Aircraft turbulence is a significant meteorological event impacting flight safety.This study analyzes the temporal and spatial distribution characteristics of aircraft turbulence on major air routes across China,as well as the underlying causes of observed turbulence patterns.The analysis utilizes 6 498 Pilot Reports (PIREPs),employing data quality control and kernel density analysis.Results reveal that aircraft turbulence over China exhibits a distinct multi-scale temporal distribution.From 2011 to 2016,the incidence of turbulence showed an increasing trend,stabilizing after 2013.Seasonally,turbulence frequency and intensity peak during winter and spring,while they diminish during summer and autumn.Monthly variations follow a “funnel-shaped” pattern,and daily variations exhibit a clear “three-peak” characteristic.Regionally,turbulence frequency is higher in eastern China compared to western regions.Notably,turbulence along the main north-south air routes forms a large “comma” shape,stretching from North China through Nanchang to Chengdu.The altitude of turbulence also shows regional distinctions:North China experience the most high-altitude turbulence,while mid-altitude turbulence predominates in East and Southwest China.Xinjiang is notable for its prevalence of low-altitude turbulence.The spatiotemporal distribution of turbulence in China is primarily influenced by the upper-level jet stream,with wind shear contributing to low-altitude turbulence in Xinjiang.