Meteorology Flashcards
What is the lowest level of the atmosphere called?
Troposphere
What is the average level of the tropopause?
36000ft
Does oxygen, as a percentage of the atmosphere, change with altitude?
No, constant at all levels
What is the percentage of nitrogen content in the atmosphere?
78%
How high above sea level do you have to go to experience a reduction in 2hPa?
60ft
(Rate of change - 1hPa per 27ft [approx. 30ft])
The atmosphere is mainly heated as a result of…
Long wave radiation from the earths surface
Solar heating of the earths surface is…
Greater at low altitudes
How does cloud cover affect heating?
It reduces the heating of the Earths surface through solar radiation by day and its cooling by night
What is the Fahrenheit to Centigrade formulae?
°C = 5/9*(°F -32)
What is the ISA desnsity (ρ)?
1.225kgm^-3
Or 1225grams/m^3
In ISA conditions, what is the temperature at 4500ft?
6°C
15 [sea level temp]- (1.98x4.5) [2°C per 1000ft] = 6°C
What is the line on a chart joining places of equal temperature called?
Isotherm
What’s the pressure band around the equator known as?
The equatorial trough
What are the lines on a chart joining places of equal atmospheric pressure called?
Isobars
What is the extended area projecting from an anti-cyclone called?
Ridge
What is the coriolis force,
The turning effect imparted to wind flowing from the poles towards the equator
What weather is generally associated with cols
Foggy in winter, Hot in summer
What can the surface wind direction to be used to predict?
It can be an indication of the position of the centre of a pressure system
When flying away from a low-pressure centre without making adjustments to the subscale, what does the altimeter do?
Indicates a lower altitude that it’s actually at
What is the term used to describe an area with wind speed and direction changes over a short distance?
Area of shear
What do backing and veering mean?
Change in wind direction
Backing - anti-clockwise
Veering - clockwise
In the northern hemisphere, what direction does the wind move in relation to the centre of depression?
Anti-clockwise
Where does geostrophic wind exist?
From an average of 2000ft above the surface level
Wind gradient causes wind direction changes. What can direction changes due to wind gradient be up to?
30°
Wind gradient is usually…
More noticeable at night
What is the term describing when a sea breeze meets an opposing prevailing wind?
Convergence
It is normally expected that the surface wind strength will be…
Less that the upper wind
For a given pressure gradient, what will the wind strength around an anti-cyclone compared to the wind strength around a depression be?
Stronger
Define a Katabatic wind
Cold air flowing down valley sides
What effects can you expect to experience when flying up wind of hills?
Hill lift
Lee waves, rotor and downdrafts can be felt downwind
Alto cumulus lenticularis clouds are and indication of ….
Standing waves
What type of cloud may be associated with Lenticular cloud?
Roll cloud
What is the dew point?
The temperature at which a particular mass of air reaches 100% humidity
Relative humidity is directly affected by…
Tempurature
As the relative humidity of a partake of air increases, what happens to the density of the air?
Decreases
Define condensation
The change of state of water vapour to liquid
If the moisture content of a parcel of air is such that its dew point is 7°C and surface temperature is 15°C, what level above ground will cloud form in the rising air?
2660ft
Dew point - 3°C/1000ft
15-7=8 Then 8/3=2.66 -> 2660ft
The environmental lapse rate (ELR) is…
Variable at any level
If the ELR is lower then the average the atmosphere will be…
Stable
The Dry Adiabatic Lapse Rate (DALR) is a constant value. What is the value?
3°C per 1000ft
Or 3/1000
When does rising air at 100% relative humidity cool?
SALR (saturated adiabatic lapse rate)
1.5/1000
What is the name of the warming and drying effect on airflows as a result of passing over a mountain and shedding moisture as rain?
The foehn effect
The water particles held in the atmosphere as cloud are in…
Suspension
What is the base hight for medium level clouds?
6500ft
What is the minimum base hight for High level clouds?
18000-20000ft
A cloud of a flat layered appearance is known as…
Stratus type
Cloud made of ice crystal is called…
Cirrus
What are lines of cumulus running parallel with the wind direction called?
Streets
What does the cloud abbreviation CS stand for?
Cirrostratus
Ci - Cirrus
Cu - cumulus
CB - cumulonimbus
What is a stratocumulus cloud abbreviated by?
Sc
S - Stratus
c - cumulus
Where do Orographic clouds form?
Close to ground features
What is Virga?
Rain that falls from the base of clouds, but evaporates before reaching the ground
What is snow?
Ice crystals
(Hail is frozen rain)
What cloud types usually produce rain?
Cumuliform, cumulus, stratus
In the UK, unstable, showery conditions are likely to prevail with a…
Polar maritime airflow
A south easterly airflow onto the British isles would be described as…
Tropical continental flow
What do tropical maritime flows on the British isles create?
Mild, damp conditions
What is the average warm front slope gradient?
1:150
When a warm front approaches your position, high cloud ahead of the surface front can be up to how far from the front?
600nm
What cloud may you see at the base of a warm front?
Nimbostratus
What is the average slope angle for a cold front?
1:50
Cloud at the base of a cold front might be….
Cumulus
What cloud type could be associated with a vigorous cold front?
Cumulo-nimbus
What normally moves faster? Cold or warm front?
Cold front
It is normal in the UK to expect that wind direction will…
Veer at the passing of a front
What will happen I f air air the base of a cold front is at 5°C and in front of the base of a warm front, the air is at 6°C?
A cold occlusion will occur
What cloud will normally be found in warm sector of a frontal system?
Fracto stratus followed by cumulus
Anticyclonic conditions can lead to the formation of what?
Fog
What is the cause of visibility being reduced to less than 1km at the surface, due to presence of water particles?
Fog
When does Smog (a mixture of fog and smoke giving reduced visibility) occur?
During the existence of temperature inversion
How does hoar frost occur?
When water Vapor changes directly to a solid
What is a sheet of ice formed over a wing made up of?
Clear Ice
What is the type of ice formed on a wing adversely affecting aerodynamic performance?
Rime ice
How far can gusts associated with individual thunderstorms be felt?
10miles or more from the cloud
Lee airflows (those behind high ground) are likely to be less turbulent behind where?
Rolling downlands
What does radiation fog formation depend on?
A high relative humidity and light wind
What condition is needed for the formation of advection fog?
Wind
How would you describe Wind flow from the west at 25knts?
270/25
What direction are met office reports related to?
True north
What does a line on a weather chart with semicircles on indicate?
A warm front
How would a 2 okra cloud report be indicated?
FEW
Few FEW -1-2 oktas
Scattered SCT - 2-4 oktas
Broken BKN - 5-7 oktas
Overcast OVC - 8 oktas
Measures cloud cover on a scale of 1-8
What is the minimum visibility for a CAVOK report?
10km
What does SCT020 mean?
Scattered clouds at 2000ft