Chapter 8.3 - Stability, Clouds and Precipitation Flashcards
What is defined as a stable atmosphere?
A parcel of air moving upwards returns to its original position.
What is defined as an unstable atmosphere?
A parcel of air moving upwards continues to rise rather than return to its original position.
What is defined as a neutrally stable atmosphere?
A parcel of air which remains displaced.
What is defined as adiabatic cooling?
A parcel of air which is cooled by the decrease in pressure, assuming no other heat energy is transferred.
What does DALR stand for?
Dry Adiabatic Lapse Rate.
Define DALR?
The rate at which the temperature of unsaturated air changes through the atmosphere.
What is the DALR?
-3°C per 1000ft.
What does SALR stand for?
Saturated Adiabatic Lapse Rate.
Define SALR?
The rate at which the temperature of saturated air changes through the atmosphere.
What is the SALR?
-1.5°C per 1000ft.
Stable air occurs when ELR is?
Less than the SALR.
Name two effects of a stable atmosphere?
- Stratiform clouds.
- Poor visibility.
Unstable air occurs when ELR is?
Higher than the DALR.
Name two effects of a stable atmosphere?
- Cumuliform clouds.
- Good visibility.
If the ELR falls between the SALR and DALR what factor is dependent in understanding the stability of the atmosphere?
Humidity.
True or False. The temperature lapse rate in the atmosphere varies depending on the surface?
True.
What is defined as a surface/radiation inversion layer?
When the air adjacent to the surface becomes colder than the air above.
What is defined as a turbulence inversion layer?
When dry air within a thin layer close to the ground is mixed by turbulence.
What is defined as a frontal inversion layer?
When two air masses of different temperatures meet, the cool air forces the warmer air aloft.
When will a frontal layer occur?
At the boundary between two air masses.
A subsidence inversion layer is associated with which weather phenomenon?
Anticyclone/High Pressure.
What effect would a decrease in density (when ascending through an inversion layer) have on an Aircraft?
Loss in lift and power.
What effect would a decrease in density (when ascending through an inversion layer) have on flight instruments?
The Airspeed Indicator will fluctuate.
True or False. A decrease in density (when ascending through an inversion layer) will have a major effect on the operation of an Aircraft?
False.
True or False. Reduced visibility can effect an inversion layer?
False. It affects the layer below.
What type of flights are affected by reduced visibility below an inversion?
Visual Flights.
True or False. Turbulence exists in an inversion layer?
False. As inversion layers are stable.
An Aircraft climbing/descending through an inversion layer will be subjected to an alteration in what?
Drift.
What the two main classifications of clouds?
- Cumuliform.
- Stratiform.
Name three cloud groups and their height?
- Low Cloud = surface to 8500ft.
- Medium Cloud = 8500ft to 20 000ft.
- High Cloud = 20 000ft and above.
What is the abbreviation and base of Stratus clouds?
- ST.
- Base = 500/2000ft.
What is the abbreviation and base of Stratocumulus clouds?
- SC.
- Base = 2000/5000ft.
What is the abbreviation and base of Cumulonimbus clouds?
- CB.
- Base = 2000/5000ft.
What is the abbreviation and base of Towering Cumulus clouds?
- TCU.
- Base = 2000/5000ft.
What is the abbreviation and base of Cumulus clouds?
- CU.
- Base = 2000/5000ft.
What is the abbreviation and base of Altocumulus clouds?
- AC.
- Base = 8500/20 000ft.
What is the abbreviation and base of Altostratus clouds?
- AS.
- Base = 8500/20 000ft.
What is the abbreviation and base of Nimbostratus clouds?
- NS.
- Base = 500/8500ft.
What is the abbreviation and thickness of Cirrocumulus clouds?
- CC.
- Usually only a thin layer.
What is the abbreviation and thickness of Cirrostratus clouds?
- CS.
- Usually only a thin layer.
What is the abbreviation and thickness of Cirrus clouds?
- CI.
- Usually only a thin layer.
How many OKTAs are there in SKC?
0.
How many OKTAs are there in FEW?
1-2.
How many OKTAs are there in SCT?
3-4.
How many OKTAs are there in BKN?
5-7.
How many OKTAs are there in OVC?
8.
Cumuliform clouds have a large (horizontal/vertical) extent?
Vertical.