The atmospheric boundary layer height during FESSTVaL derived from in-situ and ground-based remote sensing profile measurements

The height of the atmospheric boundary layer (hABL) is an important integral variable to characterise the state of the lower atmosphere with respect to different applications such as the assessment of trace gas and aerosol transport and mixing, the prediction of low-level clouds, the description of sound propagation, and the scaling of ABL profiles for use in engineering models and parametrizations. Different methods have been suggested and qualified to derive hABL based on profile measurements of atmospheric state and process variables with ground-based in-situ and remote sensing techniques. During the Field Experiment on Sub-Mesoscale Spatio-Temporal Variability in Lindenberg (FESSTVaL) which took place around the Lindenberg Meteorological Observatory – Richard-Aßmann-Observatory (MOL-RAO) of the German Meteorological Service (DWD) in summer 2021, a suite of ground-based remote sensing systems (including Doppler wind lidars, DWL, ceilometers, and microwave radiometer profilers, MWRP) was operated to characterize the status of the ABL over a heterogeneous land surface. Data from these instruments were used to derive estimates of hABL from the ceilometer backscatter intensity profiles, from the profiles of the vertical velocity variance measured with an upward looking DWL and from the wind and temperature profiles obtained from DWL and MWRP using the bulk Richardson number method. As an independent in-situ reference, different hABL estimates derived from 6-hourly operational radiosonde ascents were considered. In the presentation we discuss both case studies and results of a statistical comparison of the different hABL retrievals. Each of the methods employed has its strengths and weaknesses suggesting a synergistic approach to construct a reliable hABL composite data set.