scholarly journals Teleconnection Between ENSO and Wind-Wave Climate Under the Influence of Monsoon in the Bay of Bengal Region

2020 ◽  
Vol 15 (3) ◽  
pp. 463-469
Author(s):  
Mourani Sinha ◽  
Amitava Jana
Keyword(s):  
Bay Of Bengal ◽  
El Niño ◽  
Wind Wave ◽  
El Nino ◽  
Southern Oscillation ◽  
Function Analysis ◽  
Deep Ocean ◽  
Principal Component ◽  
Wavelet Coherence ◽  
Enso Indices

Wind-wave parameters like the significant wave height (SWH)impacts considerably deep ocean and maritime activities and lives of all those dwelling near the coast.Prediction of such a parameter has immense utility during extreme conditions. Teleconnection features are explored between the most widely studied climate mode, the El Niño-Southern Oscillation or ENSO and the SWHparameter in the Bay of Bengal (BB) region under the influence of monsoon in this study.In two separate experiments the SWH data of the BB region for the period 1958-2001 and the period 2006-2016 is subjected to empirical orthogonal function analysis to split the data into spatial and temporal parts.The temporal variations are of annual periodicity for both the data sets. On analysis teleconnection feature of lower (higher) SWH during El Niño (La Niña) episodes is observed in the BB region. Significant correlationis observed between SWH and the ENSO indices during the summer monsoon months.The continuous wavelet power spectrum is generated using the first principal component (PC1) extracted above. It exhibits significant regions in the 0.5-1 year band resembling the monsoon variability in the BB region. To determine how SWH is related to the ENSO indices wavelet coherence is applied for the BB region.The higher coherency regions are found in the 0.5-1 year band which maybe related to the monsoon oscillation having similar periodicity. Thus the SWH and ENSO relationship in the BB region is influenced by the monsoon significantly.

scholarly journals Teleconnections between Monthly Rainfall Variability and Large-Scale Climate Indices in Southwestern Colombia

Water ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1863 ◽  
Author(s):  
Teresita Canchala ◽  
Wilfredo Alfonso-Morales ◽  
Wilmar Loaiza Cerón ◽  
Yesid Carvajal-Escobar ◽  
Eduardo Caicedo-Bravo
Keyword(s):  
Water Resources ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Rainfall Variability ◽  
Monthly Rainfall ◽  
Wavelet Coherence ◽  
Climate Indices ◽  
Annual Scale ◽  
Wavelet Coherence Analysis

Given that the analysis of past monthly rainfall variability is highly relevant for the adequate management of water resources, the relationship between the climate-oceanographic indices, and the variability of monthly rainfall in Southwestern Colombia at different time scales was chosen as the research topic. It should also be noted that little-to-no research has been carried out on this topic before. For the purpose of conducting this research, we identified homogeneous rainfall regions while using Non-Linear Principal Component Analysis (NLPCA) and Self-Organizing Maps (SOM). The rainfall variability modes were obtained from the NLPCA, while their teleconnection in relation to the climate indices was obtained from Pearson’s Correlations and Wavelet Transform. The regionalization process clarified that Nariño has two regions: the Andean Region (AR) and the Pacific Region (PR). The NLPCA showed two modes for the AR, and one for the PR, with an explained variance of 75% and 48%, respectively. The correlation analyses between the first nonlinear components of AR and PR regarding climate indices showed AR high significant positive correlations with Southern Oscillation Index (SOI) index and negative correlations with El Niño/Southern Oscillation (ENSO) indices. PR showed positive ones with Niño1 + 2, and Niño3, and negative correlations with Niño3.4 and Niño4, although their synchronous relationships were not statistically significant. The Wavelet Coherence analysis showed that the variability of the AR rainfall was influenced principally by the Niño3.4 index on the 3–7-year inter-annual scale, while PR rainfall were influenced by the Niño3 index on the 1.5–3-year inter-annual scale. The El Niño (EN) events lead to a decrease and increase in the monthly rainfall on AR and PR, respectively, while, in the La Niña (LN) events, the opposite occurred. These results that are not documented in previous studies are useful for the forecasting of monthly rainfall and the planning of water resources in the area of study.

