| Summary: | The primary objective of this dissertation is to examine the drivers, consequences and associations of the diel variability in high-resolution lake surface water temperature. This dissertation consists of the high temporal resolution monitoring of up to 100 lakes, the creation of a predictive method to estimate the diel temperature range, and the development of an open source numerical program called Lake Heat Flux Analyzer, designed to calculate accurately the surface energy fluxes in lakes and reservoirs. A method for estimating the onset of thermal stratification from surface temperature measurements is also provided, where the association between the diel temperature range and the depth of the upper mixed layer allows accurate predictions of stratification onset with a root mean square error of 2.1 days. The relationship between the diel temperature range and lake specific characteristics is examined by a number of statistical approaches, varying from simple linear correlations to more complex additive models. The diel range in surface temperature is influenced significantly by lake surface area and water clarity. A statistically significant correlation between the diel temperature range and lake area is observed in the summer months caused by the larger lakes experiencing higher wind speeds, in turn leading to larger shear and ultimately wind mixing, and consequently leading to greater mixing depths and thus to low diel temperature range. For 100 lakes, the diel range in surface water temperature is shown to be influenced significantly by lake surface area where the influence of lake area is most important for lakes smaller than 3.2 km². Compared to the seminal work in physical limnology, the work presented in this dissertation highlights the importance of much smaller, and numerically dominant, lakes which have historically been under-represented in estimates of inland waters.
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