Estimation of Turbulence Dissipation Rate and its Uncertainty from Sonic Anemometer and Wind Doppler Lidar During the XPIA Field Campaign

Despite turbulence being a fundamental transport process in the boundary layer, the capability of current numerical models to represent it is undermined by the limits of the adopted assumptions, notably that of local equilibrium. Here we leverage the potential of extensive observations in determining the variability of turbulence dissipation rate (ε). These observations can provide insights towards the understanding of the scales at which the major assumption of local equilibrium between generation and dissipation of turbulence is invalid.

Typically, observations of ε require time- and labor-intensive measurements from sonic and/or hot-wire anemometers. We explore the capability of wind Doppler lidars to provide measurements of ε. We refine and extend an existing method to accommodate different atmospheric stability conditions. To validate our approach, we estimate ε from four wind Doppler lidars during the 3-month XPIA campaign at the Boulder Atmospheric Observatory (Colorado), and we assess the uncertainty of the proposed method by data inter-comparison with sonic anemometer measurements of ε. The good agreement between ε from different instruments can be seen in Figure 1, which shows a 4-day time series of ε at 100m AGL from the sonic anemometer and the four wind Doppler lidars.

Our analysis of this extensive dataset provides understanding of the climatology of turbulence dissipation over the course of the campaign. Further, the variability of ε with atmospheric stability, height, and wind speed is also assessed. Finally, we present how ε increases as nocturnal turbulence is generated during low-level jet events.