Meteorology Flashcards
What conditions are required for airframe ice to form?
Visible moisture is required.
Temps below freezing point.
How does a tornado form?
When rotational velocity below a Cumulonimbus is increased due to surface convergence.
What are the characteristics of a heat type (convective localized) thunderstorm?
More common in afternoons & can persist for long periods of time.
What type of cloud is most likely to cause the formation of rime ice?
Altostratus
Where will clear ice form in relation to the freezing level
Between the freezing level & 6000/8000ft above the freezing level
What is the most predominant method through which cooling, leading to cloud formation takes place?
Widespread ascent of air
How does the adiabatic process affect anabatic winds?
The adiabatic cooling of rising air helps to oppose the upwards flow
When air with few condensation nuclei is cooled & condensation is delayed beyond the temperature where it should have occurred, the condition is known as what?
Super saturation
What is occurring when the process of conduction is taking place
Contact occurs between molecules at different temperatures & sensible heat is transferred.
What is the primary factor which determines the stability of an airmass?
Environmental temperature lapse rate (ELR)
An adiabatic lapse rate means the rate of change in what?
Temperature within parcels of air as a result of compression or expansion
What are the characteristics of an orographic thunderstorm
Long lasting with heavy precipitation
Two columns of air have the same QNH, if the pressure indicated on a barometer at 10000” in the warm column is 700hPa, what will the barometer indicate when placed in the cold column at the same altitude?
Less than 700hPa
During winter months when comparing the surface air temps & pressure in continental regions with these in oceanic regions, it can be said that in continental regions generally?
The temps are lower & pressures are higher
What occurs over the land to terrestrial radiation, conduction & convection during a clear Nighy that follows a sunny winters day.
Terrestrial radiation, convection & conduction all continue.
Describe the process involved in the formation of freeing rain.
Rain drops fall through a layer of freezing air, become super cooled & form clear ice upon contact with an object.
Does the amount of water content in the cloud effect the rate of ice accretion?
Yes, the higher the water content the greater the rate of ice accretion.
The temperature of the Troposphere is most influenced by heating from what?
Below by terrestrial radiation & convection
What is the process whereby microbursts can occur beneath high base mature CB’sc with warm dry air beneath the base?
Descending rain from the CB evaporates & in doing so draws large amounts of latent heat from the air, cooling the air & creating a microburst substantially cooler than the environment air
Define QNH
Aerodrome level pressure corrected to MSL using ISA temp lapse rates. When set on altimeter, the instrument will read altitude above MSL
What is hail?
Ice embryo gaining a layer of rime ice on an updraft, then a layer of clear ice on a downdraft & once too heavy to be supported, falls, or ejected as hail.
What is cold advection?
Cold air moving towards warmer regions.
Lower layers will heat up creating instability.
What is warm advection?
Warm air moving towards colder regions.
Lower layers cool, condense & usually form stable, layer type cloud.
What causes dissipation of radiation fog?
- An increase in wind dispersing the warm vs cold layers.
- Sun’s heat penetrates fog & warms the earth thus evaporating water droplets from ground up.
Following the passage of a warm front, the dew point is said to be what?
Higher than before the front.
What is the decaying stage of a thunderstorm?
- Updrafts cease
- Downdraft remain
- Smoother conditions in the cloud but conditions below remain unchanged.
- Precipitation is normally heavy below the base.
What are the characteristics of a Polar Mairitime air mass?
Cold & slightly moist
What is the horizontal & vertical extent of a sea breeze?
25 - 40km inland
Below 2000-3000ft
What is the result of having too few condensation nuclei in the air?
Condensation will be delayed
What happens to relative humidity after a warm front has passed?
Higher than before the front
List things which can affect the amount of incoming solar radiation reaching the surface
- Dust
- Water vapour
- Ozone
When is time ice most commonly encountered?
When super-cooled water droplets are small in size & temps between -15°C & -30°C
What is the effect of an increase in temp on atmospheric density & pressure lapse rate?
Both air density & pressure lapse rate decreases
Compare cold & warm front in regards to temp, pressure, cloud & precipitation.
Cold front
- Temp steady then falling
- Pressure falling the rising
- Cloud some Stratiform & Cb followed by Cu & TCu
- Precipitation +TSRA & possible hail followed by showers
Warm front
- Temp rising then steady
- Falling then steady
- Cloud increasing of cloud with slowly lowering bases then clearing
- Precipitation Virga then light rain for 12-24 hrs
Define the stratosphere.
Second layer of thr earth’s atmosphere. Extends from approx 11km up to 50km above earth.
Temp increased from average of -56°C at the bottom to -2°C at the top.
Define the troposphere
Lowest layer of the atmosphere on average 35,090ft.
Temp generally decreases with height & is the layer in which almost all aerosols & water vapour is found.
What weather elements are most likely to occur in an “Inactive Intertropical Convergence Zone”
Few cloud if any.
If clouds present, will be cumuliform.
Light & variable winds.
Occasional showers.
What can be determined from the presence of Lenticular Clouds?
Mountain waves present but may not carry severe turbulence.
How will the pressure, Temperature, visibility & dew point change as a warm front passes over a ground station?
Pressure - Arrests or falls
Temp - Increase
Vis - Very poor
Dew Point - Steady
What flight conditions will be most likely encountered when a pilot flies towards a layer of convective clouds?
Good visibility above the cloud & turbulent conditions below
You are flying through light precipitation & whisps of cloud in a turbine aircraft. The OAT Guage is indicating -5°C.
What type of icing are you likely to encounter?
Clear ice
State the average heights & temps of the tropopause at
- Equator
- Poles
- Mid latitudes
56,000” -75°C
26,000” -45°C
36,000” -56°C
Is latent heat required or delivered during condensation?
Released
Describe the western sequence of a cold front.
Rapid lifting of warm moist air causes development of Cu, TCu & Cb clouds.
Brief intense downpours.
Move at 25-40 kts.
Last 2-3 hours typically.
Describe weather & wind conditions associated with La Nina
Stronger easterly winds.
More active & stronger cyclone activity.
Low level convergence.
Sublimation is what & is latent heat required or released?
Solid changing to a Gas
Latent heat required.
Deposition is what & is latent heat required or released?
Gas changing to a Solid
Latent heat released
Describe solar radiation & terrestrial radiation
Solar radiation
Direct absorbed radiation from the sun. Short wavelength radiation.
Terrestrial radiation
“Bounced” radiation off the earth back into the atmosphere. Long wavelength radiation.
Describe weather & winds associated with El Nino
Stronger westerly winds
Low level divergence
Low level convergence over Pacific Ocean
What is atmospheric convection?
The rising of air caused by heating between different layers of air
What are the vertical & horizontal dimensions of a turbulent zone?
Twice the height
15 times the height horizontally
What are some favorable conditions for the development of a sea breeze?
- Coastal situation
- Fine weather & especially summertime.
- Slack pressure gradient
- Mid-morning to late afternoon for onset
What type of surface has the highest Albedo value?
Snow or Ice
Adiabatic cooling is said to occur when a parcel of air does what?
Ascends
Expands
Cools without loss/gain of heat from the surrounding environment
True or false
Horizontal wind is produced by air moving from an area of LOW pressure to an area of HIGH pressure.
False
Wind always wants to flow to a low.
As latitude increases coriolis force does what?
Increases
Describe the weather sequence of s warm front.
Warm moist air pushes up & over cooler air.
Development of As, Ns, SC, St clouds.
Continuous rain & can also deliver sleet, snow & very low cloud.
