scholarly journals El Niño Southern Oscillation and Its Impact on Rainfall Distribution and Productivity of Major Agricultural Crops: The Case of Kemabata Tembaro Zone, Southern Ethiopia

2020 ◽  
Author(s):  
Bereket Tesfaye Haile ◽  
Kassahun Ture Bekitie ◽  
Gudina Legesse Feyissa ◽  
Tadesse Terefe Zeleke
Keyword(s):  
Southern Oscillation ◽  
Crop Productivity ◽  
Temperature Data ◽  
Southern Ethiopia ◽  
Agricultural Crops ◽  
Cereal Crop ◽  
Rainfall Distribution ◽  
Enso Events ◽  
Central Statistical ◽  
The Impact

This study was conducted to investigate the impact of El Niño Southern Oscillation on rainfall distribution and productivity of major Agricultural crops in the Kembta Tembaro Zone of Southern Ethiopia over the past 30 years. Precipitation and temperature data were obtained from the National Meteorology Agency, crop data from the Central Statistical Agency of Ethiopia, and the Sea Surface Temperature data from the NOAA website. The rainfall trend had shown decreasing trend with high variability at all the stations (p<0.05). Over the same period, El Niño and La Niña event were observed and highly affected rainfall distribution. It was found that Coefficient Variation was greater than 30%, which indicates the area was prone to drought episodes. The impacts of the ENSO events on the yield of Maize, Wheat, Barely, Sorghum and Enset were assessed. Wheat and Maize were highly affected by the ENSO events. Enset was found to be more resistant crop to the influence of ENSO. Barely and Sorghum were affected at varying magnitude. Among the five chosen crop for this investigation two of the crops were seriously affected during the two extremes, i.e. El Niño and La Niña. From this investigation it is conclude that the overall cereal crop productivity was decreased and precipitation variability was noticed. So, having the information about ENSO phase in advance can be used to forecast ENSO and select crop types and varieties to maximize agricultural rain fed cereal crop productivity while minimizing the crop risk associated with seasonal rainfall and ENSO phases.

Impact of strong El Niño events on river discharge in South America

2021 ◽  
Author(s):  
Markus Deppner ◽  
Bedartha Goswami
Keyword(s):  
Machine Learning ◽  
Missing Data ◽  
South America ◽  
River Discharge ◽  
Amazon Basin ◽  
Missing Values ◽  
Southern Oscillation ◽  
Enso Events ◽  
Streamflow Data ◽  
The Impact

<p>The impact of the El Niño Southern Oscillation (ENSO) on rivers are well known, but most existing studies involving streamflow data are severely limited by data coverage. Time series of gauging stations fade in and out over time, which makes hydrological large scale and long time analysis or studies of rarely occurring extreme events challenging. Here, we use a machine learning approach to infer missing streamflow data based on temporal correlations of stations with missing values to others with data. By using 346 stations, from the “Global Streamflow Indices and Metadata archive” (GSIM), that initially cover the 40 year timespan in conjunction with Gaussian processes we were able to extend our data by estimating missing data for an additional 646 stations, allowing us to include a total of 992 stations. We then investigate the impact of the 6 strongest El Niño (EN) events on rivers in South America between 1960 and 2000. Our analysis shows a strong correlation between ENSO events and extreme river dynamics in the southeast of Brazil, Carribean South America and parts of the Amazon basin. Furthermore we see a peak in the number of stations showing maximum river discharge all over Brazil during the EN of 1982/83 which has been linked to severe floods in the east of Brazil, parts of Uruguay and Paraguay. However EN events in other years with similar intensity did not evoke floods with such magnitude and therefore the additional drivers of the 1982/83  floods need further investigation. By using machine learning methods to infer data for gauging stations with missing data we were able to extend our data by almost three-fold, revealing a possible heavier and spatially larger impact of the 1982/83 EN on South America's hydrology than indicated in literature.</p>

Impact of Indo-Pacific Feedback Interactions on ENSO Dynamics Diagnosed Using Ensemble Climate Simulations

