| Summary: | Thesis (M.S.) University of Alaska Fairbanks, 2011 Polar lows are intense mesoscale maritime cyclones, often associated with strong winds that can damage high-latitude coastal environments and infrastructure. These systems have been historically infrequent in the Chukchi and Beaufort seas, but this behavior is expected to change along with the amplified changes in Arctic climate. This study investigates the unusual occurrence of a polar low in this region on October 9-10, 2009. Sensitivity experiments with the Weather Research and Forecasting model indicate that using ERA-Interim as large-scale forcing and performing spectral nudging at all simulation hours yield the most realistic simulation. The simulations are highly sensitive to physical parameterizations, where Morrison rnicrophysics and Yonsei University boundary layer produce the smallest errors. Surface forcings were not important for the polar low development and their influence could not extend above 850 hPa due to a stable lower atmosphere. A convergence zone between the Aleutian Low and the Beaufort High established a southerly flow that created favorable conditions by continuously adverting heat and moisture from lower latitudes. The polar low had a hybrid development and was likely triggered by the interaction between a deep-penetrating upper-level potential vorticity anomaly and a low-level baroclinic zone, which were driven northward by the jet stream. Department of Interior/Bureau of Ocean Energy Management, Regulation and Enforcement, Contract M06PC00018. National Science Foundation/Office of Polar Program, grant ARC-1023592. Japanese Agency of Marine and Earth Science and Technology. 1. Introduction -- 1.1. Overview on Polar lows -- 1.2. A polar low process in the Chukchi and Beaufort Seas -- 1.3. Motivation and goals -- 2. Model simulations of the Polar low: optimization of model physics and validation of model results -- 2.1. General model configuration -- 2.2. Data and methods used to validate model simulations -- 2.3. Sensitivity to ...
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