scholarly journals ENSO and Extreme Rainfall Events in South America

2009 ◽  
Vol 22 (7) ◽  
pp. 1589-1609 ◽  
Author(s):  
Alice M. Grimm ◽  
Renata G. Tedeschi
Keyword(s):  
South America ◽  
Extreme Events ◽  
El Niño ◽  
El Nino ◽  
Extreme Rainfall ◽  
La Niña ◽  
Enso Cycle ◽  
Extreme Rainfall Events ◽  
Rainfall Events ◽  
La Nina

Abstract The influence of the opposite phases of ENSO on the frequency of extreme rainfall events over South America is analyzed for each month of the ENSO cycle on the basis of a large set of daily station rainfall data and compared with the influence of ENSO on the monthly total rainfall. The analysis is carried out with station data and their gridded version and the results are consistent. Extreme events are defined as 3-day mean precipitation above the 90th percentile. The mean frequencies of extreme events are determined for each month and for each category of year (El Niño, La Niña, and neutral), and the differences between El Niño and neutral years and La Niña and neutral years are computed. Changes in the mean intensity of extreme events are also investigated. Significant ENSO signals in the frequency of extreme events are found over extensive regions of South America during different periods of the ENSO cycle. Although ENSO-related changes in intensity show less significance and spatial coherence, there are some robust changes in several regions, especially in southeastern South America. The ENSO-related changes in the frequency of extreme rainfall events are generally coherent with changes in total monthly rainfall quantities. However, significant changes in extremes are much more extensive than the corresponding changes in monthly rainfall because the highest sensitivity to ENSO seems to be in the extreme range of daily precipitation. This is important, since the most dramatic consequences of climate variability result from changes in extreme events. The pattern of frequency changes produced by El Niño and La Niña episodes with respect to neutral years is roughly symmetric, but there are several examples of nonlinearity in the ENSO regional teleconnections.

scholarly journals The Effect of Non-Seasonal Climate Variations on Extreme Rainfall Events in Early Rainy Season Onset in Southest West Java Province

2020 ◽  
Vol 10 (2) ◽  
pp. 173
Author(s):  
Agus Safril ◽  
Hadi Saputra ◽  
Siswanto Siswanto ◽  
Aulia Nisa’ul Khoir ◽  
Aditya Kusuma Al Arif
Keyword(s):  
El Niño ◽  
Rainy Season ◽  
El Nino ◽  
Extreme Rainfall ◽  
Local Circulation ◽  
West Java ◽  
Extreme Rainfall Events ◽  
Rainfall Events ◽  
Seasonal Climate ◽  
La Nina

The region of Tasikmalaya, Garut, and Pangandaran (hereafter mentioned as Southeast West Java Province) experienced extreme precipitation that occurred on September 16, 2016, October 6, 2017, and November 5, 2018, which then followed by flood. The characteristics of these extreme rainfall events need to be communicated to the related disaster management agency and the local citizens as a part of understanding the risks and disaster mitigation. This paper aims to determine the relation between extreme rainfall and non-seasonal climate variations such as Madden Julian Oscillation (MJO), El Niño Southern Oscillation (ENSO), tropical storm, and local circulation that occur simultaneously. Atmosphere and ocean data, including daily rainfall, precipitable water, cloud satellite imagery, wind and sea surface temperature were used. Descriptive statistical analysis, atmospheric dynamics, and physical atmosphere were applied to characterize the event, spatially and temporally. The results showed that the MJO was a non-seasonal factor that always exists in these three early rainy season extreme rainfall events in the region. Other non-seasonal factors such as interaction between La Nina and tropical disturbance; La Nina and local circulation; and El Nino and local circulation also affected the extreme rainfall events. We conclude that the intra-seasonal climate variation of MJO and inter-annual climate anomaly of La Nina/ El Nino, tropical storm, and local circulation are among the weather generators for extreme rainfall during early rainy season (September to November) in the Southeast West Java Province.

scholarly journals Tropical cyclone contribution to extreme rainfall over southwest Pacific Island nations

2021 ◽  
Author(s):  
Anil Deo ◽  
Savin S. Chand ◽  
Hamish Ramsay ◽  
Neil J. Holbrook ◽  
Simon McGree ◽  
...  
Keyword(s):  
Tropical Cyclone ◽  
El Niño ◽  
El Nino ◽  
Extreme Rainfall ◽  
Pacific Island ◽  
Extreme Rainfall Events ◽  
Rainfall Events ◽  
Southwest Pacific ◽  
Inactive Phase ◽  
Pacific Island Nations

