scholarly journals Droughts and floods over the upper catchment of the Blue Nile and their connections to the timing of El Niño and La Niña Events

2013 ◽  
Vol 10 (8) ◽  
pp. 10971-10995 ◽  
Author(s):  
M. A. H. Zaroug ◽  
E. A. B. Eltahir ◽  
F. Giorgi
Keyword(s):  
El Niño ◽  
River Flow ◽  
El Nino ◽  
La Niña ◽  
Blue Nile ◽  
El Niño Event ◽  
La Nina ◽  
Extreme Flood ◽  
Droughts And Floods ◽  
The Impact

Abstract. The Blue Nile originates from Lake Tana in the Ethiopian Highland and contributes about 67% of the discharge in the main Nile River. Previous studies investigated the relationship of sea surface temperature (SST) in the Pacific Ocean (Nino 3.4 region) to occurrence of floods and droughts in rainfall and river flow over the Nile basin. In this paper we focus on the dependence of occurrence of droughts and floods in the upper catchment of the Blue Nile on the timing of El Niño and La Niña events. Different events start in different times of the year and follow each other exhibiting different patterns and sequences. Here, we study the impact of this timing and temporal patterns on the Nile droughts and floods. We analyze discharge measurements (1965–2012) at the outlet of the upper catchment of the Blue Nile in relation to the El Niño index. When an El Niño event is followed by a La Niña event, there is a 67% chance for occurrence of an extreme flood. The association of start dates of El Niño with occurrence of droughts in the upper catchment of the Blue Nile is evaluated. An El Niño event that starts in (April–June) is associated with a significant drought occurrence in 83% of the cases. We propose that observations as well as global model forecasts of SST during this season could be used in seasonal forecasting of the Blue Nile flow.

scholarly journals Droughts and floods over the upper catchment of the Blue Nile and their connections to the timing of El Niño and La Niña events

2014 ◽  
Vol 18 (3) ◽  
pp. 1239-1249 ◽  
Author(s):  
M. A. H. Zaroug ◽  
E. A. B. Eltahir ◽  
F. Giorgi
Keyword(s):  
El Niño ◽  
El Nino ◽  
La Niña ◽  
Blue Nile ◽  
La Nina ◽  
The Pacific ◽  
Extreme Flood ◽  
Droughts And Floods ◽  
Relationship Of ◽  
The Impact

Abstract. The Blue Nile originates from Lake Tana in the Ethiopian Highlands and contributes about 60–69% of the main Nile discharge. Previous studies investigated the relationship of sea surface temperature (SST) in the Pacific Ocean (Niño 3.4 region) to occurrence of meteorological and hydrological droughts in the Nile Basin. In this paper we focus on the dependence of occurrence of droughts and floods in the upper catchment of the Blue Nile on the timing of El Niño and La Niña events. Different events start at different times of the year and follow each other, exhibiting different patterns and sequences. Here we study the impact of these timing and temporal patterns on the Blue Nile droughts and floods. The comparison between the discharge measurements (1965–2012) at the outlet of the upper catchment of the Blue Nile and the El Niño index shows that when an El Niño event is followed by a La Niña event, there is a 67% chance for occurrence of an extreme flood. Furthermore, we also found that 83% of El Niño events starting in April–June resulted in droughts in the upper catchment of the Blue Nile. Although the current study is limited by the reduced number of samples, we propose that observations as well as global model forecasts of SST during this season could be used in seasonal forecasting of the Blue Nile flow.

The Impact of ENSO on Wave Breaking and Southern Annular Mode Events

2010 ◽  
Vol 67 (9) ◽  
pp. 2854-2870 ◽  
Author(s):  
Tingting Gong ◽  
Steven B. Feldstein ◽  
Dehai Luo
Keyword(s):  
El Niño ◽  
Wave Breaking ◽  
El Nino ◽  
Southern Annular Mode ◽  
La Niña ◽  
Background Flow ◽  
Austral Spring ◽  
Annular Mode ◽  
La Nina ◽  
The Impact

