scholarly journals An Investigation of the Southern Ocean Surface Temperature Variability Using Long-Term Optimum Interpolation SST Data

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Megha Maheshwari ◽  
Rajkumar Kamaljit Singh ◽  
Sandip Rashmikant Oza ◽  
Raj Kumar
Keyword(s):  
Southern Ocean ◽  
El Niño ◽  
El Nino ◽  
Linear Trend ◽  
Critical Role ◽  
La Niña ◽  
Optimum Interpolation ◽  
La Nina ◽  
Sst Anomaly

An attempt is made to understand the long-term variability of SST using NOAA optimum interpolation SST data for the period (1982–2011) in the Southern Ocean. This dataset has been used (i) to study the interannual variability in SST anomaly and (ii) to carry out regression analysis to compute linear trend in the annual averaged Southern Ocean SST. It is observed that summer season exhibits more variability than winter. Moreover, El Nino/La Nina events apparently play a critical role in the variability of Southern Ocean SST. Thus, higher SST anomalies were observed in El Nino years (e.g., 1983), while cooler anomalies were seen during La Nina years (e.g., 1985). In addition, the eastern and western sides of Antarctica experience episodes of warm and cold SST. Western parts of the Southern Ocean experienced higher anomalies during 1992, 1993, and 1994, while the eastern part experienced positive anomalies in 1997, 1998, 2002, and 2003. The paper also highlights the different regions of the Southern Ocean showing statistically significant positive/negative trends in the variability of interannual average SST. However, in general, the Southern Ocean as a whole is showing a weak interannual cooling trend in SST.

scholarly journals Switch Between El Nino and La Nina is Caused by Subsurface Ocean Waves Likely Driven by Lunar Tidal Forcing

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Jialin Lin ◽  
Taotao Qian
Keyword(s):  
El Niño ◽  
El Nino ◽  
Ocean Waves ◽  
La Niña ◽  
Slow Phase ◽  
Enso Events ◽  
The Past ◽  
La Nina ◽  
Subsurface Ocean ◽  
Sst Anomaly

Abstract The El Nino-Southern Oscillation (ENSO) is the dominant interannual variability of Earth’s climate system, and strongly modulates global temperature, precipitation, atmospheric circulation, tropical cyclones and other extreme events. However, forecasting ENSO is one of the most difficult problems in climate sciences affecting both interannual climate prediction and decadal prediction of near-term global climate change. The key question is what cause the switch between El Nino and La Nina. For the past 30 years, ENSO forecasts have been limited to short lead times after ENSO sea surface temperature (SST) anomaly has already developed, but unable to predict the switch between El Nino and La Nina. Here, we demonstrate that the switch between El Nino and La Nina is caused by a subsurface ocean wave propagating from western Pacific to central and eastern Pacific and then triggering development of SST anomaly. This is based on analysis of all ENSO events in the past 136 years using multiple long-term observational datasets. The wave’s slow phase speed and decoupling from atmosphere indicate that it is a forced wave. Further analysis of Earth’s angular momentum budget and NASA’s Apollo Landing Mirror Experiment suggests that the subsurface wave is likely driven by lunar tidal gravitational force.

scholarly journals The Seasonal Development of an SST Anomaly in the Indian Ocean and Its Relationship to ENSO

2007 ◽  
Vol 20 (1) ◽  
pp. 38-52 ◽  
Author(s):  
Motoki Nagura ◽  
Masanori Konda
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
El Nino ◽  
Surface Wind ◽  
La Niña ◽  
Seasonal Development ◽  
La Nina ◽  
The Indian Ocean ◽  
Dipole Pattern ◽  
Sst Anomaly

Abstract The seasonal development of the sea surface temperature (SST) anomaly in the Indian Ocean is investigated in relation to El Niño–Southern Oscillation (ENSO), using NOAA optimally interpolated SST and NCEP reanalysis data. The result shows that the onset season of El Niño affects the seasonal development of surface wind anomalies over the equatorial eastern Indian Ocean (EEIO); these surface wind anomalies, in turn, determine whether the SST anomaly in the EEIO evolves into the eastern pole of the dipole pattern. In years when the dipole pattern develops, surface zonal wind anomalies over the EEIO switch from westerly to easterly in spring as La Niña switches to El Niño. The seasonal zonal wind over the EEIO also switches from westerly to easterly in spring, and the anomalous wind strengthens seasonal wind from winter to summer. Stronger winds and resultant thermal forcings produce the negative SST anomaly in the EEIO in winter, and its amplitude increases in summer. The SST anomaly becomes the eastern pole of the dipole pattern in fall. In contrast, if the change from La Niña to El Niño is delayed until late summer/fall or if La Niña persists throughout the year, a westerly anomaly persists from winter to summer over the EEIO. The persistent westerly anomaly strengthens the wintertime climatological westerlies and weakens the summertime easterlies. Therefore, negative SST anomalies are produced in the EEIO in winter, but the amplitude decreases in summer, and the eastern pole is not present in fall. The above explanation also applies to onset years of La Niña if the signs of the anomalies are reversed.

scholarly journals Can small pelagic fish landings be used as predictors of high-frequency oceanographic fluctuations in the 1–2 El Niño region?

