Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2002. / Includes bibliographical references (p. 205-224). / In this thesis I combine high resolution seismic tomography and realistic flow modeling to constrain mantle convection. The bulk of the data used in the tomographic imaging are millions of P, pP and pwP travel time residuals, read from high frequency seismic records. The distribution of earthquakes and stations results in uneven data coverage and to improve the model I use core phases (PKP, Pdiff) for the deep mantle and surface reflected phases (PP) for the shallow mantle. Since narrow rays are not adequate for low frequency measurements, I construct broad 3-D sensitivity kernels to relate some of the added data to earth's structure. Furthermore, the parameterization of the tomographic model is adapted to data density and the model shows, among other details, the varying style of subduction in the shallow mantle and complex flow patterns around the transition zone between the upper and lower mantle. I develop a novel and efficient method of modeling buoyancy driven mantle flow in spherical geometry. Here, the linear Stokes equation is solved using a Green's function approach and 3-D surfaces, representing the boundaries of dense material, such as subducting slabs, are tracked through time. / by Hrafnkell Kárason. / (cont.) I describe the basis of the approach, represent tests, and investigate the thickening and slowing of subducting slabs for different viscosity contrasts between the upper and lower mantle. I compare seismic tomography, flow modeling and reconstructed plate motions associated with the collision of India to mainland Asia, in particular, the south and south-west motion of the Sunda block. This way I can evaluate subduction scenarios and make quantitative comparison between tomography and plate reconstructions. I conclude that a viscosity increase of -200 in the lower mantle, resulting in -10 times higher viscosity than previously estimated, best fits the observations. Juxtaposing the tomography, the flow models and inversion tests using the flow models as input, indicates that the results are robust. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1989. / Science copy is bound in 2 v. / Includes bibliographical references (leaves 326-332). / by Peter Morse Roberts. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1989. / Includes bibliographical references (leaves 194-199). / by Thomas W. Trull. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences, 1986. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND LINDGREN. / Bibliography: leaves 278-284. / by James Louis Davis. / Ph.D.

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 19-23). / Bubble bursting at the ocean surface generates smaller film-burst particles and larger jet drop particles that differ in composition. The chemical composition of sea spray aerosols is an important parameter for the evaluation of their impact on the global climate system. This study investigates the role of particle chemistry on the heterogeneous ice nucleation potential of laboratory-generated sea spray aerosols. Cultures of Procholorococcus, a highly abundant marine phytoplankton species, were used as a model source of organic sea spray aerosols. Results show that smaller particles generated from the lysed Procholorococcus cultures were organically enriched and effectively activated as ice nucleating particles at warmer temperatures and lower supersaturations than larger particles. The role of chemical composition in the activation of the particles was studied by measuring the nucleation abilities of single component organic molecules that mimic proteins, lipids, and carbohydrates in Procholorococcus. Amylopectin, agarose, and aspartic acid exhibited nucleation behaviors similar to particles generated from Procholorococcus cultures. Therefore, carbohydrates and proteins with numerous and well-ordered hydrophilic functional groups may determine the ice nucleation potential of organic sea spray aerosols. / by Lilian A. Dove. / S.B.

Thesis: S.M., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 102-109). / Determining the correct number of layers as input for ID resistivity inversion is important for constructing a model that represents the subsurface accurately. Current common methods to select the number of layers are performed in one of three ways: by trial-and-error and choosing the best model data-fit, by using the modified F-test, or through trans-dimensional model parameterization. Although these methods are creative approaches, they are computationally expensive, as well as time-consuming and painstaking in practice. In this thesis, I provide a method that solves the problem of choosing the correct number of layers represented by the apparent resistivity curve. The method follows the two-steps approach suggested by Simms and Morgan (1992) to systematically resolve the optimum number of layers. The first step is to run a fixed thickness inversion using a large number of layers in which the number of layers and layer thicknesses are fixed, and resistivity values are inversion parameters. I then integrate the outcome of the first inversion (the resistivity model) to determine the optimum number of layers based on changes of the slope. The detected number of layers is used as an input parameter for the second step; which is running a variable-thickness inversion (layer thicknesses and resistivities are both inversion parameters) for the outcome, the final resistivity model. Each step uses the Ridge Trace damped least-square inversion. The two inversion steps are integrated into a software program that performs the steps sequentially. The software determines all inversion parameters from the data file in a self-consistent manner. This proposed method uses a robust ridge trace regression algorithm, which has proven to be stable, accurate, and at least a hundred times faster than current methods. / by Ammar Mohammed Alali. / S.M.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2014. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references (pages 141-146). / The ubiquity of cloud clusters and their role in modulating radiative cooling and the moisture distribution underlines the importance of understanding how and why tropical convection organizes. In this work, the fundamental mechanism underlying the self-aggregation of convection is explored using a cloud resolving model. The objective is to identify and quantify the interactions between the environment and the convection that allow the convection to spontaneously organize into a single cluster. Specifically, the System for Atmospheric Modeling is used to perform 3-d cloud system resolving simulations of radiative-convective equilibrium in a non-rotating framework, with interactive radiation and surface fluxes and fixed sea surface temperature. Self-aggregation only occurs at sea surface temperatures above a certain threshold. As the system evolves to an aggregated state, there are large changes to domain averaged quantities important to climate, such as radiative fluxes and moisture. Notably, self-aggregation begins as a dry patch that expands, eventually forcing all the convection into a single clump. Thus, when examining the initiation of self-aggregation, we focus on processes that can amplify this initial dry patch. Sensitivity tests suggest that wind-dependent surface fluxes and interactive longwave radiative fluxes are important for permitting self-aggregation. A novel method is introduced to quantify the magnitudes of the various feedbacks that control self-aggregation within the framework of the budget for the spatial variance of column - integrated frozen moist static energy. The absorption of shortwave radiation by atmospheric water vapor is found to be a key positive feedback in the evolution of aggregation. In addition, there is a positive wind speed - surface flux feedback whose role is to counteract a negative air-sea enthalpy disequilibrium - surface flux feedback. The longwave radiation - water vapor feedback transitions from positive to negative in the early and intermediate stages of aggregation. The long-wave radiation - cloud feedback is the dominant positive feedback that maintains the aggregated state once it develops. Importantly, the mechanisms that maintain the aggregated state are distinct from those that instigate the evolution of self-aggregation. These results and those of a companion study suggest that the temperature dependence of self-aggregation enters through the longwave feedback term. / by Allison A. Wing. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1993. / Includes bibliographical references (p. 113-117). / by Dana Elizabeth Hartley. / Ph.D.

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2006. / Cataloged from PDF version of thesis. Pages 25 and 37-39 missing from original thesis. / Includes bibliographical references (page 28). / Digital technology has become completely engrained in the process of scientific research. Grade schools are beginning to incorporate computers and other digital devices into the learning process as tools for learning other subjects, including science. Educators have experimented with a variety of programs that incorporate computers, such as digital tutors, simulations of natural systems, and interactive simulations. This study aimed to demonstrate that handheld computers are a useful resource in problem-based learning environments. A "mini-curriculum", focused on making handheld computer-aided measurements of the key environmental parameters in marine estuaries, was designed and taught to eleven students from the Palmetto Ridge High School in Naples, Florida over a two week period. Students' reactions to both the curriculum and the computers were overwhelmingly positive. This proof-of-concept trial indicates that handheld computers have the potential to be a very useful tool in problem-based learning. / by Emma Bassein. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences, 1985. / Microfiche copy available in Archives and Science. / Bibliography: leaves 158-161. / by Thomas Nehrkorn. / Ph.D.