Spatial and temporal variability of turbulence dissipation rate in complex terrain

Bodini, Nicola; Lundquist, Julie K.; Krishnamurthy, Raghavendra; Pekour, Mikhail; Berg, Larry K.; Choukulkar, Aditya

To improve parameterizations of the turbulence dissipation rate (inline-formulaϵ) in numerical weather prediction models, the temporal and spatial variability of inline-formulaϵ must be assessed. In this study, we explore influences on the variability of inline-formulaϵ at various scales in the Columbia River Gorge during the WFIP2 field experiment between 2015 and 2017. We calculate inline-formulaϵ from five sonic anemometers all deployed in a inline-formula∼4 kminline-formula2 area as well as from two scanning Doppler lidars and four profiling Doppler lidars, whose locations span a inline-formula∼300 km wide region. We retrieve inline-formulaϵ from the sonic anemometers using the second-order structure function method, from the scanning lidars with the azimuth structure function approach, and from the profiling lidars with a novel technique using the variance of the line-of-sight velocity. The turbulence dissipation rate shows large spatial variability, even at the microscale, especially during nighttime stable conditions. Orographic features have a strong impact on the variability of inline-formulaϵ, with the correlation between inline-formulaϵ at different stations being highly influenced by terrain. inline-formulaϵ shows larger values in sites located downwind of complex orographic structures or in wind farm wakes. A clear diurnal cycle in inline-formulaϵ is found, with daytime convective conditions determining values over an order of magnitude higher than nighttime stable conditions. inline-formulaϵ also shows a distinct seasonal cycle, with differences greater than an order of magnitude between average inline-formulaϵ values in summer and winter.

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Bodini, Nicola / Lundquist, Julie K. / Krishnamurthy, Raghavendra / et al: Spatial and temporal variability of turbulence dissipation rate in complex terrain. 2019. Copernicus Publications.

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Rechteinhaber: Nicola Bodini et al.

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