2016 ◽  
Vol 42 ◽  
pp. 61-72 ◽  
Author(s):  
Franklin Isaac Ormaza-González ◽  
Alejandra Mora-Cervetto ◽  
Raquel María Bermúdez-Martínez ◽  
Mario Armando Hurtado-Domínguez ◽  
Manuel Raúl Peralta-Bravo ◽  
...  
Keyword(s):  
Linear Correlation ◽  
El Niño ◽  
El Nino ◽  
Pelagic Fish ◽  
La Niña ◽  
Negative Slope ◽  
South American ◽  
Small Pelagic Fish ◽  
La Nina

Abstract. A group of small pelagic fish captured between 1981 and 2012 within El Niño area 1–2 by the Ecuadorian fleet was correlated with the oceanographic Multivariate ENSO Index (MEI), and the Oceanographic El Niño Index (ONI) referred to El Niño region 3–4. For the period 1981–2012, total landings correlated poorly with the indexes, but during 2000–2012 (cold PDO) they proved to have a 14–29 % association with both indexes; the negative slope of the curves suggested higher landing during cold events (La Niña) and also indicated a tendency to decrease at extreme values ( >  0.5 and  < −1.0). Round herring (Etrumeus teres) fourth-quarter (Q4) landings were related to the MEI in a nonlinear analysis by up to 80 %. During moderate or strong La Niña events landings noticeably increased. Bullet tuna (Auxis spp.) catches showed a negative gradient from cold to warm episodes with an R2 of 0.149. For Chilean jack mackerel (Trachurus murphyi) irregular landings between 2003 and 2007 were observed and were poorly correlated (R2 < 0.1) with ONI or MEI. Anchovy (Engraulis ringens) captured in Ecuadorian waters since 2000 had an R2 of 0.302 and 0.156 for MEI and ONI, respectively, but showed a higher correlation with the cold Pacific Decadal Oscillation (PDO). South American pilchard (Sardinops sagax) was higher than −0.5 for the ONI and MEI, and landings dramatically decreased; however, Q4 landings correlated with ONI and MEI, with R2 of 0.109 and 0.225, respectively (n = 3). Linear correlation of Q4 indexes against the following year's Q1 landings had a linkage of up to 22 %; this species could therefore be considered a predictor of El Niño. Chub mackerel (Scomber japonicus) landings did not have a significant linear correlation with the indexes for 1981–2012 and therefore could not be considered a valid predictor. Chuhueco (Cetengraulis mysticetus) is a local species with high landings during El Niño years and, conversely, remarkably low landings during La Niña years. Additionally, chuhueco availability and landings were negatively affected by cold PDOs. Pacific thread herring (Opisthonema spp.) showed a 24 and 36 % relationship between landings (Q1) and the MEI and ONI (Q4). Therefore, results suggest that the South American pilchard and Pacific thread herring could be considered good species to use as predictors of El Niño in region 1–2 (Ecuador), especially when average Q4 MEI ∕ ONI is used against the next trimester Q1 landing. All species were prone to lower landings and/or fishing availability during strong–extreme events (ONI/MEI,  >  1.0 and  <  −1.0), and were also shown to be affected by the PDO. In the long term, landings decreased under warm PDO and vice versa, and therefore PDO fluctuations could be used to help manage these fisheries and to help the industry in long-term planning.

scholarly journals The Predictability of Interdecadal Changes in ENSO Activity and ENSO Teleconnections

2006 ◽  
Vol 19 (19) ◽  
pp. 4755-4771 ◽  
Author(s):  
Scott Power ◽  
Malcolm Haylock ◽  
Rob Colman ◽  
Xiangdong Wang
Keyword(s):  
Time Scales ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
La Niña ◽  
Enso Teleconnections ◽  
La Nina ◽  
Sst Anomaly ◽  
The Relationship ◽  
Interdecadal Changes

