MET PT1 Flashcards
How does temperature change with height in the atmosphere up to FL650? (050.01.01.01)
Temperature drops with height up to the tropopause, where it then stays constant until the ozone layer at approx FL650.
List the different layers and their main qualitative characteristics up to FL650. (050.01.01.01)
Troposphere - Up to tropopause, temperature drops at a constant rate.
Tropopause - Boundary between troposphere and stratosphere. It is the point where the temperature does not drop further, but remains constant. In ISA, at 11km (36,090ft).
Stratosphere - Temperature remains constant up to the ozone layer at approx FL650.
Describe the troposphere and its main characteristics. (050.01.01.02)
Lowest layer of atmosphere, average height (ISA) is 11km. Contains 75% of total atmosphere in weight and contains almost all weather. Temperature decreases with height. Decrease is constant in ISA. Upper boundary is tropopause.
What are the proportions of the main gases in the air in the troposphere? (050.01.01.02)
Nitrogen - 78%
Oxygen - 21%
Other gases - 1%
This remains ‘constant’ up to at least 60km.
Describe the variations of the FL and temperature of the tropopause from the poles to the equator. (050.01.01.02)
The tropopause will be lower at the poles at approx 8-10km and higher at the equator at approx 16-18km. This is mainly due to temperature, as cold air contracts and hot air expands. The tropopause is warmer ion polar regions, and colder in tropical regions than in mid-latitude areas.
What are the average heights and temperatures of the main air masses, and what are the breaks along their boundaries? (050.01.01.02)
Poles: 8km, -45°C
Mid-latitude: 11km, -56°C
Equator: 16km, -80°C
The main air masses, polar, mid-latitude, and tropical, are broken by the polar front jet stream, and the subtropical jet stream at approx 30° North and 60° North (and similarly for South).
How does the FL of the tropopause vary with the seasons and variations of atmospheric pressure? (050.01.01.02)
In winter, the tropopause will be lower, and higher in the summer.
Describe the stratosphere up to FL650. (050.01.01.03)
Temperature is constant up to approx FL650 (20km) until it starts approaching the Ozone. Then it increases by 0.3°C/1000ft.
How does the ozone layer affect jet cruise altitudes? (050.01.01.01)
Define atmospheric pressure, and list the units used in aviation. (050.01.03.01)
Atmospheric pressure is the force per unit area exerted by the atmosphere on any surface in contact with it. Can be considered as the weight of the column of air above it.
Measured in hectopascal’s (hPa), millibars (mb) which are equal, and inches of mercury (inHg). ISA at MSL is 1013.25hPa/mb and 29.92inHg. 1 hectopascal = 100 pascals.
1 pascal = 1N/1m^2.
What are barometers? (050.01.03.01)
A barometer is used to measure atmospheric pressure. Can be either a mercury barometer, using a vacuum tube and mercury, or an aneroid barometer, using partially evacuated capsules which responds to changes in pressure by expanding and contracting.
Aircraft use aneroid barometers.
Define and describe isobars. (050.01.03.01)
Lines which join points of equal atmospheric pressure on a surface pressure chart. The lines are separated by 2 or 4 hPa.
Isobars build up patterns of low or high pressure. When isobars are close together, the wind is strong. When isobars are far apart, the wind is light.
Define high, low, trough, ridge, and col. (050.01.03.01)
Explain pressure variation with height and describe the variation of the barometric lapse rate. (050.01.03.02)
This is the drop in atmospheric pressure with an increase in height, and pressure change is higher at lower altitudes, and lower at higher altitude’s.
i.e. Barometric lapse rate reduces as altitude increases.
At what height does pressure change by 50%, and density change by 50% and 25% compared to MSL using ISA? (050.01.03.02)
Pressure change to 50% of MSL is at 18,000ft.
Density change to 50% of MSL is at 22,000ft.
Density change to 25% of MSL is at 40,000ft.
Define QFF. (050.01.03.03)
How does QFE relate to QFF at MSL. (050.01.03.03)
How is QFF used in surface weather charts? (050.01.03.03)
What is the relationship between surface pressure systems and upper air pressure systems, and how would you illustrate this? (050.01.03.04)
Define ‘Air Temperature’, and list the units of measurements used. (050.01.02.01)
A measure of how hot or cold the air is. It is most commonly measured weather parameter.
K = C + 273
C = (F - 32)/1.8
F = (C*1.8) + 32
C = °Celsius, F = °Fahrenheit, K = °Kelvin.
