Mechanical Turbulence Wind forms eddies as it blows around hanger, stands of trees or other obstructions

Transcription

1 Turbulence Low-level Turbulence below 15,000 feet consists of Mechanical Turbulence Convective Turbulence Frontal Turbulence Wake Turbulence

2 Mechanical Turbulence Wind forms eddies as it blows around hanger, stands of trees or other obstructions

3 Convective Turbulence Thermal Turbulence is a daytime phenomena which occurs over land in fair weather Capping stable layer begins at the top of the convective layer. It can be identified by a layer of cumulus clouds, haze or dust

4 Frontal Turbulence Occurs in the narrow zone just ahead of a fast-moving cold front

5 Wake Turbulence Wingtip vortices occurs when an airplane generates lift They can exceed the roll rate of an aircraft Greatest when an aircraft is heavy, slow and clean

6 Wingtip Vortices Tend to sink below the flight path of the generating aircraft Most hazardous during light, quartering tailwinds Land beyond where a large aircraft has touched down

7 Wingtip Vortices Lift off before the point a large aircraft departing in from of you lifted off climb out above his flight path or turn upwind Helicopters in forward flight produce wingtip vortices like circulation of air

8 Clear Air Turbulence Turbulence above 15,000 feet AGL not associated with cumuliform cloudiness is reported as CAT CAT is common in a upper trough on the polar side of the jet stream

9 Jet Stream A curving jet stream associated with a deep low pressure trough can be expected to cause great turbulence Jet stream can sometime be identified by long streaks of cirrus clouds

10 Mountain Wave Turbulence Greatest turbulence occurs approaching the lee side of a mountain range in strong headwinds Standing lenticular and rotor clouds indicate the possibility of strong turbulence

11 Reporting Turbulence Light - slight erratic changes in altitude or attitude Moderate - aircraft remains in positive control Severe - large abrupt changes in altitude and attitude and may be momentarily out of control

12 Wind Shear Sudden, drastic shift in wind speed and/or direction over a short distance May be associated with a strong low-level level temperature inversion, a jet stream, a thunderstorm or a frontal zone

13 WIND SHEAR WIND SHEAR ZONE WIND

14 Microbursts Intense, localized downdrafts seldom lasting longer than 15 minutes Downdrafts can be as strong as 6,000 feet per minute Performance changes drastically as an aircraft flies through a microburst

15 Downbursts X Y Z The aircraft encounters point X, where it enters the microburst zone; a headwind causes it to rise above the normal glideslope. At the center of the microburst, point Y, there is a downdraft causing the aircraft to sink. The aircraft now enters the most lethal zone, point Z, where a sudden tailwind causes the aircraft to lose airspeed.

16 Low-Level Level Wind Shear Systems LLWAS - system of anemometers compares wind speed at several locations around the airport Terminal Doppler Weather Radar provide a clearer, more detailed picture of a thunderstorm Visual - Virga

17 Turbulence Mechanical What s the big deal?

18 Turbulence Mechanical Has anything changed?

19 Turbulence Frontal

20 Turbulence Wake and Jet Engine Blast

21 Clear Air Turbulence Usually above 15,000 feet Sometimes in non-convective clouds Often around the jet stream Often in narrow bands

22 The jet streams You ve probably heard about this on the weather, so what is it? This is an upper atmosphere air current (9-12 km) that moves from west to east. There are two jet streams. The polar jet stream is located at the south end of the polar front. Due to the movement of the ITCZ, the polar jet stream moves north in the northern hemisphere winter. The speed of the polar jet stream is approximately 110 km/hr in the winter and 55 km/hr in the summer. The subtropical jet stream is located at the northern boundary of the Hadley cell. The two jet streams are very turbulent.

23 Jet streams continued

24 Jet streams continued

25 Current jet stream position

26 Current jet stream position

27 Visible images view the atmosphere by registering the intensity of reflected shortwave radiation and are available only during the daytime.

28 Infrared images are based on measurements of longwave radiation emitted (not reflected) from below.

29 Water vapor image obtained from GOES 8 satellite.

30 Restrictions to Visibility Fog, haze, smoke, smog and dust Fog requires moisture and condensation nuclei Industrial areas produce much fog since they have more condensation nuclei

31 Fog Radiation Fog - ground fog - forms over fairly flat land on clear, calm nights Advection fog- forms near coastal areas when moist air moves over colder ground or water

32 Fog Upslope fog forms when moist stable air is forced up a sloping land mass Steam fog occurs as cool air moves over warmer water Precipitation-induced induced fog forms when warm rain falls through a layer of cooler air near the surface

33 Fog Ice fog occurs in cold weather when the temperature is much below freezing and water vapor sublimates directly as ice crystals