Meteorology Flashcards
What types of meteorological hazards are there?
- Visibility
- Fog
- Wind/Changes in wind
- Cloud height
- Turbulence (E.g. in clouds)
- Icing
- Lightning
- Weather fronts
What does WAFS stand for and what does it do?
- World Area Forecast System
- Supplies meteorological authorities and other users with forecasts of global meteorological parameters like upper wind and temperature information as well as forecasts of significant weather phenomena.
What does WAFC stand for?
There are 2 WAFCs within the WAFS. Where are these located?
- World Area Forecast Centre
- London and Washington
Why has an ICAO/International Standard atmosphere been defined?
To establish standards for:
- Calibration of instruments.
- Vertical separation of ACFT.
- To compare power parameters of different ACFT and engines.
Describe ISA at MSL
- Temperature: +15°C
- Pressure: 1013.25 hPA = 29.92 inch HG
- Barometric Lapse Rate: 30ft/1hPA
- Density: 1.225kg/m^3
- Relative humidity: 0%
What is the gas composition of ISA?
What is the maximum percentage composition that water can reach within the atmosphere?
- 78% Nitrogen (N2)
- 21% Oxygen (O2)
- 0.9% Argon (Ar)
- 0.03% Carbon Dioxide (CO2)
- No water by ISA Definition (In reality can be up to 4% all within the troposphere)
Describe the ISA Troposphere in terms of vertical limits and temperature gradient.
What is the name of the boundary between the troposphere and the stratosphere?
- Extends from MSL to approximately 6-8km (pole), 11km/36100ft (45° latitude) and 16-18km (Equator).
- Temperature Gradient: approximately -2(°C)/1000ft.
- Boundary between troposphere and stratosphere called the Tropopause.
Describe the ISA Lower Stratosphere in terms of vertical limits and temperature gradient.
- Extends from tropopause to around 20km/65600ft.
- Isothermal Layer - Temperature remains constant - around -56.5°C.
Describe the ISA Upper Stratosphere in terms of vertical limits and temperature gradient.
Where does ISA definition end?
- Extends from around 20km/65600ft to around 50km.
- Inversion - Temperature begins to increase.
- Temperature Gradient: around +0.3K(°C)/1000ft.
ISA definition ends at around 32km/105,000ft.
How is heat transferred from the surface to the overlying atmospheric layers?
Mainly by conduction and convection.
Where do almost all clouds and weather occur and why?
Within the troposphere due to water content.
Why do high temperatures occur in the upper stratosphere?
- Because of the presence of ozone between 20km and 50km which absorbs ultra violet radiation from the sun.
Note: Up to 50°C.
What is the atmospheric layer above the stratosphere called?
What are the vertical limits of this layer?
What happens to temperature with altitude within this later?
- Mesosphere.
- Extends from stratosphere to around 80km.
- Temperature decreases with altitude.
What is the atmospheric layer above the mesosphere called?
What are the vertical limits of this layer?
What happens to temperature with altitude within this later?
- Ionosphere
- Extends from mesosphere to around 400km
- Temperature increases again due to low air density - very little energy is required from the sun to heat the air.
What is the layer beyond the ionosphere called?
Exosphere
How is air pressure measured?
Which units are used?
Barometer (hPA, inch Hg)
How is air temperature measured?
Which units are used?
Thermometer (°C)
How is air density measured?
Which units are used?
It is calculated (kg/m^3)
How is dew point measured?
Which units are used?
It is calculated (°C)
How is relative humidity measured?
Which units are used?
Hygrometer (%)
How is cloud cover measured?
Which units are used?
Ceilometer (okta)
How is cloud base measured?
Which units are used?
Ceilometer (ft)
How is precipitation measured?
Which units are used?
Rain gauge (mm)
How is ground visibility measured?
Which units are used?
Estimated by observer (m)
How is RVR measured?
Which units are used?
Transmissometer (m)
How is wind direction measured?
Which units are used?
Wind vane/wind sock (°)
How is wind speed measured?
Which units are used?
Anemometer (kt)
What does RSMC stand for?
Regional Specialised Meteorological Centre
What does MWO stand for?
Meteorological Watch Office
What does VAAC stand for?
Volcanic Ash Advisory Centre
What TCAC stand for?
Tropical Cyclone Advisory Centre
What is SADIS and what is its purpose?
SATellite DIStribution
- High quality, cost effective and error free satellite data distribution system developed on behalf of ICAO.
- Provides vital flight info to aviation users around the worlds.
At what temperature does water have its highest density?
4°C
What is sublimation and deposition?
- Sublimation is when a solid turns into a gas without going through the liquid phase.
- Deposition is when a gas turns into a solid without going through the liquid phase.
What is the energy spent during a change in phase called?
Latent heat
Define humidity
Humidity is the content of water vapour in the atmosphere expressed as a %. It is measured using a hygrometer, psychrometer or dew point mirror.
What does it mean when air is unsaturated, saturated or supersaturated?
Unsaturated - If maximum content of water vapour has not been reached
Saturated - If water vapour content is at its maximum
Supersaturated - If more water vapour is added to saturated air it condenses spontaneously and forms droplets of fog or cloud
What is the dew point?
The temperature at which condensation occurs.
What is spread?
What would a high or low spread indicate?
The difference between the temperature and the dew point. A higher spread would signal a low probability of fog while a low spread would signal high probability of fog.
True or false - At higher temperatures, air can contain more water vapour than at lower temperatures
True
What are the 2 types of barometer used to measure pressure?
Mercury and aneroid barometer
How does an aneroid barometer work?
Operates on difference between air pressure and pressure of the atmosphere within the aneroid cell. Pressure changes cause the cell to deform.
What happens to pressure with altitude?
Decreases exponentially.
Note: It drops by around half every 18000ft.
How is the atmosphere heated? (7)
- Short wave radiation from the Sun absorbed as latent heat. Earth re-radiates long wave terrestrial radiation.
- Absorption of ultra-violet by the ozone.
- Scattering by air molecules
- Reflection by surface (ice especially!) and clouds
- Latent heat released by condensation.
- Conduction between air and surface.
- Long wave radiation absorbed by clouds and water vapour.