# Influence of Atmospheric Flow Structure on Optical Turbulence Characteristics
## 2 Used Methods
### Method to Estimate the Strength of Small-Scale (Optical) Turbulence
#### Analysis of Structure of Atmospheric Flows in the Lower Layers  
In order to determine the influence of meso-scale structures in the lower layers on small-scale and optical turbulence, we performed a spectral analysis of the wind speed. Figures 7-10 show the spatial changes of wind speeds along the meridian, passing through  
Figure 6: Spatial distributions of wind speeds in the third domain, with a horizontal resolution of 500 m, measured in the morning and at night. The streamlines are shown by arrows. The red marker corresponds to the BAO location. The yellow dotted line is the coastline of Lake Baikal. the BAO (104.89166 E) (black lines). The blue lines correspond to spatial variations in the high-frequency components of wind speed fluctuations (spatial scales over 12 km were filtered). These figures also show the dimensionless energy spectra of wind speed fluctuations without filtering (blue lines in the lowest panels) and with low-frequency filtering (orange lines). The green lines correspond to the dependence of the power spectral density (PSD) of wind speed fluctuations on the scale to the power of \"5/3\". Statistics of the wind field are listed in Table 2. The second column of the table shows the wind speed averaged over Lake Baikal. The third and fourth columns show the spectral characteristics of wind speed fluctuations. In particular, the spectral characteristic \(E_{n}\) is calculated by the formula:  
\[E_{n}=\frac{\sigma}{\sigma_{max}}, \tag{7}\]  
where \(\sigma\) is the mean square deviation of high-frequency fluctuations in wind speed determined over land and \(\sigma_{max}\) is the maximum value of \(\sigma\). Figure 7: Distributions of atmospheric characteristics along meridian 104.89166 E at 13 h 12 min under low image quality conditions, including **(a)** wind speed and **(b)** high-frequency wind speed fluctuations. Subfigure **(c)** shows the energy spectra of spatial wind speed fluctuations calculated without filtering (blue lines) and with low-pass filtering (orange lines). Subfigures **(d–f)** show atmospheric characteristics as in figures **(a–c)**, but at 14 h 09 min. The parameter \(E_{n}\) characterizes the spatial variability of high-frequency fluctuations in wind speed over land on a scale ranging from 500 m to 12 km. To identify features in the scales of wind speed fluctuations, we also calculated the integral of the power spectral density of wind speed fluctuations over the entire range of scales. Table 2 shows the integral normalized to its maximum value \(Int\). Figure 8: Distributions of atmospheric characteristics along meridian 104.89166 E at 14 h 51 min, including (**a**) wind speed and (**b**) high-frequency wind speed fluctuations. Subfigure (**c**) shows the energy spectra of spatial wind speed fluctuations calculated without filtering (blue lines) and with low-pass filtering (orange lines). Subfigures (**d–f**) show atmospheric characteristics as in figures (**a–c**), but at 15 h 54 min. Figure 9: Distributions of atmospheric characteristics along meridian 104.89166 E in the evening (17 h 09 min), including (**a**) wind speed and (**b**) high-frequency wind speed fluctuations. Subfigure (**c**) shows the energy spectra of spatial wind speed fluctuations calculated without filtering (blue lines), and with low-pass filtering (orange lines). Subfigures (**d–f**) show atmospheric characteristics as in figures (**a–c**), but at night (00 h 00 min). Spatially inhomogeneous fields of wind speeds were formed in the vicinity of the BAO. Despite the existence of a meso-scale vortex structure with an anticyclonic direction of airflows above the BAO, the intensity of optical turbulence along the line of sight was significant. In this case, the energy of atmospheric turbulence was predominantly determined by large-scale atmospheric processes, characterized by rather high wind speeds. Figure 10: Characteristic distributions of atmospheric characteristics along the meridian 104.89166 E in the morning, including (**a**) wind speed and (**b**) high-frequency wind speed fluctuations.