Meterology Flashcards
What does the atmosphere consist of?
78% Nitrogen
21% Oxygen
<1% carbon dioxide
How do you describe “station pressure” for an aerodrome?
The weight of air above the airport (NOT with ISA or MSL).
Flying through cloud after accumulating moderate icing, you begin to see ice crystals in cloud. Icing conditions will:
Improve.
How does the liquid water content in layered-type clouds change by altitude?
Icing becomes severe near the tops of these clouds where the temperature is just barely below freezing.
In a layered-type cloud, what temperature range would give you the most severe icing conditions?
0 to -15.
What is the main difference between icing in layered cloud vs icing in cumulus clouds?
Cumulus clouds will have a more intense icing icing over a vertical extent.
What type of icing would you get flying through a cumulus cloud and at what catch rate?
Clear ice & a high catch rate.
What vapor/droplet conditions are found in the lower section of a cumulus cloud?
Large supercooled water droplets! CLEAR ICING.
Severe icing in towering cumulus clouds can be found at temperatures as low as:
-25 degrees.
Flying through (towards) a winter warm front, what will you encounter at low level and at high level?
Low level: snow, ice pellets, freezing rain, then rain (on the other side of the frontal surface)
High level: snow, freezing rain, rain (on the other side of the frontal surface)
Where is a “roll cloud” usually on a thunderstorm:
On the LEADING EDGE of a thunderstorm.
What is the first sign that a thunderstorm is in the dissipation stage?
Large downdrafts near the centre of the cell.
What temperature rage is best for lightning?
-5 to +5.
Where is the greatest amount of turbulence found at a thunderstorm?
In the middle to the upper regions of the cell.
What precipitation gives off the strongest radar echoes?
Wet hail
what type of precipitation gives the strongest weather radar returns?
Wet hail.
What does a “hook” or “finger” on radar indicate?
Hail and turbulence.
What does a dashed orange line indicate on a GFA:
An area of obstruction to vision not associated with precipitation. (smoke, smog, haze)
When are GFA winds posted?
When wind is 20kts or stronger, or if there is a gust factor of more than 30kts.
What should a pilot be aware of when using a surface weather map for IFR flight?
It shows condition that existed 2 to 3 hours before the weather map was issued. Be aware that the weather has moved!
It shows the past. VERY IMPORTANT WITH SURFACE ANALYSIS CHARTS! Issued 2 or 3 hours AFTER observation.
Surface pressure patterns can be considered from:
3,000ft
What does OCNL EMBD CB signify?
Embedded thunderstorms with little or no separation.
What does FRQ CB signify?
Area of thunderstorms with coverage of more than 75%.
Under what circumstances is RVR posted in a METAR:
If the prevailing visibility is 1SM or less AND/OR the RVR is 6000ft or less.
What is a TEMPO?
TEMPO is a fluctuation that are expected to last less than 1 hour in duration and are not going to cover more than half of the forecasted period.
What are the unorganized cloud formations?
SKC, FEW, SCT.
Absolute instability:
ELR > SALR/DALR
Conditional stability:
DLAR >ELR > SALR
If its unsaturated, its stable.
If its saturated, its unstable.
Absolute stability:
ELR < SALR/DALR
To determine stability of the air, you must compare:
The lapse rate between the rising air and the non-rising.
What is mean sea level pressure?
Pressure at mean sea level, based upon an average temperature over the last 12 hours. Also assumes standard lapse rate of 1.98 degrees per 1000ft.
Used for surface pressure charts.
Station pressure (actual weight of air above station) Mean Sea level pressure (based upon average temperature over last 12 hours, used for surface weather analysis charts) Altimeter setting (station pressure reduced to mean sea level using standard atmospheric conditions)
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What is station pressure?
The actual weight of air above station.
What is an altimeter setting?
It is station pressure reduced to mean sea level using standard atmospheric conditions.
Station, to MSL, to standard atmosphere
What is a process that causes the dewpoint spread to reach zero:
TWO WAYS:
- Cooling the atmosphere (by a cooling process like expansional cooling) to the dewpoint
- Adding moisture content to the atmosphere; i.e. raising the dewpoint temperature to the OAT
What is radiation fog?
Must be clear skies and 5/10kmh winds during the night for it to form.
If there are no winds, dew or frost will form.
When the ground is cooled from the night with moist air, as the sun rises, it mixes the cool air and creates radiation fog.
Occurs in valleys (RADIATIOR SPRINGS)
What is the main difference between radiation fog and advection fog?
Radiation fog is restricted to only occuring over land, whereas advection fog can form over land and sea.
What is advection fog?
Forms when a warm, moist air mass travels over a colder land mass or body of water.
What is advection fog?
Forms when a warm. moist air mass travels over a colder land mass or body of water.
What is steam fog?
Forms when water vapor is added to an air mass.
What is frontal fog?
Frontal fog forms ahead of a WARM FRONT within 50 to 100 NM ahead of it.
ADVECTION FOG WILL FORM after the passage of a warm front! (warm air, cool ground)
What defines an air mass:
Large section of the troposphere with uniform properties of temperature and moisture in the HORIZONTAL.
Continental arctic (cA):
Originates over the arctic with snow and ice; very cold and dry properties. VERY STABLE because of cooling from below.
In Winter:
Flows south over prairies where temperatures are mild; route is generally cold and dry, so it slams those zones with cold temperatures.
Over the Great Lakes:
Cold air flows over warm Great Lakes, heating from below = unstable = cloud and snow showers
In Summer:
Becomes Maritime Arctic! the “cA” does not affect North America in the summer months.
DEFINITION: Dry, stable, very low tropopause