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8/12/2019 Lecture - Air Masses
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Anticyclone
Name for a system of high pressure.
Small pressure gradientlight winds
Classed as COLDor WARM
Can be Permanent or Semi-permanent.
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Formation of Anticyclone
Cold Anticyclone
Air mass is cooled by
the landthe cold air
has a greater densitythan warm air
= high pressure
Warm anticyclone
Larger than normal
amounts of warm air
over an area(subsidence in the
horse latitudes)
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Subsidence
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Air Masses
Air masses are large bodies of air which
have the same characteristics throughout.
The air must remain over an area for
several days.
The ideal conditions will be found where
there is a permanent anticyclone.
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Description of air masses
Air masses are either warm or cold
Source region
Polaror tropical.
Air masses either form at sea or land
SeaMaritime
Land - Continental
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Qu. What is an air mass?
An air mass is a large body of air with
similar temperatureand/or humidity.
Qu. Where do air masses form.
They form in stable source regions such
as the sub tropics or near the poles.
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Source regions of Air Masses
Permanent
anticyclone
Azores
Sahara
Greenland
Siberia
Arctic
Air mass (name)
Tropical Maritime
Tropical Continental
Polar Maritime
Polar Continental
Arctic
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Air Mass Characteristics
Cold & MoistArctic Maritime
Cold & dryPolar Continental (Pc)
Cool & moistPolar Maritime (Pm)
Warm & dryTropical Continental
(Tc)
Mild & moistTropical Maritime (Tm)
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Tropical maritime (Tm)
Source region
Azores (Caribbean)
Cooled by the sea
Stable Little or no moisture
lost
Coastssea fog Weathersouth west
dull, warm ocast.
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Tropical
Continental
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Tropical continental (Tc)
Source region Sahara
(North Africa)
Cooled from below
Stable (Un?) Dry air mass
Heat wave in Summer
Usually good vis(haze? Pollution)
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Polar Maritime (Pm)
Most common
Source region
Greenland
Warmed by the seaunstable
Showers on West
coast
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Polar
Continental
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Polar Continental (Pc)
Source regionSiberia
Reaches UK with NE or E
winds.
High pressure North ofUK
Mainly wintertime
May pick up moisture
(track?) Perhaps clouds
Vis varies
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Arctic
Maritime
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Returning Polar Maritime
Source region
Greenland but travels
south before turning
North towards the UK
Cold air mass which is
warmed heading south
and cooled heading north
leads to a wide variety
of weather Stratus cloudhill fog or
Cb clouds and showers
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Characteristics of air masses
reaching the UK
Air
Mass
Source Temp. RH Sky AirCondition
Tm
Tc
Pm
Pc
A
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Characteristics of air masses
reaching the UK
Air
Mass
Source Temp. RH Sky AirCondition
Tm Azores
Tc Sahara
Pm Greenland
Pc Siberia
A Arctic
Ocean
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Characteristics of air masses
reaching the UK
Air
Mass
Source Temp. RH Sky AirCondition
Tm Azores High
Tc Sahara VeryHigh
Pm Greenland Low /
HighPc Siberia Very
Low
A Arctic
Ocean
Very
Low
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Characteristics of air masses
reaching the UK
Air
Mass
Source Temp. RH Sky AirCondition
Tm Azores High High
Tc Sahara VeryHigh
Low
Pm Greenland Low /
High
Medium
Pc Siberia Very
Low
Low
A Arctic
Ocean
Very
Low
Low
Medium
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Characteristics of air masses
reaching the UK
Air
Mass
Source Temp. RH Sky AirCondition
Tm Azores High High Covered
with StTc Sahara Very
High
Low Clear
Pm Greenland Low /
High
Medium Cu
Pc Siberia Very
Low
Low St?
(turb)
A Arctic
Ocean
Very
Low
Low
Medium
Cu
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Characteristics of air masses
reaching the UK
Air
Mass
Source Temp. RH Sky AirCondition
Tm Azores High High Covered
with St
Stable
Tc Sahara VeryHigh
Low Clear Stable
Pm Greenland Low /
High
Medium Cu Unstable
Pc Siberia Very
Low
Low St?
(turb)
Stable
A Arctic
O
Very
L
Low
M di
Cu Unstable