scholarly journals On Changing El Niño: A View from Time-Varying Annual Cycle, Interannual Variability, and Mean State

2011 ◽  
Vol 24 (24) ◽  
pp. 6486-6500 ◽  
Author(s):  
Cheng Qian ◽  
Zhaohua Wu ◽  
Congbin Fu ◽  
Dongxiao Wang
Keyword(s):  
Interannual Variability ◽  
Annual Cycle ◽  
El Niño ◽  
El Nino ◽  
Warm Period ◽  
Secular Change ◽  
Enso Events ◽  
El Niño Event ◽  
The Impact ◽  
Mean State

Abstract This study investigates changes in the frequency of ENSO, especially the prolonged 1990–95 El Niño event, in the context of secular changes in the annual cycle, ENSO interannual variability, and background mean state of the tropical eastern Pacific sea surface temperature (SST). The ensemble empirical mode decomposition (EEMD) method is applied to isolate those components from the Niño-3 SST index for the period 1880–2008. It is shown that the annual cycle [referred to as a refined modulated annual cycle (MAC)] has strong interannual modulation and secular change in both amplitude and phase: a clear transition from increasing to decreasing amplitude around 1947/48, with both linear trends before and after this turning point statistically significant and the amplitude decreasing by 14% since then, and a significant phase delay trend for the period 1881–1938, but hardly any thereafter. A clear transition from significant deceasing to increasing by about 30% in the amplitude of the ENSO interannual variability around 1937 is also found. When El Niño events are represented as the collective interannual variability, their frequency is found to be almost equivalent to that of La Niña events after 1976. A method for conducting synthetic experiments based on time series analysis further reveals that the apparent prolonged 1990–95 El Niño event was not caused solely by ENSO interannual variability. Rather, the 1991/92 warm period is attributable to an interannual variation superimposed by change in the background mean state; the 1993 warm period is attributable to change in the mean state; and the 1994/95 warm period is attributable to a residual annual cycle, which cannot be fully excluded by a 30-yr mean annual cycle approach. The impact that changing base periods has on the classification of ENSO events and possible solutions is also discussed.

scholarly journals Model study of the cross-tropopause transport of biomass burning pollution

2007 ◽  
Vol 7 (14) ◽  
pp. 3713-3736 ◽  
Author(s):  
B. N. Duncan ◽  
S. E. Strahan ◽  
Y. Yoshida ◽  
S. D. Steenrod ◽  
N. Livesey
Keyword(s):  
Biomass Burning ◽  
El Niño ◽  
Fossil Fuels ◽  
Extreme Event ◽  
El Nino ◽  
Deep Convection ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
El Niño Event ◽  
The Impact

Abstract. We present a modeling study of the troposphere-to-stratosphere transport (TST) of pollution from major biomass burning regions to the tropical upper troposphere and lower stratosphere (UT/LS). TST occurs predominately through 1) slow ascent in the tropical tropopause layer (TTL) to the LS and 2) quasi-horizontal exchange to the lowermost stratosphere (LMS). We show that biomass burning pollution regularly and significantly impacts the composition of the TTL, LS, and LMS. Carbon monoxide (CO) in the LS in our simulation and data from the Aura Microwave Limb Sounder (MLS) shows an annual oscillation in its composition that results from the interaction of an annual oscillation in slow ascent from the TTL to the LS and seasonal variations in sources, including a semi-annual oscillation in CO from biomass burning. The impacts of CO sources that peak when ascent is seasonally low are damped (e.g. Southern Hemisphere biomass burning) and vice-versa for sources that peak when ascent is seasonally high (e.g. extra-tropical fossil fuels). Interannual variation of CO in the UT/LS is caused primarily by year-to-year variations in biomass burning and the locations of deep convection. During our study period, 1994–1998, we find that the highest concentrations of CO in the UT/LS occurred during the strong 1997–1998 El Niño event for two reasons: i. tropical deep convection shifted to the eastern Pacific Ocean, closer to South American and African CO sources, and ii. emissions from Indonesian biomass burning were higher. This extreme event can be seen as an upper bound on the impact of biomass burning pollution on the UT/LS. We estimate that the 1997 Indonesian wildfires increased CO in the entire TTL and tropical LS (>60 mb) by more than 40% and 10%, respectively, for several months. Zonal mean ozone increased and the hydroxyl radical decreased by as much as 20%, increasing the lifetimes and, subsequently TST, of trace gases. Our results indicate that the impact of biomass burning pollution on the UT/LS is likely greatest during an El Niño event due to favorable dynamics and historically higher burning rates.