Describe the mean vertical distribution of temperature up to FL650. (050.01.02.02)
Why does the air cool in the troposphere with increasing altitude. (050.01.02.02)
How would you calculate the temperature or temperature deviations in relation to ISA at specified levels. Calculate both for 18,000ft, where the actual temperature is -27 Celsius. (050.01.02.02)
ISA Temp = 15 - (2altitude), altitude in 1000ft. Can be converted to km by changing the 2 to 6.5.
ISA Deviation = Actual temperature - ISA temperature.
ISA Temp = 15-(218) = -21.
ISA Dev = -27 - (-21) = -6.
For positive ISA deviation must include +.
How do local cooling or warming processes result in transfer of heat? (050.01.02.03)
Describe radiation. (050.01.02.03)
Radiation is the emission or transmission of energy in the form of electromagnetic waves.
How does solar radiation reach the Earth? (050.01.02.03)
Solar radiation is short wave radiation. Some is reflected by clouds, and some is reflected by water, ice, snow or vegetation. The rest is absorbed by the Earth’s surface - insolation.
What is the significance of tropopause height? (050.01.01.02)
Upper limit of most weather Presence of jet streams Maximum wind speeds Presence of clear air turbulence Max height of significant cloud
What are the atmospheric hazards in the stratosphere? (050.01.01.03)
Ozone: Above 50,000ft ozone exceeds normal tolerance limits. Ozone is filtered out via air conditioning system and its effects are negated by aircraft design. Strongest at 20-30km.
Cosmic Radiation: Lower flight levels may be necessary at times of solar flare activity.
What is the filtering effect of the atmosphere on solar radiation? (050.01.02.03)
The ozone absorbs a lot of the solar radiation in ultra-violet. Some is reflected by air and clouds. There is then some reflected at the surface.
Describe terrestrial radiation, and how is it absorbed by some components of the atmosphere? (050.01.02.03)
Heat is generated from the Earth as long wave radiation. Water, CO2, and other greenhouse gasses absorb heat, but re-radiate terrestrial radiation back to the surface. More heat is absorbed and re-transmitted at dense lower level, leading to a lapse rate.
How is the effect of absorption and radiation related to clouds? (050.01.02.03)
Clouds reflect short wave radiation. They also absorb long wave radiation that is being radiated by the surface, and then re-radiate it back out.
Explain the process of conduction, and what is its role in the cooling and warming of the atmosphere? (050.01.02.03)
Conduction is the transfer of heat through direct contact. During the day, air close to the Earth’s surface is warmed by conduction. At night, the air close to the Earth’s surface is cooled by conduction. This does not affect air at higher levels as air is a poor conductor, and an inversion occurs.
Explain the process of convection, and when would it occur? (050.01.02.03)
The vertical movement of heat by the transfer and movement of the particles. During the day, warm air in contact with the surface is less dense. This warm air rises and mixes with the cooler air above and transfers heat to upper layers of the atmosphere via convection currents. It is called subsidence when cool air comes back down. Convection is more likely to occur over built up areas.
Explain the process of advection, and when would it occur? (050.01.02.03)
Horizontal movement of air which allows heat transfer across horizontal distances. It can occur due to localised winds or larger air mass movement.
Describe the transfer of heat by turbulence? (050.01.02.03)
Results in movement of air both vertically and horizontally. It allows for heat transfer in multiple directions.
Describe the transfer of latent heat. (050.01.02.03)
Latent heat is released when a heating process occurs, such as condensation or freezing.
What is the pressure lapse rate for ISA, and what are some common altitude and pressure values? (050.01.03.00 - No specific LO)
MSL - 30ft/hPa. Actual figure is 27, but 30 is used for calculations. 20,000ft - 50ft/hPa 40,000ft - 100ft/hPa. MSL - 1013 5,000 - 850 10,000 - 700 18,000 - 500 24,000 - 400 30,000 - 300 38,000 - 200
Pressure lapse rates (050.01.02.04)
Actual pressure lapse rate can be calculated using: H=(96*T)/P, where H=height change(ft/hPa), T=mean temperature(K), and P=mean pressure(hPa).
Describe the development and types of inversions. (050.01.02.05)
An inversion occurs when temperature increases with height.
Types: ground, turbulence, tropopause, frontal, and subsidence.
Explain characteristics of the types of inversion. (050.01.02.05)
Ground: At night we can expect an inversion above the surface.
Turbulence: Can cause an inversion in the layers close to the surface due to friction.
Tropopause: The temperature may rise as you enter the tropopause, for the same reason as turbulence inversion.
Frontal: Warm air can easily rise above cold air as the air masses meet at a front.
Subsidence: In high pressure systems, air descends in the centre, which causes adiabatic warming, causing an inversion above a cold surface.