2012 ◽  
Vol 25 (21) ◽  
pp. 7743-7763 ◽  
Author(s):  
A. Santoso ◽  
M. H. England ◽  
W. Cai
Keyword(s):  
Indian Ocean ◽  
Climate Model ◽  
Southern Oscillation ◽  
Ocean Basin ◽  
Climate Feedback ◽  
Enso Events ◽  
Thermocline Feedback ◽  
Enso Dynamics ◽  
The Indian Ocean ◽  
The Impact

The impact of Indo-Pacific climate feedback on the dynamics of El Niño–Southern Oscillation (ENSO) is investigated using an ensemble set of Indian Ocean decoupling experiments (DCPL), utilizing a millennial integration of a coupled climate model. It is found that eliminating air–sea interactions over the Indian Ocean results in various degrees of ENSO amplification across DCPL simulations, with a shift in the underlying dynamics toward a more prominent thermocline mode. The DCPL experiments reveal that the net effect of the Indian Ocean in the control runs (CTRL) is a damping of ENSO. The extent of this damping appears to be negatively correlated to the coherence between ENSO and the Indian Ocean dipole (IOD). This type of relationship can arise from the long-lasting ENSO events that the model simulates, such that developing ENSO often coincides with Indian Ocean basin-wide mode (IOBM) anomalies during non-IOD years. As demonstrated via AGCM experiments, the IOBM enhances western Pacific wind anomalies that counteract the ENSO-enhancing winds farther east. In the recharge oscillator framework, this weakens the equatorial Pacific air–sea coupling that governs the ENSO thermocline feedback. Relative to the IOBM, the IOD is more conducive for ENSO growth. The net damping by the Indian Ocean in CTRL is thus dominated by the IOBM effect which is weaker with stronger ENSO–IOD coherence. The stronger ENSO thermocline mode in DCPL is consistent with the absence of any IOBM anomalies. This study supports the notion that the Indian Ocean should be viewed as an integral part of ENSO dynamics.

scholarly journals Interactions of ENSO, the IOD, and the SAM in CMIP3 Models

2011 ◽  
Vol 24 (6) ◽  
pp. 1688-1704 ◽  
Author(s):  
Wenju Cai ◽  
Arnold Sullivan ◽  
Tim Cowan
Keyword(s):  
Southern Oscillation ◽  
Global Climate ◽  
Coupled Model ◽  
Southern Annular Mode ◽  
Enso Events ◽  
Intercomparison Project ◽  
Wave Trains ◽  
Induced Signal ◽  
The Impact ◽  
The Relationship

Abstract Simulations of individual global climate drivers using models from the Coupled Model Intercomparison Project phase 3(CMIP3) have been examined; however, the relationship among them has not been assessed. This is carried out to address several important issues, including the likelihood of the southern annular mode (SAM) forcing Indian Ocean dipole (IOD) events and the possible impact of the IOD on El Niño–Southern Oscillation (ENSO) events. Several conclusions emerge from statistics based on multimodel outputs. First, ENSO signals project strongly onto the SAM, although ENSO-forced signals tend to peak before ENSO. This feature is similar to the situation associated with the IOD. The IOD-induced signal over southern Australia, through stationary equivalent Rossby barotropic wave trains, peak before the IOD itself. Second, there is no control by the SAM on the IOD, in contrast to what has been suggested previously. Indeed, no model produces a SAM–IOD relationship that supports a positive (negative) SAM driving a positive (negative) IOD event. This is the case even in models that do not simulate a statistically significant relationship between ENSO and the IOD. Third, the IOD does have an impact on ENSO. The relationship between ENSO and the IOD in the majority of models is far weaker than the observed. However, the ENSO’s influence on the IOD is boosted by a spurious oceanic teleconnection, whereby ENSO discharge–recharge signals transmit to the Sumatra–Java coast, generating thermocline anomalies and changing IOD properties. Without the spurious oceanic teleconnection, the influence of the IOD on ENSO is comparable to the impact of ENSO on the IOD. Other model deficiencies are discussed.

