تاثير الريح الواطئ على الطيران فوق مدينة بغداد == EFECTS OF LOW LEVEL WIND ON AVIATION ABOVE BAGHDAD CITY
Author name:
علي منصور حيدر الربيعي
Supervisor name:
بدور ياسين حمود العامري
General topic:
Meteorology
Specific topic:
Atmospheric Sciences
Degree:
Master
University:
Mustansiriyah University - College Of Science - Department Of Atmospheric Sciences
Language:
Arabic
University location:
Baghdad
First pages:
32T93 - p.pdf
Abstract:
Wind shear is defined as a change in wind speed and / or direction within a short distance. It can be in either a horizontal or vertical direction or both. This change causes a shearing effect on aircraft performance during landing or takes off. In this research studying the vertical wind shear have been done within a layer of few hundred meters above Baghdad airport for cases having a wind speed more than 10 m/sec at heights not more than 250 m through low level jet stream (LLJ) that sets over night. With LLJ the wind at surface is very light and the wind speed increases in speed up to an altitude of few hundred meters above the ground. 23 cases have been observed with maximum wind speed values reaching 20 m/sec with more frequent values were between 15 - 18 m/sec through height not more 500 m under the condition that the wind speed in these cases having a value more than 10 m/sec at heights below 250 m for its importance on aviation . The results have shown that the most cases occurred through summer months and the vertical change of velocities was between 11 m/sec - 15 m/sec as difference between the speed values at the surface of the station and heights not more than 500 m, whereas the difference was nearly from 10 m/sec to 15 m/sec between the velocities at altitude of 250 m and the surface. The vertical change of the wind speeds for normal nocturnal cases showed values not more than 5 m/sec for the same heights , and the duirnal wind speed profiles gave lower values due to the turbulent motion and the mixing of the air masses . The direction of the incoming wind is from the north west for most the cases except that of the winter months where the incoming wind is from south east. By analyzing the wind vectors to vertical components. They showed that the vertical shear of longitudinal( north - south ) components is greater than the shear of lateral components through the successive levels of the layer , where h1 represent a layer from the surface to the height of 50 m , h2 a layer starting from height 100 m to 150 m and the layer h is of depth 150 m from the surface, the vertical shear of longitudinal components having a value of about 2.5 m/sec per 50 m during winter months decreased to 1.3 m/sec/50 m during autumn months , whereas the shear of the lateral components decreased from a value of 1.38 m/sec to 0.6 m/sec per 50 m for the same seasons and for the same layer (h) which is of depth 150 m from the surface . The resultant values of the components for this layer were between 7 - 8 m/sec and reached to more than 9 m/sec for some cases. These values gave a shear between 2.3 - 2.6 m/sec/50m , whereas the vertical shear through the layer (h1) the nearest to the surface showed a higher values of about 3.5 m/sec or more , decreased to a value between 1.5 - 2.5 m/sec/ 50 m through the layer (h2) at height 100 m above the surface , knowing that a vertical shear of value 1.6 - 1.7 m/sec per 50 m consider hazardous to air craft performance during landing and take off . The vertical profiles of temperature for the cases under study showed an inversion in which the temp increased with height with rate between 1°C - 3.5°C per 100 m, and the inversion extended to a depth of 400 m after which the profile changed to laps with rate closer to the dray adiabatic laps rate - 1°C / 100 m up to height 1000 m or more. The normal nocturnal cases showed an increase of the temp with height at rate between 3°C - 11°C / 100 m within version depth of 180 m. These result showed an inverse relation between the depth of the inversion and the vertical change of the temp (dt/dz). Another relation was pointed out between the intensity of the inversion (the difference between the temp at the top of the inversion and the surface temp) and the surface wind speed values. As the surface wind speed values increased the inversion intensity decreased and finally the inversion disappeared and replaced by lapse started from the surface up to the higher altitude when the surface wind speed was greater than 8 m/sec