Abstract This study examines the relationship between intraseasonal southern annular mode (SAM) events and the El Niño–Southern Oscillation (ENSO) using daily 40-yr ECMWF Re-Analysis (ERA-40) data. The data coverage spans the years 1979–2002, for the austral spring and summer seasons. The focus of this study is on the question of why positive SAM events dominate during La Niña and negative SAM events during El Niño. A composite analysis is performed on the zonal-mean zonal wind, Eliassen–Palm fluxes, and two diagnostic variables: the meridional potential vorticity gradient, a zonal-mean quantity that is used to estimate the likelihood of wave breaking, and the wave breaking index (WBI), which is used to evaluate the strength of the wave breaking. The results of this investigation suggest that the background zonal-mean flow associated with La Niña (El Niño) is preconditioned for strong (weak) anticyclonic wave breaking on the equatorward side of the eddy-driven jet, the type of wave breaking that is found to drive positive (negative) SAM events. A probability density function analysis of the WBI, for both La Niña and El Niño, indicates that strong anticyclonic wave breaking takes place much more frequently during La Niña and weak anticyclonic wave breaking during El Niño. It is suggested that these wave breaking characteristics, and their dependency on the background flow, can explain the strong preference for SAM events of one phase during ENSO. The analysis also shows that austral spring SAM events that coincide with ENSO are preceded by strong stratospheric SAM anomalies and then are followed by a prolonged period of wave breaking that lasts for approximately 30 days. These findings suggest that the ENSO background flow also plays a role in the excitation of stratospheric SAM anomalies and that the presence of these stratospheric SAM anomalies in turn excites and then maintains the tropospheric SAM anomalies via a positive eddy feedback.

scholarly journals The Impact of Obliquity Change on El Niño Southern Oscillation (ENSO) and La Niña Climate Episodes

2022 ◽  
Author(s):  
Paul C. Rivera
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Global Climate ◽  
Global Climate Model ◽  
La Niña ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
La Nina ◽  
The Impact

An alternative physical mechanism is proposed to describe the occurrence of the episodic El Nino Southern Oscillation (ENSO) and La Nina climatic phenomena. This is based on the earthquake-perturbed obliquity change (EPOCH) model previously discovered as a major cause of the global climate change problem. Massive quakes impart a very strong oceanic force that can move the moon which in turn pulls the earth’s axis and change the planetary obliquity. Analysis of the annual geomagnetic north-pole shift and global seismic data revealed this previously undiscovered force. Using a higher obliquity in the global climate model EdGCM and constant greenhouse gas forcing showed that the seismic-induced polar motion and associated enhanced obliquity could be the major mechanism governing the mysterious climate anomalies attributed to El Nino and La Nina cycles.

scholarly journals EL NINO, LA NINA, DAN PENAWARAN PANGAN DI JAWA, INDONESIA

2011 ◽  
Vol 12 (2) ◽  
pp. 257
Author(s):  
Arini Wahyu Utami ◽  
Jamhari Jamhari ◽  
Suhatmini Hardyastuti
Keyword(s):  
El Niño ◽  
Time Series Data ◽  
El Nino ◽  
Southern Oscillation ◽  
Regression Function ◽  
La Niña ◽  
Series Data ◽  
Cross Sectional ◽  
La Nina ◽  
The Impact

Paddy and maize are two important food crops in Indonesia and mainly produced in Java Island. This research aimed to know the impact of El Nino and La Nina on paddy and maize farmer’s supply in Java. Cross sectional data from four provinces in Java was combined with time series data during 1987-2006. Paddy supply was estimated using log model, while maize supply used autoregressive model; each was estimated using two types of regression function. First, it included dummy variable of El Nino and La Nina to know their influence into paddy and maize supply. Second, Southern Oscillation Index was used to analyze the supply changing when El Nino or La Nina occur. The result showed that El Nino and La Nina did not influence paddy supply, while La Nina influenced maize supply in Java. Maize supply increased when La Nina occurred.

scholarly journals Reexamining El Niño and Cholera in Peru: A Climate Affairs Approach

2013 ◽  
Vol 5 (2) ◽  
pp. 148-161 ◽  
Author(s):  
Iván J. Ramírez ◽  
Sue C. Grady ◽  
Michael H. Glantz
Keyword(s):  
El Niño ◽  
Elevated Temperatures ◽  
El Nino ◽  
Southern Oscillation ◽  
La Niña ◽  
Enso Cycle ◽  
Holistic View ◽  
La Nina ◽  
Cholera Epidemic ◽  
The Impact