Simulating ENSO SSTAs from TAO/TRITON Winds: The Impacts of 20 Years of Buoy Observations in the Pacific Waveguide and Comparison with Reanalysis Products

2017 ◽  
Vol 30 (3) ◽  
pp. 1041-1059 ◽  
Author(s):  
Andrew M. Chiodi ◽  
D. E. Harrison
Keyword(s):  
Wind Stress ◽  
Southern Oscillation ◽  
Surface Wind ◽  
Major Elements ◽  
Ocean Model ◽  
Tropical Pacific ◽  
Wind Fields ◽  
Enso Events ◽  
The Pacific ◽  
The Impact

Abstract The fundamental importance of near-equatorial zonal wind stress in the evolution of the tropical Pacific Ocean’s seasonal cycle and El Niño–Southern Oscillation (ENSO) events is well known. It has been two decades since the TAO/TRITON buoy array was deployed, in part to provide accurate surface wind observations across the Pacific waveguide. It is timely to revisit the impact of TAO/TRITON winds on our ability to simulate and thereby understand the evolution of sea surface temperature (SST) in this region. This work shows that forced ocean model simulations of SST anomalies (SSTAs) during the periods with a reasonably high buoy data return rate can reproduce the major elements of SSTA variability during ENSO events using a wind stress field computed from TAO/TRITON observations only. This demonstrates that the buoy array usefully fulfills its waveguide-wind-measurement purpose. Comparison of several reanalysis wind fields commonly used in recent ENSO studies with the TAO/TRITON observations reveals substantial biases in the reanalyses that cause substantial errors in the variability and trends of the reanalysis-forced SST simulations. In particular, the negative trend in ERA-Interim is much larger and the NCEP–NCAR Reanalysis-1 and NCEP–DOE Reanalysis-2 variability much less than seen in the TAO/TRITON wind observations. There are also mean biases. Thus, even with the TAO/TRITON observations available for assimilation into these wind products, there remain oceanically important differences. The reanalyses would be much more useful for ENSO and tropical Pacific climate change study if they would more effectively assimilate the TAO/TRITON observations.

scholarly journals The Impact of El Niño - Southern Oscillation Events on South America

2006 ◽  
Vol 6 ◽  
pp. 221-225 ◽  
Author(s):  
J. L. Santos
Keyword(s):  
South America ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Ultra Violet ◽  
Risk Groups ◽  
Natural Ecosystems ◽  
Enso Events ◽  
Ultra Violet Radiation ◽  
The Impact

Abstract. The presence of ENSO Events in South America is felt in two ways: a) through its effects on both the atmosphere and ocean systems, and b) through its impacts on natural ecosystems (both marine and terrestrial) and on societal and economical sectors (like fisheries, health, and agriculture). The main effects of El Niño/La Niña are: Increment/Decrement of sea surface temperature and salinity, Increment/Decrement of sea level and wave activity, Increment/Decrement of air temperature and amount of ultra violet radiation reaching the surface of the earth, and Changes in the rainfall and evaporation patterns. It is not easy to make an "average" pattern of ENSO impacts for a variety of reasons: the impacts depend greatly of factors like geographical extent and position of the oceanic anomalies, and intensity and timing of the anomalies; also the influence of social, economic and political structures determines whether climate anomalies caused by ENSO in a particular region will lead to severe societal and economical impacts. The scientific community also plays a potential role in the extent of the impacts that ENSO can produce, if scientists can provide information on the impact of the presence of ENSO by identifying and focusing on its precursors, intervention could be taken early enough. There is however, something to be said against that: information can be misleading, target inappropriate at-risk groups, or generate a false sense of security.

scholarly journals Minimal impact of model biases on northern hemisphere ENSO teleconnections

2020 ◽  
Author(s):  
Nicholas L. Tyrrell ◽  
Alexey Yu. Karpechko
Keyword(s):  
Northern Hemisphere ◽  
General Circulation ◽  
Southern Oscillation ◽  
Polar Vortex ◽  
Aleutian Low ◽  
Enso Events ◽  
Model Biases ◽  
The Impact ◽  
Strong Enso ◽  
Bias Corrections

Abstract. Correctly capturing the teleconnection between the El Niño–Southern Oscillation (ENSO) and Europe is of importance for seasonal prediction. Here we investigate how systematic model biases may affect this teleconnection. A two–step bias–correction process is applied to an atmospheric general circulation model to reduce errors in the climatology. The bias–corrections are applied to the troposphere and stratosphere separately and together to produce a range of climates. ENSO type sensitivity experiments are then performed to reveal the impact of differing climatologies on ENSO–Europe teleconnections. The bias–corrections do not affect the response of the tropical atmosphere, nor the Aleutian Low, to strong ENSO anomalies. However, the anomalous upward wave flux and the response of the northern hemisphere polar vortex differs between the climatologies. We attribute this to a reduced sensitivity of waves to the strength of the Aleutian Low. Despite the differing responses of the polar vortex, the NAO response is similar between the climatologies, implying that for strong ENSO events a stratospheric response may not be necessary for the ENSO–North Atlantic teleconnection.

