Relationships Between Surface Fluxes and Boundary Layer Dynamics: Statistics at the Land-Atmosphere Feedback Observatory (LAFO)

Abstract. We used a combination of two Doppler lidars (DLs) and an eddy covariance station at the Land-Atmosphere Feedback Observatory (LAFO), Stuttgart, Germany, to investigate relationships between surface fluxes, convective boundary layer (CBL) height, and profiles of vertical wind variance, horizontal wind variance and turbulent kinetic energy (TKE). One DL was operated in vertical-pointing mode and the other in six-beam scanning mode. Daytime statistics were derived from 20 convective days from May to July 2021. In this data set, the mean CBL height ⟨𝑧𝑖⟩ showed a maximum of (1.53 ±0.07) km between 13:00 and 14:00 UTC, which is about 1.5 to 2.5 hours after local noon. We found counterclockwise hysteresis patterns between the CBL height and the surface fluxes. In the development phase, these relationships were approximately linear. In the early afternoon, the relationships reached a peak phase with both large fluxes and high values of ⟨𝑧𝑖⟩. At 12:00 UTC, just after local noon, the maximum values of vertical, horizontal, and total TKE were 0.55 m²s^-2, 1.26 m²s^-2 and 1.71 m²s^-2 at heights of (0.30 ± 0.06)⟨𝑧𝑖⟩ , (0.56 ± 0.06)⟨𝑧𝑖⟩, and (0.40 ± 0.06)⟨𝑧𝑖⟩, respectively. In the decay phase in the late afternoon, the relationships show non-linear patterns with larger values of ⟨𝑧𝑖⟩ for the same surface fluxes than in the morning. Furthermore, we show relationships between the vertical and horizontal components and total TKE.