The study looked at how wind speed changes with height in hilly areas in Northern Shaanxi. They used data from six wind towers over a year to see how wind speed varies during the day, month, and season. They found that wind speed generally increases with height in most areas. Terrain affects wind speed patterns, with smaller differences during the day and larger differences at night. The wind speed changes with the season and varies at different wind speeds. Wind shear index can help assess wind resources for wind power plants, especially when wind speeds are between 3 to 12 m/s.