Multidecadal Modulations of ENSO influence on cyclogenesis in the Tropical Atlantic

2020 ◽  
Author(s):  
Adama Badiane ◽  
Belén Rodríguez-Fonseca ◽  
Teresa Losada ◽  
Abdou Lahat Dieng ◽  
Saidou Moustapha Sall
Keyword(s):  
Southern Oscillation ◽  
Deep Convection ◽  
Vertical Wind Shear ◽  
Tropical Atlantic ◽  
Enso Events ◽  
Tropical North Atlantic ◽  
Development Region ◽  
Decadal Variations ◽  
The Impact ◽  
Sst Anomalies

<p align="justify"><span>The impact of ENSO (El Niño Southern Oscillation) events on the cyclogenesis of the eastern tropical North Atlantic is highlighted, focusing on decadal variations of the interannual relationship at the Senegalese coast, which is the main cyclone development region (MDR). SST anomalies in the Equatorial Pacific associated with ENSO events affect vertical wind shear over the eastern Atlantic, by inducing strong subsidence of dry air over the eastern Atlantic which tends to inhibit deep convection and thus be unfavorable to cyclonic activity. Based on 20yr- correlations between the number of cyclones that are born in the MDR and ENSO index, we have selected two different periods of study (period1: 1950-1969; and period2: 1996-2015).The results show that period2 presents the highest scores of negative correlations between ENSO and tropical Atlantic cyclogenesis. Although there is an intensification of ENSO events during period2 compared to period1, we have found that decadal changes in climatology have a more significant effect on the MDR than the interannual changes. Additionally, the changes in the interannual signal appear to be related to the concomitant action of interannual SST anomalies over the whole tropical basins.</span></p>

scholarly journals Evaluation of the Hydrological Cycle in the ECHAM5 Model

2006 ◽  
Vol 19 (16) ◽  
pp. 3810-3827 ◽  
Author(s):  
Stefan Hagemann ◽  
Klaus Arpe ◽  
Erich Roeckner
Keyword(s):  
General Circulation ◽  
Hydrological Cycle ◽  
Southern Oscillation ◽  
Regional Scale ◽  
Vertical Resolution ◽  
Model Simulations ◽  
Enso Events ◽  
Precipitation Response ◽  
Simulated Precipitation ◽  
The Impact

Abstract This study investigates the impact of model resolution on the hydrological cycle in a suite of model simulations using a new version of the Max Planck Institute for Meteorology atmospheric general circulation model (AGCM). Special attention is paid to the evaluation of precipitation on the regional scale by comparing model simulations with observational data in a number of catchments representing the major river systems on the earth in different climate zones. It is found that an increased vertical resolution, from 19 to 31 atmospheric layers, has a beneficial effect on simulated precipitation with respect to both the annual mean and the annual cycle. On the other hand, the influence of increased horizontal resolution, from T63 to T106, is comparatively small. Most of the improvements at higher vertical resolution, on the scale of a catchment, are due to large-scale moisture transport, whereas the impact of local water recycling through evapotranspiration is somewhat smaller. At high horizontal and vertical resolution (T106L31) the model captures most features of the observed hydrological cycle over land, and also the local and remote precipitation response to El Niño–Southern Oscillation (ENSO) events. Major deficiencies are the overestimation of precipitation over the oceans, especially at higher vertical resolution, along steep mountain slopes and during the Asian summer monsoon season, whereas a dry bias exists over Australia. In addition, the model fails to reproduce the observed precipitation response to ENSO variability in the Indian Ocean and Africa. This might be related to missing coupled air–sea feedbacks in an AGCM forced with observed sea surface temperatures.

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