Doppler Lidar Observations of the Mixing Height in Indianapolis Using an Automated Composite Fuzzy Logic Approach

Abstract

A Halo Photonics Stream Line XR Doppler lidar has been deployed for the Indianapolis Flux Experiment (INFLUX) to measure profiles of the mean horizontal wind and the mixing layer height for quantification of greenhouse gas emissions from the urban area. To measure the mixing layer height continuously and autonomously, a novel composite fuzzy logic approach has been developed that combines information from various scan types, including conical and vertical-slice scans and zenith stares, to determine a unified measurement of the mixing height and its uncertainty. The composite approach uses the strengths of each measurement strategy to overcome the limitations of others so that a complete representation of turbulent mixing is made in the lowest km, depending on clouds and aerosol distribution. Additionally, submeso nonturbulent motions are identified from zenith stares and removed from the analysis, as these motions can lead to an overestimate of the mixing height. The mixing height is compared with in situ profile measurements from a research aircraft for validation. To demonstrate the utility of the measurements, statistics of the mixing height and its diurnal and annual variability for 2016 are also presented. The annual cycle is clearly captured, with the largest and smallest afternoon mixing heights observed at the summer and winter solstices, respectively. The diurnal cycle of the mixing layer is affected by the mean wind, growing slower in the morning and decaying more rapidly in the evening with lighter winds.

Atmospheric Boundary Layer Classification With Doppler Lidar

“…In this study, the presence of turbulent mixing is diagnosed from the dissipation rate of TKE, which is calculated from vertically pointing data using the method presented by O'Connor et al (): where the a = 0.55 is the Kolmogorov constant, is the standard deviation of the mean radial velocity of a selected time averaging window (O'Connor et al, ), L is the length scale of the largest eddies that pass completely through the lidar beam during the averaging window, and L 1 describes the length scale of the scattering volume dimension per single sample in the averaging window. It is important to note that, if present, the impact of wave motions to the observed and henceforth to the ε should be taken into account because the wave motions do not cause turbulent mixing (Bonin et al, ).…”

Spatiotemporal visualization of wind turbulence from measurements by a Windcube 200s lidar in the atmospheric boundary layer

“…Fig.5(c) means that the estimate of the integral scale of turbulence exceeds 500 m. In the distributions for the dissipation rate and the kinetic energy, we can clearly see how the thickness of the layer of intense turbulent mixing of air masses changed in time, achieving approximately 700 m at the maximum (at 13:30 Local Time). Some methods for determination of the thickness of the mixing layer mix h have been developed earlier [17][18][19][20][21]. In contrast to these methods, we determined mix h from the drop of the vertical profile ( ) k h ε down to the level of 4 10 − m 2 /s 3 .…”

A Review of Progress and Applications of Pulsed Doppler Wind LiDARs

“…In the experiment, MLH was below the lowest vertical range for more than 40% of the time at Limassol, Cyprus and Loviisa, Finland [147]. To take advantage of different scan patterns, Bonin et al [148] proposed a fuzzy logic-based composite technique to estimate MLH from the surface up to several kilometers. They applied this technique to analyze the MLH in suburban Indianapolis in 2016, revealing that the afternoon MLH was larger around the summer solstice, while the nocturnal MLH was larger in winter because of stronger near-surface winds in winter.…”