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Author: Hubert Teyssedre Publisher: ISBN: Category : Languages : en Pages : 228
Book Description
L'ozone est un constituant minoritaire de l'atmosphere qui protege la vie sur terre en absorbant le rayonnement ultra-violet. Pour connaitre l'etat actuel de la couche d'ozone, des mesures satellitaires ont ete analysees sur la decennie 1979-1988. Il y apparait clairement une reduction de la couche d'ozone, notamment aux latitudes polaires suite aux episodes de trou d'ozone antarctique. Nous avons egalement pu etablir une climatologie de l'ozone total pour la confronter aux resultats de modeles. Des modeles de circulation generale, incluant une parametrisation de la photochimie de l'ozone, ont reproduit son evolution pour la decennie 1979-1988 de maniere realiste avec la climatologie precedente. Tant a partir des mesures que des modeles, nous avons evalue l'impact sur l'ozone des oscillations basse frequence de l'atmosphere moyenne equatoriale. Nous avons mis en evidence sur le vent zonal modelise un signal coherent avec l'oscillation quasi-biennale et l'importance des ondes de gravite d'origine orographique ou convective sur l'oscillation semi-annuelle de la stratopause. A partir d'une simulation tridimensionnelle de 10 ans, nous avons calcule la circulation diabatique que nous avons utilise pour forcer un modele bidimensionnel photochimique. Les distributions des constituants chimiques simulees par ce modele sont coherentes avec les observations disponibles. De plus, les resultats presentent une forte variabilite tant inter-hemispheriques qu'inter-annuelle. Avec ce modele de photochimie, nous avons alors evalue l'impact qu'aurait sur l'atmosphere une flotte d'avions supersoniques. Toutes les simulations effectuees confirment que ces avions entraineraient une augmentation de l'ozone tropospherique par les cycles de production lies au methane et au monoxyde de carbone. Au contraire, l'ozone serait detruit dans la stratosphere en oxydant le monoxyde d'azote rejete par les avions. Cette reduction est moins importante lorsque les reactions de chimie heterogene sur les particules d'aerosol sont prises en compte: les oxydes d'azote rejetes sont alors convertis en grande partie sous forme d'acide nitrique, chimiquement inerte vis a vis de l'ozone. Malgre les nombreuses incertitudes, une telle flotte perturberait toute l'atmosphere, avec un maximum probable aux moyennes latitudes de l'hemisphere nord
Author: Hubert Teyssedre Publisher: ISBN: Category : Languages : en Pages : 228
Book Description
L'ozone est un constituant minoritaire de l'atmosphere qui protege la vie sur terre en absorbant le rayonnement ultra-violet. Pour connaitre l'etat actuel de la couche d'ozone, des mesures satellitaires ont ete analysees sur la decennie 1979-1988. Il y apparait clairement une reduction de la couche d'ozone, notamment aux latitudes polaires suite aux episodes de trou d'ozone antarctique. Nous avons egalement pu etablir une climatologie de l'ozone total pour la confronter aux resultats de modeles. Des modeles de circulation generale, incluant une parametrisation de la photochimie de l'ozone, ont reproduit son evolution pour la decennie 1979-1988 de maniere realiste avec la climatologie precedente. Tant a partir des mesures que des modeles, nous avons evalue l'impact sur l'ozone des oscillations basse frequence de l'atmosphere moyenne equatoriale. Nous avons mis en evidence sur le vent zonal modelise un signal coherent avec l'oscillation quasi-biennale et l'importance des ondes de gravite d'origine orographique ou convective sur l'oscillation semi-annuelle de la stratopause. A partir d'une simulation tridimensionnelle de 10 ans, nous avons calcule la circulation diabatique que nous avons utilise pour forcer un modele bidimensionnel photochimique. Les distributions des constituants chimiques simulees par ce modele sont coherentes avec les observations disponibles. De plus, les resultats presentent une