Meteorology Flashcards
What conditions are necessary for the formation of radiation fog.
Clear skies at night - fog producing surface layers must be chilled to due point temperature, which requires the surface of the ground to become very cold during the night.
Light winds - produce mixing and a much greater amount of air is brought into contact with the cold surface.
Humid air - more likely for due point to be reached.
Describe the stages of a thunderstorm.
The developing stage - all air movement is upwards within the cloud. The edges and tops are growing rapidly and large water droplets and often snow flakes are suspended.
The mature stage - water droplets within the cloud grow too large to be supported by the updrafts and begin to fall from the base as precipitation. Both updrafts and downdrafts exist during this stage. Lightning is most frequent.
Dissipating or dying stage - cessation of the updrafts. All of the cell is now cooler than the environment air and as it subsides it warms. Cloud begins to evaporate.
How does low cloud affect the safety of a flight?
Low cloud poses risk of entering cloud during flight - reducing vision. It is difficult to escape when caught in a cloud.
How does poor visibility affect the safety of a flight?
More reliance on instruments to fly the aircraft.
How does turbulence affect the safety of a flight and what should a pilot do to reduce this?
Reduces effectiveness and accuracy of controls in a light aircraft. A pilot encountering turbulence has three options: change altitude, alter course, or ride out the roughness.
How does a thunderstorm affect the safety of a flight?
Severe turbulence which results in impossibility of accurate control of light aircrafts. Can cause airframe ice which reduce performance. Lightning, which can damage electrical equipment and pose a fire danger.
Signs that indicate the presence of turbulence.
Strong wind flow on mountains, warm rising air, rapidly changing wind direction and speed, Strong Surface Winds With Obstructions Nearby, temperature inversions, jagged clouds.
Signs that indicate the presence of thermals.
A thermal is a column of hot rising air, caused due to a plowed field (dark colour absorbs sunlight), city.
Signs that indicate the presence of dust devils.
Dust devils form when extremely hot air near the surface rises quickly through a small pocket of cooler low pressure air above it. If conditions are just right, air may begin to rotate and suck dust from the surface. Conditions for formation include clear skies, low windshear, flat terrain.
Signs that indicate the presence of windshear (wind gradient) and what should a pilot do to minimise the effect of windshear?
Wind shear is a change in wind speed and/or direction over a short distance. It can occur either horizontally or
vertically and is most often associated with strong temperature inversions or density gradients. Wind shear can occur at high or low altitude.
Wind shear may occur if:
• The temperature difference across the front at the surface is 10 oF (5 oC) or more.
• The front is moving at a speed of at least 30 knots
Inversions
Temperature reduces with altitude however it can at times increase which causes a temperature inversion. Usually after a clear cool night, the surface cools faster than the air above, creating conditions of very poor visibility.
Effect of mountain waves on flight and pilot actions to minimise this effect.
When strong winds are blowing at right angles to a mountain range, a wave action can be set up after the air has passed over the mountain range. This undulating flow produces strong downdrafts and severe turbulence downstream of the mountain range. A pilot encountering turbulence has three options: change altitude, alter course, or ride out the roughness.
Effect of downdrafts associated with terrain and cloud on flight and pilot actions to minimise this effect.
Downdraft is a small-scale column of air that rapidly sinks toward the ground, usually accompanied by precipitation as in a shower or thunderstorm. Effects of this is that it reduces visibility and turbulence may accompany thunderstorm. This increases pilots reliance on instruments and decreases effectiveness of flight controls.