Abstract El Niño–Southern Oscillation (ENSO) in a century-long integration of a Bureau of Meteorology Research Centre (BMRC) coupled general circulation model (CGCM) drives rainfall and temperature changes over Australia that are generally consistent with documented observational changes: dry/hot conditions occur more frequently during El Niño years and wet/mild conditions occur more frequently during La Niña years. The relationship between ENSO [as measured by Niño-4 or the Southern Oscillation index (SOI), say] and all-Australia rainfall and temperature is found to be nonlinear in the observations and in the CGCM during June–December: a large La Niña sea surface temperature (SST) anomaly is closely linked to a large Australian response (i.e., Australia usually becomes much wetter), whereas the magnitude of an El Niño SST anomaly is a poorer guide to how dry Australia will actually become. Australia tends to dry out during El Niño events, but the degree of drying is not as tightly linked to the magnitude of the El Niño SST anomaly. Nonlinear or asymmetric teleconnections are also evident in the western United States/northern Mexico. The implications of asymmetric teleconnections for prediction services are discussed. The relationship between ENSO and Australian climate in both the model and the observations is strong in some decades, but weak in others. A series of decadal-long perturbation experiments are used to show that if these interdecadal changes are predictable, then the level of predictability is low. The model’s Interdecadal Pacific Oscillation (IPO), which represents interdecadal ENSO-like SST variability, is statistically linked to interdecadal changes in ENSO’s impact on Australia during June–December when ENSO’s impact on Australia is generally greatest. A simple stochastic model that incorporates the nonlinearity above is used to show that the IPO [or the closely related Pacific Decadal Oscillation (PDO)] can appear to modulate ENSO teleconnections even if the IPO–PDO largely reflect unpredictable random changes in, for example, the relative frequency of El Niño and La Niña events in a given interdecadal period. Note, however, that predictability in ENSO-related variability on decadal time scales might be either underestimated by the CGCM, or be too small to be detected by the modest number of perturbation experiments conducted. If there is a small amount of predictability in ENSO indices on decadal time scales, and there may be, then the nonlinearity described above provides a mechanism via which ENSO teleconnections could be modulated on decadal time scales in a partially predictable fashion.

scholarly journals Relative Roles of Dynamic and Thermodynamic Processes in Causing Evolution Asymmetry between El Niño and La Niña*

2016 ◽  
Vol 29 (6) ◽  
pp. 2201-2220 ◽  
Author(s):  
Mingcheng Chen ◽  
Tim Li ◽  
Xinyong Shen ◽  
Bo Wu
Keyword(s):  
El Niño ◽  
El Nino ◽  
Heat Budget ◽  
La Niña ◽  
Budget Analysis ◽  
La Nina ◽  
Sign Change ◽  
Sst Anomaly ◽  
Second Year ◽  
Thermodynamic Processes

Abstract Observed SST anomaly (SSTA) in the equatorial eastern Pacific exhibits an asymmetric evolution characteristic between El Niño and La Niña. While El Niño is characterized by a rapid decay after its peak and a fast phase transition to a cold episode in the following winter, La Niña is characterized by a weaker decay after its peak and a reintensification of cold SSTA in the second year. The relative roles of dynamic (wind field) and thermodynamic (heat flux) processes in causing the asymmetric evolutions are investigated through a mixed layer heat budget analysis. The result shows both dynamic and thermodynamic processes contribute to the evolution asymmetry. The former is related to asymmetric wind responses in the western Pacific, whereas the latter is associated with asymmetric cloud–radiation–SST and evaporation–SST feedbacks. A strong negative SSTA tendency occurs during El Niño decaying phase, compared to a much weaker positive SSTA tendency during La Niña decaying phase. Such a difference leads to an SSTA sign change for El Niño but no sign change for La Niña by the end of summer of the second year. A season-dependent coupled instability kicks in during northern fall, leading to the development of a La Niña by end of the second year for El Niño, but the reoccurrence of a La Niña episode by end of the second year for La Niña. The overall heat budget analysis during the entire ENSO evolutions indicates the thermodynamic process is as important as the dynamic process in causing the El Niño–La Niña evolution asymmetry. The fundamental difference of the current result with previous theories is further discussed.

scholarly journals The Relationship between Contiguous El Niño and La Niña Revealed by Self-Organizing Maps

2015 ◽  
Vol 28 (20) ◽  
pp. 8118-8134 ◽  
Author(s):  
Xin Li ◽  
Chongyin Li ◽  
Jian Ling ◽  
Yanke Tan
Keyword(s):  
El Niño ◽  
El Nino ◽  
La Niña ◽  
Ocean Dynamics ◽  
Self Organizing Maps ◽  
Onset Type ◽  
La Nina ◽  
Phase Type ◽  
Sst Anomaly ◽  
Self Organizing