Abstract In the 1990s Peru experienced the first cholera epidemic after almost a century. The source of emergence was initially attributed to a cargo ship, but later there was evidence of an El Niño association. It was hypothesized that marine ecosystem changes associated with El Niño led to the propagation of V. cholerae along the coast of Peru, which in turn initiated the onset of the epidemic in 1991. Earlier studies supported this explanation by demonstrating a relationship between elevated temperatures and increased cholera incidence in Peru; however, other aspects of El Niño–Southern Oscillation (ENSO) and their potential impacts on cholera were not investigated. Therefore, this study examines the relationship between El Niño and cholera in Peru from a holistic view of the ENSO cycle. A “climate affairs” approach is employed as a conceptual framework to incorporate ENSO’s multidimensional nature and to generate new hypotheses about the ENSO and cholera association in Peru. The findings reveal that ENSO may have been linked to the cholera epidemic through multiple pathways, including rainfall extremes, La Niña, and social vulnerability, with impacts depending on the geography of teleconnections within Peru. When the definition of an ENSO event is examined, cholera appears to have emerged either during ENSO neutral or La Niña conditions. Furthermore, the analysis herein suggests that the impact of El Niño arrived much later, possibly resulting in heightened transmission in the austral summer of 1992. In conclusion, a modified hypothesis with these new insights on cholera emergence and transmission in Peru is presented.

scholarly journals Incidencia de los eventos El Niño y La Niña en el comportamiento de glaciares tropicales en perú

2019 ◽  
pp. 21-27
Keyword(s):  
El Niño ◽  
El Nino ◽  
La Niña ◽  
Glacier Surface ◽  
Cordillera Blanca ◽  
Box Counting ◽  
La Nina ◽  
Para Determinar ◽  
Normalized Difference Snow Index ◽  
The Impact

Incidencia de los eventos El Niño y La Niña en el comportamiento de glaciares tropicales en perú Incidence of events El Niño and La Niña in the behavior of tropical glaciers in peru Gilberto Medina y Abel Mejía Universidad Nacional Agraria de la Selva, Tingo María 156 Universidad Nacional Agraria La Molina, Lima2 DOI: https://doi.org/10.33017/RevECIPeru2010.0016/ RESUMEN Los eventos El Niño y La Niña en el Océano pacífico tropical se dan de manera periódica y tienen una clara incidencia en el crecimiento y mantenimiento de la superficie glaciar de los nevados. Aplicando la técnica multifractal, el método de la caja de contar, la diferencia normalizada del índice de nieve NDSI y la relación de bandas de imágenes satelitales 3/5 se analizó el comportamiento de la superficie glaciar de dos nevados tropicales, el Huandoy y el pastoruri, en la Cordillera Blanca de perú, en años en que se presentaron los eventos El Niño y La Niña. Las modernas técnicas multifractales devinieron muy versátiles, prácticas y sensibles para mostrar la incidencia de los eventos El Niño y La Niña en el espectro multifractal y para estimar la superficie glaciar. El Huandoy y el pastoruri disminuyeron aproximadamente un 10% de su área glaciar en un periodo de 22 años. La estimación de la superficie glaciar por métodos convencionales y multifractales resultó no significativa en un análisis como muestras relacionadas o pareadas, lo cual significa que es indistinto utilizar el SIG o multifractales para determinar el área glaciar. La dimensión D0 para la superficie glaciar fue de 1,8. Descriptores: el niño y la niña, cambio climático, retroceso glaciar, nDsi, relación de bandas 3/5, multifractales. ABSTRACT The events el niño and la niña in the tropical Pacific ocean occur periodically over time and have a clear incidence on growth and maintenance of the glacier surface of snow-capped mountains. The behaviour of the glacier surfaces of two snowy tropicals, the Pastoruri and the huandoy, located in the cordillera blanca of Perú were studied in the years when the events el niño and la niña occurred. This study was done applying a multifractal technique, the method of box counting, the normalized difference snow index nDsi and the relationship of bands of satellital images 3/5. multifractals modern techniques became very versatile, practical and sensitive in showing the impact of el niño and la niña in the multifractal spectral and for the estimation of glacier surface. The huandoy and Pastoruri decrease in average glacier surface was 10% in the last 22 years. The estimation of glacier surface for the conventional or multifractal methods was not significantly different in analysis such as related samples, which means that there is no distinction when using the siG or multifractals for determining the glacier area. The dimension D0 for the glacier surface was 1,8. Keywords: el niño and la niña, climate change, glacier retreat, nDsi, ratio of bands 3/5, multifractals.

