Meteorology Flashcards
What are the ISA conditions?
+15C, 1013.25hpa, 1.225 Kg/m^3 density
What are the ISA lapse Rates?
Temperature = 1.98C/1000ft to 36090ft at -56.4C tropopause.
Pressure = 30ft/hpa to 5000ft then at a slower rate after
Density = 120ft per unit of density change for every 1C change.
What are the main requirements for thunderstorm formation
Warm & Moist Air
Unstable Atmosphere
Trigger Mechanism for lifting
Mechanism for buildup of electrical charge difference
What are the 3 stages of a thunderstorm’s life cycle?
Growing Stage
Maturing Stage
Decaying Stage
What are the primary differences between radiation fog and advection fog?
Radiation fog is formed due to a surface cooling, advection fog requires a surface already cold.
Radiation fog mainly forms during the night. Advection Fog can form anytime and last much longer.
Radiation for cannot form over the water, advection fog can form over land or water.
What are the primary requirements for radiation fog?
Clear sky - to allow terrestrial radiation to escape
light wind - to encourage mixing of air
stable atmosphere, so cool air settles near surface.
High relative humidity.
What is relative humidity?
Relative humidity is the amount of water vapour in the air compared to the amount of water vapour that could be in the air if it were 100% saturated.
When are METAR’s and Auto METAR’s issued?
METAR issued every 1 hour.
Auto METAR issued every 30 minutes.
When are SPECI’s issued?
SPECI’s are issued off the hour in METAR code.
What are METARs?
METARs are manual reports based off observation. They are issued every hour.
What are Auto METAR?
Auto METAR’s are automated observations which are issued by Automatic Weather Stations every 30 minutes.
What are SPECI’s?
Special Aerodrome Reports issued off the hour. They are provided as part of METARs. Only if weather has changed significantly.
What is a trend?
TREND is appended to auto METAR at NZAA, NZCH, NZWN and to military METAR.
RVR
Used to report visibility less than 1500m. Installed at Auckland.
What does // mean?
WX not detected due sensor temporarily inoperative.
What does /// mean?
Clod detected but cannot differentiate between TCU and CB.
What does //// mean?
Visibility not detected due to faulty sensor.
What does /////// mean?
Cloud not detected due to faulty sensor.
What are the layers in the atmosphere in ascending order?
Troposphere
Tropopause
Stratosphere
Stratopause
Mesosphere
Mesopause
Thermosphere
How high is the troposphere’s vertical extent?
Around 30,000 ft
What are the low, mid and high-level clouds at
Low-level (Surface up to 6500ft)
Mid layer (6500ft to 25,000ft)
High level cloud (25000ft to 50,000ft)
What is a cold front?
A cold front occurs when a cold airmass catches up and overtakes a warmer air mass, forcing it up.
Cold fronts travel relatively quickly and are steep in gradient. They may travel anywhere from 20knots to over 30knots depending on the type.
What is a warm front?
When a warm airmass overtakes a colder one. The warm air is forced up a shallow slope over the cold air.
This type of front is relatively slow compared to a cold front, only 10-15knots.
What is a stationary front?
When an advancing cold airmass meets an advancing warm airmass and is equally opposed. Weather is often weaker than in a cold or warm front.
What is Buy Ballot’s law?
In the southern hemisphere, if your back is to the wind, the low pressure will be to your right.
What is coriolis effect?
An effect of the earth’s rotation, coriolis force causes air travelling from a high to low pressure system in the southern hemisphere to be deflected to the left. (It would be the opposite in the northern hemisphere).
What are the conditions for a Fohn Wind
Substantial Mountain Range
Moist Air
Wind speed of sufficient strength (At least 15 knots) & blowing roughly 90 degrees over mountains
What are the conditions for a sea breeze? & Strength
Day-time, rising air creates low pressure near surface,
Air flows over surface from sea to land due to pressure gradient (usually 10-15 knots & travelling up to 25-40km inland of coast).
What are the conditions for a land-breeze? & Strength
Night Time, Land cools faster than sea. Air settles, creating area of relatively high pressure over the land compared to the sea.
Usually only 3-4 knots due to lower pressure gradient,
What are the conditions of mountain waves?
Mountain range of substantial size
Strong wind (at least 15 knots, and increasing with height) that is at right angles to mountain
Unstable atmosphere low level, stable atmosphere high level