scholarly journals Deep ocean mass fluxes in the coastal upwelling off Mauritania from 1988 to 2012: variability on seasonal to decadal timescales

2015 ◽  
Vol 12 (21) ◽  
pp. 17643-17692 ◽  
Author(s):  
G. Fischer ◽  
O. Romero ◽  
U. Merkel ◽  
B. Donner ◽  
M. Iversen ◽  
...  
Keyword(s):  
El Niño ◽  
Coastal Upwelling ◽  
El Nino ◽  
Southern Oscillation ◽  
Deep Ocean ◽  
Dust Particles ◽  
Boreal Winter ◽  
Ocean Mass ◽  
Mass Fluxes ◽  
Sahel Region

Abstract. A more than two-decadal sediment trap record from the Eastern Boundary Upwelling Ecosystem (EBUE) off Cape Blanc, Mauritania, is analyzed with respect to deep ocean mass fluxes, flux components and their variability on seasonal to decadal timescales. The total mass flux revealed interannual fluctuations which were superimposed by fluctuations on decadal timescales possibly linked to the Atlantic Multidedadal Oscillation (AMO). High winter fluxes of biogenic silica (BSi), used as a measure of marine production mostly by diatoms largely correspond to a positive North Atlantic Oscillation (NAO) index during boreal winter (December–March). However, this relationship is weak. The highest positive BSi anomaly was in winter 2004–2005 when the NAO was in a neutral state. More episodic BSi sedimentation events occurred in several summer seasons between 2001 and 2005, when the previous winter NAO was neutral or even negative. We suggest that distinct dust outbreaks and deposition in the surface ocean in winter but also in summer/fall enhanced particle sedimentation and carbon export on rather short timescales via the ballasting effect, thus leading to these episodic sedimentation events. Episodic perturbations of the marine carbon cycle by dust outbreaks (e.g. in 2005) weakened the relationships between fluxes and larger scale climatic oscillations. As phytoplankton biomass is high throughout the year in our study area, any dry (in winter) or wet (in summer) deposition of fine-grained dust particles is assumed to enhance the efficiency of the biological pump by being incorporated into dense and fast settling organic-rich aggregates. A good correspondence between BSi and dust fluxes was observed for the dusty year 2005, following a period of rather dry conditions in the Sahara/Sahel region. Large changes of all fluxes occurred during the strongest El Niño–Southern Oscillation (ENSO) in 1997–1999 where low fluxes were obtained for almost one year during the warm El Niño and high fluxes in the following cold La Niña phase. Bakun (1990) suggested an intensification of coastal upwelling due to increased winds ("Bakun upwelling intensification hypothesis", Cropper et al., 2014) and global change. We did not observe an increase of any flux component off Cape Blanc during the past two and a half decades which might support this hypothesis. Furthermore, fluxes of mineral dust did not show any positive or negative trends over time which would have suggested enhanced desertification or "Saharan greening" during the last few decades.

scholarly journals A skewed perspective of the Indian rainfall–El Niño–Southern Oscillation (ENSO) relationship

2020 ◽  
Vol 24 (11) ◽  
pp. 5473-5489 ◽  
Author(s):  
Justin Schulte ◽  
Frederick Policielli ◽  
Benjamin Zaitchik
Keyword(s):  
Time Series ◽  
Time Domain ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Wavelet Coherence ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
The Time Domain ◽  
Time Domain Correlation

Abstract. Wavelet coherence is a method that is commonly used in hydrology to extract scale-dependent, nonstationary relationships between time series. However, we show that the method cannot always determine why the time-domain correlation between two time series changes in time. We show that, even for stationary coherence, the time-domain correlation between two time series weakens if at least one of the time series has changing skewness. To overcome this drawback, a nonlinear coherence method is proposed to quantify the cross-correlation between nonlinear modes embedded in the time series. It is shown that nonlinear coherence and auto-bicoherence spectra can provide additional insight into changing time-domain correlations. The new method is applied to the El Niño–Southern Oscillation (ENSO) and all-India rainfall (AIR), which is intricately linked to hydrological processes across the Indian subcontinent. The nonlinear coherence analysis showed that the skewness of AIR is weakly correlated with that of two ENSO time series after the 1970s, indicating that increases in ENSO skewness after the 1970s at least partially contributed to the weakening ENSO–AIR relationship in recent decades. The implication of this result is that the intensity of skewed El Niño events is likely to overestimate India's drought severity, which was the case in the 1997 monsoon season, a time point when the nonlinear wavelet coherence between AIR and ENSO reached its lowest value in the 1871–2016 period. We determined that the association between the weakening ENSO–AIR relationship and ENSO nonlinearity could reflect the contribution of different nonlinear ENSO modes to ENSO diversity.

