Journal Article
Atmospheric Chemistry and Physics, vol. 19, iss. 7, pp. 4367-4382, 2019
Authors
Nicola Bodini, Julie K. Lundquist, Raghavendra Krishnamurthy, Mikhail Pekour, Larry K. Berg, Aditya Choukulkar
Abstract
Abstract. To improve parameterizations of the turbulence dissipation rate (ϵ)
in numerical weather prediction models, the temporal and spatial variability
of ϵ must be assessed. In this study, we explore influences on the
variability of ϵ at various scales in the Columbia River Gorge
during the WFIP2 field experiment between 2015 and 2017. We calculate
ϵ from five sonic anemometers all deployed in a ∼4 km2
area as well as
from two scanning Doppler lidars and four profiling
Doppler lidars, whose locations span a ∼300 km wide region.
We retrieve ϵ 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 ϵ, with the correlation between
ϵ at different stations being highly influenced by terrain.
ϵ shows larger values in sites located downwind of complex
orographic structures or in wind farm wakes. A clear diurnal cycle in
ϵ is found, with daytime convective conditions determining values
over an order of magnitude higher than nighttime stable conditions.
ϵ also shows a distinct seasonal cycle, with differences greater
than an order of magnitude between average ϵ values in summer and
winter.
