Precipitation Patterns Associated with the High Index Phase of the Southern Oscillation

Ropelewski, Chester F.; Halpert, Michael S.

doi:10.1175/1520-0442(1989)002<0268:ppawth>2.0.co;2

Cited by 992 publications

(420 citation statements)

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“…Much of the area receives more than 75% of its annual mean rainfall during these 6 months (Ropelewski and Halpert, 1987;Ropelewski, 1989). Previous studies have suggested that the rainfall decrease in NEA is mainly a summer phenomenon (Nicholls, 2006), and trends in half-year rainfall over the period 1952-2002 dominate the trends in annual rainfall over the full period of 1901-2002(Smith, 2004.…”

Section: Selection Of the Analysis Periodmentioning

confidence: 99%

A possible cause of decreasing summer rainfall in northeast Australia

Li¹,

Feng²,

Li³

2011

Intl Journal of Climatology

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ABSTRACT:The NCEP/NCAR reanalysis and precipitation data from the Australian Bureau of Meteorology are used to analyse variability in rainfall during the austral summer (December-March, DJFM) in northeast Australia (NEA). NEA rainfall shows a marked decrease over the past 50 years, mainly in the austral summer. Our analysis reveals that the summer rainfall decrease in NEA is generally an interdecadal phenomenon. The declining trend has an imprint in the tropical Australian summer monsoon (TASM). Not only does TASM have a phase-to-phase influence on NEA summer rainfall at the interannual scale, it is also closely linked with interdecadal variation in NEA summer rainfall. Thus, the decrease in NEA at the interdecadal scale could be attributed to corresponding variation in TASM. Moreover, the coupled linkage between TASM and NEA summer rainfall appears to be largely independent of El Niño-Southern Oscillation. One possible reason for the interdecadal weakening trend in TASM is a sustained interdecadal warming trend in sea surface temperature (SST) over the Wharton Basin (100°-130°E, 20°-5°S). When the Wharton Basin is in a cold state, anomalous westerlies occur in the lower troposphere in the TASM region, and cyclonic circulation anomalies and rising flows occur in the low and middle troposphere over NEA, which are associated with a strong TASM situation, consequently favouring enhanced rainfall over NEA; the opposite occurs in the case of a warm Wharton Basin. SST over the Wharton Basin has shown a continuous warming trend over the past 60 years, contributing to the weakening of TASM and, consequently, a decrease in NEA summer rainfall.

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Section: Selection Of the Analysis Periodmentioning

confidence: 99%

A possible cause of decreasing summer rainfall in northeast Australia

Li¹,

Feng²,

Li³

2011

Intl Journal of Climatology

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“…Many researchers support this view in relation to southern African rainfall variability (Ropelewski and Halpert, 1989;Matarira, 1990;Reason et al, 2000;Makarau and Jury, 1997;Matarira and Jury, 1992). As a result, the recent development of seasonal forecasting techniques for southern Africa tend to rely heavily on ENSO-related predictability.…”

Section: Introductionmentioning

confidence: 99%

The impact of the positive Indian Ocean dipole on Zimbabwe droughts

Manatsa

Chingombe

Matarira

2008

Intl Journal of Climatology

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A comparative study of the impact of the anomalous positive Indian Ocean SST gradient, referred to as the Indian Ocean Dipole/Zonal Mode (IODZM), and El Niño-Southern Oscillation (ENSO) on Zimbabwe seasonal rainfall variability for the period 1940-1999, is documented. Composite techniques together with simple and partial correlation analyses are employed to segregate the unique association related to IODZM/ENSO with respect to the Zimbabwe seasonal rainfall.The analysis reveals that the IODZM impact on the country's summer rainfall is overwhelming as compared to that of ENSO when the two are in competition. The IODZM influence remains high (significant above 99% confidence level), even after the influence of ENSO has been removed, while that of ENSO collapses to insignificance (even at 90% confidence level) when the IODZM contribution is eliminated. The relationship between ENSO and Zimbabwe seasonal rainfall seems to be sustained through El Niño occurring in the presence of positive IODZM events. However, when the co-occurring positive IODZM and El Niño events are removed from the analysis, it is apparently clear that ENSO has little to do with the country's rainfall variability. On the other hand, positive IODZM is mostly associated with the rainfall deficits, whether or not it co-occurs with El Niño. However, the co-occurrence of the two events does not necessarily suggest that El Niño influences droughts through the positive IODZM events. The El Niño event components during co-occurrence seem to be unrelated (at least linearly) to the droughts, while the positive IODZM events display a relatively strong relationship that is significant above the 95% confidence level. It thus becomes important to extend the study of this nature to cover the whole of southern Africa, so that the extent of the impact of the phenomena can be realized over the whole region.

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“…Temperatures in the southeastern United States are usually below normal, and temperatures in the northwestern United States, western Canada, Alaska, and to a lesser degree the plains of the northern United States and southern Canada, are above normal (Barnston et al, 1999;Cohen and Jones, 2011). El Niño is also associated with above-normal precipitation from coast to coast across the southern United States, along with below-normal precipitation across the northern United States, especially the Pacific Northwest and the Great Lakes (Ropelewski and Halpert, 1989;Barnston et al, 1999).…”

Section: Introductionmentioning

confidence: 99%