forte variabilite tant inter-hemispheriques qu'inter-annuelle. Avec ce modele de photochimie, nous avons alors evalue l'impact qu'aurait sur l'atmosphere une flotte d'avions supersoniques. Toutes les simulations effectuees confirment que ces avions entraineraient une augmentation de l'ozone tropospherique par les cycles de production lies au methane et au monoxyde de carbone. Au contraire, l'ozone serait detruit dans la stratosphere en oxydant le monoxyde d'azote rejete par les avions. Cette reduction est moins importante lorsque les reactions de chimie heterogene sur les particules d'aerosol sont prises en compte: les oxydes d'azote rejetes sont alors convertis en grande partie sous forme d'acide nitrique, chimiquement inerte vis a vis de l'ozone. Malgre les nombreuses incertitudes, une telle flotte perturberait toute l'atmosphere, avec un maximum probable aux moyennes latitudes de l'hemisphere nord
Book Description
Le rôle joué par la stratosphère sur le climat est aujourd’hui avéré. Le couplage du système troposphère-stratosphère implique que les processus dynamiques de grande amplitude de la moyenne atmosphère perturbent l’équilibre atmosphérique et l’écoulement dans les plus basses couches. Parmi ces phénomènes dynamiques, les échauffements stratosphériques soudains sont les plus emblématiques. Cette étude s’intéresse à l’impact de ces événements sur la variabilité de la moyenne atmosphère et sur l’estimation des tendances de température. Nous cherchons également à mieux caractériser l’évolution spatio-temporelle des échauffements stratosphériques, depuis leurs causes jusqu’à leurs conséquences. Tout d’abord, une méthodologie novatrice d’analyse statistique de séries temporelles est développée et testée sur des mesures lidar de l’Observatoire de Haute-Provence. L’impact des événements dynamiques les plus importants peut ainsi être efficacement isolé de la contribution radiative de fond, ce qui explique les différences observées entre l’été et l’hiver. Ensuite, une simulation du Canadian Middle Atmosphere Model nous permet de valider la méthodologie et d’étendre notre étude à l’ensemble du globe. On montre que les variations spatiales sont elles aussi majoritairement causées par l’activité dynamique. Les conditions de formation d’un échauffement stratosphérique sont également étudiées, à l’aide de tests de sensibilité du modèle RACCORD. On prouve l’importance du rappel vers la météorologie pour produire un échauffement majeur, particulièrement dans le cas d’une rupture du vortex. Enfin, la méthode et nos résultats sont mis à profit dans une analyse de l’hiver 2012-2013.
Book Description
LE TROU D'OZONE RESTE LA DEMONSTRATION LA PLUS SPECTACULAIRE DE L'IMPACT DES ACTIVITES HUMAINES SUR LA COMPOSITION ET LE COMPORTEMENT A GRANDE ECHELLE DE L'ATMOSPHERE TERRESTRE. SON APPARITION, TOTALEMENT IMPREVUE, A ENTRAINE LA COMMUNAUTE SCIENTIFIQUE DANS LA PERIODE DE RECHERCHES LA PLUS INTENSE QU'AIT JAMAIS CONNU L'ETUDE DE LA STRATOSPHERE. BIEN QUE LE SCENARIO GLOBAL DU TROU D'OZONE SOIT AUJOURD'HUI MIEUX COMPRIS, DE GRANDES INCERTITUDES SUBSISTENT, TANT SUR LE DETAIL DES MECANISMES COMPLEXES MIS EN JEU QUE SUR LEUR EVOLUTION DANS LES PROCHAINES ANNEES. CETTE THESE SE PROPOSE D'APPORTER QUELQUES ELEMENTS NOUVEAUX A LA CONNAISSANCE DES PHENOMENES DE DESTRUCTION D'OZONE QUI OPERENT EN REGION POLAIRE. DANS CE BUT, L'AUTEUR ANALYSE LES RESULTATS D'UNE METHODE ORIGINALE DE CALCUL DE L'OZONE TOTAL A PARTIR DE RADIANCES INFRA-ROUGES. ON DECRIT AINSI POUR LA PREMIERE FOIS LA FORMATION DU TROU D'OZONE PAR UN INSTRUMENT SATELLITAIRE AUTRE QUE LE SPECTROMETRE ULTRA-VIOLET TRADITIONNELLEMENT UTILISE POUR RENDRE COMPTE DU PHENOMENE. LES MESURES PRESENTEES DANS CE TRAVAIL REVELENT UN SCENARIO QUELQUE PEU DIFFERENT DE CE QUI ETAIT JUSQU'ICI OBSERVE. EN PARTICULIER, ELLES SUGGERENT QUE LES NUAGES STRATOSPHERIQUES FORMES DE CRISTAUX DE GLACE SOIENT UN FACTEUR DETERMINANT POUR QU'UNE DESTRUCTION A GRANDE ECHELLE PUISSE AVOIR LIEU A L'INTERIEUR DU VORTEX, ET