Airmasses and fronts Flashcards
what happens to an airmass when it goes pass a warm, moist ocean
- 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
what happens to an airmass when it goes over an cold continent.
- cold: no mixing of airmass, remains stable
- continent: airmass is dry. longer continental track: even drier
describe the tropical continental airmass(Tc) in summer, with respect to its temp., humidity, stability, weather and visibility
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)
describe the tropical continental airmass(Tc) in winter, with respect to its temp., humidity, stability, weather and visibility
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.)
describe the tropical maritime airmass(Tm) in exposed area, with respect to its temp., humidity, stability, weather and visibility
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)
describe the tropical maritime airmass(Tm) in sheltered area (lee side of mountains), with respect to its temp., humidity, stability, weather and visibility
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)
describe the Polar continental airmass(Pc) with long sea track, with respect to its temp., humidity, stability, weather and visibility
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)
describe the Polar continental airmass(Pc) with short sea track, with respect to its temp., humidity, stability, weather and visibility
temp- very cold humidity- very dry stability- stable weather- clear (cold air- no clouds) visibility- moderate
describe the polar maritime airmass(Pm) in summer, with respect to its temp., humidity, stability, weather and visibility
temp- similar to the ocean temp, cool humidity- very moist stability- unstable (since its moist) weather- showers visibility- good
describe the polar maritime airmass(Pm) in winter, with respect to its temp., humidity, stability, weather and visibility
temp- even cooler humidity- very moist stability- unstable weather- showers, hail or thunders in hilly areas visibility- good
describe the returning polar maritime airmass(rPm) all year long, with respect to its temp., humidity, stability, weather and visibility
temp- warm (warmer than Pm) humidity- very moist stability- unstable weather- with clouds, possible showers visibility- good
describe the arctic maritime airmass(Am) in summer, with respect to its temp., humidity, stability, weather and visibility
temp- cold humidity- rather moist stability- unstable weather- heavy showers/thunderstorm visibility- good
describe the arctic maritime airmass(Am) in winter, with respect to its temp., humidity, stability, weather and visibility
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
general rules for different airmass
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
define front
the transition between 2 different airmasses
what types of clouds are associated with warm front?
thick stratus clouds mainly.
stratus, nimbostratus, altostratus, cirrostratus, cirrus
a temperature inversion will be experienced during the passage of a warm front, what does this mean
temperature usually decreases with height, however with warm front, since air is warm, temperature increases with height, causing inversion
what is the wind direction with the passage of warm front
veering. clockwise direction
true or false:
the frontal surface of warm front is steeper than cold front
false
true or false:
front moves slower than wind therefore u can feel rain before the passage of front
true. therefore you first feel the rain then the sudden change in temp
if you see a halo, what does it indicate
warm front is approaching, bringing rain
in a cold front, why does the underlying cold air curves at the ground.
due to friction. so the slope might be vertical near ground, or even slope the other way
cold front travels _______ than warm front
faster
why does the dew point decreases in the passage of a cold front
less water content can be held in cold air, hence dew point decreases (less water needed to reach saturation)
what does pressure increase with the passage of cold front
cold air is denser, hence has a higher pressure.
what types of clouds are associated with cold front
medium to high clouds
altocumulus, cumulonimbus, cirrostratus,cirrus
what are ana fronts and kata fronts
ana- classical textbook fronts (less common in uk)
kata- weaker fronts (more common in uk) more low clouds associated
what are the characteristics of clouds in warm and cold front
warm- thick clouds, formed behind the front
cold- thin elongated clouds, formed in advanced of front, mainly high clouds and medium clouds
life cycle of a midlatitude cyclone
- disturbance in the stationary polar front in the mid latitude
- 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
- 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
- low-pressure is deepened, warm sector formed.
- occlusion is formed when cold air catches up with the warm front
- once occluded front is formed, power decays as there is no pgf.
- warm air has completely risen and cooled. temperature difference is quelled out occluded front then disappeared, leaving a low pressure system.
cold occlusion
- very cold air behind the cold front
- common in summer as it is warmer inland
- clouds and precipitation are behind the occlusion
warm occlusion
- cooler (warm) behind the cold front
- common in winter as it is colder inland
- clouds ad precipitation in advance of the passage of occlusion
how is the weather after occlusion?
- rainy, breezy with belt of clouds
- wind veers
fronts are first clearly described by the ___________ in the early 1920s
Bergen School
