Studies of climate variability in a simple coupled model

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2007.Includes bibliographical references (p. 74-76).The mechanisms of variability of a coupled atmosphere-ocean model are investigated through the study of two coupled configurations: an aquaplanet in which gyres are absent, and an aquaplanet in which a ridge extending from pole to pole supports gyres. Empirical Orthogonal Functions (EOFs) are used to explore the main features of variability exhibited by extended integrations of both configurations. In the aquaplanet a decadal variability is observed in the atmosphere and the ocean. Stochastic driving of the annular modes in the atmosphere generates an anomalous Sea Surface Temperature (SST) dipole through latent heat fluxes and Ekman pumping. A feedback of this SST dipole on the atmosphere enables a damping slow enough for anomalies to persist over decadal time scales. This air-sea feedback combined with a slow advection of the anomalies by mean ocean currents result in the observed decadal oscillation. A simple stochastic model captures the essence of this mechanism. In the ridge decadal variability is absent but centennial variability is observed in the atmosphere and the ocean. Stochastic driving of the annular modes in the atmosphere generates a weak SST tripole due to latent heat fluxes. The weak amplitude of this tripole prevents the existence of any significant air-sea feedback, implies a stronger damping than in the aquaplanet, and ultimately results in the absence of oscillations. The classic stochastic model of Hasselmann [19] explains the evolution of the SST anomaly through time. Within a delay of one year stochastic atmospheric variability additionally generates a baroclinic streamfunction as well as baroclinic Rossby waves at the eastern boundary of the basin. The former is slowly advected by the mean flow while the latter propagates towards the western boundary, inducing a feedback on the atmosphere with a delay of sixty years. A simple model is found to capture the essence of this mechanism. The results of the aquaplanet and the ridge are used to interpret the Drake, a third configuration in which a band of land extends from the North Pole to the line of -45' of latitude. In the northern hemisphere of the Drake mean state and variability are similar to the ones observed in the ridge. The observed centennial oscillation would correspond to a decadal oscillation in the Atlantic. In the southern hemisphere of the Drake, mean state and variability have elements of both the ridge and the aquaplanet.by Claude Abiven.S.M

A Hybrid Dynamically Adaptive, Super Spatio-Temporal Resolution Digital Particle Image Velocimetry for Multi-Phase Flows

A unique, super spatio-temporal resolution Digital Particle Image Velocimetry (DPIV) system with capability of resolving velocities in a multi-phase flow field, using a very sophisticated novel Dynamically Adaptive Hybrid velocity evaluation algorithm has been developed The unique methodology of this powerful system is presented, its specific distinctions are enlightened, confirming its flexibility, and its superior performance is established by comparing it to the most established best DPIV software implementations currently available. Taking advantage of the most recent advances in imaging technology coupled with state of the art image processing tools, high-performing validation schemes including neural networks, as well as a hybrid digital particle tracking velocimeter (DPTV), the foundation for a unique system was developed. The presented software enables one to effectively resolve tremendously demanding flow-fields. The resolution of challenging test cases including high speed cavitating underwater projectiles as well as high pressure spray demonstrate the power of the developed device. iii Acknowledgments In the first place, I would like to express my deepest thanks to Dr Pavlos Vlachos, whose constant support, insightful guidance, knowledge, and encouragements led me throughout the completion of this dissertation. During one year and a half, he certainly made me benefit from his invaluable skills. I wish to show my gratitude to Dr D. Telionis, who gave me the opportunity to come to study at Virginia Tech, and whose instructive comments greatly improved the quality of my work. I am grateful to the Personal of the Department of Engineering Science and Mechanics, especially Loretta Tickle for her administrative assistance. I also thank the people from the fluid..

Aliénor d’Aquitaine dans trois romans historiques pour la jeunesse

Aliénor d’Aquitaine, femme emblématique de l’Histoire de France et d’Angleterre, fut à l’origine de conflits entre les deux royaumes. En effet, à peine son premier mariage annulé avec le roi de France, elle devient reine d’Angleterre par son nouvel époux. Elle sera mère et grand-mère de plusieurs rois et reines, dont Richard Cœur de Lion. Elle a œuvré pour la libération des mœurs, l’amour courtois et la culture médiévale des troubadours. Nous voulons montrer les choix de trois auteures qui on..

Fictions historiques pour la jeunesse en France et au Québec

Comme leurs aînés, les jeunes lecteurs apprécient les fictions historiques, les romans, les BD, les albums qui les plongent dans un univers révolu. Les collections en édition jeunesse se multiplient pour donner à lire le passé, comprendre le présent ou parfois simplement proposer des histoires dans lesquelles l’Histoire constitue un décor aux couleurs attrayantes. Fictions historiques pour la jeunesse en France et au Québec s’attache à décrire ce phénomène éditorial, littéraire et culturel. En s’appuyant sur des travaux portant sur la France et sur le Québec, cet ouvrage montre que la littérature jeunesse n’échappe pas aux conséquences économiques et culturelles de la mondialisation et qu’il existe bien des formes de fictions historiques communes. Pour autant, le contexte sociopolitique de production rend plus ou moins aisée l’évocation de certains pans du passé. Or, l’histoire et la mémoire participent, de manière particulièrement sensible, des constituants des consciences nationales. Ce livre s’inscrit au croisement de plusieurs domaines : littérature, histoire, histoire des arts, ou études culturelles. De l’Antiquité à octobre 1970, des trappeurs aux héroïnes du Grand Siècle, de la mémoire de l’esclavage à celle de la guerre d’Algérie, les questionnements variés permettent d’appréhender les fictions historiques pour la jeunesse dans leur diversité