Condensation Flashcards
3 types of rainfall:
- orographic
- conventional
- frontal/cyclonic/depression
(Orographic)The air at ground level…
is warm and therefore can hold moisture.
(Orographic) A wind forces the moist air to…
move and barrier causes the air to rise on the windward side of the mountain.
(Orographic) As the air rises, it…
cools adiabatically, reaching 100% relative humidity=condensation.
Adiabatic cooling is the process…
that provides air cooling by expanding the volume of air.
Close to the surface, the pressure is…
higher, so the air is denser, therefore it warms up. Due to higher pressure, it can hold more water particles.
As the air rises, the atmospheric pressure…
decreases, so the air is less dense, molecules are further apart, so it cools down.
The relative humidity is…
the amount of moisture in the air compared to what the air can “hold” at that temperature.
(Orographic) precipitation on…
the face and peak.
After orographic rainfall, the air descends on…
the leeward side, warming by contraction=cloud dispersal.
Convectional rainfall is associated with…
tropical/equatorial areas.
(Convectional rainfall) The air above surface heats by…
conduction, expands and becomes less dense. This causes the air to rise.
(Convectional rainfall) As the air rises…
it cools, until dew point is reached=condesation.
(Convectional rainfall) In tropics, the rising air is usually warmer than…
surrounding air, so it rises continuously, creating unstable air. Large cumulonimbus clouds develop and convectional thunderstorms are common.
Unstable air is created when…
the air above the rising parcel of warm air is colder. This creates depressions. So the ELR is lower than SALR or DALR.
(Frontal rainfall) is common at…
mid to high latitudes.
(Frontal rainfall) is a result of the meeting of…
two different masses(e.g. polar air and subtropical air)
(Frontal rainfall) lighter air(warm) is forced to…
rise along the front, very rapidly, so there is sudden drop in temperature .
(Frontal rainfall) sudden drop in temperature, increases…
the chance of 100% relative humidity from happening.
Clouds appear to be darker at…
the base, because it is denser there.
Clouds are made of many…
tiny water droplets held in suspension caused by the updraft and atmospheric winds.
Bergen theory suggests that…
water particles collide with hygroscopic nuclei, causing immediate cooling and condensation on impact.
Coalescence theory suggests that…
water particles collide and stick together. forming droplet. If the water droplet is greater than 2mm, it falls.
ELR is…
Environmental Lapse Rate and it is the actual measured decrease in temperature with height above the ground.
ELR is generally…
6 degrees per 1000m, but it varies and depends on local air conditions.
DALR is…
Dry Adiabatic Lapse Rate, applies only when parcel of air has RH less than 100%.
DALR is approximately…
10 degrees per 1000m
SALR is…
Saturated Adiabatic Lapse Rate, infulenced by the fact that latent heat is released when water condenses.
In SALR, Once the air cooled to dew point…
and water started condensing the parcel of air cools more slowly.
The SAlR varies from…
4-9 degrees per 1000m depending to the amount of latent heat released.
Warm saturated air will have…
lower SALR than less saturated warm air.
Clouds are classified in following way:
- form and shape (e.g. stratifrom-layers and cumuliform-heaped)
- height-low(less than 2000m), medium (2000-7000m) and high (7000-13000m)
High altitude clouds are mainly…
ice crystals (cirrus, cirrocumulus and cirostratus)
Medium altitude clouds are…
mainly water droplets.
Low clouds indicate…
poor weather, stratus-dense,grey
nimbostratus-produce rain
Vertical development of clouds suggests…
upward movement.
Cumulus clouds are…
flat bottomed and heaped.
High clouds:
cirrus, cirrostratus and cirrocumulus
Medium clouds:
alostratus, altocumulus
Low clouds:
strato-cumulus, stratus, nimbostratus
Clouds with vertical development:
cumulonimbus, cumulus,
In cirrus clouds, because the water droplets are ice crystals it has the ability to…
enhance insolation-scattering SW radiation.
Banner clouds are formed by…
orographic uplift.
Clouds have a radiative…
force, as they re-emit LW radiation back towards the ground.
In clouds, there is more…
hygroscopic nuclei, so more LW is reflected.
Radiation cooling is…
the LW radiation which is radiated from the heated ground during the night.
Rain refers to…
liquid drops with diameter between 0.5mm-5mm. It is heavy enough to fall to the ground.
Drizzle is a type of…
rainfall with droplets less than 0.5mm.
Hail is…
alternate concentric rings of clear and opaque ice, formed by raindrops, carried up vertically up and down in large cumulonimbus clouds.
The pellet in the hail freezes and…
partially melts several times, before it is large enough to overcome the strong updraughts of air and escape from the cloud.
Hailstones may collide with…
droplets of supercooled water and freeze on impact, forming a layer of opaque ice around the hailstone.
Frost on vegetation is caused by…
contact cooling, which results in sublimation.
Frost happens when…
the temperature of the surface falls below 0 and water vapour in air parcels comes into contact.
Dew is…
the direct deposition of water droplets onto a surface/
Dew occurs in anti-
cyclonic conditions, where there is a rapid radiation cooling during the night.
Dew forms when the temperature reaches…
dew point and further cooling causes direct precipitation onto the vegetation.
Fog is…
cloud at ground level.
Radiation fog is formed…
in low-lying areas, during calm weather. Winter
(Radiation fog) Due to radiation cooling…
the air above the ground is rapidly cooled down and condenses. Light winds and turbulences cause uplift and low stratus sheet is formed.
A temperature inversion is when…
cooler air is above the warmer one.
Due to temperature inversion…
smog may develop.
Fog is common in…
anti-cyclonic conditions, with low wind speeds
Advection fog is formed when…
warm moist air flows horizontally over a cooler land or sea surface. Winter or spring
Steam fog is formed when…
cold air blows over much warmer water. Evaporation from water quickly saturates the air and condensation leads to steaming.
