# Experimental Simulation of Thunderstorm Profiles in an Atmospheric Boundary Layer Wind Tunnel
## 2 Literature Review
### Turbulence Properties  
Regarding the turbulent fluctuation, little information is available. Most scientific articles are related to the intensity of the longitudinal turbulence component, while, for the lateral and vertical components, fewer data are provided. More recent studies [2; 28] have employed a directional decomposition to separate the longitudinal turbulence from the lateral one, and it has been shown that the longitudinal turbulence component derived from the classical and directional decompositions are similar. Full-scale measurements of thunderstorms have shown that the intensity of the longitudinal turbulence component varies with time and height with a trend opposite to the mean wind speed profile [2; 41]. [PERSON] et al. [42] examined the anemometric data recorded in the ports of the Northern Tyrrhenian Sea and provided mean values for each anemometer in the ports, which range from 7% to 17% with a mean value of 12% for all of them. These low values may be related to the proximity of the wind monitoring network to the sea. However, higher values of turbulence intensity during thunderstorms were provided by [PERSON] [43] at 10 and 20 m height in Singapore. The values at 10 m (40-65%) tend to be higher than the ones at 20 m (35-60%) for most of the directions. [PERSON] et al. [2] analyzed multi-point LiDAR data measured in the Livorno and Genova ports and studied the time-dependent variation along the height of the longitudinal and lateral turbulence intensity. For most thunderstorms, it was observed that, for both turbulence components, the maximum mean value of the intensity appears below the nose, and then it decreases  
Figure 1: Comparison of the normalized mean wind speed profile [34; 35; 36; 37; 38; 39]: (a) \(\overline{U}/\overline{U}_{m}\); (b) \(\overline{U}/\overline{U}_{ref}\). above following different trends. However, in most cases, turbulence intensity increases again above 180 m. For each analyzed event, the mean values of the intensity of the two turbulence components were in the range of 5-12%. [PERSON] [44] analyzed the data measured at four heights on a tall tower and observed values around 23% near to the ground during the peak velocity, while maximum values of turbulence intensity around 30% were found to appear before the peak velocity. Most of the full-scale measurements available correspond to anemometric records and are characterized by the uncertainty of the downdraft position with respect to the anemometer location. Turbulence intensity values at different locations with respect to the downdraft position have been provided based on experimental tests in 3D wind simulators. [PERSON] et al. [8] presented the variation of the longitudinal turbulence intensity along the height at different radial distances for a microburst reproduced by an impinging-jet-based microburst simulator located at Iowa State University, showing a sudden increase above 60 m in full-scale, reaching maximum values of 37% at 120 m approximately, at the radial distance \(r_{m}\) where \(\overline{U}_{m}\) appears. However, the highest values of longitudinal turbulence intensity were observed beyond the center, ranging from 14 to 38%. [PERSON] et al. [45] generated a downburst wind field in the WindEEE Dome Laboratory and analyzed the vertical profile of the longitudinal turbulence intensity and its variation with the radial distance from the center of the downdraft. Values in the range of 11-14% were observed close to the location of the peak radial velocity. [PERSON] et al. [10] reported mean values of turbulence intensity at \(r_{m}\) in the ranges of 8-12% during isolated downbursts reconstructed at WindEEE, while, in accordance with [PERSON] et al. [8], the highest values were found farther from the center (13-20%). Since a consolidated model of the turbulence intensity profile has not been developed, it is common to consider time-averaged values of turbulence intensities as reference values.