scholarly journals Precipitação na América do Sul: Médias Climáticas e Padrões da Variabilidade no Período entre 1979 e 2008

2016 ◽  
Vol 9 (1) ◽  
pp. 032
Author(s):  
Éder Leandro Maier ◽  
Juliana Costi ◽  
Sandra Barreira ◽  
Jefferson Cardia Simões
Keyword(s):  
South America ◽  
North Atlantic ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Principal Component ◽  
Monthly Precipitation ◽  
Tropical Regions ◽  
The North ◽  
North Atlantic Variability

Este artigo discute os principais padrões médios e anômalos da precipitação sobre a América do Sul no período 1979–2008. Para isso foram manipulados dados mensais da precipitação observada em 890 estações meteorológicas localizadas na Argentina, Bolívia, Brasil, Paraguai e Uruguai ao longo desse período de trinta anos. As médias climáticas foram subtraídas das amostras, originando as anomalias, as quais foram agrupadas por meio da Análise das Componentes Principais em dois modos. No modo T se identificou 6 componentes principais, que explicam 35% da variância e representam 12 padrões espaciais anômalos originados, principalmente, pelo fenômeno El Niño–Oscilação Sul (ENOS) e pela variabilidade do Atlântico Norte. No modo S foram identificadas 8 zonas em que a variabilidade temporal das séries anômalas é semelhante, sendo que o ENOS prevalece no controle das anomalias nas zonas situadas na região equatorial e extratropical, além disso, a variabilidade do Atlântico Norte pode maximizar ou minimizar os impactos do ENOS. A frequência de recorrência desses estresses hídrico variam entre 20 e 60 meses.  This article discusses mean and anomalous rainfall patterns over South America in the period 1979–2008. For that we handled monthly precipitation data observed at 890 meteorological stations located in Argentina, Bolivia, Brazil, Paraguay and Uruguay over this thirty years period. Climatic means were subtracted from the data, resulting in anomalies that were grouped by Principal Component Analysis in two modes. We identified 6 main components in the T mode, which explain 35% of the variance and represent 12 anomalous spatial patterns originated mainly by El Niño–Southern Oscillation (ENSO) phenomenon and the North Atlantic variability. In mode S, we identified eight zones where the series temporal variability is also anomalous, and the ENOS prevails as the anomalies controller in the equatorial and extra tropical regions. Further, North Atlantic variability may maximize or minimize the ENSO impact. The frequency of these recurrent water stresses range from 20 to 60 months. Keywords: Precipitation, South America, PCA  

scholarly journals Wavelet coherence between ENSO indices and two precipitation database for the Andes region of Colombia

2020 ◽  
Author(s):  
Diana Cristina Díaz G. ◽  
Nancy Villegas
Keyword(s):  
El Niño ◽  
El Nino ◽  
La Niña ◽  
Wavelet Coherence ◽  
La Nina ◽  
El Niño Events ◽  
Wavelet Coherence Analysis ◽  
El Nino Events ◽  
Enso Indices