Abstract This study introduces a new methodology for identifying El Niño and La Niña events. Sea surface temperature (SST) anomaly patterns for El Niño and La Niña onset, peak, and end phases are classified by self-organizing maps (SOM) analysis. Both onset and end phases for El Niño and La Niña exhibit eastern Pacific (EP) and central Pacific (CP) types. The SST anomaly patterns in peak phase can be classified into EP, EP-like, and CP types for El Niño, and EP, mixed (MIX), and CP types for La Niña. The general type of each El Niño or La Niña event is then defined according to the SST type for each of the three phases. There is no robust connection between the general types of the contiguous El Niño and La Niña except that the MIX La Niña rarely induces a subsequent CP El Niño. However, there are strong relationships between the end-phase type of El Niño and the onset-phase type of the subsequent La Niña. The EP-end-type El Niño favors transition to the CP-onset-type La Niña, while the CP-end-type El Niño favors transition to the EP-onset-type La Niña. On the other hand, the CP-end-type La Niña favors transition to EP-onset-type El Niño. Furthermore, an El Niño that occurs after the decay of La Niña favors initiating as an EP-onset type. These relationships are driven by different atmosphere–ocean dynamics, such as coupled air–sea feedback, thermocline feedback, slow SST mode, and Bjerknes feedbacks.

Cross-basin Interactions between the Tropical Atlantic and Pacific in the ECMWF Hindcasts

2020 ◽  
pp. 1-39
Author(s):  
Jing Ma ◽  
Shang-Ping Xie ◽  
Haiming Xu ◽  
Jiuwei Zhao ◽  
Leying Zhang
Keyword(s):  
El Niño ◽  
El Nino ◽  
La Niña ◽  
Tropical Atlantic ◽  
Ensemble Spread ◽  
La Nina ◽  
Ensemble Mean ◽  
Sst Warming ◽  
Leading Mode ◽  
Sst Anomaly

AbstractUsing the ensemble hindcasts of the European Centre for Medium-Range Weather Forecasts (ECMWF) coupled model for the period of 1980-2005, spatio-temporal evolution in the covariability of sea surface temperature (SST) and low-level winds in the ensemble mean and spread over the tropical Atlantic is investigated with the month-reliant singular value decomposition (SVD) method, which treats the variables in a given monthly sequence as one time step. The leading mode of the ensemble mean represents a co-evolution of SST and winds over the tropical Atlantic associated with a phase transition of El Niño from the peak to decay phase, while the second mode is related to a phase transition from El Niño to La Niña, indicating a precursory role of the north tropical Atlantic (NTA) SST warming in La Niña development.The leading mode of ensemble spread in SST and winds further illustrates that an NTA SST anomaly acts as a precursor for El Niño-Southern Oscillation (ENSO). A north-tropical pathway for the delayed effect of the NTA SST anomaly on the subsequent ENSO event is identified; the NTA SST warming induces the subtropical Northeast Pacific SST cooling through the modulation of a zonal-vertical circulation, setting off a North Pacific Meridional Mode (NPMM). The coupled SST-wind anomalies migrate southwestward to the central equatorial Pacific and eventually amplify into a La Niña event in the following months due to the equatorial Bjerknes feedback. Ensemble spread greatly increases the sample size and affords insights into the inter-basin interactions between the tropical Atlantic and Pacific, as demonstrated here in the NTA SST impact on ENSO.

scholarly journals Long-Term Variation in Survival of A Neotropical Freshwater Turtle: Habitat and Climatic Influences

Diversity ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 97 ◽  
Author(s):  
Mario F. Garcés-Restrepo ◽  
John L. Carr ◽  
Alan Giraldo
Keyword(s):  
El Niño ◽  
Transition Probabilities ◽  
El Nino ◽  
Southern Oscillation ◽  
La Niña ◽  
Freshwater Turtle ◽  
Freshwater Turtles ◽  
La Nina ◽  
Enso Phases

Few long-term demographic studies have been conducted on freshwater turtles of South America, despite the need for this type of inquiry to investigate natural variation and strengthen conservation efforts for these species. In this study, we examined the variation in demography of the Chocoan River Turtle (Rhinoclemmys nasuta) based on a population from an island locality in the Colombian Pacific region between 2005 and 2017. We calculated survival, recapture, and transition probabilities, and the effects of stream substrate and El Niño–Southern Oscillation (ENSO) phases (El Niño, Neutral, La Niña) on these variables using a multi-state model. We found differences in survival probabilities between ENSO phases, likely as a consequence of an increase in flood events. In addition, we found support for survival being greater in muddy streams than rocky streams, possibly because it is easier to escape or hide in mud substrates. Recapture probabilities varied by life stages; differences in the probability of recapture between size classes were associated with the high fidelity to territories by adults. The present increases in frequency and severity of El Niño and La Niña may exacerbate the consequences of climatic regimes on natural populations of turtles by increasing the mortality caused by drastic phenomena such as floods.

