Kristie J. Franz, Department of Geolofical and Atmospheric Sciences, Iowa State University


A certain degree of variability in atmospheric and hydrological elements can be attributed to atmospheric oscillations. This study aimed to uncover how much variance could be explained by atmospheric oscillations at a Midwest freshwater lake, Lake Okoboji, IA. The following variables were used to detect variability: Temperature, Precipitation, number of snowy days, number of ice-residence days, and lake gauge height (lake level). Atmospheric Oscillations used were the: Southern Oscillation (SOI), Artic Oscillation (AO), North Atlantic Oscillation (NAO), Pacific North-American Pattern (PNA), and the Pacific Decadal Oscillation (PDO). A 30-year climate period from 1981 to 2010 defined the period of analysis. The study utilized 210 Spearman correlations, whereby each oscillation was subdivided into a positive, neutral, and negative part. Likewise, variables were split into four seasons. Thirteen correlations returned strong to very strong measures of either direct or inverse relationships amid variables and oscillations. Seven of the thirteen occurred over the December, January, February mean, possibly suggesting more oscillatory influence in the winter months. Five of thirteen correlations included the positive phase of the PNA, suggesting the PNA may be the most indicative of the five indices analyzed. Five multiple linear regressions proposed a percentile of variance that oscillations could explain in a given variable. Three of five regressions returned an explained variance of ≥ 10%. Beta coefficients further broke down the explained variance contributed by each oscillation. A maximum variation of about 3˚F, four snowy days, and seven days of ice on the lake can be attributed to the five oscillations analyzed in this study.

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Chadrick D. Skyberg


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