Gravity and mountain waves and their phenomena in Fairbanks, Alaska: a comparative case study

Abstract

The area of Fairbanks, Alaska is in a valley surrounded by mountains from the Alaska Range to the South, the Brooks Range to the north, and the eastern mountain range that extends into Canada. The topographical nature of this subarctic area brings unique atmospheric features to the Fairbanks area, such as temperature inversions and mountain wave perturbation. This thesis will examine two case studies of gravity wave phenomena; one a mountain wave from December 2017, the other a non-mountainous gravity wave from December 2016. Data was collected from radiosondes and Global Data Assimilation Model (GDAS) maps, with the former smoothed for comparative purposes. Profiles of the atmosphere were created to see direct changes that mountain waves create on atmospheric parameters and the subarctic valley area. Methods were explored to separate mountain wave buoyancy effects from other atmospheric buoyancy effects, and then used to compare mountain wave buoyancy effects with frontal motion buoyancy effects. In all cases, the polar jet stream was found to have signicant influence on gravity wave effects in the Fairbanks area. Attention to the polar jet stream location can help predict mountain wave effects and associated atmospheric perturbations. Weather phenomena localized by altitude due to gravity waves were also identified. These include localized short-term surface pressure systems on the day of gravity wave cases. Mountain waves were found to be strongly linked to synoptic temperature events in Fairbanks, Alaska, and the mountain wave case was found to have more pronounced atmospheric effects than the gravity wave case.