AbstractSouthwest Pacific nations are among some of the worst impacted and most vulnerable globally in terms of tropical cyclone (TC)-induced flooding and accompanying risks. This study objectively quantifies the fractional contribution of TCs to extreme rainfall (hereafter, TC contributions) in the context of climate variability and change. We show that TC contributions to extreme rainfall are substantially enhanced during active phases of the Madden–Julian Oscillation and by El Niño conditions (particularly over the eastern southwest Pacific region); this enhancement is primarily attributed to increased TC activity during these event periods. There are also indications of increasing intensities of TC-induced extreme rainfall events over the past few decades. A key part of this work involves development of sophisticated Bayesian regression models for individual island nations in order to better understand the synergistic relationships between TC-induced extreme rainfall and combinations of various climatic drivers that modulate the relationship. Such models are found to be very useful for not only assessing probabilities of TC- and non-TC induced extreme rainfall events but also evaluating probabilities of extreme rainfall for cases with different underlying climatic conditions. For example, TC-induced extreme rainfall probability over Samoa can vary from ~ 95 to ~ 75% during a La Niña period, if it coincides with an active or inactive phase of the MJO, and can be reduced to ~ 30% during a combination of El Niño period and inactive phase of the MJO. Several other such cases have been assessed for different island nations, providing information that have potentially important implications for planning and preparing for TC risks in vulnerable Pacific Island nations.

scholarly journals Quasi-stationary waves in the Southern Hemisphere during El Niño and La Niña events

2004 ◽  
Vol 22 (3) ◽  
pp. 789-806 ◽  
Author(s):  
V. Brahmananda Rao ◽  
J. P. R. Fernandez ◽  
S. H. Franchito
Keyword(s):  
South America ◽  
Southern Hemisphere ◽  
Rossby Wave ◽  
El Niño ◽  
General Circulation ◽  
El Nino ◽  
Numerical Study ◽  
La Niña ◽  
Austral Spring ◽  
La Nina

Abstract. Characteristics of quasi-stationary (QS) waves in the Southern Hemisphere are discussed using 49 years (1950–1998) of NCEP/NCAR reanalysis data. A comparison between the stationary wave amplitudes and phases between the recent data (1979–1998) and the entire 49 years data showed that the differences are not large and the 49 years data can be used for the study. Using the 49 years of data it is found that the amplitude of QS wave 1 has two maxima in the upper atmosphere, one at 30°S and the other at 55°S. QS waves 2 and 3 have much less amplitude. Monthly variation of the amplitude of QS wave 1 shows that it is highest in October, particularly in the upper troposphere and stratosphere. To examine the QS wave propagation Plumb's methodology is used. A comparison of Eliassen-Palm fluxes for El Niño and La Niña events showed that during El Niño events there is a stronger upward and equatorward propagation of QS waves, particularly in the austral spring. Higher upward propagation indicates higher energy transport. A clear wave train can be identified at 300hPa in all the seasons except in summer. The horizontal component of wave activity flux in the El Niño composite seems to be a Rossby wave propagating along a Rossby wave guide, at first poleward until it reaches its turning latitude in the Southern Hemisphere midlatitudes, then equatorward in the vicinity of South America. The position of the center of positive anomalies in the austral spring in the El Niño years over the southeast Pacific, near South America, favors the occurrence of blocking highs in this region. This agrees with a recent numerical study by Renwick and Revell (1999). Key words. Meteorology and atmospheric dynamics (climatology; general circulation; ocean-atmosphere interactions)

The Influence of the Indian Ocean on ENSO Stability and Flavor

2017 ◽  
Vol 30 (7) ◽  
pp. 2601-2620 ◽  
Author(s):  
Claudia E. Wieners ◽  
Henk A. Dijkstra ◽  
Will P. M. de Ruijter
Keyword(s):  
Indian Ocean ◽  
Spatial Pattern ◽  
El Niño ◽  
East Coast ◽  
El Nino ◽  
La Niña ◽  
Enso Cycle ◽  
Central Pacific ◽  
La Nina ◽  
The Indian Ocean

The effect of long-term trends and interannual, ENSO-driven variability in the Indian Ocean (IO) on the stability and spatial pattern of ENSO is investigated with an intermediate-complexity two-basin model. The Pacific basin is modeled using a fully coupled (i.e., generating its own background state) Zebiak–Cane model. IO sea surface temperature (SST) is represented by a basinwide warming pattern whose strength is constant or varies at a prescribed lag to ENSO. Both basins are coupled through an atmosphere transferring information between them. For the covarying IO SST, a warm IO during the peak of El Niño (La Niña) dampens (destabilizes) ENSO, and a warm IO during the transition from El Niño to La Niña (La Niña to El Niño) shortens (lengthens) the period. The influence of the IO on the spatial pattern of ENSO is small. For constant IO warming, the ENSO cycle is destabilized because stronger easterlies induce more background upwelling, more thermocline steepening, and a stronger Bjerknes feedback. The SST signal at the east coast weakens or reverses sign with respect to the main ENSO signal [i.e., ENSO resembles central Pacific (CP) El Niños]. This is due to a reduced sensitivity of the SST to thermocline variations in case of a shallow background thermocline, as found near the east coast for a warm IO. With these results, the recent increase in CP El Niño can possibly be explained by the substantial IO (and west Pacific) warming over the last decades.