The influence of El Niño Southern Oscillation (ENSO) on Colombia's hydrological variables has been shown in different studies. Most of the methodologies implemented have identified linear relationships and have associated the warm (cold) phase called El Niño (La Niña) with negative (positive) rainfall and streamflow anomalies. One of the most adverse impacts founded is the reduction in water supply during the warm phase. Therefore, it is necessary to study the linkage between ENSO and precipitation variability for efficient management of water resources. Consequently, the present paper has two purposes. The first one is to explore nonlinear correlations of the ENSO-precipitation relationship, particularly for specific regions where the freshwater resources have been significantly reduced during El Niño events. The second one is to identify which indices will enable in improving the predictability of hydro-climatological variables. The research was based on the wavelet coherence analysis of monthly precipitation time series from 1981-2016 and the ENSO indices for the same period. The results show that ENSO events influence the precipitation as periods of rainfall deficit or excess. Also, precipitation is organized in bands and that the 2–8-year scales explain most of their variance. The most significant sectors are those that cover El Niño events. In contrast, sectors are smaller when La Niña episodes. Then impacts on precipitation tend to be greater for warm events. Results also allowed to identify that El Niño 3, Niño 3,4, ONI, and BEST indices can be good indicators for forecasting work in these specific places. The use of two kinds of data, one in situ and the other from CHIRPS program, allows to establish the feasibility of using data from satellite origin in regions without enough information; the results showed that CHIRPS data tend to report fewer anomalies than data in situ. However, the coherence structure is similar, but in periods between 36 and 48 months, there were discrepancies of pi/4 in the phase difference, that is, between 3 and 6 months of difference in lags calculated with each database.

scholarly journals Global fire activity patterns (1996–2006) and climatic influence: an analysis using the World Fire Atlas

2008 ◽  
Vol 8 (7) ◽  
pp. 1911-1924 ◽  
Author(s):  
Y. Le Page ◽  
J. M. C. Pereira ◽  
R. Trigo ◽  
C. da Camara ◽  
D. Oom ◽  
...  
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Function Analysis ◽  
European Space Agency ◽  
Global Scale ◽  
Fire Dynamics ◽  
Fire Activity ◽  
Fire Atlas ◽  
The Impact

Abstract. Vegetation fires have been acknowledged as an environmental process of global scale, which affects the chemical composition of the troposphere, and has profound ecological and climatic impacts. However, considerable uncertainty remains, especially concerning intra and inter-annual variability of fire incidence. The main goals of our global-scale study were to characterise spatial-temporal patterns of fire activity, to identify broad geographical areas with similar vegetation fire dynamics, and to analyse the relationship between fire activity and the El Niño-Southern Oscillation. This study relies on 10 years (mid 1996–mid 2006) of screened European Space Agency World Fire Atlas (WFA) data, obtained from Along Track Scanning Radiometer (ATSR) and Advanced ATSR (AATSR) imagery. Empirical Orthogonal Function analysis was used to reduce the dimensionality of the dataset. Regions of homogeneous fire dynamics were identified with cluster analysis, and interpreted based on their eco-climatic characteristics. The impact of 1997–1998 El Niño is clearly dominant over the study period, causing increased fire activity in a variety of regions and ecosystems, with variable timing. Overall, this study provides the first global decadal assessment of spatial-temporal fire variability and confirms the usefulness of the screened WFA for global fire ecoclimatology research.

scholarly journals Deep ocean mass fluxes in the coastal upwelling off Mauritania from 1988 to 2012: variability on seasonal to decadal timescales

2016 ◽  
Vol 13 (10) ◽  
pp. 3071-3090 ◽  
Author(s):  
Gerhard Fischer ◽  
Oscar Romero ◽  
Ute Merkel ◽  
Barbara Donner ◽  
Morten Iversen ◽  
...  
Keyword(s):  
El Niño ◽  
Large Scale ◽  
Coastal Upwelling ◽  
El Nino ◽  
Southern Oscillation ◽  
Deep Ocean ◽  
Dust Particles ◽  
Ocean Mass ◽  
Mass Fluxes ◽  
Sahel Region

