Seasonal Diagnostic and Predictability of Rainfall in Subtropical South America Based on Tropical Pacific SST

Montecinos, Aldo; Díaz, Álvaro; Aceituno, Patricio

doi:10.1175/1520-0442(2000)013<0746:sdapor>2.0.co;2

Cited by 146 publications

(127 citation statements)

References 20 publications

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“…Circles represent the anomalies that are significant at the 90% confidence level. The non-significant anomalies are represented by triangles basin is partly similar to that described for southeastern South America (SESA) (Aceituno, 1988;Montecinos et al, 2000;Grimm et al, 2000). In the Ecuadorian Amazon basin (lowlands and Andean eastern slopes), some evidence of above-normal rainfall is observed during El Niño.…”

Section: Per Basin Analysissupporting

confidence: 72%

Interannual rainfall variability in the Amazon basin and sea‐surface temperatures in the equatorial Pacific and the tropical Atlantic Oceans

Ronchail¹,

Cochonneau²,

Molinier³

et al. 2002

Intl Journal of Climatology

229

188

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Rainfall variability in the Amazon basin is studied in relation to sea-surface temperatures (SSTs) in the equatorial Pacific and the northern and southern tropical Atlantic during the 1977-99 period, using the HiBAm original rainfall data set and complementary cluster and composite analyses.The northeastern part of the basin, north of 5°S and east of 60°W, is significantly related with tropical SSTs: a rainier wet season is observed when the equatorial Pacific and the northern (southern) tropical Atlantic are anomalously cold (warm). A shorter and drier wet season is observed during El Niño events and negative rainfall anomalies are also significantly associated with a warm northern Atlantic in the austral autumn and a cold southern Atlantic in the spring. The northeastern Amazon rainfall anomalies are closely related with El Niño-southern oscillation during the whole year, whereas the relationships with the tropical Atlantic SST anomalies are mainly observed during the autumn. A time-space continuity is observed between El Niño-related rainfall anomalies in the northeastern Amazon, those in the northern Amazon and south-eastern Amazon, and those in northern South America and in the Nordeste of Brazil.A reinforcement of certain rainfall anomalies is observed when specific oceanic events combine. For instance, when El Niño and cold SSTs in the southern Atlantic are associated, very strong negative anomalies are observed in the whole northern Amazon basin. Nonetheless, the comparison of the cluster and the composite analyses results shows that the rainfall anomalies in the northeastern Amazon are not always associated with tropical SST anomalies.In the southern and western Amazon, significant tropical SST-related rainfall anomalies are very few and spatially variable. The precipitation origins differ from those of the northeastern Amazon: land temperature variability, extratropical perturbations and moisture advection are important rainfall factors, as well as SSTs. This could partially explain why: (a) the above-mentioned signals weaken or disappear, with the exception of the relative dryness that is observed at the peak of an El Niño event and during the dry season when northern Atlantic SSTs are warmer than usual; (b) rainfall anomalies tend to resemble those of southeastern South America, noticeably at the beginning and the end of El Niño and La Niña events; (c) some strong excesses of rain are not associated with any SST anomalies and merit further investigation.

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Section: Per Basin Analysissupporting

confidence: 72%

Interannual rainfall variability in the Amazon basin and sea‐surface temperatures in the equatorial Pacific and the tropical Atlantic Oceans

Ronchail¹,

Cochonneau²,

Molinier³

et al. 2002

Intl Journal of Climatology

229

188

View full text Add to dashboard Cite

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“…This region is approximately coincident with that for which different researchers have reported statistically significant correlation between ENSO and precipitation variability on seasonal time scales, e.g. Halpert (1987, 1989), Montecinos et al (2000) and Berri et al (2002). It should be stressed that this period was characterized by strong SST anomalies in the tropical Pacific Ocean, which have a significant influence on climate variability over southeast South America.…”

Section: Data Used For the Validationsupporting

confidence: 82%

“…For example, Berri and Flamenco (1999) on seasonal river flow predictions based on Niño3 SST observations and predictions, Montecinos et al (2000) on rainfall predictability over subtropical South America, and Mason and Goddard (2001) on the robustness of ENSO teleconnections. Other physically based model predictions became available operationally from the Centro de Previsao do Tempo e Estudos Climaticos (CPTEC), Brazil (Marengo et al, 2003).…”

Section: Current Approaches To Seasonal Prediction and The Southeast mentioning

confidence: 99%

Evaluation of the Climate Outlook Forums' seasonal precipitation forecasts of southeast South America during 1998-2002

Berri

Antico

Goddard³

2005

Int. J. Climatol.

