Thesis: S.M., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 81-91). / The effects of volatile transport on Pluto's surface on ground-based observations of Pluto's light curve were studied. Due to Pluto's eccentricity of 0.249, obliquity of 123 degrees, and atmosphere, the transfer of volatiles may cause global surface change over the course of Pluto's orbit. Magellan visible and near infrared data were gathered one month before the New Horizons flyby in order to compare ground-based observing with spacecraft data. Furthermore, a model was created in order to predict how volatile transport will affect ground-based observations in the future. The near-infrared data show large scale surface composition as a function of longitude and confirm New Horizons' compositional results. The model determines that the composition of the underlying layer on Pluto's north pole can be determined by monitoring the J - Ks ratio, if the nitrogen ice currently located on the north pole is sublimated due to volatile transport. Therefore, ground based observing can monitor volatile transport and global surface changes can be monitored after the New Horizon's flyby. / by Molly Kosiarek. / S.M.

Thesis: S.M. in Atmospheric science, Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 51-53). / As a global leading agricultural producer, Southeast Asian (SEA) economy and livelihood rely on water supply from the monsoon precipitation during the rainy season. However, SEA monsoon system is still understudied. Here, we focus on the Mainland SEA monsoon because of its geographical simplicity. We find that the total precipitation of the Mainland SEA monsoon has experienced a reversing trend from a four-decade-long drying by 0.18 mm day-1 decade-1 to increasing by 0.13 day-1 decade-1 starting from 1989. The increased energy and moisture post-reversal comes from the strengthened Hadley and Walker cell due to the increasing meridional equivalent potential temperature ([theta]e) gradient. The meridional [theta]e gradient shows significant correlation with the precipitation time-series at r = 0.52 (p = 0.0015), despite [theta]e gradient has reversed ahead of precipitation for 4-5 years. Even though the overall precipitation trend of Mainland SEA in recent decades is increasing, the north of Myanmar and the south of China shows a decreasing trend. The surface wind analysis shows that surface southwesterly is weakening in the Northern Hemisphere, so the north of Mainland SEA receives less moisture, but also allow more moisture from the South China Sea to access the south of Mainland SEA. The surface wind change also corresponds with the rising branch of Hadley cell shifting southward. Lastly, we find that the Mainland SEA monsoon is a mixed convection system, composing of deep, moist convection directly over the region at 10-20°N, and a shallow, dry convection just north of the region at 35°, aligning with further assessment using zonal-mean precipitation, [theta], and [theta]e,. The deep, moist convection coincides with the zonal-mean [theta]e peak. The shallow, dry convection coincides with the zonal-mean [theta] peak. / by Warittha Panasawatwong. / S.M. in Atmospheric science

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1992. / Includes bibliographical references (p. 237-244). / by Stephen Arthur Cohn. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 50). / ExoplanetSat is the prototype of a CubeSat-based space telescope for the discovery of transiting exoplanets around the nearest and brightest Sun-like stars. It is capable of monitoring a single target star from low Earth orbit, going through an orbit day-night cycle. In order to limit the noise induced by variable temperature, the temperature of the imaging device needs to be controlled within a steady level over the approximately 30 minutes of orbit night when the telescope is actively observing. In this thesis I present the design of a cold-biased system that controls the temperature of the irnager through passive cooling and active heating. The temperature is controlled by the system being heated to a slightly higher temperature than it's environment. The active control over the heater maintains the system at the target temperature within the 30 millikelvin range, with the best performance of 5 millikelvin control. The temperature control system can be used at various phases of ExoplanetSat development, including laboratory simulation of the temperature control of the ExoplanetSat imager during orbit night, characterizing the temperature response of any potential imager, and part of the design can be applied to the flight model of the prototype of ExoplanetSat for irnager temperature control. / by Luyao Li. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2002. / Includes bibliographical references (p. 181-200). / We measured spectral and time-domain properties of seismic events over a size range that spans magnitudes M [approx.] -2 to 8 in order to study earthquake source processes. In addition, we conducted laboratory experiments to study interseismic behaviors that can influence earthquake nucleation and we developed a model of eathquake rupture to explain the scaling behaviors we observe. To bridge the scale gap between laboratory data and global seismic observations, we studied data from five deep gold mines in the Far West Rand region of South Africa. These mines are seismically active due to daily underground blasting and record [approx.] 1000 events per day from -2 =/< M =/< 3+ close to their sources. Frequency-magnitude relations, spatio-temporal clustering relations and observations of seismic spectra provide evidence that there are two types of events that occur in these mines, which we designate as Type A and Type B. Type-A events are fracture-dominated ruptures of previously intact rock and show an upper magnitude cutoff at M [approx.] 0.5. They are tightly clustered in space and time and occur close to active stope faces. They have scaling properties that agree with other studies of fresh-fracturing seismicity in that apparent stress decreases with magnitude and stress drop increases with magnitude. / In contrast, Type-B events are temporally and spatially distributed throughout the active mining region. They have a lower magnitude cutoff at M [approx.] 0. From frictional scaling laws and observations of source spectra, we deduce that that this lower magnitude cutoff represents the critical patch size for earthquake nucleation in this mining environment. We find that the critical patch size is on the order of 10 m with a critical slip distance on the order of 10-4 m. Type-B events have scaling properties that match extrapolations from tectonic earthquakes. For example, apparent stress and particle velocity increase with magnitude. We develop a kinematic model of increasing rupture velocity with increasing source size to account for the observed scaling of frictional shear events. / by Eliza Bonham Richardson. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 215-227). / I study fundamental mechanisms of atmosphere-ocean-sea ice interaction. Hierarchies of idealized models are invoked to argue that multiple equilibria and abrupt change are robust features of the climate system. The main finding is that meridional structure in poleward oceanic energy transport, which is set by the wind forcing, gives rise to preferred latitudes for the sea ice edge, including a stable large ice cap extending into mid-latitudes. I review multiple equilibria in energy balance models (EBMs), and extend the EBM to include explicit ocean heat transport (OHT) and insulating sea ice. I derive a method for simultaneously satisfying global energy and angular momentum budgets through a diffusive closure for potential vorticity, enabling a prediction of the basic shape of the surface wind stress. An idealized model of wind-driven gyres links this stress to OHT, and gives significant structure on sub-hemispheric scales in agreement with observations. This model predicts a stable large ice cap solution not found in the classic EBM, made possible by convergence of OHT in mid-latitudes. Analogous multiple equilibria are found in coupled atmosphere-ocean-sea ice general circulation model (GCM) simulations with idealized geometry (a pure aquaplanet and a "ridgeworld" with a global-scale ocean basin). Despite differing ocean dynamics, both configurations support similar equilibria: an ice-free climate, a cold climate with mid-latitude sea ice edge, and a completely ice-covered Snowball state. Multiple states persist despite a seasonal cycle and vigorous internal variability. Simulations with slowly-evolving thermal forcing show that some transitions between the ice-free and large ice cap states are abrupt. Multiple equilibria are explored in uncoupled simulations with prescribed OHT. The large ice cap is stabilized by wind-driven convergence of OHT at the poleward edge of the subtropical thermocline. The size of the large ice cap is sensitive to the meridional and seasonal distribution of OHT convergence. The ice-free state persists in the absence of high-latitude OHT. Mid-latitude convergence of OHT warms the poles by driving increased atmospheric heat transport to the poles. This effect is captured in a simple diffusive EBM. I discuss the significance of these findings for understanding the paleoclimate record. / by Brian E. J. Rose. / Ph.D.