Climate Variability in Southern South America Associated with El Niño and La Niña Events

2000 ◽  
Vol 13 (1) ◽  
pp. 35-58 ◽  
Author(s):  
Alice M. Grimm ◽  
Vicente R. Barros ◽  
Moira E. Doyle
Keyword(s):  
South America ◽  
Climate Variability ◽  
El Niño ◽  
El Nino ◽  
La Niña ◽  
Southern South America ◽  
La Nina

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 The ENSO–Asian Monsoon Interaction in a Coupled Ocean–Atmosphere GCM

2007 ◽  
Vol 20 (20) ◽  
pp. 5164-5177 ◽  
Author(s):  
Ying Li ◽  
Riyu Lu ◽  
Buwen Dong
Keyword(s):  
El Niño ◽  
Asian Monsoon ◽  
El Nino ◽  
Southern Oscillation ◽  
La Niña ◽  
Enso Cycle ◽  
Central Pacific ◽  
La Nina ◽  
Ocean Atmosphere ◽  
The Relationship

Abstract In this study, the authors evaluate the (El Niño–Southern Oscillation) ENSO–Asian monsoon interaction in a version of the Hadley Centre coupled ocean–atmosphere general circulation model (CGCM) known as HadCM3. The main focus is on two evolving anomalous anticyclones: one located over the south Indian Ocean (SIO) and the other over the western North Pacific (WNP). These two anomalous anticyclones are closely related to the developing and decaying phases of the ENSO and play a crucial role in linking the Asian monsoon to ENSO. It is found that the HadCM3 can well simulate the main features of the evolution of both anomalous anticyclones and the related SST dipoles, in association with the different phases of the ENSO cycle. By using the simulated results, the authors examine the relationship between the WNP/SIO anomalous anticyclones and the ENSO cycle, in particular the biennial component of the relationship. It is found that a strong El Niño event tends to be followed by a more rapid decay and is much more likely to become a La Niña event in the subsequent winter. The twin anomalous anticyclones in the western Pacific in the summer of a decaying El Niño are crucial for the transition from an El Niño into a La Niña. The El Niño (La Niña) events, especially the strong ones, strengthen significantly the correspondence between the SIO anticyclonic (cyclonic) anomaly in the preceding autumn and WNP anticyclonic (cyclonic) anomaly in the subsequent spring, and favor the persistence of the WNP anomaly from spring to summer. The present results suggest that both El Niño (La Niña) and the SIO/WNP anticyclonic (cyclonic) anomalies are closely tied with the tropospheric biennial oscillation (TBO). In addition, variability in the East Asian summer monsoon, which is dominated by the internal atmospheric variability, seems to be responsible for the appearance of the WNP anticyclonic anomaly through an upper-tropospheric meridional teleconnection pattern over the western and central Pacific.

scholarly journals An Alert Classification System for Monitoring and Assessing the ENSO Cycle

2007 ◽  
Vol 22 (2) ◽  
pp. 353-371 ◽  
Author(s):  
V. E. Kousky ◽  
R. W. Higgins
Keyword(s):  
El Niño ◽  
Classification System ◽  
Scientific Community ◽  
El Nino ◽  
La Niña ◽  
Enso Cycle ◽  
Intensity Scale ◽  
La Nina ◽  
Real Time Information ◽  
Time Information

Abstract An alert classification system for the ENSO cycle is introduced. The system includes watches, advisories, and a five-class intensity scale for warm and cold phases of the ENSO cycle. A watch is issued when conditions are favorable for the formation of an El Niño or La Niña within the next 6 months. An advisory is issued when El Niño or La Niña conditions are present, based on NOAA’s operational definitions. The intensity scale, referred to as the ENSO Intensity Scale (EIS), is used for operational and retrospective assessments of the intensity of warm (El Niño) and cold (La Niña) episodes, without being prescriptive concerning ENSO-related anomalies or impacts. The Climate Prediction Center’s (CPC’s) monthly Climate Diagnostics Bulletin and ENSO Diagnostic Discussions will serve as the primary vehicles for disseminating real-time information concerning the ENSO alert status to the scientific community and public at large. An objective method that relates the EIS to anomalies is used to assess the effects of warm and cold episodes. The method is illustrated using precipitation in the global Tropics and subtropics and in the conterminous United States. The methodology is quite general and can be used to relate the ENSO cycle to other quantities.

El Niño and La Niña influence on mean river flows of southern South America in the 20th century

2019 ◽  
Vol 64 (8) ◽  
pp. 900-909 ◽  
Author(s):  
Guillermo J. Berri ◽  
Emilio Bianchi ◽  
Gabriela V. Müller
Keyword(s):  
South America ◽  
20Th Century ◽  
El Niño ◽  
El Nino ◽  
La Niña ◽  
River Flows ◽  
Southern South America ◽  
La Nina
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