# Coastal Wind Measurements Using a Single Scanning LiDAR
## 3 Results
### Validation of 10-Minute Mean Wind Speeds and Wind Directions  
#### 3.2.1 Sensitivity to the Azimuth Angle Settings  
Following the validation approaches recommended in previous studies [10; 28; 29], the accuracy of the offshore wind measurements using a single scanning LiDAR and the VVP method was quantitatively evaluated. The observations recorded during low wind conditions, when the V1 wind speeds were less than 2 m/s, were excluded from the analysis. Finally, as the measurements of V1 for wind directions around 207\({}^{\circ}\) were directly influenced by the wind turbines situated on the coast, the observations with a wind direction range of 207\({}^{\circ}\)\(\pm\) 10\({}^{\circ}\) were also excluded from the analysis. Figure 6 shows the scatter plots comparing wind speeds from the V1 (\(U_{\rm V1}\)) and 100s (\(U_{\rm 100s}\)) for Cases 1-5. In order to quantitatively compare the accuracies between experiment cases, the deviations of the V1 and 100s wind speeds (\(\varepsilon_{U}=U_{\rm 100s}-U_{\rm V1}\)) were first calculated. The mean deviation and the standard deviation of the deviation were then computed. Table 3 presents the number of samples (\(N\)),  
Figure 4: Time series of (**a**) wind speeds and (**b**) wind directions obtained from V1 at a height of 107 m above sea level (ASL) for the period from January to September 2019 at Hazaki Oceanographical Research Station (HORS). Figure 5: Distributions of (**a**) the wind speeds and (**b**) wind directions at a height of 107 m ASL for the period from January to September 2019 at HORS. the mean wind speeds of the V1 (\(\overline{U}_{\rm V1}\)) and 100s (\(\overline{U}_{\rm 100s}\)), the mean deviation (\(\overline{\epsilon}_{U}\)), and the standard deviation of the deviation (\(\sigma(\epsilon_{U})\)). In addition, the coefficient of the regression line (\(y=\text{mx}\)) and the determination coefficient (\(R^{2}\)) are also presented. For the mean deviation and the standard deviation, the relative values, which are normalized by the mean wind speeds of V1, are also given. In terms of the regression line, according to a previous study [10], one-parameter fitting was used for the validations of wind speed, while two-parameter fitting was used for the validations of wind direction. The comparisons between the experiments with different azimuth ranges (Cases 1 to 4) show that the accuracy of the VVP-based wind speed retrieval was significantly affected by the azimuth angle range. The results for Case 1 and Case 2, which had azimuth angle ranges of \(60^{\circ}\) and \(45^{\circ}\), were found to have good agreement with the V1 wind speeds. On the other hand, the measurement accuracy decreased as the azimuth range narrowed, as shown in the figures for Case 3 and Case 4. In Case 5, the settings are identical to those in Case 4 except for the scan rate. The slower scan rate in Case 5 \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Case**} & \multirow{2}{*}{\(\mathbf{U}_{\text{ref}}\)} & \multirow{2}{*}{\(\mathbf{N}\)} & \(\overline{U}_{\text{ref}}\) & \(\overline{U}_{\text{100s}}\) & \(\overline{\epsilon}_{\text{100s}}\) & \(\sigma(\mathbf{x})\) & \(\mathbf{y}=\text{mx}\) & \(\mathbf{R^{2}}\) \\  & & & (**-)** & **(m/s)** & **(m/s, \%)** & **(m/s, \%)** & **m** & **(-)** \\ \hline
1 & V1 & 644 & 7.83 & 7.85 & 0.03, 0.3\% & 0.21, 2.6\% & 1.001 & 0.997 \\
2 & V1 & 436 & 7.04 & 7.11 & 0.07, 1.0\% & 0.31, 4.5\% & 1.002 & 0.994 \\
3 & V1 & 424 & 6.44 & 6.67 & 0.24, 3.7\% & 0.40, 6.2\% & 1.032 & 0.983 \\
4 & V1 & 411 & 5.40 & 5.88 & 0.48, 8.9\% & 0.60, 11.1\% & 1.072 & 0.951 \\
5 & V1 & 754 & 5.54 & 5.81 & 0.27, 4.9\% & 0.43, 7.8\% & 1.039 & 0.967 \\
6 & V1 & 602 & 6.20 & 6.23 & 0.03, 0.5\% & 0.17, 2.7\% & 1.004 & 0.998 \\
7 & V1 & 531 & 8.19 & 8.20 & 0.01, 0.1\% & 0.23, 2.8\% & 1.001 & 0.995 \\
8 & V1 & 8039 & 5.92 & 5.97 & 0.04, 0.7\% & 0.24, 4.0\% & 1.006 & 0.992 \\
9 & SA & 3557 & 5.08 & 4.90 & \(-0.17,\)\(-3.4\%\) & 0.55, 10.8\% & 0.959 & 0.963 \\ \hline \hline \end{tabular}
\end{table}