Theses and Dissertations at Montana State University (MSU)
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Item Atmospheric processes related to deep persistent slab avalanches in the western United States(Montana State University - Bozeman, College of Letters & Science, 2019) Schauer, Andrew Robert; Chairperson, Graduate Committee: Jordy HendrikxDeep persistent slab avalanches are a natural hazard that are particularly difficult to predict. These avalanches are capable of destroying infrastructure in mountain settings, and are generally unsurvivable by humans. Deep persistent slab avalanches are characterized by a thick (> 1 m) slab of cohesive snow overlaying a weak layer in the snowpack, which can fail due to overburden stress of the slab itself or to external triggers such as falling cornices, explosives, or a human. While formation of such snowpack structure is controlled by persistent weather patterns early in the winter, a snowpack exhibiting characteristics capable of producing a deep persistent slab avalanche may exist for weeks or months before a specific weather event such as a heavy precipitation or rapid warming pushes the weak layer to its breaking point. Mountain weather patterns are highly variable down to the local scale (1-10 m), but they are largely driven by atmospheric processes on the continental scale (1000 km). This work relates atmospheric circulation to deep persistent slab events at Mammoth, CA; Bridger Bowl, MT; and Jackson, WY. We classify 5,899 daily 500 millibar geopotential height maps into 20 synoptic types using Self-Organizing Maps. At each location, we examine the frequency of occurrence of each of the 20 types during November through January during major deep persistent slab seasons and compare those frequencies to seasons without deep persistent slab avalanches. We also consider the 72-hour time period preceding deep persistent slab avalanches at each location and identify synoptic types occurring frequently, as well as those rarely occurring prior to onset of activity. At each location, we find specific synoptic types that tend to occur at a higher rate during major deep persistent slab years, while minor years are characterized by different circulation patterns. We also find a small number of synoptic types dominating the 72-hour period prior to onset of deep slab activity. With this improved understanding of the atmospheric processes preceding deep persistent slab avalanches, we provide avalanche practitioners with an additional tool to better anticipate a difficult to predict natural hazard.Item Snow drift and avalanche activity in a high arctic maritime snow climate(Montana State University - Bozeman, College of Letters & Science, 2016) Hancock, Holt John; Chairperson, Graduate Committee: Jordy HendrikxSnow drift endangers human life and infrastructure in alpine and arctic environments by contributing to snow avalanche formation in steep terrain and impacting transportation through reduced visibilities and drift deposition on roadways. Understanding the local and synoptic scale meteorological conditions just prior to and during hazardous snow drift conditions is a crucial element in forecasting for -- and mitigating the hazards associated with -- snow drift processes. This is especially true in Svalbard, a High Arctic Norwegian archipelago, where snow drift processes have been linked to avalanche activity and hazardous travel conditions in the region's unique, direct-action maritime snow climate. This study uses a record of road closures due to drifting snow on a mountain road to further investigate Svalbard's snow climate and avalanche regime by characterizing meteorological conditions leading to regional snow drift events and exploring the relationship between these periods of snow drift and regional avalanche activity. A nine-year record of road closures is coupled with local meteorological observations and NCEP/NCAR synoptic composite maps to characterize the local and synoptic weather conditions leading to and occurring during periods of snow drift near Longyearbyen, Svalbard's primary settlement. This record of snow drift events is then compared with regional avalanche observations using a case study approach to illustrate the relationship between snow drift and avalanche activity in Svalbard. Results show snow drift events result from five distinct synoptic circulation types and are characterized by increased wind speeds, higher precipitation totals, and elevated air temperatures relative to average winter conditions. Four case studies qualitatively illustrate the interactions between local and synoptic weather patterns, snow drift processes, and regional avalanche activity. In addition to the suggested mitigation strategies provided, these results will help advance avalanche forecasting efforts throughout the region.Item Development of an eye-safe diode-laser-based micro-pulse differential absorption lidar (mp-DIAL) for atmospheric water-vapor and aerosol studies(Montana State University - Bozeman, College of Engineering, 2011) Nehrir, Amin Reza; Chairperson, Graduate Committee: Kevin S. RepaskyThis dissertation describes the design, construction, and testing of an all diode-laser-based