# Wind Characteristics in Mountainous Valleys Obtained through Field Measurement
## 3 Results
### Mean Characteristics
#### Wind Profile
During the same time period, the wind angle remained generally stable at all heights and was distributed around 300\({}^{\circ}\) at all heights. This direction is roughly consistent with the direction of the horn pointing downstream of the river in this topography. The analysis of the large number of samples showed that when the wind direction angle was discrete at all heights, the wind speed distribution was also discrete. Additionally, the wind speed and wind direction showed a correlation in terms of distribution stability. Figure 5: Form of wind profile: (**a**) messy type; (**b**) exponential type; (**c**) regular distribution type; (**d**) reverse type; (**e**) large zigzag type; (**f**) small zigzag type. Figure 6: Sample distribution of wind profile index: (**a**) \(\alpha\) histogram of exponential frequency distribution; (**b**) normal probability plot of the \(\alpha\) index. Oblique wind effects are not usually considered in structural analysis, so it was necessary to analyze the wind profile of the cross-bridge with the incoming flow. Figure 8 is the result of fitting the cross-bridge direction wind profile for the same time period as in Figure 7, which breaks down the actual wind speed to the cross-bridge direction for this study. Figures 7 and 8 show a similar pattern of distribution of measured wind speed values, with the cross-bridge to wind profile fit index being slightly smaller than the actual wind speed result. In areas where the terrain changes dramatically, the wind direction tends to vary considerably throughout the year. Even during the day, the wind direction tends to vary in the morning, midday, and evening. The probability statistics for the \(\alpha\) index in Figure 6 reflect the large dispersion of the \(\alpha\) index, so the dispersion of the index in the wind profile is likely to be related to wind direction. Figure 7b shows that during 10 min, the wind direction changed little in the range of 30 to 200 m along the vertical direction. The mean value of the wind direction for this time period was taken as a representative value of its wind direction. Figure 9 describes the relationship between the \(\alpha\) index and the mean wind direction in polar coordinates using the mean wind direction and the \(\alpha\) value as variables, respectively. We found that the distribution of the mean wind direction had a clear tendency to be concentrated between NWW and NNW, which is the same conclusion as that obtained from the wind rose diagram. However, the \(\alpha\) values are discrete in all wind angle intervals where the \(\alpha\) index appears, so there is no evidence of a relationship between the \(\alpha\) index and the mean wind direction. There is a pattern in the orientation with the \(\alpha\) values of the wind profiles: few data are distributed between SW and WNW and between NNE and ESE, partly because of the small amount of data in this wind direction and partly because the wind profiles located in these two azimuthal regions are chaotic and do not conform to the exponential law. This means that the incoming currents between  
Figure 8: Schematic diagram of cross-bridge windward profile (\(\alpha=0.33\)). Figure 7: Simultaneous wind profile and wind direction angle: (**a**) wind profile with \(\alpha=0.35\); (**b**) height distribution of the wind direction angle. these two azimuthal regions are heavily disturbed by the topography and cannot take the form of an exponential law. The shape of a wind profile tends to change dramatically at different times of the day, particularly in mountainous areas. The Doppler radar system automatically records the 10 min mean wind speed data for the whole day from 00:00 to 24:00. The wind speed waterfall was plotted on a certain day for the four seasons of spring, summer, autumn, and winter, as shown in Figure 10. Figure 10 corresponds to 14 November 2017 in the fall, which had higher wind speeds throughout the day.