British Isles Climate Flashcards
Define climate
Average weather over an area, in case of the British Isles usually taken from records of the last 30 years.
What are anticyclones ?
How are they shown on a map?
High pressure weather systems
Pressure increases towards centre
Isobars far apart little pressure difference
When do anticyclones form?
Characteristics of them
Cold air sinks downwards, warms adiabatically and no condensation or clouds occur.
Move slowly and are stable features, can remain stationary over an area for several days or even weeks.
3000km wide depressions smaller.
What does temp of air mass depend on?
Origin and subsequent journey over land or sea
Two main regions where majority of air masses come from?
High pressure belts in subtropics form tropical air masses
And the poles source region for polar air masses
Source of origin for polar maritime
North Canada or Greenland (arctic regions)
Crosses North Atlantic - gains moisture and temp- increase instability.
North westerly winds
What weather does polar maritime bring?
Frequent showers at any time of year
Winter; snow, sleet or hail.
Affects western and northern side of British Isles. Mostly west.
AV temp in winter is 7 degrees
AV temp in summer is 16-17 degrees
Returning polar maritime has a longer sea track.
Source region of tropical maritime?
Source region is over waters of Atlantic between Azores and Bermuda.
Air is very warm lots of moisture in lower layers making it originally unstable .
Tropical maritime’s journey ?
Across Atlantic which is cooler making it more stable.
What weather does tropical maritime bring?
Varies considerably
Summer- temp above AV of 25
Fog
Clear skies in land and drizzle.
In winter
Low cloud
Drizzle
Hill fog and stratus clouds over Dartmoor.
Arctic maritime, source region?
Source region is Arctic Ocean, close to North Pole, pulled south wards by high pressure systems. Over North Sea but shorter sea track than polar maritime.
Very cold air warms up and becomes unstable.
Weather the Arctic maritime brings?
Winter?
Most severe winter weather
Can lead to snowfall over Scotland and heavy snowfall over British Isles but otherwise inland areas free of cloud in winter months.
Hail showers
Cold temp 1-2 degrees.
Summer?
Uncommon, it’s a winter phenomenon but when it happens it brings showers/storms over Scotland.
Unusually low temp in July 12-13 degrees.
Spring - hail showers.
Coldest air mass for northern Scotland but over rest of uk, not as cold As polar continental.
Journey and source region of polar continental ?
Source ; Eurasian landmass such as Siberia or Scandinavia Occurs usually in British Isles when there is high pressure.
In summer, landmass is warmed and therefore no high pressure cell to push air over, only affects British Isles when Hp and easterly wind.
Dry cold air but as it passes over born sea, warms and picks up moisture, short sea track over British channel.
However, if longer sea track over North Sea warmed by 8 degrees and become more unstable.
Weather of polar continental?
Winter phenomenon
Freezing temperature
Below minus 10 degrees at night and remain freezing in day.
If longer sea track over North Sea it will cause snow and showers on east coast due to added moisture.
Summer - rare as winter phenomenon- temp above AV. Of 25 degrees. Cools over North Sea can cause gov.
Tropical continental ? Source region and track?
Origin Sahara and North Africa, very warm region so air mass very warm temp and low moisture content.
Across med sea
