Basic 2

Question 1

What is an air mass?

Answer 1

Air mass is a large volume of air of a single origin, characterised by horizontally uniform temperature, humidity and pollution.

Question 2

List classification of an air mass by the lattitude of its origin

Answer 2

90
Arctic air
70
Polar air
45
Tropocal air
Equatorial air

Question 3

Transformation of air mass

Answer 3

Unstable (wet air): maritime arctic/polar, maritime tropical

Stable (dry air): continental arctic/polar, continental tropical

Question 4

What are fronts?

Answer 4

Fronts are boundaries or transition zones between air masses. Fronts are regions of upward motion and consequently of bad weather.

Question 5

Describe warm front

Answer 5

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

Question 6

Describe passive cold front?

Answer 6

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

Question 7

Describe active cold front

Answer 7

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

Question 8

Describe sqall lines

Answer 8

Active cold fronts are particularly severe in summer when surface warming adds to their instability, abbreviation: SQL

Question 9

List pressure systems

Answer 9

Low (cyclones): dynamic low (fronts), thermal low

High (anticyclones): cold (siberian high), warm (dynamic high), intermediate (between dynamic lows)

Question 10

Describe dynamic lows

Answer 10

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

Question 11

Describe occlusions

Answer 11

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

Question 12

Decribe thermal lows

Answer 12

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

Question 13

Describe cold anticyclones

Answer 13

Extended highs usually fron above the cold continents in higher latitudes in winter, for example the russian and sibiria anticyclone.

Question 14

Describe warm anticyclones

Answer 14

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

Question 15

Describe intermediate high

Answer 15

An intermediate high is a region of relative high pressure between two dynamic lows, weather is calming down, cool and dry.

Question 16

Describe through and ridge

Answer 16

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.

Question 17

What is fog?

Answer 17

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.

Question 18

How is RVR measured?

Answer 18

RVR is measured with transmissometer

Question 19

List the types of fog

Answer 19

Radiaton fog, advection fog, mixing fog, steam fog and upslope fog

Question 20

Describe radiation fog

Answer 20

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.

Question 21

MIFG

Answer 21

Shallow fog

Question 22

BCFG

Answer 22

Fog patches

Question 23

Describe advection fog

Answer 23

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

Question 24

Describe mixing fog

Answer 24

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

Question 25

Describe steam fog

Answer 25

Steam fog formes, when cold air is overlaying a warm moist surface. The warmer the surface the higher the rate of evaporation.
Example: heated pools, warm lakes, arctic sea smoke, sun heating the ground after a heavy rain shower

Question 26

Describe upslope fog

Answer 26

Clouds that form in mountain regions may lie upon higher grounds and appear as fog on the slopes.