Abstract. A more than two-decadal sediment trap record from the Eastern Boundary Upwelling Ecosystem (EBUE) off Cape Blanc, Mauritania, is analysed with respect to deep ocean mass fluxes, flux components and their variability on seasonal to decadal timescales. The total mass flux revealed interannual fluctuations which were superimposed by fluctuations on decadal timescales. High winter fluxes of biogenic silica (BSi), used as a measure of marine production (mostly by diatoms) largely correspond to a positive North Atlantic Oscillation (NAO) index (December–March). However, this relationship is weak. The highest positive BSi anomaly was in winter 2004–2005 when the NAO was in a neutral state. More episodic BSi sedimentation events occurred in several summer seasons between 2001 and 2005, when the previous winter NAO was neutral or even negative. We suggest that distinct dust outbreaks and deposition in the surface ocean in winter and occasionally in summer/autumn enhanced particle sedimentation and carbon export on short timescales via the ballasting effect. Episodic perturbations of the marine carbon cycle by dust outbreaks (e.g. in 2005) might have weakened the relationships between fluxes and large-scale climatic oscillations. As phytoplankton biomass is high throughout the year, any dry (in winter) or wet (in summer) deposition of fine-grained dust particles is assumed to enhance the efficiency of the biological pump by incorporating dust into dense and fast settling organic-rich aggregates. A good correspondence between BSi and dust fluxes was observed for the dusty year 2005, following a period of rather dry conditions in the Sahara/Sahel region. Large changes of all bulk fluxes occurred during the strongest El Niño-Southern Oscillation (ENSO) in 1997–1999 where low fluxes were obtained for almost 1 year during the warm El Niño and high fluxes in the following cold La Niña phase. For decadal timescales, Bakun (1990) suggested an intensification of coastal upwelling due to increased winds (''Bakun upwelling intensification hypothesis''; Cropper et al., 2014) and global climate change. We did not observe an increase of any flux component off Cape Blanc during the past 2 and a half decades which might support this. Furthermore, fluxes of mineral dust did not show any positive or negative trends over time which might suggest enhanced desertification or ''Saharan greening'' during the last few decades.

scholarly journals The polar expression of ENSO and sea-ice variability as recorded in a South Pole ice core

2002 ◽  
Vol 35 ◽  
pp. 430-436 ◽  
Author(s):  
Eric A. Meyerson ◽  
Paul A. Mayewski ◽  
Karl J. Kreutz ◽  
L. David Meeker ◽  
Sallie I. Whitlow ◽  
...  
Keyword(s):  
Sea Ice ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Function Analysis ◽  
Ice Core ◽  
South Pole ◽  
Proxy Record ◽  
Sea Ice Extent ◽  
Southeastern Pacific

AbstractAn annually dated ice core recovered from South Pole (2850 m a.s.l.) in 1995, that covers the period 1487–1992, was analyzed for the marine biogenic sulfur species methanesulfonate (MS). Empirical orthogonal function analysis is used to calibrate the high-resolution MS series with associated environmental series for the period of overlap (1973–92). Utilizing this calibration we present a ~500 year long proxy record of the polar expression of the El Niño–Southern Oscillation (ENSO) and southeastern Pacific sea-ice extent variations. These records reveal short-term periods of increased (1800–50, 1900–40) and decreased sea-ice extent (1550–1610, 1660–1710, 1760–1800). In general, increased (decreased) sea-ice extent is associated with a higher (lower) frequency of El Niño events.

scholarly journals An interaction network perspective on the relation between patterns of sea surface temperature variability and global mean surface temperature

2014 ◽  
Vol 5 (1) ◽  
pp. 1-14 ◽  
Author(s):  
A. Tantet ◽  
H. A. Dijkstra
Keyword(s):  
Community Structure ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Function Analysis ◽  
Sea Surface ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation

Abstract. On interannual- to multidecadal timescales variability in sea surface temperature appears to be organized in large-scale spatiotemporal patterns. In this paper, we investigate these patterns by studying the community structure of interaction networks constructed from sea surface temperature observations. Much of the community structure can be interpreted using known dominant patterns of variability, such as the El Niño/Southern Oscillation and the Atlantic Multidecadal Oscillation. The community detection method allows us to bypass some shortcomings of Empirical Orthogonal Function analysis or composite analysis and can provide additional information with respect to these classical analysis tools. In addition, the study of the relationship between the communities and indices of global surface temperature shows that, while El Niño–Southern Oscillation is most dominant on interannual timescales, the Indian West Pacific and North Atlantic may also play a key role on decadal timescales. Finally, we show that the comparison of the community structure from simulations and observations can help detect model biases.

Sign in / Sign up

Export Citation Format

Share Document