Integrated quadrant analysis: A new method for analyzing turbulent coherent structures

Authors: MANGAN, MARY ROSE - University Of California, Davis; OLDROYD, HOLLY - University Of California, Davis; PAW U, KYAW THA - University Of California, Davis; CLAY, JENAE' - University Of California, Davis; DRAKE, STEPHEN - University Of Nevada; Kelley, Jason; SUVOCAREV, KOSANA - University Of California, Davis

Submitted to: Boundary Layer Meteorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/3/2022
Publication Date: 5/14/2022
Citation: Mangan, M., Oldroyd, H.J., Paw U, K., Clay, J.M., Drake, S.A., Kelley, J.R., Suvocarev, K. 2022. Integrated quadrant analysis: A new method for analyzing turbulent coherent structures. Boundary Layer Meteorology. 184:45-69. https://doi.org/10.1007/s10546-022-00694-w.
DOI: https://doi.org/10.1007/s10546-022-00694-w

Interpretive Summary: A novel method is demonstrated that is used to assess turbulent flux rates, termed Integrated Quadrant Analysis (IQA). This method is useful because it can identify coherent structures in atmospheric flows, and these flows are responsible for the principle part of atmospheric fluxes such as evapotranspiration and carbon dioxide transport. IQA accounts for complex flow patterns that are not otherwise easily detected using other methods. This also allows for new techniques to visualize and quantify atmospheric flow patterns. The method was validated using data from two field experiments. The first experiment was conducted to measure turbulent energy exchange in the atmospheric boundary layer during a total solar eclipse. The second experiment was conducted to measure turbulent exchange within an orchard canopy. The novel method identified unexpected patterns of flow in each of these two cases, demonstrating the utility of IQA in quantifying atmospheric turbulence.

Technical Abstract: Integrated quadrant analysis is a novel technique to identify and characterize the trajectory and strength of turbulent coherent structures in the atmospheric surface layer. By integrating the three-dimensional velocity field characterized by traditional quadrant analysis with respect to time, the trajectory history of individual coherent structures can be preserved with Eulerian turbulence measurements. We developed a method to identify the ejection phase of coherent structures based on turbulent kinetic energy (TKE). Identifying coherent structures using TKE performs better than identifying them with the streamwise and vertical velocity components because some coherent structures are dominated by the cross-stream velocity. By combining this identification method with integrated quadrant analysis, one can animate or plot the trajectory of individual coherent structures. This procedure connects a coherent ejection with the subsequent sweep and quiescent period in time to visualize and quantify the strength and the duration of a coherent structure. We developed and verified the method of integrated quadrant analysis with data from two field studies: the Eclipse Boundary Layer Experiment in Corvallis, OR in August 2017 and the Vertical Cherry Array Experiment (VACE) in Linden, CA in November 2019. Integrated quadrant analysis is a promising addition to conditional sampling techniques and coherent structure characterization because it identifies coherent structures and connects the sweep and ejection components in space. In an orchard, IQA verifies that one coherent structure is dominated by a sweep. Conversely, above the roughness sublayer, much of the coherent structure consists of an ejection.