Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmosphere and Planetary Sciences, 1987. / Bibliography: leaves 24-25. / by Anita M. Killian. / M.S.

Thesis: Ph. D. in Atmospheric Science, Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2018. / 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 187-207). / This thesis is an exploration of two seemingly unrelated questions: First, how do water vapor and ozone variations radiatively influence the thermal structure of the tropopause region? Second, what sets the thermodynamic limits of tropical cyclone intensity across the seasonal cycle? The link between these subjects is tropical cyclone outflow, which often reaches into the tropopause region, allowing the thermal structure there to impact tropical cyclone potential intensity. A radiative transfer model is employed to calculate the radiative effects of the 2000 and 2011 tropopause region abrupt drops -- events in which temperatures, water vapor, and ozone plunge suddenly to anomalously low levels. Results show that radiative effects partially offset in the region above the tropopause, but nonlocally combine to cool the layers below the tropopause. Persistently low water vapor concentrations associated with the abrupt drops spread to extratropical latitudes, and produce a total negative radiative forcing that offsets <12% of the carbon dioxide forcing over 1990-2013. Next, the importance of local and nonlocal radiative heating/cooling for tropopause region temperature seasonal cycles is examined. The radiative effects of water vapor seasonality are weak and local to the tropopause, whereas ozone radiatively amplifies temperature seasonality in the tropopause region by 30%, in part because stratospheric ozone seasonality nonlocally affects the tropopause region thermal structure. To determine how the tropopause region thermal structure affects thermodynamic limits on tropical cyclone intensity, this study presents the first comprehensive seasonal cycle climatology of potential intensity. Perennially warm sea surface temperatures in the Western Pacific result in outflow altitudes that are near the tropical tropopause region throughout the seasonal cycle, whereas the seasonalities of other ocean basins are less influenced by the tropopause region. Probing the potential intensity environmental drivers reveals that the seasonality of near-tropopause temperatures in the Western Pacific damps potential intensity seasonal variability by <30%. Incorporating a best track tropical cyclone archive shows that this result is relevant for real-world tropical cyclones: the tropopause region thermal structure permits intense Western Pacific tropical cyclones in every month of the year, which may have critical consequences for coastal societies. / by Daniel Michael Gilford. / Ph. D. in Atmospheric Science

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1997. / Includes bibliographical references (p. 207-217). / by Xinyu Zheng. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1992. / Includes bibliographical references (leaves 165-168). / by David Walsh. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences, 1985. / Microfiche copy available in Archives and Science. / Vita. / Bibliography: leaves 152-162. / by Ronald Alan Remillard. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1992. / Includes bibliographical references (p. 127-132) and index. / by Stan Heckman. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2007. / Includes bibliographical references. / Lavas derived from long-lived mantle plumes provide important information of mantle compositions and the processes that created the geochemical heterogeneity within the mantle. Kerguelen and Hawaii are two long-lived mantle plumes and lavas associated with them have very different geochemical characteristics. In this thesis I studied the geochemical compositions of the lavas associated with Kerguelen plume (Mt. Capitole in Kerguelen Archipelago) and Hawaiian plume (Mauna Kea, East Molokai and West Molokai volcanoes) to understand what processes contributed to the geochemical variations observed in Kerguelen and Hawaiian lavas and the geochemical structure of the mantle beneath them. Mt. Capitole is in the central part of the Kerguelen Archipelago and is attributed to Cenozoic volcanism arising from the Kerguelen hotspot. Based on the study of Mt. Capitole and previous isotopic data for the Kerguelen Plateau, Kerguelen Archipelago and Heard Island, I propose that two stages of mixing can explain the significant Sr, Nd, Hf and Pb isotopic heterogeneity. The first mixing process, best shown by the submarine lavas from Northern Kerguelen Plateau, is between a depleted component (i.e., relatively low 87Sr/86Sr with high 143Nd/144Nd and 176Hf/177Hf), probably related to Southeast Indian Ocean mid-ocean ridge basalt, but possibly intrinsic to the Kerguelen plume, and an enriched Kerguelen plume component. From -34 Ma to <1 Ma, on average the proportion of the depleted component decreased. Subsequently, a second mixing process involved addition of a component with relatively high 87Sr/86Sr (>0.7060) and low 143Nd/144Nd (<0.5125) and 176Hf/177Hf (<0.2827) and non-radiogenic Pb isotope ratios (<17.9 for 206Pb/204Pb). / (cont.) I infer that this component was lower continental crust. At Hawaii there are systematic geochemical differences between the < 3 My Hawaiian shields forming the subparallel spatial trends, known as Loa and Kea. East Molokai (> 1.5 Ma), the oldest volcano on the Kea-trend, maintains the Kea-like geochemical characteristics. As East Molokai and other Kea-trend volcanoes (Mauna Kea, Kohala, Haleakala and West Maui) migrate away from the hotspot and evolve from the shield to postshield stage, isotopic ratios of 87Sr/86Sr decrease and 143Nd/144Nd and 176Hf/177Hf increase in postshield lavas; however, all Kea postshield lavas have similar ratios of Sr, Nd, Hf and Pb showing that the periphery of the hotspot sampled by Kea-trend postshield lavas had long-term geochemical homogeneity (>1.5 My). The temporal changes in Sr, Nd and Hf isotope ratios are attributed to incorporation of a depleted component that dominantly sampled by rejuvenated stage lavas. This depleted component has Kea-trend Pb isotopic characteristics, relatively low 208Pb/204pb at a given 206Pb/204Pb, and it is probably not related to oceanic lithosphere or the source of mid-ocean ridge basalt. The Loa-Kea spatial geochemical differences end at West Molokai shield (- 1.9 Ma) which is the oldest Loa-trend volcano on the double parallel chains. West Molokai shield includes lavas with Loa- and Kea-like geochemical characteristics; a mixed Loa- Kea source is required. In contrast, West Molokai postshield lavas are exclusively Kea-like. This change in source geochemistry can be explained by the observed change in strike of the Pacific plate near Molokai Island so that as West Molokai volcano moved away from a mixed Loa-Kea source it sampled only the Kea side of a bilaterally zoned plume (Abouchami et al., Nature, v434, 2005). / by Guangping Xu. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1996. / Includes bibliographical references (leaves 60-62). / by Muhammed M. Saggaf. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1987. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND LINDGREN. / 8 maps in pocket of volume 1. / Bibliography: leaves 215-223. / by Peter Gerhard Tilke. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1993. / Includes bibliographical references (p. 190-203). / by De-Zheng Sun. / Ph.D.