QUE LEUR IMPACT SUR L'OZONE ENVIRONNANT EST PLUS RAPIDE QUE CE QUI EST HABITUELLEMENT ADMIS. LE BIAIS SYSTEMATIQUE DONT SOUFFRENT LES MESURES ULTRA-VIOLETTES AU VOISINAGE DE LA NUIT POLAIRE OU EN PRESENCE DE NUAGES STRATOSPHERIQUES EST EGALEMENT DEMONTRE. EN ARCTIQUE, LES OBSERVATIONS CONDUITES EN JANVIER 1989 ET FEVRIER 1990 REVELENT LA FORMATION DE NUAGES STRATOSPHERIQUES D'ETENDUE COMPARABLE AU CAS RENCONTRES PENDANT LA FORMATION DU TROU D'OZONE. L'EPISODE DE FEVRIER 1990 FAIT L'OBJET D'UNE ETUDE DETAILLEE, ALLIANT OBSERVATIONS SATELLITAIRES ET IN-SITU AUX SIMULATIONS A HAUTE RESOLUTION D'UN MODELE DE CIRCULATION GENERALE. LA CAPACITE DE CE MODELE A VOCATION CLIMATIQUE A REPRODUIRE CET EVENEMENT EST EXAMINEE. PUIS, A L'AIDE D'UN TRACEUR DONNANT LE TEMPS PASSE PAR LES PARTICULES D'AIR A L'INTERIEUR DU NUAGE, ON ETUDIE LE DEGRE DE PERTURBATION CHIMIQUE DE L'AIR ARCTIQUE, QUI SUGGERE FINALEMENT QU'UNE IMPORTANTE DESTRUCTION D'OZONE LOCALISEE AIT PU INTERVENIR EN AVAL DU NUAGE STRATOSPHERIQUE DE FEVRIER 1990
Author: Leo Miguel Paolo M. Baylon Publisher: ISBN: Category : Languages : en Pages : 142
Book Description
Baseline ozone refers to observed concentrations of tropospheric ozone at sites that have a negligible influence from local emissions. In 2004, the Mount Bachelor Observatory (MBO) was established to examine baseline air masses as they arrive to North America from the west. In the western U.S., air quality is impacted by local, regional, and trans-Pacific sources, which can be natural or anthropogenic. Because of increasing baseline O3 and tighter air quality standards, it is therefore important to understand the nature and the impact of high-ozone events on urban air quality in the western U.S. This dissertation is focused on three types of high-ozone events that we typically observe at MBO and in other surface sites in the western U.S.: (1) upper troposphere/lower stratosphere (UT/LS) episodes, (2) biomass burning (BB) plumes, and (3) long-range transport (LRT) events. First, I looked at an anomalously high-O3 springtime episode in May 2012, where I observed an O3 increase of 2.0–8.5 ppbv in monthly average maximum daily 8–hour average O3 mixing ratio (MDA8 O3) at MBO and numerous other sites in the western U.S. compared to previous years. This shift in the O3 distribution had a strong effect on the number of exceedance days. I also observed a good correlation between daily MDA8 variations at MBO and at downwind sites. This is consistent with previous studies that show that under specific meteorological conditions, synoptic variation in O3 at MBO can be observed at other surface sites in the western U.S. At MBO, the elevated O3 concentrations in May 2012 are associated with low CO values and low water vapor values, consistent with transport from the upper troposphere/lower stratosphere (UT/LS). The Real-time Air Quality Modeling System analyses indicate that a large flux of O3 from the UT/LS in May 2012 contributed to the observed enhanced O3 across the western U.S. Results from this component suggest that a network of mountaintop observations, LiDAR and satellite observations of O3 could provide key data on daily and interannual variations in baseline O3. Second, I studied BB events that I observed at MBO during the summer of 2015. Regional BB has the potential to increase ozone in the western U.S. especially during summer. I explored the photochemical environment in BB plumes, which remains poorly understood. Because I am interested in understanding the effect of aerosols only (as opposed to the combined effect of aerosols and clouds), I carefully selected three cloud-free days in August and investigate the photochemistry in these plumes. At local mid-day (solar zenith angle, SZA = 35o), j(NO2) values were slightly higher (0.2-1.8%) in the smoky days compared to the smoke-free day, presumably due to enhanced scattering by the smoke aerosols. At higher SZA (70o), BB aerosols decrease j(NO2) by 14-21%. I also observe