The aim of this work is to quantify the influence of the position and intensity of the South Pacific High (SPH) over seasonal rainfall in Argentina. Some indices were defined to measure the position ...and intensity of the SPH, and they were correlated with seasonal precipitation to study the relationship between them. Results indicate that the intensity of the SPH affects precipitation mainly in northern Argentina during spring and in the southern region in autumn and winter. The latitudinal shift of the SPH has proved to have a relevant impact on precipitation in the northeast in summer and winter, and in some regions of southern and central Argentina during winter and spring. When studying the possibility to foresee precipitation behaviour with a one‐month lag, these metrics were not able to predict precipitation effectively in the northwest. On the contrary, the SPH intensity showed significant lagged correlations with rainfall mainly in the northeast, central‐east and south during spring and summer while the position of the SPH is mostly significantly correlated with summer and winter precipitation in the northeast and central Argentina. Results suggest that the situation of SPH can provide some rainfall predictability.
The position and intensity of the South Pacific High can have a solid influence over seasonal rainfall in Argentina. The intensity of this system has an effect over precipitation during spring, autumn and winter whereas its position can affect rainfall during winter, spring and summer. These parameters can also help estimate rainfall anomalies in advance, suggesting there is some predictability, especially in spring and summer when considering its intensity and during summer and winter regarding changes in its position.
This work proposes a probabilistic forecast of seasonal precipitation in the basins of the Limay, Neuquén, and Negro rivers in the north of Argentine Patagonia. The Comahue region is particularly ...important because part of the country’s hydroelectric energy is generated there. The amount of winter precipitation modulates the flow of rivers, and therefore, prior knowledge of possible precipitation thresholds is very useful for decision-makers. Ensembles made up of statistical models that explain more than 50% of the precipitation were used and were generated with multiple techniques such as linear regression, generalized additive models, support vector regression, and artificial neural networks. The result showed that the forecasts are better in Limay and Neuquén river basins in winter than in Negro River basin. Brier Skill Score values indicate that the probabilistic forecast is better than the climatology in winter, in Neuquén and Limay basins for below and above normal categories.
The objective of this work is to quantify the influence of the position and intensity of the Atlantic High (AH) on seasonal rainfall in Argentina. Monthly precipitation data in 68 stations from the ...National Meteorological Service of Argentina, the Secretariat of Water Resource and the Territorial Authority of the Limay, Neuquén, and Negro rivers basins (AIC) were used. Correlation was the methodology used to identify the link between seasonal rainfall and some indices especially defined to detect the position and intensity of the anticyclone. Precipitation composites of the years when the value of these indices was extremely high (greater than their second tercile) and extremely low (lower than their first tercile) were built for every season. They were analysed and compared with humidity anomaly transport composites for the same sets of years in order to study circulation patterns associated with seasonal rainfall anomalies. Results indicate that when the AH is intensified, winter rainfall increases in central Argentina and spring rainfall increases in northern Cuyo region. When the AH is displaced towards the north of its mean position, autumn rainfall is favoured in the northeast and central and south Patagonia, meanwhile winter and spring rainfall decreases in central Argentina. When the AH is displaced towards the east of its mean position, summer rainfall decreases in central Andes. Finally, AH indices were used to detect the influence on rainfall in advance. Correlations between seasonal rainfall and the defined indices that characterize the anticyclone in the previous month suggest that there is some rainfall predictability, especially during spring in almost every region in Argentina.
The position and intensity of the Atlantic High can have a strong influence on seasonal rainfall. When this anticyclone is intensified, rainfall increases in central Argentina in winter and in northern Cuyo during spring. In addition, when it is displaced north of its mean position, autumn rainfall is favoured in Patagonia. These parameters of the anticyclone were also used to foretell seasonal rainfall anomalies and results suggest that there is some predictability, especially during spring in almost every region.
This paper attempts to design statistical models to forecast annual precipitation in the Neuquen and Limay river basins in the Comahue region of Argentina. These forecasts are especially useful as ...they are used to better organize the operation of hydro-electric dams, the agriculture in irrigated valleys and the safety of the population. In this work, multiple linear regression statistical models are built to forecast mean annual rainfall over the two river basins. Since the maximum precipitation occurs in the winter (June-August), forecasting models have been developed for the beginning of March and for the beginning of June, just before the rainy season starts. The results show that the sea-surface temperatures of the Indian and Pacific oceans are good predictors for March models and explain 42.8% of the precipitation index variance. The efficiency of the models increases in June, adding more predictors related to the autumn circulation.
