Basic 2 Flashcards
What is an air mass?
Air mass is a large volume of air of a single origin, characterised by horizontally uniform temperature, humidity and pollution.
List classification of an air mass by the lattitude of its origin
90 Arctic air 70 Polar air 45 Tropocal air Equatorial air
Transformation of air mass
Unstable (wet air): maritime arctic/polar, maritime tropical
Stable (dry air): continental arctic/polar, continental tropical
What are fronts?
Fronts are boundaries or transition zones between air masses. Fronts are regions of upward motion and consequently of bad weather.
Describe warm front
The warm front is that air mass boundary where the warm air moves towards the cold air.
Clouds: CI, CS, AS, NS, CB
Migration speed: 20 kts
Weather: RA, SN, FZRA, PL
Wind: turns to the right, S to W
Pressure: decreases
Temperature: increases
Ceiling: decreases till ground
Visibility: decreases, possibly mixing FG
Flight hazards: light to moderate icing, no VMC
Describe passive cold front?
Passive (anabatic) cold front the wind decreases with growing height, the cold air pushes itself underneath the warm air, large patches of clouds are produced which fall behind the cold front on the ground Clouds: NS, AS, CS, CI, EMBD CB Migration speed: 30 kts Weather: SHRA, SHSN, TS Wind: gusty, turns to the right, W to N Pressure: increases Temperature: decreases Ceiling: rapidly decreasing/low Visibility: bad during rain Hazards: icing, EMBD C, TS, gusty wind
Describe active cold front
Active (catabatic) cold front the wind increases with griwing height, violent vertical movements are produced a thin convective band of cloud is produced at the cold front
Clouds: CU, CB, TCU
Migration speed: up to 50 kts
Weather: +SHRA, +SHSN, GR, GS, +TS
Wind: strong, gusty, turns to the right W to N
Pressure: rapidly increasing
Temperature: notable decrease
Ceiling: rapidly increasing
Visibility: bad during rain
Hazards: heavy turbulence, gusts up to 50 kts, severe icing, wind shear, CB, TS
Describe sqall lines
Active cold fronts are particularly severe in summer when surface warming adds to their instability, abbreviation: SQL
List pressure systems
Low (cyclones): dynamic low (fronts), thermal low
High (anticyclones): cold (siberian high), warm (dynamic high), intermediate (between dynamic lows)
Describe dynamic lows
Low pressure system with fronts and different air masses, it is caused and transported by a jet stream
Three stages: wave stage, ideal (mature) cyclone, occluded stage
Describe occlusions
When cloud systems of the warm and cold fronts merge, one or the other may dominate, depending on the season
During winter: warm front occludes, cold air is more dominant
During summer: cold front occludes, warm air is more dominant
Decribe thermal lows
Stationary areas of low pressure at the surface which appear in climatic charts above the continents in summer, they are caused by a strong surface heating.
Moist thermal lows: indian monsoon, ITCZ (innertropical convergence zone), tropical cyclones
Dry thermal lows: sahara, Arizona
Describe cold anticyclones
Extended highs usually fron above the cold continents in higher latitudes in winter, for example the russian and sibiria anticyclone.
Describe warm anticyclones
Warm areas of high pressure are mainly produced in subtropical areas.
Weather in summer: dry, clear, warm, during day flat cumulus clouds, gusty, during night no clouds, wind calm
Weather in winter: below the surface inversion fog nor stratus with drizzle or light snow; top of mountain above the inversion clear of cloud and relative warm
Describe intermediate high
An intermediate high is a region of relative high pressure between two dynamic lows, weather is calming down, cool and dry.
Describe through and ridge
They form a wave-like sreaming pattern in the constant pressure charts. They cause the widespread rising or sinking of the air masses. Rising leads to the formation of clouds and percipitation as well as lower surface pressure, and sinking leads to disolving of existing clouds and the surface pressure increases.
What is fog?
Fog is a cloud lying on the ground, it reduces the visibility to less than 1 km. Still one of the main reasons for flight delays and accidents.
How is RVR measured?
RVR is measured with transmissometer
List the types of fog
Radiaton fog, advection fog, mixing fog, steam fog and upslope fog
Describe radiation fog
Cooling is accomplished by outgoing radiation at night. Conditions are: clear sky or only few cluds, a solid surface, weak winds (<10kt), sufficient moisture. It intensifies during the rest of the night and remains confined to a thin layer, mostly well below 1000ft. Radiation fog is quickly dissolved by the morning sun.
MIFG
Shallow fog
BCFG
Fog patches
Describe advection fog
When a warm moist air is horizontally transported by the wind onto a cold surface, at least as cold as the dew point of the advected surface
Describe mixing fog
Mixing fog is generated by the mixing of two air volumes, one cold, one warm, and both humid. Examples: breathing in winter, condensation trails, warm fronts