water-vapor differential absorption lidar (DIAL) instrument through two distinct stages of development. A second generation low pulse energy, high pulse repetition frequency DIAL instrument was developed to overcome the power limitations of the first generation instrument which required unrealistic integration times approaching 1 hour. The second generation DIAL transmitter used a custom built external cavity diode laser (ECDL) as the seed source for an actively current pulsed tapered semiconductor optical amplifier (TSOA), yielding a maximum output transmitter pulse energy of 2 microjoules over a 1 microsecond duration pulse width at a 20 kHz pulse repetition frequency, decreasing the required integration Period to approximately 20-30 minutes. Nighttime and daytime water-vapor profiles were collected with the second generation DIAL instrument which showed good agreement with collocated radiosonde measurements from near the surface up to the top of the planetary boundary layer. Aerosol optical properties were also measured using the calibrated offline channel returns using the iterative Fernald solution to the lidar equation. Most recently, a third generation DIAL transmitter has been developed to further increase the output pulse energy and to also decrease the DIAL atmospheric spectral sampling time. Two custom built high power ECDL's and an electro-mechanical based fiber optic switch are used to sequentially seed a single stage actively current pulsed TSOA in order to minimize the systematic errors introduced in the DIAL retrievals resulting from air-mass miss-sampling between the two DIAL wavelengths. Peak output pulse energies of 7 microjoules have been measured over 1 microsecond pulse durations at a 10 kHz pulse repetition frequency with a 1-6 second DIAL spectral switching time, further decreasing the total required integration period to 20 minutes for both nighttime and daytime operation. The increased performance of the third generation transmitter has allowed for nighttime and daytime water vapor profiling under varying atmospheric conditions that shows good agreement with collocated radiosonde measurements up to ~ 6 km and ~ 3 km, respectively. A detailed description of the second and third generation DIAL instrument performance as well as data retrievals are presented in this dissertation. Future work to improve the current third generation DIAL instrument for full-time autonomous measurements of atmospheric water-vapor and aerosols is also discussed.Item Hybrid learning : a study of the impacts felt by students and veteran teacher alike during the completion of a hybrid online module rich in 21st century skills(Montana State University - Bozeman, Graduate School, 2012) McGeehan, Miles Michael; Chairperson, Graduate Committee: Peggy Taylor.A hybrid online unit was built by the researcher and implemented by a host teacher with the purpose of identifying the impacts hybrid methodology has on students and veteran teacher alike. The hybrid unit, which combines traditional classroom instruction with the best-of online course tools and activities, was implemented into a 7th grade science elective classroom located in rural Montana over the course of 16 weeks. The host teacher possessed a doctorate in education and concurrently instructed online graduate courses in Action Research. Neither the host nor students had prior experience with hybrid instruction. The hybrid course topic focused on climate science and was designed congruent to 21st century technology standards. The unit included a wide variety of vibrant online activities coupled with face-to-face classroom interactions and hands-on science labs. All student work, whether online or face-to-face, was completed digitally and uploaded within the online course. Data was collected from a variety classroom assessment techniques including student performance on summative assessments, frequent student surveys, host teacher journaling, host teacher interviews and surveys, researcher observations, and researcher journaling. Partial member checking was utilized for verification of data collection and analysis. In the end, an overwhelming majority of students preferred hybrid instruction to traditional classroom instruction. A majority of students found the course to be fun, easy to navigate, and they felt they remembered more from hybrid than traditional lecture or bookwork. Students showed strong academic gains in climate science topics, especially historically low performing students. The host teacher enjoyed the diverse curricular activities and approved using the unit again in future elective classes. The host also indicated interest in experimenting with creating his own hybrid course in future academic years once technology resources became more readily available. As a result of the hybrid unit implementation, the host teacher also noted secondary observations in students' improved computer literacy, problem solving, and expository writing skills. At the outcome of this study, it was evident that hybrid instruction benefits students in a variety of manors thus instructors should consider this methodology as technology becomes increasingly available within classrooms.