Regional change under agricultural expansion in the Chaco of Argentina is determined by interactions of rainfall change, infrastructure development, socio-economic actions and values, and the social ...perceptions of change. Our study focused on adaptation in the socio-environmental system which is the key to understanding opportunities, uncertainties and risk in the context of historical change. Change in land use from extensive grazing through mixed farming and on to industrial-scale soybean production was made possible by a trend of increasing rainfall that reduced the risk of crop failure from drought since the 1970s. Rainfall change coincided with a period in which the Chaco forest was suffering extensive degradation from long-term extractive use. The degradation aided agricultural expansion since the degraded state of the ecosystem justified public policies of deforestation. In parallel to these resource-based processes, public policy changed in the late 70s and 80s toward favoring privatization of state land and exclusion of small producers. This permitted the land concentration needed for industrial-scale production. Technological innovation in both water and land resource management reinforced the process of concentration because small producers rarely have the financial or educational capital to develop or implement emerging technologies. One of the results of the intensification and expansion of agriculture is that soil surface sealing, waterlogging and flood risk are now effective at a landscape scale. To address these risks, private enterprise and government efforts must now come together toward innovative policies in integrated landscape management.
A detailed statistical analysis was performed at the Neuquén river basin using precipitation data for 1980–2007. The hydrological year begins in March with a maximum in June associated with rainfall ...and another relative maximum in October derived from snow-break. General features of the rainy season and the excess or deficits thereof are analyzed using standardized precipitation index (SPI) for a six-month period in the basin. The SPI has a significant cycle of 14.3 years; the most severe excess (SPI greater than 2) has a return period of 25 years, while the most severe droughts (SPI less than −2) have a return period of 10 years. The SPI corresponding to the rainy season (April–September) (SPI9) has no significant trend and is used to classify wet/dry years. In order to establish the previous circulation patterns associated with interannual SPI9 variability, the composite fields of wet and dry years are compared. There is a tendency for wet (dry) periods to take place during El Niño (La Niña) years, when there are positive anomalies of precipitable water over the basin, when the zonal flow over the Pacific Ocean is weakened (intensified) and/or when there are negative pressure anomalies in the southern part of the country and Antarctic sea. Some prediction schemes using multiple linear regressions were performed. One of the models derived using the forward stepwise method explained 42% of the SPI9 variance and retained two predictors related to circulation over the Pacific Ocean: one of them shows the relevance of the intensity of zonal flow in mid-latitudes, and the other is because of the influence of low pressure near the Neuquén River basin. The cross-validation used to prove model efficiency showed a correlation of 0.41 between observed and estimated SPI9; there was a probability of detection of wet (dry) years of 80% (65%) and a false alarm relation of 25% in both cases.
The Chaco plain region in Argentina is located in the north of the country and east of Los Andes where the main activity is the agriculture. As such activity is highly affected by interannual ...rainfall variability, the influence of some of the principal atmospheric and oceanic forcing is investigated in this paper. Results show that the factors which affect precipitation highly depend on the season and the subregion. The position of the South Atlantic Height and the sea surface temperature in the coast of southern Brazil and Buenos Aires seem to be the factors that affect rainfall, all over the year. The El Niño-Southern Oscillation phenomenon affects summer and spring rainfall and the Southern Annular Mode involves spring precipitation but both only in the east of the study region. Furthermore, enhanced convection in Central Brazil, mainly influences autumn and spring rainfall.
El objetivo del presente trabajo es estudiar la variabilidad de la precipitación en escalas temporales mayores al añoo en una zona en el centro de Argentina. Las tendencias de precipitación ...resultaron máximas en la estación estival, mostrando una disminución en la cantidad de lluvia sobre todo en el oeste de la región de estudio y en el periodo más reciente. El estudio de ciclos significativos evidenció la presencia de ciclos de aproximadamente 15, 23 y 30 años. La variabilidad interanual de la precipitación de verano se estudió en 3 sub-regiones diferentes basándose en la comparación del comportamiento de las variables atmosféricas y oceánicas en años con deficit y con exceso de precipitación. La altura geopotencial fue la variable que discriminó mejor dichos casos. La lluvia sobrenormal estuvo asociada al debilitamiento del anticiclón y de las bajas subpolares en el Océano Pacifico, y la intensificación del Anticiclón del Océano Atlántico en la región de entrada al continente. El calentamiento del Océano Pacifico central (fase positiva del ENOS-El Niño Oscilación del Sur) fue otro factor relacionado con la precipitación en toda la región. Un modelo de regresión lineal múltiple fue desarrollado para la región oriental y explicó el 43,3% de la varianza de la precipitación estival.
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