Technical note: Fourier approach for estimating the thermal attributes of streams
Hydrology and Earth System Sciences Discussions
Temperature models that directly predict ecologically important thermal attributes across spatio-temporal scales are still poorly developed. This study developed an analytical method to estimate seasonal and diel periodicities as well as irregularities in stream temperature at data-poor sites based on Fourier analysis. We first quantified the thermal attributes of a glacier-fed stream in the Swiss Alps using 2-years of hourly-recorded temperature. Stream temperature was accurately decomposed to
... ately decomposed to an average 3.8 °C, diel periodicity spanning 4.9 °C, seasonal periodicity spanning 7.5 °C, and an irregularity having an average of 0.0 °C but spanning 9.7 °C. These thermal attributes then were used to estimate thermal attributes at spot-measured sites along the river, resulting in a different relative contribution (weighting) of attributes among sites. The results confirm that the developed method can infer stochastic behaviors in stream thermal attributes at spot-measured sites. Additional ways to further improve the methodological approach are discussed.