Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1993. / Includes bibliographical references (leaves 180-187). / by Sergio Kostek. / Ph.D.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1991. / Includes bibliographical references (p. 241-261). / Sc.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 147-154). / Tropical cyclone size remains an unsolved problem in tropical meteorology, yet size plays a significant role in the damage caused by tropical cyclones due to wind, storm surge, and inland freshwater flooding. This work explores size, defined as the radius of vanishing wind, in observations and at equilibrium in an idealized numerical model. First, a climatology of size is created from the QuikSCAT database of near-surface wind vectors for the years 1999-2008. Globally, the distribution of the outer radius is found to be log-normal, with statistically significant variation across ocean basins, but with minimal correlation with various dynamic and thermodynamic parameters. Second, the sensitivity of the structure of a numerically-simulated axisymmetric tropical cyclone at statistical equilibrium to the set of relevant model, initial, and environmental external parameters is explored. The analysis is performed in a highly-idealized state of radiative-convective equilibrium (RCE). The non-dimensional equilibrium radial wind profile is found to be modulated primarily by a single nondimensional parameter given by the ratio of the storm radial length scale to the parameterized eddy radial length scale. The relevant storm length scale is shown to be the ratio of the potential intensity to the Coriolis parameter, matching the prediction for the "natural" storm length scale in prevailing axisymmetric tropical cyclone theory. The outer storm circulation is further modulated by a second non-dimensional parameter that represents the non-dimensional Ekman suction rate. Third, size is explored in three-dimensional "tropical cyclone world" simulations, with preliminary results confirming the relevant length scale obtained in axisymmetry. Ultimately, the results of the equilibrium storm analysis are insufficient to explain the observed distribution of tropical cyclone size, but they provide the first steps toward a more fundamental understanding of the dynamics of size. / by Daniel Robert Chavas. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references. / The history of life on Earth is punctuated by mass extinction, the cause of which has often been attributed to rapid changes in global climate and/or ocean chemistry that are inferred to accompany the eruption of large igneous provinces (LIPs). Implicating LIP eruptions as the trigger of the biologic crises has relied on the approximate coincidence in time between these two events. To test this causal link and to understand the mechanisms driving extinction requires a more accurate and precise temporal record of both events than currently exists. With higher precision, the ability to resolve the relative timing of mass extinction and magmatism outside the analytical uncertainty on dates populating age models is possible, allowing detailed investigation of a causal connection. The current work develops zircon and perovskite minerals as accurate, high-precision geochronometers on the mafic rocks that commonly characterize LIP magmas. These advances are coupled with the latest techniques in U/Pb geochronology to generate highprecision age models which are used to evaluate the relative timing of (1) the end- Permian mass extinction, which is the most severe in the Phanerozoic, and the Siberian Traps LIP, which is the largest continental magmatic event in the Phanerozoic, and (2) the Karoo-Ferrar LIP and the early-Jurassic biotic crisis and global ocean anoxia. With these datasets, age-models for both mass extinction and LIP magmatism precise to a maximum of ~0.02% are developed, enabling, for the first time, resolution of the relative timing of eruption and extinction outside of uncertainty. This work conclusively indicates that (1) Siberian Traps LIP magmatism precedes onset of the end-Permian mass extinction and continued through the mass extinction interval, into the early Triassic biotic recovery interval, and (2) Karoo-Ferrar LIP magmatism likely preceded the onset of early-Jurassic extinction and ocean anoxic event and continued through this interval, over ~ 1 Ma. / by Seth Douglas Burgess. / Ph. D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, February 2000. / Includes bibliographical references (p. 84-87). / An inverse box model of the tropical Pacific Ocean from 321S - 10N is constructed from two zonal and six meridional hydrographic sections. This data is supplemented with LADCP data close to the equator where geostrophy fails. A consistent solution is found despite the presence of a number of mid-ocean crossing points and the data being spread over many years and seasons. The total upwelling across the ... = 23.5 isopycnal surface in a 60 latitude band centered on the equator is estimated to be 55 ± 27Sv. The zonal mean cross-isopycnal velocity for the same surface in the same latitude band is estimated to be 6.88 t 3.23 x 10 4 cms- 1. The addition of radiocarbon data places a strong constraint on the vertical transfers in the model and significantly reduces the error on the estimated vertical transport and velocity. When radiocarbon constraints are included, the upwelling across the ... = 23.5 isopycnal surface in the equatorial zone is estimated to be 52 ± 16Sv and the zonal mean cross-isopycnal velocity across the same surface is estimated as 7.15 t 1.90 x 10- 4 cms-1 . That a consistent solution can be found is encouraging but it remains unclear whether one-time data is representative of mean conditions in a region which is known to be highly variable. / by Sarah Louise Samuel. / S.M.

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1990. / Includes bibliographical references (leaves 245-255). / by John Edward Foley. / Sc.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1996. / Includes bibliographical references (p. 193-199). / Natalie Marie Mahowald. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 40-42). / We use a 2-D finite difference method to numerically calculate the seismic response of a single finite fracture in a homogeneous media. In our experiments, we use a point explosive source and ignore the free surface effect, so the fracture scattering wave field contains two parts: P-to-P scattering and P-to-S scattering. We vary the fracture compliance within a range considered appropriate for field observations, 10-12 m/Pa to 10-9 m/Pa, and investigate the variation of the scattering pattern of a single fracture as a function of normal and tangential fracture compliance. We show that P-to-P and P-to-S fracture scattering patterns are sensitive to the ratio of normal to tangential fracture compliance and different incident angle, while radiation pattern amplitudes scale as the square of the compliance. We find that, for a vertical fracture system, if the source is located at the surface, most of the energy scattered by a fracture propagates downwards, specifically, the P-to-P scattering energy propagates down and forward while the P-to-S scattering energy propagates down and backward. Therefore, most of the fracture scattered waves observed on the surface are, first scattered by fractures, and then reflected back to the surface by reflectors below the fracture zone, so the fracture scattered waves have complex ray paths and are contaminated by the reflectivity of matrix reflectors. / by Xinding Fang. / S.M.

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2000. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 21-22). / Under the auspices of NASA's Global Tropospheric Experiment (GTE), the Pacific Exploratory Missions (PEM) have collected numerous air samples of many regions of the troposphere. Data from PEM-West B (February 7 to March 15, 1994), and PEM-Tropics A (August 15 to October 5, 1996) have been used here to study non-methane hydrocarbon (NMHC) ratios and to compare pollution transport by large scale convection and subsidence, as well as horizontal transport across the Pacific. For PEM-Tropics A, 7 cases are studied, each involving different aspects of transport. Persistent circulation features in the South Pacific played a significant role in NIMHC ratio distribution and processing. For PEM-West B, sources of a large pollution region are studied and compared to equatorial transport. NMHC ratios were found to be useful tracers of pollution distribution through the troposphere. The contrasts of these ratios across relatively small distances, particularly on either side of the South Pacific Convergence Zone in PEM-Tropics A, suggest that convection shapes pollution transport and distribution, particularly in the South Pacific. / This work was supported by the NASA GTE program under grant NAG1-1758 and NAG1-2173 / by Christopher Chay Casso. / S.B.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1994. / Includes bibliographical references (p. [193]-[198]). / by Kyle William Blasch. / M.S.