Airmasses and fronts

Question 1

what happens to an airmass when it goes pass a warm, moist ocean

Answer 1

• warm: heating the airmass, cause the lower layer to be unstable
• moist: increase moisture in the airmass, esp. in the lower layer due to evaporation of the ocean surface

Question 2

what happens to an airmass when it goes over an cold continent.

Answer 2

• cold: no mixing of airmass, remains stable

- continent: airmass is dry. longer continental track: even drier

Question 3

describe the tropical continental airmass(Tc) in summer, with respect to its temp., humidity, stability, weather and visibility

Answer 3

temp- very warm (from Sahara)
humidity- dry (continental track)
stability- generally unstable (warming of air)
weather- clear, thundery shower (warmth, sunshine)
visibility- moderate/poor (pollutant from continent)

Question 4

describe the tropical continental airmass(Tc) in winter, with respect to its temp., humidity, stability, weather and visibility

Answer 4

temp- average (cooling of airmass)
humidity- rather moist (pick up some from the ocean)
stability- relatively stable (cooling)
weather- cloudy
visibility- moderate/poor (pollutant fr. cont.)

Question 5

describe the tropical maritime airmass(Tm) in exposed area, with respect to its temp., humidity, stability, weather and visibility

Answer 5

temp- similar to sea temp.
humidity- very moist 
stability- rather stable (its journey is over cool water)
weather- low cloud, drizzly fog (coast)
visibility- poor (due to fog)

Question 6

describe the tropical maritime airmass(Tm) in sheltered area (lee side of mountains), with respect to its temp., humidity, stability, weather and visibility

Answer 6

temp. - warm (clouds break releases latent heat)
humidity- moist
stability- stable aloft (latent heat warms the bottom)
weather- clear, clouds break; dry
visibility- moderate (dissipation of fog)

Question 7

describe the Polar continental airmass(Pc) with long sea track, with respect to its temp., humidity, stability, weather and visibility

Answer 7

longer sea track - pick up properties from ocean
temp- cold (ocean warms up a bit)
humidity- moist in the low layer (due to ocean)
stability- unstable at the low layer
weather- rain, shower (moist)
visibility- good (ocean wash away pollutant)

Question 8

describe the Polar continental airmass(Pc) with short sea track, with respect to its temp., humidity, stability, weather and visibility

Answer 8

temp- very cold
humidity- very dry
stability- stable 
weather- clear (cold air- no clouds)
visibility- moderate

Question 9

describe the polar maritime airmass(Pm) in summer, with respect to its temp., humidity, stability, weather and visibility

Answer 9

temp- similar to the ocean temp, cool
humidity- very moist
stability- unstable (since its moist)
weather- showers
visibility- good

Question 10

describe the polar maritime airmass(Pm) in winter, with respect to its temp., humidity, stability, weather and visibility

Answer 10

temp- even cooler
humidity- very moist
stability- unstable 
weather- showers, hail or thunders in hilly areas
visibility- good

Question 11

describe the returning polar maritime airmass(rPm) all year long, with respect to its temp., humidity, stability, weather and visibility

Answer 11

temp- warm (warmer than Pm)
humidity- very moist
stability- unstable 
weather- with clouds, possible showers
visibility- good

Question 12

describe the arctic maritime airmass(Am) in summer, with respect to its temp., humidity, stability, weather and visibility

Answer 12

temp- cold
humidity- rather moist
stability- unstable
weather- heavy showers/thunderstorm
visibility- good

Question 13

describe the arctic maritime airmass(Am) in winter, with respect to its temp., humidity, stability, weather and visibility

Answer 13

temp- very cold
humidity- moist (less moisture than summer as cold air holds less water)
stability- unstable 
weather- heavy shower, hails, thunder
visibility- very good

Question 14

general rules for different airmass

Answer 14

continental- weather is usually clear
maritime- weather is usually showery
if airmass contains some warmth- weather is cloudy
warmth hitting coast- weather is foggy

humidity: in winter, colder air, hold less water–> less moist than it is in summer

Question 15

define front

Answer 15

the transition between 2 different airmasses

Question 16

what types of clouds are associated with warm front?

Answer 16

thick stratus clouds mainly.

stratus, nimbostratus, altostratus, cirrostratus, cirrus

Question 17

a temperature inversion will be experienced during the passage of a warm front, what does this mean

Answer 17

temperature usually decreases with height, however with warm front, since air is warm, temperature increases with height, causing inversion

Question 18

what is the wind direction with the passage of warm front

Answer 18

veering. clockwise direction

Question 19

true or false:

the frontal surface of warm front is steeper than cold front

Answer 19

false

Question 20

true or false:

front moves slower than wind therefore u can feel rain before the passage of front

Answer 20

true. therefore you first feel the rain then the sudden change in temp

Question 21

if you see a halo, what does it indicate

Answer 21

warm front is approaching, bringing rain

Question 22

in a cold front, why does the underlying cold air curves at the ground.

Answer 22

due to friction. so the slope might be vertical near ground, or even slope the other way

Question 23

cold front travels _______ than warm front

Answer 23

faster

Question 24

why does the dew point decreases in the passage of a cold front

Answer 24

less water content can be held in cold air, hence dew point decreases (less water needed to reach saturation)

Question 25

what does pressure increase with the passage of cold front

Answer 25

cold air is denser, hence has a higher pressure.

Question 26

what types of clouds are associated with cold front

Answer 26

medium to high clouds

altocumulus, cumulonimbus, cirrostratus,cirrus

Question 27

what are ana fronts and kata fronts

Answer 27

ana- classical textbook fronts (less common in uk)

kata- weaker fronts (more common in uk) more low clouds associated

Question 28

what are the characteristics of clouds in warm and cold front

Answer 28

warm- thick clouds, formed behind the front

cold- thin elongated clouds, formed in advanced of front, mainly high clouds and medium clouds

Question 29

life cycle of a midlatitude cyclone

Answer 29

1. disturbance in the stationary polar front in the mid latitude
2. cold air from the pole pushes the cold front to the south and the tropical air pushes the warm from to the north, creating a low pressure in the middle
3. cold air has a higher pressure while warm air has a lower pressure, this creates a pgf and this powers the development of the cyclone
4. low-pressure is deepened, warm sector formed.
5. occlusion is formed when cold air catches up with the warm front
6. once occluded front is formed, power decays as there is no pgf.
7. warm air has completely risen and cooled. temperature difference is quelled out occluded front then disappeared, leaving a low pressure system.

Question 30

cold occlusion

Answer 30

• very cold air behind the cold front
• common in summer as it is warmer inland
• clouds and precipitation are behind the occlusion

Question 31

warm occlusion

Answer 31

• cooler (warm) behind the cold front
• common in winter as it is colder inland
• clouds ad precipitation in advance of the passage of occlusion

Question 32

how is the weather after occlusion?

Answer 32

• rainy, breezy with belt of clouds

- wind veers

Question 33

fronts are first clearly described by the ___________ in the early 1920s

Answer 33

Bergen School