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The series of 16 Climate Outlook Forums' (COFs') seasonal precipitation forecasts for southeast South America since December 1997 are verified. The COFs' forecasts consist of a probabilistic tercile distribution of precipitation for the upcoming 3 months period, over a domain in South America between 20 and 40°S, to the east of the Andes Mountains. The COFs' forecast is the result of the consensus agreement between atmosphere model predictions, physically based statistical model predictions, results of diagnostic analysis and published research on climate variability over the region, and expert interpretation of this information in the context of the current situation. The validation is conducted by means of the hit score (HS), which expresses the percentage of forecasts verified in the dominant predicted category, and the ranked probability skill Score (RPSS), which measures the difference between the probability distribution of the forecasts and the observed categories. The HS reveals that over most of the region the categorical agreement is low and close to 33%, which is the result that would be obtained by a three-category random forecast, and only sparse regions achieve a categorical agreement between 40 and 50%. The regions with positive RPSS (i.e. forecasts better than climatology and potentially useful for applications) represent 30% of the total area considered by the COFs. There are significantly large regions with negative RPSS, i.e. forecasts worse than climatology. The result of the COFs' forecasts is compared with that of the IRI Net Assessment forecasts, the only source of physically based seasonal forecasts regularly available at the COFs' discussions. There is general coincidence in the regions with positive and negative skill. Although one might expect the consensus of the COFs' forecasts to improve upon the skill of the IRI forecast, this was not the case during this period.

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“…O Rio Grande do Sul, situado no extremo meridional do Brasil, pertence à chamada Região Sudeste da Amé-rica do Sul (Sul do Brasil, Nordeste da Argentina, Uruguai e Sul do Paraguai), que apresenta forte sinal do fenômeno El Niño Oscilação Sul (ENOS), especialmente em relação à precipitação pluvial (Ropelewski & Halpert, 1987;Rao & Hada, 1990;Studzinski & Diaz, 1994;Diaz et al, 1998;Grimm et al, 1998;Montecinos et al, 2000). O ENOS é um fenômeno de interação oceano-atmosfera, que ocorre no Oceano Pacífico tropical, e é considerado como a principal causa da variabilidade climática em diversas regiões do Globo.…”

Section: Introductionunclassified

Associação entre El Niño Oscilação Sul e a produtividade do milho no Estado do Rio Grande do Sul

Berlato

Farenzena

Fontana

2005

Pesq. agropec. bras.

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Resumo -A alta variabilidade interanual da produtividade de milho, no Rio Grande do Sul, é determinada, principalmente, pela variabilidade da precipitação pluvial, e esta, em grande parte está associada ao fenômeno El Niño Oscilação Sul (ENOS). A disponibilidade, hoje, de previsões sazonais do ENOS faz vislumbrar a possibilidade de uso dessas informações para minimizar prejuízos e maximizar a produtividade. Há necessidade, porém, de se avaliar a vulnerabilidade da produtividade do milho a esse fenômeno. O objetivo deste trabalho foi quantificar a associação entre a produtividade de milho e a variabilidade da precipitação pluvial, causada pelo ENOS. Para a análise, foram tomadas séries históricas de produtividade, de precipitação pluvial mensal, de ocorrência das fases do ENOS (El Niño e La Niña), de Temperatura da Superfície do Mar (TSM) no Pacífico equatorial, e do Índice de Oscilação Sul (IOS). Há forte tendência do El Niño em favorecer a cultura do milho, o que dá oportunidade à alta produtividade, ao passo que em anos de ocorrência de La Niña há alta freqüência de baixa produtividade. A precipitação pluvial mais associada à produtividade do milho é a integrada de outubro a março. Essas informações são úteis para decisões quanto a alternativas de manejo da cultura, frente a uma previsão de El Niño ou La Niña.Termos para indexação: Zea mays, La Niña, precipitação pluvial. Association between El Niño Southern Oscillation and corn yield in Rio Grande do Sul StateAbstract -The high interannual variability of corn yield in Rio Grande do Sul State is determined mostly by the variability of rainfall, which is mainly associated to El Niño Southern Oscillation (ENSO). Current availability of seasonal ENSO forecasts shows the possibility of using this information to minimize losses and maximize yield. However, it is necessary to assess the vulnerability of corn yield to this phenomenon. The objective of this work was to quantify the association between corn yield and rainfall variability due to ENSO. In order to perform the analysis, historical series of yields, monthly rainfalls, ENSO (El Niño and La Niña) phases, Sea Surface Temperature (SST) in equatorial Pacific, and the Southern Oscillation Index (SOI) were used. Results show that there is a strong trend for El Niño to favor corn crops, providing opportunities for high yields, while in years when La Niña occurs there is a high frequency of low yields. The rainfall most associated with corn yields is the integrated one from October to March. This information is useful for decision making as to crop management alternatives when there is a forecast of El Niño or La Niña.

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Seasonal Diagnostic and Predictability of Rainfall in Subtropical South America Based on Tropical Pacific SST

Cited by 146 publications

References 20 publications

Interannual rainfall variability in the Amazon basin and sea‐surface temperatures in the equatorial Pacific and the tropical Atlantic Oceans

Interannual rainfall variability in the Amazon basin and sea‐surface temperatures in the equatorial Pacific and the tropical Atlantic Oceans

Evaluation of the Climate Outlook Forums' seasonal precipitation forecasts of southeast South America during 1998-2002

Associação entre El Niño Oscilação Sul e a produtividade do milho no Estado do Rio Grande do Sul

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