a greater decrease in the actinic flux at 310-350 nm, compared to 350-420 nm, presumably due to absorption in the UV by brown carbon. I compare my measurements with results from the TUV5.2 model and find a good agreement during cloud-free conditions. I perform sensitivity runs and find that j(NO2) is not sensitive to O3 column input. If I keep single scattering albedo and aerosol optical depth constant, an increase in the total ozone from 280 to 400 DU leads to only a 0.8% decrease in j(NO2). Finally, I used the extended Leighton relationship to estimate mid-day HO2 and RO2 concentrations and P(O3) in the fire plumes. I calculate HO2 and RO2 values from 49-185 pptv, and compute ozone production rates of ~2 ppbv/hour in these fire plumes. Finally, I looked at an LRT event on Spring 2015. I observed O3 and CO enhancements of up to 40 ppbv and 80 ppbv, respectively, at MBO. I also used measurements from the NOAA WP-3D Orion research aircraft during the Shale Oil and Natural Gas Nexus (SONGNEX) campaign in Spring 2015. One of the flights during the SONGNEX campaign intercepted the Siberian plume. Ground-based, satellite, and LiDAR data suggest that the Siberian plume was transported at high elevation, did not encounter a high-pressure system that would have led to air subsidence, and therefore did not cause any surface O3 enhancement. I compare our measurements at MBO with aircraft observations and conclude that the Siberian airmass split into two plumes in the eastern Pacific. One plume moved eastward and was sampled by MBO. The other moved over to Alaska and then down to the U.S. Midwest; this second plume was intercepted by the aircraft. sp/CO enhancement ratios for the Siberian 2015 plume were higher than similarly aged plumes in previous studies, owing to dust and the absence of particulate matter loss because of the relatively intact nature of the Siberian plume. O3/CO ratio observed at MBO was higher than the aircraft because of PAN decomposition. I look at the plume’s reactive nitrogen speciation using data from the aircraft and find that ~75% of the NOy is stored as PAN. For ozone production to take place, the plume has to warm up (i.e., descend) to re-form NOx. But given the high elevation of the plume and stable atmospheric conditions, this likely did not take place. The results of this dissertation have important policy implications. They suggest that at the current standard, high-ozone events such as BB plumes, UT/LS episodes, and LRT events would affect the attainment status of a site if they were not identified as exceptional events, which the EPA defines as an uncontrollable event that affected air quality. Understanding the nature and year-to-year variability of these events is therefore critical for an effective implementation of the US NAAQS. Long-term measurements aimed at observing exceptional events would be valuable. MBO is the only high-elevation site on the U.S. West Coast that routinely observes high-O3 events in the FT; however, it provides measurements at only a single point. High-frequency measurements of O3, water vapor and CO at a network of mountaintop sites would be valuable at observing exceptional events. Vertical profiles of O3 and water vapor from LiDAR and ozonesondes, and satellite retrievals would also be helpful. This network of mountaintop observations, LiDAR and satellite observations of ozone could also provide key data on daily and interannual variations in baseline O3. Forecasting exceptional events would be possible using high-resolution chemical transport models that have been evaluated and verified with free troposphere observations.
Author: Bruno Voituriez Publisher: UNESCO ISBN: Category : Science Languages : en Pages : 132
Book Description
El Nino, caprice of the heavens, scapegoat for every calamity? The general public cannot really understand what is behind the El Nino phenomenon. The book offers a tour of the Earth's climate to understand one of its normal but extreme components.
