scholarly journals Evolution of 1996-1999 La Niña and El Niño conditions off the western coast of South America: A remote sensing perspective

2002 ◽  
Vol 107 (C12) ◽  
pp. 29-1-29-16 ◽  
Author(s):  
Mary-Elena Carr ◽  
P. Ted Strub ◽  
Andrew C. Thomas ◽  
Jose Luis Blanco
Keyword(s):  
Remote Sensing ◽  
South America ◽  
El Niño ◽  
El Nino ◽  
La Niña ◽  
Western Coast ◽  
La Nina

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)

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

scholarly journals A diagnosis of rainfall over South America during 1997/98 El Niño and 1998/99 La Niña events: Comparison between TRMM PR and GPCP rainfall estimates

2009 ◽  
Vol 118 (3) ◽  
pp. 193-207
Author(s):  
Sergio H. Franchito ◽  
V. Brahmananda Rao ◽  
Ana C. Vasques ◽  
Clovis M. E. Santo ◽  
Jorge C. Conforte
Keyword(s):  
South America ◽  
El Niño ◽  
El Nino ◽  
La Niña ◽  
La Nina ◽  
Trmm Pr ◽  
Rainfall Estimates

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 ENSO Influence on Regional Atmospheric Circulation and Thermodynamics Over Northern South America

2021 ◽  
Author(s):  
Melissa Ruiz-Vásquez ◽  
Paola A. Arias ◽  
J. Alejandro Martínez
Keyword(s):  
South America ◽  
El Niño ◽  
El Nino ◽  
La Niña ◽  
Atmospheric Moisture ◽  
La Nina ◽  
Thermodynamic Conditions ◽  
El Niño Events ◽  
Northern South America ◽  
El Nino Events

Abstract The interannual variability of hydroclimatic conditions in Northern South America (NOSA), specially precipitation, is mainly influenced by the El Niño-Southern Oscillation (ENSO). We explored potential mechanisms that affect precipitation occurrence in NOSA during El Niño and La Niña events over the period 1980-2019, using data from the ERA5 reanalysis. We looked at the atmospheric moisture contribution from different sources using the Dynamic Recycling Model to track water vapour trajectories. Interestingly, conditions with reduced precipitation during El Niño events can take place along with increased precipitable water. To understand this, we analyzed thermodynamic conditions in the atmosphere that are necessary for precipitation to occur over the region, such as convective available potential energy, convective inhibition, lifting condensation level and low--level relative humidity. With this approach, we found more favorable atmospheric conditions for the occurrence of precipitation during La Niña events, even if the content of water vapor was equal or even less than during El Niño events. We also looked at the structure of the regional Hadley circulation in both types of events and found a weakening of the rising motion of the cell during El Niño, which further reduces convective processes over this region. This study provides an integral picture of how precipitation anomalies over NOSA during ENSO events are related both to thermodynamic conditions and sources of atmospheric moisture.

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