On Abnormally Strong Currents Observed on the Northern Coast of Peru during the 2015-2016 El Niño

2021 ◽  
Vol 8 (4) ◽  
pp. 205-210
Author(s):  
Chang-Woong Shin ◽  
Dimitri Gutiérrez
Keyword(s):  
Mixed Layer ◽  
El Niño ◽  
El Nino ◽  
Current Data ◽  
Kelvin Waves ◽  
Coastal Current ◽  
Northern Coast ◽  
El Niño Event ◽  
Strong Current ◽  
The Impact

The northern coast of Peru is a region that can rapidly detect the impact of an El Niño. To investigate the effects of the 2015-2016 El Niño on the oceanographic environment of the northern coast of Peru, the temperature and current data obtained from moored equipment at an oil platform were analyzed. Strong coastal along-shore currents of more than 0.60 m·s-1 were observed three times, although the mean current speed was 0.10 m·s-1 flowing toward the south-southwest. After the first strong current, the bottom temperature increased and the mixed layer deepened and remained there during the El Niño event. The temperature reached a maximum after the strong coastal current, then decreased gradually. An analysis of wind and sea surface height anomalies revealed that the coastal strong current was caused by Kelvin waves and the deepening of the mixed layer was not related to local winds, but to coastal Kelvin waves from the equator during the El Niño event.

scholarly journals Reversed Spatial Asymmetries between El Niño and La Niña and Their Linkage to Decadal ENSO Modulation in CMIP3 Models

2011 ◽  
Vol 24 (20) ◽  
pp. 5423-5434 ◽  
Author(s):  
Jin-Yi Yu ◽  
Seon Tae Kim
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Interaction Mechanism ◽  
Tropical Pacific ◽  
La Niña ◽  
Enso Events ◽  
La Nina ◽  
Spatial Asymmetries ◽  
Mean State

Abstract This study examines preindustrial simulations from Coupled Model Intercomparison Project, phase 3 (CMIP3), models to show that a tendency exists for El Niño sea surface temperature anomalies to be located farther eastward than La Niña anomalies during strong El Niño–Southern Oscillation (ENSO) events but farther westward than La Niña anomalies during weak ENSO events. Such reversed spatial asymmetries are shown to force a slow change in the tropical Pacific Ocean mean state that in return modulates ENSO amplitude. CMIP3 models that produce strong reversed asymmetries experience cyclic modulations of ENSO intensity, in which strong and weak events occur during opposite phases of a decadal variability mode associated with the residual effects of the reversed asymmetries. It is concluded that the reversed spatial asymmetries enable an ENSO–tropical Pacific mean state interaction mechanism that gives rise to a decadal modulation of ENSO intensity and that at least three CMIP3 models realistically simulate this interaction mechanism.

scholarly journals Inter ENSO variability and its influence over the South American monsoon system

2006 ◽  
Vol 6 ◽  
pp. 167-171 ◽  
Author(s):  
A. R. M. Drumond ◽  
T. Ambrizzi
Keyword(s):  
Interannual Variability ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Low Frequency ◽  
Austral Summer ◽  
Phase Changes ◽  
The South ◽  
Enso Variability ◽  
Enso Events

