| Xining Caojiapu Airport is located in the northeast of the Qinghai-Tibet Plateau,with high altitude and complicated terrain,and there are many mountain valleys on both sides of the airport.The wind field above the airport is affected by the northwest airflow and terrain.The turbulence changes significantly,and the wind shear frequency changes.It has repeatedly caused aircraft go-arounds and alternate landings,posing a threat to the safety of the national economy and people's aviation activities.In this paper,based on high-resolution and high-precision all-fiber coherent laser wind radar detection data,the fine structure of low-level turbulence in Xining Airport is studied,and the real-time wind field data of laser wind radar is used to retrieve the turbulence dissipation rate and temperature advection,Vertical speed standard deviation and vertical speed skewness,and quantitative analysis was carried out on this basis.By analyzing the low-level horizontal winds and vertical airflows in different seasons,the turbulence diurnal variation structure and the turbulence diurnal variation structure in different weather conditions are analyzed.Combining the three special processes of “crosswind ”,“clear turbulence under clear skies” and“low-level jets” that endangered the safety of aviation activities encountered at Xining Airport,the fine structure analysis of turbulent activities and the application of flight meteorological services were carried out The following conclusions:(1)According to statistics,xining caojiapu airport is mainly affected by the weather system brought by the northwest airstream.As the runway is located in the east-west river valley,the prevailing wind in xining airport is southeast wind and northwest wind.The probability of wind in spring and winter is large.The low level wind field has obvious characteristics of valley wind,with low wind speed in summer and high wind speed in winter.The lower level of the airport is mainly for cold air activity in daytime,and the cold and warm air flow alternates at night.The cold and warm air flow is the weakest in summer and the strongest in winter.The turbulence dissipation rates in the four seasons range from 10-6 to 10-4.4 m2s-3.The turbulence range and intensity are greater during the day than at night,the strongest in winter and the weakest in summer.Turbulence is highest in summer and lowest in winter.The standard deviation of vertical flow reflects the strength of turbulence pulsation kinetic energy.The skewness of vertical velocity indicates the direction of turbulent kinetic energy and the source of vertical velocity.The statistical results show that the downdraft of the airport is stronger at night than at day,and the updraft is mainly over 2.7km.Turbulent pulsation kinetic energy is strongest in winter and weakest in summer.The direction and vertical velocity of turbulent kinetic energy are diurnal.When solar radiation is enhanced,the turbulence kinetic energy and turbulent kinetic energy are transferred upward.When the solar radiation decreases,the vertical velocity perturbation kinetic energy and turbulent kinetic energy are transmitted downward.Affected by vertical wind shear at night,vertical velocity perturbation kinetic energy and turbulent kinetic energy are transported upward.(2)The diurnal variation characteristics of horizontal wind and vertical velocity in sunny,cloudy and windy days are as follows: wind direction is stable and temperature advection is the strongest.When the wind layer expands downward,the cold advection strength and range are also enhanced in the middle and lower layers,and turbulence intensity is enhanced at the junction of westerly wind and easterly wind.In a windy day,the subsidence motion is the strongest.In the afternoon,the ascending motion alternates with the descending motion,and the turbulence pulsation kinetic energy is small.Wind shear causes vertical velocity perturbation kinetic energy and turbulent kinetic energy to be transported upward.On cloudy days,the wind direction and wind speed vary greatly,and the turbulence intensity is the strongest.Rising motion is stronger than sinking motion.The turbulence pulsation kinetic energy is stronger in the middle layer before 14 h,and stronger in the lower layer after 14 h.The vertical velocity perturbation kinetic energy and turbulent kinetic energy were transmitted downward in the early morning,upward after 06 o 'clock,and upward at 15 o 'clock.In sunny days,the wind direction changes little,the low layer is cold advection,and the middle layer alternates cold and warm advection.When the wind direction changes,the turbulence intensity increases.In sunny days,the vertical motion is the weakest,and the kinetic energy of turbulence pulsation is small.The vertical velocity disturbance kinetic energy and turbulent kinetic energy were transmitted downward in the early morning,upward at 05 and downward at 19.(3)The crosswind in autumn is caused by the enhanced southeast airflow before the evening,blocked by the northwest airflow in front of the 700 h Pa north high pressure ridge,which was generated by the sloping mountains on the north side of the runway.The lidar detection map clearly shows: under the combined effect of maintaining northwest wind in the middle and high air,westward westward wind in the lower layer and thermal turbulence in the mountain groove on the north side of the airport,the subtle evolution of the wind direction at both ends of the runway The convergence line formed after the wind meets and the whole process of the formation,strengthening,and westward movement of the near-ground gale zone to the out of the runway.The detection found that strong sinking motion occurred at 16: 40-16: 45 and16: 56-17: 30,the vertical wind shear was large,and the turbulence was strong and weak.(4)On April 26,2018,at 13:23,a small-scale cyclonic circulation appeared at the entrance of the runway at 4.05 km and at a height of 475 m.At 13:28,during the landing,a small downburst was encountered at 1 nautical mile at the entrance of the runway.The lidar image showed a strong divergent airflow with a range of about600m2 from the center.The strong cold air sank to the ground and formed a thunderstorm high pressure.The airflow diverged outwards,forming a strong turbulence that caused the aircraft to go around.(5)The wind velocity of the low-level jet reaches its strongest at 20 m/s,the height of the jet axis is 0.6-1.1 km,and the thickness is 0.5-1.2km.The wind speed of the low-level jet increases with height first and then decreases.The internal wind field is more uniform,and the intensity and thickness decrease with time.The height of the jet axis increases with time.There is strong cold and warm advection in the center of the jet,which weakens as the jet decreases At the top of the jet,the wind direction is reversed with height,the wind speed changes greatly,and the turbulence is strong.At1:30,with the intrusion of cold air,the jet structure is destroyed and the intensity of turbulence reaches the maximum.After 21:00,turbulent clusters were found in the low-level jet stream,the wind speed fluctuated more obviously,and the scale of the turbulent clusters increased first and then decreased. |
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