Two Tropical Routes for the Remote Influence of the Northern Tropical Atlantic on the Indo−western Pacific Summer Climate

2020 ◽  
pp. 1-51
Author(s):  
Yuhei Takaya ◽  
Naoaki Saito ◽  
Ichiro Ishikawa ◽  
Shuhei Maeda
Keyword(s):  
El Niño ◽  
El Nino ◽  
Walker Circulation ◽  
La Niña ◽  
Western Pacific ◽  
Tropical Atlantic ◽  
Summer Climate ◽  
La Nina ◽  
The Impact ◽  
Northern Tropical Atlantic

AbstractThis study investigates the influence of sea surface temperature (SST) in the northern tropical Atlantic (NTA) on the Indo−western Pacific summer climate by analyzing record-high NTA SSTs summer in 2010. In that time, a decaying El Niño and developing La Niña were accompanied by widespread anomalous climate conditions in the Indo-western Pacific. These conditions are typical of summers that follow El Niño events and are often explained as being due to the influence of Indian Ocean warming induced by the El Niño. Meanwhile, the record high NTA SSTs that also resulted from the influence of the El Niño, the negative phase of the North Atlantic Oscillation as well as the interdecadal-and-longer NTA SST variability, is one of possible causes of anomalous conditions in the Indo−western Pacific. The results of sensitivity experiments using a coupled atmosphere−ocean model clearly indicate that the high NTA SSTs had a considerable influence on the summer weather in the Indo−western Pacific via two tropical routes: an eastbound route that involved a reinforcement of the atmospheric equatorial Kelvin wave and a westbound route that involved altering the Walker circulation over the Atlantic−Pacific region. The altered Walker circulation facilitated the transition to La Niña, amplifying the impact on the western North Pacific monsoon. Further evaluation reveals that both the interannual and interdecadal-and-longer variability of the NTA SST contributed to the anomalous Indo−western Pacific summer. The results highlight the interannual to multidecadal predictability of the Indo−western Pacific summer climate that originates in the NTA.

scholarly journals An assessment of El Niño and La Niña impacts focused on monthly and seasonal rainfall and extreme dry/precipitation events in mountain regions of Colombia and México

2016 ◽  
Vol 42 ◽  
pp. 23-33 ◽  
Author(s):  
María Carolina Pinilla Herrera ◽  
Carlos Andrés Pinzón Correa
Keyword(s):  
El Niño ◽  
El Nino ◽  
Dry Season ◽  
La Niña ◽  
Seasonal Rainfall ◽  
Seasonal Precipitation ◽  
La Nina ◽  
Mountain Landscapes ◽  
The Impact ◽  
Precipitation Events

Abstract. The influence of El Niño and La Niña on monthly and seasonal rainfall over mountain landscapes in Colombia and México was assessed based on the Oceanic Niño Index (ONI). A statistical analysis was develop to compare the extreme dry/precipitation events between El Niño, La Niña and Neutral episodes. For both areas, it was observed that El Niño and La Niña episodes are associated with important increases or decreases in rainfall. However, Neutral episodes showed the highest occurrence of extreme precipitation/dry events. For a better understanding of the impact of El Niño and La Niña on seasonal precipitation, we did a compound and a GIS analyses to define the high/low probability of above, below or normal seasonal precipitation under El Niño, La Niña and cold/warm Neutral episodes. In San Vicente, Colombia the below-normal seasonal rainfall was identified during El Niño and Neutral episodes in the dry season JJA. In this same municipality we also found above-normal seasonal rainfall during La Niña and Neutral episodes, especially in the dry season DJF. In Tancítaro México the below-normal seasonal rainfall was identified during La Niña winters (DJF) and El Niño summers (JJA), the above-normal seasonal rainfall was found during La Niña summers (JJA) and El Niño winters (DJF).

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