Author: Ira Helsloot Publisher: Charles C Thomas Publisher ISBN: 0398086834 Category : Business & Economics Languages : en Pages : 389
Book Description
We live in turbulent times with continents and nations facing ever-heightening risks such as natural disasters, intense and protracted conflicts, terrorism, corporate crises, cyber threats to infrastructures and mega-events. We are witnessing the rise of mega-crises and a new class of adversity with many unknowns. The prospect of mega-crises presents professionals and students in the field of crisis management with four major tasks. First, they should engage in “deep thinking” about the causes of the increasing occurrence of mega-crises. Second, they should identify and work through the dominant trends which complicate contemporary crisis management. Third, they should upgrade institutional crisis management capacity. Fourth, they should improve societal resilience since no institutional complex can mitigate or manage these mega-crisis on its own. This book is divided into four primary parts, each of which looks at one facet of mega-crises. Part I focuses on the concept of a mega-crisis and mega-crisis management; Part II examines crisis management of mega-natural disasters; Part III evaluates crisis management of man-made mega-crises; and Part IV identifies mega-threats and vulnerabilities. Additional major topics include Hurricane Katrina; Hurricane Gustav; the London Bombings; the Mumbai Terrorist Attacks of July 7, 2005; corporate meltdowns; the subprime crisis; the Olympic Games; electricity grids; global climate change; the Dutch Delta; risks to food security; and mega-crises and the Internet. This comprehensive text will provide practitioners and academics with the results of an across-the-board research effort in the prospects, nature, characteristics, and the effects of mega-crises.
Author: Jacques Lafontaine Publisher: Springer ISBN: 3319207350 Category : Mathematics Languages : en Pages : 408
Book Description
This book is an introduction to differential manifolds. It gives solid preliminaries for more advanced topics: Riemannian manifolds, differential topology, Lie theory. It presupposes little background: the reader is only expected to master basic differential calculus, and a little point-set topology. The book covers the main topics of differential geometry: manifolds, tangent space, vector fields, differential forms, Lie groups, and a few more sophisticated topics such as de Rham cohomology, degree theory and the Gauss-Bonnet theorem for surfaces. Its ambition is to give solid foundations. In particular, the introduction of “abstract” notions such as manifolds or differential forms is motivated via questions and examples from mathematics or theoretical physics. More than 150 exercises, some of them easy and classical, some others more sophisticated, will help the beginner as well as the more expert reader. Solutions are provided for most of them. The book should be of interest to various readers: undergraduate and graduate students for a first contact to differential manifolds, mathematicians from other fields and physicists who wish to acquire some feeling about this beautiful theory. The original French text Introduction aux variétés différentielles has been a best-seller in its category in France for many years. Jacques Lafontaine was successively assistant Professor at Paris Diderot University and Professor at the University of Montpellier, where he is presently emeritus. His main research interests are Riemannian and pseudo-Riemannian geometry, including some aspects of mathematical relativity. Besides his personal research articles, he was involved in several textbooks and research monographs.
Author: P. M. Banks Publisher: Elsevier ISBN: 1483260666 Category : Science Languages : en Pages : 445
Book Description
Aeronomy, Part A is an attempt to make a comprehensive exposition of the processes in aeronomy, the study of composition, movement, and thermal balance of the upper regions of the planetary atmosphere. The text covers topics such as atmospheric regions and atmospheric density, the temperature and molecular mass of the atmosphere; the permanent constituents and the molecular and isotonic composition of the homosphere; and the transition from the homosphere to the heterosphere. Also covered are topics such as the temperature gradient and energies in the thermosphere, conditions at 200km and above 250km, solar radiation and ionization, and aeronomic reactions. The book is recommended for scientists, especially natural physicists, who would like to know more about the field of aeronomy and its advances.
Author: Karen Beazley Publisher: MDPI ISBN: 3038977322 Category : Science Languages : en Pages : 198
Book Description
Biodiversity and Protected Areas assembles twelve topics from around the world, illustrating the complexities and promise of addressing the biodiversity crisis. Authors from Mongolia, Africa, India, Canada, Iraq, and the United States dwell on particular aspects and challenges relevant to those regions. Lessons and approaches from interesting localities, coupled with global analyses give the reader a synthetic view of emerging problems. The opportunities for understanding common issues across different geographies abound, such as comparing local conservation in sub-Saharan Africa with a distribution of very small protected areas in Massachusetts. Several topics will be of immediate interest to policymakers. The book is illustrated with numerous color maps and figures and the authors strove for clear, uncomplicated writing. The editors provide an overview of chapters, placing them in the context of other biodiversity and protected area literature. Students and conservationists attempting to broaden their views of biodiversity and protected areas should find this collection to be interesting.
Author: Hubert Teyssedre
Author: Hubert Teyssedre
Author: Guillaume Angot
Author: Franck Lefêvre
Author: Leo Miguel Paolo M. Baylon
Author: Daniel Cariolle
Author: Bruno Voituriez
Author: Ira Helsloot
Author: Jacques Lafontaine
Author: P. M. Banks
Author: Karen Beazley