The Research On The Relationship Between Airplane Turbulence And Terrain On Plateau Routes In China

The normality and security of flight are affected by turbulence seriously, especially onplateau routes. First of all, some statistical researches were analyzed on aircraft’s turbulenceon plateau routes and in plateau airport according to the QAR data from Sichuan Airlines.Secondly, the geographic contour line map of plateau was drawn based on the nationalgeographic information data, and then the relationship between the turbulence and terrain wasanalyzed. Finally, WRF model was used to simulate horizontal wind field and vertical windfield at different heights in Jiuhuang airport, and the relationship between the airflow andterrain was analyzed according to the changes of wind.The study shows that among the routes fly to plateau airport in China, Chengdu-Jiuzhai isthe most frequently turbulence appeared route, followed by Chengdu-Lhasa. It points out thatthe turbulence always occurs in the places where the contour is intensive, the height variesgreatly and slope is steep. And it also occurs on the route across the terrain contour, the routenear the high mountain, and from the basin to the plateau elevation area.Among the plateau airports in our country, turbulence appears frequently in Jiuhuangairport, followed by Kunming and Lhasa airport. As the flight path of aircraft is different indescending and climbing, the reasons why turbulence occurs are different, and the frequencyof turbulence in descending is higher than climbing. Different plateau airports are different inthe causes of turbulence occuring. The climbing phase of the route in Lhasa airport is in thecanyon of two mountains, the strong turbulence will appear because of the intensive contourand the steep slope there; The decending phase of the route is near the hillside, so turbulenceoccurs easily when the aircrafts met with the updrafts,. The reasons for turbulence occuring inclimbing and descending in Kunming airport are that the flight is influenced by isolatedmountains near the route. When airflow goes around the mountains or through the middlebetween two mountains, the wind speed will increase because of canyon effect. When thestrong wind goes from canyon to broad ground, the speed of airflow dropped sharply. Therewill occurs strong wind shear between the main flow and the sides’ flow of two mountains,which will cause strong turbulence at leeward. Jiuhuang airport is located on a gentle slope which is high in east and low in west gentle, and some peaks are lying to the sides of airportrunways. When the aircraft is climbing over the hilltop, the turbulence occurs. The decendingphase of the route is over the leeward, where the aircraft is influenced by downdrafts on theleeward, which caused the aircraft’s turbulence.Terrain has great effect on airflow in Jiuhuang airport. The high altitudes airflow ismainly affected by the large terrain. When the horizontal airflow skips over the mountain,vertical airflow will rise at windward slope and drop at leeward slope. At the lower altitudes,when horizontal airflow goes around the high mountains the wind speed will increase incanyon. The airflow rises rapidly at windward slope and drops obviously at leeward slope.Updrafts are in the entrance of the canyon while downdrafts are in the exit. At much loweraltitudes, the speed of horizontal airflow is very small and airflow mainly appears the canyoneffect, and then there is little airflow around the mountain. Vertical airflow is mainly appearedin the low land, it goes down when enters the low land and goes up when goes uphill. At thesame time, the wind speed will decrease, too.