Abstract: The turbulence of aircraft is a leading cause of injuries to the passengers and crew.The characteristics of low-level (below 3000 m) turbulence in Beijing during 2016 were investigated using the pilot reports accumulated by the Beijing Meteorological Center of Civil Aviation Administration of China.The frequency of turbulence in winter is the highest,and that in summer is the lowest due to the seasonal variations of wind speed.To examine the possible sources of the low-level turbulence in Beijing,the wind profiler radar data with a 120 m vertical and 6 min temporal resolution were used.The results show that the major meteorological factors and their thresholds influencing the turbulence include the horizontal wind speed (18 m·s^-1),vertical shear of horizontal wind (10 m·s^-1·km^-1),horizontal shear of horizontal wind (0.1 m·s^-1·km^-1),time shear of horizontal wind (10 m·s^-1·h^-1),and the vertical wind speed (2 m·s^-1).This paper has reference value for forecasting the low-level turbulence.

Key words: Low-level turbulence, Wind profiler radar, Wind speed