Reproduction de : Thèse de doctorat : Structure et dynamique des systèmes réactifs : Lille 1 : 2005. / N° d'ordre (Lille 1) : 3618. Titre provenant de la page de titre du document numérisé. Bibliogr. à la suite de chaque chapitre.

Reproduction de : Thèse de doctorat : Structure et dynamique des systèmes réactifs : Lille 1 : 2006. / N° d'ordre (Lille 1) : 3927. Une publication en anglais reproduite en annexe. Résumé en français et en anglais. Titre provenant de la page de titre du document numérisé. Bibliogr. p. 267-280.

Thèse de doctorat : Lasers, Molécules, Rayonnement atmosphérique : Lille 1 : 2003 ; 3358. / Articles en anglais en annexe. Résumé en français et en anglais. Bibliogr. p. 243-247.

Thesis (D.P.H.)--University of Alabama at Birmingham, 2007. / Title from PDF title page (viewed on Feb. 19, 2010). Includes bibliographical references (p. [197]-216).

Thesis (Ph. D.)--Institute of Paper Chemistry, 1972. / Includes bibliographical references (p. 145-149).

This thesis examines the response of air pollutant emissions, water use and carbon emissions from electric power supply systems (electrical grids) to market forces and natural and human disruptions. Specifically, the response of electrical grid operation decisions to emissions pricing and other factors, such as drought restrictions, is examined. The grid of the Electricity Reliability Council of Texas (ERCOT) is used as a source of data, and as a spatial and temporal test-bed. Price signals for NOx emissions have the potential to reduce NOx emissions from the ERCOT grid by up to 50%. In addition to lowering NOx, there are co-benefits to introducing NOx prices, including reductions in the emissions of SOx (24.9% to 70.9%), Hg (16.8% to 81.3%) and CO2 (8.7% to 21.1%). Water consumption was also decreased by 4.3% to 8.2%. The costs of redispatching electricity generation to reduce NOx emissions are, in many scenarios, comparable to conventional control costs. Higher CO2 prices produce many of the same changes in electricity generation as increases in NOx prices, but the simultaneous application of NOx and CO2 pricing produces complex effects. Under stress, such as drought induced water scarcity, dispatching decisions have the potential to increase water availability in regions in which drought is a concern. This dispatching had relatively small impacts on total water consumption summed over all regions of the ERCOT grid. However, the dispatching scenarios resulted in net increases in NOx, SOx, and CO2 emissions rates summed over all regions of the grid, particularly in regions that were absorbing the electricity generation that was exported out of the drought impacted regions. The costs of electricity dispatching, per volume of water consumption reduced in the drought impacted region, was generally greater than the cost of implementing dry cooling in the same facilities at high electricity demand levels, but comparable to dry cooling at low to moderate demand levels. Finally, while changes in total emissions can be used as a surrogate for air quality impacts, actual changes in air pollutant concentrations, such as ozone, exhibit complex spatial and temporal patterns in response to redispatching, including the creation of hot spots of elevated concentrations. / text

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It is the future of the stratospheric ozone layer, which protects life at Earth’s surface from harmful ultraviolet (UV) radiation, that is the focus of the present work. Fundamental changes in the composition and structure of the stratosphere in response to anthropogenic climate forcing may lead to catastrophic ozone loss under current, and even reduced, stratospheric halogen loading. In particular, the evolution toward a colder, wetter stratosphere, threatens to enhance the heterogeneous conversion of inorganic halogen from its reservoir species to its catalytically active forms, and thus promote in situ ozone loss. Water vapor concentrations control the availability of reactive surface area, which facilitates heterogeneous chemistry. Furthermore, the rates of the key heterogeneous processes are tightly controlled by the ambient humidity. Thus, credible predictions of UV dosage require a quantitative understanding of both the sensitivity of these chemical mechanisms to water vapor concentrations, and an elucidation of the processes controlling stratospheric water vapor concentrations. Toward this end, we present a set of four case studies utilizing high resolution in situ data acquired aboard NASA aircraft during upper atmospheric research missions over the past two decades. 1) We examine the broad scale humidity structure of the upper troposphere and lower stratosphere from the midlatitudes to the tropics, focusing on cirrus formation and dehydration at the cold-point tropical tropopause. The data show evidence for frequent supersaturation in clear air, and sustained supersaturation in the presence of cirrus. These results challenge the strict thermal control of the tropical tropopause. 2) We investigate the likelihood of cirrus-initiated activation of chlorine in the midlatitude lower stratosphere. At midlatitudes the transition from conditions near saturation below the local tropopause to undersaturated air above greatly reduces the probability of heterogeneous activation and in situ ozone loss in this region. 3) We probe the details of heterogeneous processing in the wintertime Arctic vortex, and find that in situ measurements of OH provide incontrovertible evidence for the heterogeneous reaction of HOCl with HCl. This reaction is critical to sustaining catalytically active chlorine and prolonging ozone loss in the springtime vortex. 4) We revisit the topic of midlatitude ozone loss with an emphasis upon the response of ozone in this region to changes in the chemical composition and thermal structure of the lower stratosphere induced by anthropogenic climate change. Specifically, we show evidence for episodic moisture plumes in the overworld stratosphere generated by the rapid evaporation of ice injected into this region by deep convection, and find that these high water vapor plumes have the potential to alter the humidity of the lower stratosphere, and drastically increase the rate of heterogeneous chemistry and in situ ozone loss, given sufficient reactive surface. / Earth and Planetary Sciences

This thesis explores the natural forces controlling variability of the tropospheric oxidants on interannual to glacial-interglacial time scales. The oxidants (primarily OH and ozone) determine the lifetime of many trace gases of human interest, including air pollutants and long-lived greenhouse gases such as methane. The oxidants respond to meteorological conditions, precursor emissions (natural and anthropogenic), and surface and overhead stratospheric boundary conditions, all of which have changed since the Last Glacial Maximum (LGM; ~21ka). This dissertation first examines in mechanistic detail the effect of variability in the lightning source of nitrogen oxides \((NO_x)\) precursors on interannual variability (IAV) of the oxidants in the recent past. An optimized technique is presented to constrain the lightning \(NO_x\) source in the GEOS-Chem global chemical transport model (CTM) to time-varying satellite data from the Lightning Imaging Sensor. This constraint improves the ability of the CTM to reproduce observed IAV in 9-year (1998-2006) hindcasts of tropical ozone and OH. IAV in ozone and OH is more sensitive to lightning than to biomass burning, despite greater IAV in \(NO_x\) from the latter source. The sensitivity of OH to lightning reflects positive chemical feedbacks on ozone production, \(HO_x\) recycling, and loss frequencies. This dissertation next introduces an offline-coupled climate-biosphere-chemistry framework for determining oxidant levels at and since the LGM. Detailed simulations of tropospheric composition are performed by GEOS-Chem driven by meteorological fields from the GISS ModelE general circulation model, land cover from the BIOME4-TG global terrestrial equilibrium vegetation model, and fire emissions from the LMfire model. Time slice simulations are presented for the present day, preindustrial, and two different possible representations of the LGM climate. Sensitivity of the results to uncertainty in lightning and biomass burning emissions is tested. Though well-buffered, all simulations find net reduced oxidative capacities relative to the present day. The most important parameters for controlling tropospheric oxidants over glacial-interglacial periods are changes in overhead ozone, tropospheric \(H_2O\), and lightning. The results are discussed in the context of the ice-core record, particularly for methane. / Engineering and Applied Sciences