Meteorology Flashcards
List four types of turbulence
- Convection turb,
- Orographic turb,
- Jetstreams/CAT,
- Wake turb.
What is an ISOTHERM?
A line joining places of equal temperature.
What causes clouds to stop rising?
When the surrounding air is warmer than/same temp as the cloud air.
Describe: IAS CAS/RAS EAS TAS GS
IAS - measure of dynamic pressure.
RAS/CAS - corrected for instrument and pressure errors (IAS with a perfect gauge).
EAS - corrected for compressibility.
TAS - actual speed of aircraft through air mass. Corrected for density.
GS - TAS ± wind component for speed across ground.
How does a thunderstorm form?
- High moisture content,
- Trigger lifting
- convection
- turbulence
- frontal
- orographic - Adiabatic cooling of the rising air
- Unstable atmosphere - once air starts to rise it continues - ELR must be greater than SLR for over 10000’.
Speed of sound at ISA sea level?
661kts.
As an aircraft moves from warm air to cold air, the altimeter will over or under read?
Over read - i.e. the aircraft will be lower than the displayed altitude.
How many feet of density altitude variation is there from pressure altitude per degree of temperature?
+120’ of altitude for every 1°c increase in temperature.
What is veering and backing with respect to wind?
Veering is wind increasing on the compass, Backing is decreasing.
At what speeds do cold and warm fronts move with respect to the geostrophic wind?
Warm fronts move slower at about 2/3 for the geostrophic wind due to the stable colder air being harder to move. A cold front moves at the same rate as the geostrophic wind.
What hazards are associated with CB’s?
- Torrential rain
- Hail
- Severe turb (3000fpm downdrafts / 6000fpm updrafts)
- Severe icing
- Wind-shear and microbursts
- Lightning
Calculate Mach Number
MN=TAS/LSS
What are the two cases where wind is reported in magnetic?
ATIS, upper winds.
What temps is lightning likely?
+10° - -10°
What are the different types of fog?
- Radiation fog
- Cloudless night
- Moist air
- Winds 2-8 knots - Advection fog
- warm moist air flows across colder surface
- light winds
- e.g. valley fog
- can be reversed - sea fog is cold air over warm water. - Frontal fog
- formed in the cold air ahead of a warm occluded front.
In what direction does Coriolis force act?
To the right in the northern hemisphere and to the left in the southern hemisphere.
What is the adiabatic process?
One in which heat is neither added nor removed from a system. Any expansion or compression of gases changes the temperature (expansion cools) but the overall energy amount remains the same.
What is the definition of CAVOK?
NSC below 5000’
Vis > 10km
No precip, TS, FG, SN
How are clouds formed?
- Moisture present
- A lifting action:
- convection
- turbulence
- frontal
- orographic - Adiabatic cooling of the rising air.
Met decodes: FG = BR = VA = GR = GS = SN = SQ = TS = SG = PRFG = PL = MIFG = FU = BCFG =
FG = Fog BR = Mist (Brume) VA = Volcanic Ash GR = Hail (GS = Small hail) SN = Snow SQ = Squall TS = Thunderstorm SG = Snow grains PRFG = Partial Fog (covering part of aerodrome) PL = Ice pellets MIFG = shallow fog FU = smoke BCFG = fog patches
What is a jetstream
A very fast upper thermal wind. Must be greater than 60kts.
Typically 1500nm long, 200nm wide and 12000’ deep.
Typically at the polar front and inter-tropical front.
What is a thermal wind?
A wind generated by difference is temp. Parallel to isotherms.
What is the ISA standard Atmosphere?
Temp: 15°c at sea level reducing by 1.98°c per 1000’ to 36090’ then steady -56.5°c.
Pressure: 1013.2 HPa at sea level
Density: 1225gm/m3
Speed of Sound: 340.3 m/s
What is gradient wind?
Geostrophic wind plus centrifugal force from the low pressure side.
How many feet does altitude deviate per hectapascal?
-30’ for every increase of 1 HPa (up to around 5000’)
What is geostrophic wind?
Balanced wind between pressure gradient and Coriolis from a westerly direction.
Describe Density Altitude
Altitude taking into account temp deviation from ISA IOT compare against pressure altitude for that same actual height.
More humid air also = higher DA.
What is the dry/wet adiabatic lapse rate
3°/1.5° per 1000’
How do you calculate the local speed of sound?
LSS=38.94 x square root of absolute temperature.
As an aircraft moves from high pressure to low pressure the altimeter…
Over reads
Describe upper winds
Caused by pressure differences at altitude which in turn are caused by temperature differences across different parcels of rising air. The sum of the thermal wind and geostrophic wind. (Westerly).
