In recent years, papers by Sun (https://scholar.google.com/scholar?hl=en&as_sdt=0%2C21&q=The+Role+of+Large-Coherent-Eddy+Transport+in+the+Atmospheric+Surface+Layer+Based+on+CASES-99+Observations&btnG=), as well as those by Mahrt (2013; 2015 within the above reference) and van de Wiel BJH (2012 within the above reference) have examined how wind speed thresholds, particularly in the neutral to stable limit, results in changes in TKE production and therefore the evolutionary characteristics of the PBL.

In the study by Sun, they derive a height dependent wind speed threshold using the CASES-99 data (Fig. 4e). They find a strong dependence of a velocity threshold on ustar, thetastar, and the theta gradient across the lower PBL; this can be understood by studying Fig. 3, 4, and 6. They emphasize a transition from a TKE/TPE framework when V < Vs (winds are less than the velocity threshold) to a TKE dominated framework. They attribute this as an eroding of the thermodynamic structure into one that is vertically uniform and a decrease in thetastar. This is also reflected in their figures.

These results are very interesting and tie in nicely to works by Zilitinkevich. There is still much work that needs to be done in the very stable limit, but from an operational perspective, these results appear potentially useful at parameterizing the PBL, especially during dynamic transitions such as the onset of LLJs, diurnal cycle, etc. With that said, this analysis was conducted over a short grass region and therefore is not generalized to characterize the impacts of different roughness types. The other references attempt to look into this, and this is somewhat examined in Fig. 4 of van de Wiel (2012); however, I have yet to see a comprehensive analysis of this as relates to surface type dependencies.

Does anyone know of a follow-up study or a group that is currently working on examining these details from an observational point of view?