| Summary: | We revisit two recent methodologies based on Monin–Obukhov Similarity Theory (MOST), the 2D method and Hybrid-Wind (HW), which are aimed at estimation of the Obukhov length, friction velocity and kinematic heat flux within the surface layer. Both methods use wind-speed profile measurements only and their comparative performance requires assessment. Synthetic and observational data are used for their quantitative assessment. We also present a procedure to generate synthetic noise-corrupted wind profiles based on estimation of the probability density functions for MOST-related variables (e.g., friction velocity) and the statistics of the noise-corrupting perturbational amplitude found during an 82-day IJmuiden observational campaign. In the observational part of the study, 2D and HW parameter retrievals from floating Doppler wind lidar measurements are compared against those from a reference mast. Overall, the 2D algorithm outperformed the HW in the estimation of all the three parameters above. For instance, when assessing the friction-velocity retrieval performance with reference to sonic anemometers, determination coefficients of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mi>ρ</mi><mrow><mn>2</mn><mi>D</mi></mrow><mn>2</mn></msubsup><mo>=</mo><mn>0.77</mn></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mi>ρ</mi><mrow><mi>H</mi><mi>W</mi></mrow><mn>2</mn></msubsup><mo>=</mo><mn>0.33</mn></mrow></semantics></math></inline-formula> were found under unstable atmospheric stability conditions, and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mi>ρ</mi><mrow><mn>2</mn><mi>D</mi></mrow><mn>2</mn></msubsup><mo>=</mo><mn>0.81</mn></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mi>ρ</mi><mrow><mi>H</mi><mi>W</mi></mrow><mn>2</mn></msubsup><mo>=</mo><mn>0.07</mn></mrow></semantics></math></inline-formula> under stable conditions, which suggests the 2D algorithm as a prominent method for estimating the above-mentioned surface-layer parameters.
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