the moisture fields.…”

Section: Spatial Patternsmentioning

confidence: 99%

An Analysis of the Atmospheric Water Balance Over the Southern Hemisphere

Howarth

Rayner

1993

Physical Geography

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An analysis of the atmospheric water balance over the Southern Hemi sphere is conducted for the time period June 1980 through May 1984 that includes the 1982-1983 El Niño event. Notable spatial and temporal variations are evident in the moisture flux divergence fields, in the mean meridional transport of water vapor, and in the moisture content of portions of the tropical atmosphere that are attributable to the 1982-1983 ENSO event. Estimates of the net gain/loss of atmospheric water are provided for 10° latitude belts; although the magnitudes of the differences between evaporation and precipitation fall within the range of previous estimates, they are most probably underestimated. [Key words: atmospheric water balance, El Niño, hydrologic cycle, southern hemisphere, water vapor flux.]

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Westerly Bursts during the 1982/83 ENSO

Cited by 30 publications

References 0 publications

Westerly Wind Bursts and Surface Heat Fluxes in the Equatorial Western Pacific in May 1982

Westerly Wind Bursts and Surface Heat Fluxes in the Equatorial Western Pacific in May 1982

Large-Scale Atmospheric Circulation Features during TOGA-COARE IOP

An Analysis of the Atmospheric Water Balance Over the Southern Hemisphere

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