Climatic Characteristics And Quantitative Diagnosis Of Aircraft Turbulence In China

Aircraft turbulence is an important aviation weather phenomenon affecting flight safety.It is the focus of aviation meteorological service and scientific research.Based on aircraft reports and ERA-Interim reanalysis data,a comparative analysis of the diagnostic effect of 7 turbulence indexes in China by combining various evaluation indexes is conducted in this paper.According to the comparative results,three indexes with better performances are selected to calculate the frequency of occurrence of MOG turbulence,and the climatic characteristics of aircraft turbulence in China are counted.Finally,from the two aspects of climate average and case analysis,this paper analyzes the corresponding relationship between the physical quantity of the indexes and turbulence,and explores the factors that influence the turbulence.The results indicate that:Evaluation indexes have different sensitivity to the changes of thresholds of different indexes.PODY and PODN have opposite trend and are sensitive to the changes of thresholds.TSS and ETS have consistent trend and are relatively sensitive to the changes of thresholds of Brown Index,Ellrod Index1 and Horizontal Temperature Gradient Index.Brown Index has the best diagnostic effect in China,and Ellrod Index1 and Horizontal Temperature Gradient Index also have good diagnostic performances.Turbulence in China mainly occurs between 400 hPa to 200 hPa,and the height of the high incidence area decreases slightly from summer to winter,which may be related to the variation of the tropopause with seasons.Mid-eastern China,eastern Tibet and northern Sichuan are high incidence area of turbulence.The frequencies of turbulence in South China and Yunnan are small.The location of high incidence area is south in winter and spring,and northwest in summer,which may be related to the seasonal changes of upper-level jet stream.The aircraft turbulence in mid-eastern China has interannual characteristics.The strong vertical wind near the jet stream is the main factor affecting the turbulence.Wind deformation,absolute vorticity,horizontal temperature gradient and horizontal wind shear are also factors that cause the turbulence in mid-eastern China.Horizontal divergence has little effect on turbulence.