Thesis: S.M., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references. / The 20 th century brought many breakthroughs in our understanding of Earth, but there are still many outstanding geophysical questions. Deep electromagnetic studies provide information on electrical conductivity from the near-surface to deep within the mantle (~1600 km) complementing seismic work aiming understand the composition, structure and dynamics of the mantle. Electromagnetic induction studies utilize the skin depth concept which relates the period of a source electromagnetic field and the conductivity of the penetrated material with the maximum depth the field can penetrate. Traditional satellite-based induction studies use signals of magnetospheric origin and considered a period range between a few days and a few months. These traditional studies are mostly sensitive to deep conducting structures because of the inductive coupling between primary and induced sources. In contrast, galvanic coupling from the oceanic tidal signal allows for studying less conductive, shallower structures by also using shorter periods. A few studies convincingly demonstrated that the magnetic fields induced by the lunar semidiurnal ocean tide can be identified in satellite observations. This result encourages using tidal satellite magnetic data to constrain subsurface electrical conductivity in oceanic regions. We perform global 3- D electromagnetic numerical simulations to investigate the sensitivity of the ocean's tidal signals magnetic amplitudes to conductivity distributions at different depths. The results of our sensitivity analysis suggest it will be promising to use oceanic signals detected at satellite altitude for probing lithospheric and upper mantle conductivity. Our simulations also suggest that seafloor electric and magnetic field data may provide complementary details to better constrain lithospheric conductivity. / by Neesha Regmi Schnepf. / S.M.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, June 2015. / Cataloged from PDF version of thesis. "June 2015." / Includes bibliographical references (pages 133-145). / This thesis investigates various aspects of the variability of the stratospheric polar vortex and the effect of this variability on tropospheric weather and climate patterns on various timescales. In the first part of this work, an improved idealized model was developed to study the coupled stratosphere-troposphere system. The model is forced by relaxation to a specified equilibrium temperature profile, which varies seasonally only in the stratosphere. This model setup permits the investigation of stratosphere-troposphere interactions on seasonal timescales, without the complication of an internal tropospheric seasonal cycle. The model is forced with different shapes and amplitudes of simple bottom topography, resulting in a range of stratospheric climates. The effect of these different kinds of topography on the seasonal variability of the strength of the polar vortex, the average timing and variability in timing of the final breakup of the vortex (final warming events), the conditions of occurrence and frequency of midwinter warming events, and the impact of the stratospheric seasonal cycle on the troposphere are explored. The inclusion of wavenumber 1 and wavenumber 2 topographies results in very different stratospheric seasonal variability. Hemispheric differences in stratospheric seasonal variability are recovered in the model with appropriate choices of wave-2 topography. In the model experiment with a realistic Northern Hemisphere-like frequency of midwinter warming events, the distribution of the intervals between these events suggest that the model has no year to year memory. When forced with wave-1 topography, the gross features of seasonal variability are similar to those forced with wave-2 topography, but the dependence on forcing magnitude is weaker. Further, the frequency of major warming events has a non-monotonic dependence on forcing magnitude, and never reaches the frequency observed in the northern hemisphere. In the second part of the thesis, the impact of stratospheric ozone depletion on the Antarctic polar vortex and its subsequent influences on southern hemisphere surface climate patterns is investigated. It is verified that stratospheric final warming events have an impact on tropospheric circulation in a simplified GCM with seasonal variations in the stratosphere only. The model produces qualitatively realistic final warming events whose influence extends down to the surface, much like what has been reported in observational analyses. The hypothesis that recent observed trends in surface westerlies in the Southern Hemisphere are directly consequent on observed trends in the timing of stratospheric final warming events is tested. It is confirmed that there is a statistically significant shift towards later final warming events in the years with large ozone depletion. However it is found that the observed trends in surface westerlies cannot be attributed simply to this shift towards later final warming events. Finally, responses of the idealized AGCM to polar stratospheric cooling that mimics the radiative effects of stratospheric ozone depletion are studied. It is found that there are two factors that play a role in setting the magnitude and persistence of the model's surface response to cooling: the seasonal cycle of tropospheric annular mode timescales, and whether or not the imposed cooling leads to the presence of stratospheric westerlies at a time when easterlies were prevalent in the control run. That is, the surface response is sensitive to the timing of the imposed polar stratospheric cooling. / by Aditi Sheshadri. / Ph. D.

Thesis: S.M., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 108-110). / We present a discrete numerical approach for forward-modeling lightcurves from stellar occultations by planetary atmospheres. Our discrete approach provides a way to arbitrarily set atmospheric properties at any radius from the occulting body, giving it flexibility for applying models of vertical variation in atmospheric conditions. The method is used to examine trends in lightcurve characteristics resulting from changes in the atmosphere of the occulting body. We find that for Pluto-like atmospheres, temperature and pressure variations affect the characteristics of the lightcurve much more than the gas composition. We also find that the half-light radius is more sensitive to atmospheric changes than either the minimum normalized flux or the slope at half-light. Temperature is found to be the most easily-constrained atmospheric parameter, as the gradients for changes in lightcurve characteristics are much more aligned with the temperature axis of the atmospheric parameter space than any other axis. Trends in lightcurve characteristics were examined in and around the parameter space occupied by the atmospheric conditions predicted for Pluto based on the 2011 and 2013 occultation events. Our error analysis method produced uncertainty values consistent with the reported uncertainties for half-light radius. This kind of lightcurve characterization is potentially useful for constraining the level of precision required in measuring given lightcurve characteristics in order to provide certain uncertainty bounds on the atmospheric conditions of the occulting body. / by Ho Chit Siu. / S.M.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences, 1987. / Microfiche copy available in Archives and Science. / Includes bibliographies. / by Mary Ruth Reid. / Ph.D.