On Estimating the Convective Mixing‑Layer Height from Near‑Surface Horizontal Wind Spectra: A Comment on Liu & Otaki (1997) with New Proposals

Abstract Estimating and monitoring the mixing‑layer height remains a crucial but difficult task, as it cannot be measured directly by routine surface observations and is typically inferred from remote-sensing measurements with limited spatial coverage. In this context, the inversion of near-surface turbulence measurements from relatively simple, low‑cost sonic anemometer offers a complementary solution. This paper reassesses the spectral approach proposed by Liu and Ohtaki in 1997 for determining the mixing-layer height, showing that its underlying assumptions are not physically justified, and presents a more consistent, although more complex, derivation. In addition, it presents two alternative methods, based on total and partial spectral integration, which yield comparatively simpler formulations.