The Energetics of El Niño and La Niña

Data from a realistic model of the ocean, forced with observed atmospheric conditions for the period 1953–92, are analyzed to determine the energetics of interannual variability in the tropical Pacific. The work done by the winds on the ocean, rather than generating kinetic energy, does work against pressure gradients and generates buoyancy power, which in turn is responsible for the rate of change of available potential energy (APE). This means interannual fluctuations in work done by the wind have a phase that leads variations in APE. Variations in the sea surface temperature (SST) of the eastern equatorial Pacific and in APE are highly correlated and in phase so that changes in the work done by the wind are precursors of El Niño. The wind does positive work on the ocean during the half cycle that starts with the peak of El Niño and continues into La Niña; it does negative work during the remaining half cycle. The results corroborate the delayed oscillator mechanism that qualitatively describes the deterministic behavior of ENSO. In that paradigm, a thermocline perturbation appearing in the western equatorial Pacific affects the transition from one phase of ENSO to the next when that perturbation arrives in the eastern equatorial Pacific where it influences SST. The analysis of energetics indicates that the transition starts earlier, during La Niña, when the perturbation is still in the far western equatorial Pacific. Although the perturbation at that stage affects the thermal structure mainly in the thermocline, at depth, the associated currents are manifest at the surface and immediately affect work done by the wind. For the simulation presented here, the change in energy resulting from adjustment processes far outweighs that due to stochastic processes, such as intraseasonal wind bursts, at least during periods of successive El Niño and La Niña events

El Niño and the delayed action oscillator

We study the dynamics of the El Niño phenomenon using the mathematical model of delayedaction oscillator (DAO). Topics such as the influence of the annual cycle, global warming, stochastic influences due to weather conditions and even off-equatorial heat-sinks can all be discussed using only modest analytical and numerical resources. Thus the DAO allows for a pedagogical introduction to the science of El Niño and La Niña while at the same time avoiding the need for large-scale computing resources normally associated with much more sophisticated coupled atmosphere-ocean general circulation models. It is an approach which is ideally suited for student projects both at high school and undergraduate level

Heat and mass balances of the South Atlantic Ocean calculated from a numerical model

The general circulation model of Bryan (1969), modified by the introduction of open boundary conditions at the Drake Passage and between Africa and Antarctica, has been used to study the mass and heat budgets of the South Atlantic Ocean. The model was initialized with the climatological annual mean values of temperature and salinity of Levitus (1982) and forced at its surface with the climatological wind stress data of Hellernian and Rosenstein (1983). After 3 years of integration the model reached a quasi-stationary state. A heat balance shows that the model transports 0.19 PW of heat toward the north across 30°S. While a large part of this heat is supplied by the atmosphere and involves the conversion of intermediate waters into surface waters, a comparison with climatological data of atmospheric heat fluxes suggests that an extra source of heat is necessary to maintain the northward heat flux.Copyrighted by American Geophysical Union

Altimeter sampling characteristics using a single satellite

This is the published version. Copyright 1998 WileyAltimetric satellites have characteristic sampling patterns in both space and time based on their repeat period and orbit inclination. Aliased phenomena measured by altimetric measurements can appear as propagating waves with both wavelength and direction of propagation different from the underlying phenomena. All signals that contribute to the altimetric measurement can be aliased and produce such patterns, not just tidal signals. For example, mesoscale energy will be aliased as will unmodeled atmospheric variations. Past discussions of aliasing have only considered spatially homogeneous signals. This paper extends this work to phenomena with finite wavelengths and considers both the north-south and east-west components of the resulting aliases

Exploring Destination Loyalty: Application of Social Media Analytics in a Nature-based Tourism Setting

User-generated content across social media platforms is playing an increasingly important role in the tourism context. Understanding tourists’ experiences and opinions about tourism destinations has led to numerous opportunities to provide tourism providers and decision-makers with greater insight. Identifying sentiments, detecting topics of interest, and exploring loyalty behaviors from user-generated content can provide valuable direction for managerial decisions. Few if any studies on social media analytics have demonstrated the support for strategic decision-making. This paper presents a novel and inclusive approach that uses different analytical techniques such as sentiment analysis and topic modeling to extract sentiments and topics of interest from tourists’ conversational data on TripAdvisor from 2002 to 2019, and also explore destination loyalty statements using a keyword clustering approach. Previous destination loyalty literature was used to develop a keyword list that was applied to search for expression of loyalty in online reviews. The robustness of loyalty clusters and optimal number of clusters was also assessed prior to final analysis. Four leading loyalty-focused categories of destination offerings were observed: glaciers, waterfalls, lakes and islands, and hiking and trails. Prioritization of visitor experience enhancements relating to these loyalty inducing destination components are discussed

Preface

The second half of the 20th century was a most remarkable period in the history of oceanography. In the 1980’s oceanographers were still determining the position of a ship at sea by means of stars and sextants, the instruments of explorers, of individualists who brave the elements and venture into uncharted territory in search of new worlds. Today it is possible to locate a ship very accurately by means of the Global Positioning System, (GPS) which depends on several satellites in space. How ..

Encyclopedia of global warming and climate change

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Océan et climat

On mesure depuis peu le rôle essentiel joué par l'océan dans les mécanismes complexes qui régissent le climat. En stockant la chaleur reçue du Soleil pour la transporter des tropiques vers les régions tempérées, l'océan interagit avec l’atmosphère, contribuant à rendre notre planète habitable. Dans le contexte du réchauffement climatique global, l'étude tes relations entre l’océan et le climat est devenue un enjeu scientifique majeur. En quelques décennies, l'océanographie physique est passée d'une approche descriptive et géographique à une approche géophysique. Cette mutation spectaculaire a été rendue possible grâce au développement de programmes internationaux sans précédent, auxquels se sont ajoutés les apports déterminants de' l’observation spatiale et de la modélisation numérique. Ce vaste déploiement de moyens techniques, scientifiques et humains est à l’origine de la découverte des mécanismes fondamentaux de la dynamique des océans, et du rôle particulier des océans tropicaux dans la variabilité climatique. Accessible à un large public, cet ouvrage retrace dans sa dimension scientifique et humaine les conquêtes d'une discipline en plein essor, à présent au cœur des questionnements sur le climat futur