Abstract. Previous studies have discussed the interannual variability of a meridional seesaw of dry and wet conditions over South America (SA) associated to the modulation of the South Atlantic Convergence Zone (SACZ). However, they did not explore if the variability inter ENSO (El Niño Southern Oscillation) can be related to the phase changes of this dipole. To answer this question, an observational work was carried out to explore the atmospheric and Sea Surface Temperature (SST) conditions related to the same ENSO signal and to opposite dipole phases. Rotated Empirical Orthogonal Function (REOF) analysis was applied over normalized Chen precipitation seasonal anomalies in order to find the dipole mode in the Austral Summer (December to February). The fourth rotated mode, explaining 6.6% of the total variance, consists of positive loading over the SACZ region and negative loading over northern Argentina. Extreme events were selected and enhanced activity of SACZ during the Summer season (SACZ+) was identified in nine years: five during La Niña events (LN) and two in El Niño episodes (EN). On the other hand, inhibited manifestations of this system (SACZ-) were identified in seven years: four in EN and two during LN. Power spectrum analysis indicated that the interannual variability of the precipitation dipole seems to be related to the low frequency and to the quasi-biennial part of ENSO variability. The ENSO events with the same signal can present opposite phases for the dipole. The results suggest that the displacement of the convection over Indonesia and western Pacific can play an important role to modulate the seesaw pattern.

scholarly journals Spatial and Temporal Analysis of El Niño Impact on Land and Forest Fire in Kalimantan and Sumatra

Agromet ◽  
2021 ◽  
Vol 35 (1) ◽  
pp. 1-10
Author(s):  
Sri Nurdiati ◽  
Ardhasena Sopaheluwakan ◽  
Pandu Septiawan
Keyword(s):  
Forest Fire ◽  
Forest Fires ◽  
El Niño ◽  
Fire Regime ◽  
El Nino ◽  
Function Analysis ◽  
Spatial And Temporal Patterns ◽  
El Niño Event ◽  
Dry Spell ◽  
The Impact

Land and forest fires in Kalimantan and Sumatra, Indonesia occurred annually at different magnitude and duration. Climate and sea interaction, like El Niño, influences the severity of dry seasons preceding the fires. However, research on the influence of El Niño intensity to fire regime in Kalimantan and Sumatra is limited. Therefore, this study aims to analyze the spatial and temporal patterns of the effects of El Niño intensity on land and forest fires in fire-prone provinces in Indonesia. Here, we applied the empirical orthogonal function analysis based on singular value decomposition to determine the dominant patterns of hotspots and rainfall data that evolve spatially and temporally. For analysis, the study required the following data: fire hotspots, dry-spell, and rainfall for period 2001-2019. This study revealed that El Niño intensity had a different impacts for each province. Generally, El Niño will influence the severity of forest fire events in Indonesia. However, we found that the impact of El Niño intensity varied for Kalimantan, South Sumatra, and Riau Province. Kalimantan was the most sensitive province to the El Niño event. The duration and number of hotspots in Kalimantan increased significantly even in moderate El Niño event. This was different for South Sumatra, where the duration and number of hotspots only increased significantly when a strong El Niño event occurred.

scholarly journals Response of stratospheric water vapor and ozone to the unusual timing of El Niño and QBO disruption in 2015–2016

2018 ◽  
Author(s):  
Mohamadou Diallo ◽  
Martin Riese ◽  
Thomas Birner ◽  
Paul Konopka ◽  
Rolf Müller ◽  
...  
Keyword(s):  
Water Vapor ◽  
Greenhouse Gases ◽  
El Niño ◽  
Lower Stratosphere ◽  
El Nino ◽  
Enso Event ◽  
Quasi Biennial Oscillation ◽  
Stratospheric Water Vapor ◽  
Enso Events ◽  
The Impact

Abstract. The stratospheric circulation determines the transport and lifetime of key greenhouse gases, including water vapor and ozone, which radiatively impact surface climate. The unusually warm El Niño Southern Oscillation (ENSO) event aligned with a disrupted Quasi-Biennial Oscillation (QBO) caused an unprecedented perturbation to this circulation in 2015–2016. Here, we quantify the impact of the alignment of these two phenomena in 2015–2016 on lower stratospheric water vapor and ozone from satellite observations. We show that the warm ENSO event substantially increases water vapor and decreases ozone in the tropical lower stratosphere. The QBO disruption significantly decreases global lower stratospheric water vapor and tropical ozone from early spring to late autumn. Thus, this QBO disruption reverses the lower stratosphere moistening triggered by the alignment of the warm ENSO event with westerly QBO in early boreal winter. Our results suggest that the interplay of ENSO events and QBO phases will be crucial for the distributions of radiatively active greenhouse gases in a changing future climate, when increasing El Niño-like conditions and decreasing lower stratospheric QBO amplitude are expected.

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.

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