Decadal and Century-Long Changes in Storminess at Long-Term Ecological Research Sites

2003 ◽  
Author(s):  
Bruce P. Hayden ◽  
Nils R. Hayden
Keyword(s):  
United States ◽  
El Niño ◽  
El Nino ◽  
La Niña ◽  
Jet Stream ◽  
Ecological Research ◽  
La Nina ◽  
Extratropical Storms ◽  
Long Term Ecological Research

Ecological disturbances at Long-Term Ecological Research (LTER) sites are often the result of extreme meteorological events. Among the events of significance are tropical storms, including hurricanes, and extratropical cyclones. Extratropical storms are low-pressure systems of the middle and high latitudes with their attendant cold and warm fronts. These fronts are associated with strong, horizontal thermal gradients in surface temperatures, strong winds, and a vigorous jet stream aloft. These storms and their attendant fronts generate most of the annual precipitation in the continental United States and provide the lifting mechanisms for thunderstorms that, on occasion, spawn tornadoes. Off the United States West and East Coasts, extratropical storms generate winds, wind waves, wind tides, and long-shore currents that rework coastal sediments, alter landscape morphology, and change the regional patterns of coastal erosion and accretion (Dolan et al. 1988). Although extratropical storms do not match hurricanes in either precipitation intensity or in the strength of the winds generated, they are much larger in size and have a more extensive geographic impact. On occasion, extratropical storms will intensify at an extraordinary rate of 1 millibar (mb) per hour for 24 hours or more. Such storms are classed as “bomb” and are comparable to hurricanes. Extratropical storms occur in all months of the year but are most frequent and more intense in winter when the north-south temperature contrast is large and dynamic support for storm intensification from the stronger jet stream aloft is great. In this chapter, we will explore the history of storminess for those LTER sites in the continental United States at which more than a century of data on storms and their storm tracks are readily available. Specifically, we will look at the record of changes in storminess at both the regional and national scales. During the 1990s, significant storms along the U.S. West Coast and droughts and fires in Florida in an El Niño year led to a hypothesis that El Niño and La Niña conditions were associated with a modulation in the frequency of storms. In addition, it has been suggested that the frequency of El Niño and La Niña events and, by inference, storminess, has increased during the past century.

scholarly journals Long-Term Trends in Root-Zone Soil Moisture across CONUS Connected to ENSO

2020 ◽  
Vol 12 (12) ◽  
pp. 2037
Author(s):  
Kenneth J. Tobin ◽  
Roberto Torres ◽  
Marvin E. Bennett ◽  
Jianzhi Dong ◽  
Wade T. Crow
Keyword(s):  
Soil Moisture ◽  
El Niño ◽  
Root Zone ◽  
El Nino ◽  
Southern Oscillation ◽  
Global Climate ◽  
Kendall Test ◽  
La Niña ◽  
La Nina

Root zone soil moisture (RZSM) is one of the least-monitored variables within the hydrologic cycle. Given the importance of RZSM to agriculture, more effort is needed to understand the potential impacts of the El Niño southern oscillation (ENSO), Pacific decadal oscillation (PDO), and Atlantic multidecadal oscillation (AMO) on this critical variable. This study focused on the CONtiguous United States (CONUS) RZSM (0 to 40 cm depth) over nearly three decades (1992 to 2018). Basic trend analysis with the Mann–Kendall test and wavelet transform coherence (WTC) was utilized. The RZSM product examined was Soil MERGE (SMERGE 2.0). More CONUS pixels exhibited drying (56 to 75%) versus wetting (25 to 44%) trends between 1992 and 2018. Seasonal wetting trends were observed particularly during winter in the Southwest and Northwest regions associated with El Nino and La Nina episodes, respectively. The noted long-term RZSM trends are more clearly attributable to oceanic-atmospheric teleconnections than global climate change. The most significant result was the strong drying trend in central CONUS reflected a shift to La Nina and cool PDO conditions during the 2000s, further amplified by a change to positive AMO corresponding with this period.

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