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Weather systems in mid-latitudes and their interaction with human environments

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Weather systems in mid-latitudes and their interaction with human environments Winter & summer anticyclones and associated weather Anticyclones Definition: An ... – PowerPoint PPT presentation

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Title: Weather systems in mid-latitudes and their interaction with human environments


1
Weather systems in mid-latitudes and their
interaction with human environments
  • Winter summer anticyclones and associated
    weather

2
Anticyclones
  • Definition An anticyclone is a large mass of
    subsiding air which produces an area of high
    pressure on the earths surface.
  • Source of subsiding air is upper atmosphere
  • Air warms at DALR as it descends
  • Pressure gradient weak as it is one air mass
  • Winds light clockwise blowing outward from
    centre
  • May be 3000km diameter

3
Anticyclones can block depressions once
established can give several days (or in extreme
cases weeks) or settled weather.
4
Summer Anticyclone
  • Polar Front moves north and Azores high pressure
    system extends northwards to cover much of UK
  • No cloud
  • Intense insolation
  • Hot sunny days (up to 30C in S)
  • Dry
  • Calm build up of pollutants in lower atmosphere
    ozone, pollen, nitric oxides
  • Any wind is southerly bringing in polluted air
    from mainland Europe
  • Rapid radiation cooling at night
  • Temperature inversions
  • Dew mist (rapidly clear in morn)
  • Coastal areas advection fogs land sea breezes
  • Highlands mountain valley winds
  • If source Tc (N Africa) then heat wave conditions
  • Increased risk of thunderstorms Spanish Plume
    (East Anglia and SE)
  • Blocking anticyclones occur when high pressure
    cell detaches from the sub tropic high and stays
    for long time block depressions leads to
    drought conditions

5
Cold, dense air flows down adjacent slopes and
collects on valley floor. Low wind speeds or calm
conditions needed.
6
Winter Anticyclone
  • Polar Front moves southwards and polar high
    pressure system moves southwards to dominate over
    UK
  • Little insolation due to the low angle of the sun
  • Night low temp, temp inversions, ground frost,
    radiation fog, freezing fog most noticeable
    inland
  • Longer to disperse in morn due to weak sun
  • When pollutants mix with fog it forms smog now
    rare in UK due to Clean Air Act 1956, but in Dec
    1952 The Great Smog of London indirectly killed
    c. 4000!
  • Pc source central Asia, moves over cold land
    mass cold, dry, stable. Over North Sea gets
    warmth moisture can cause heavy snow on the
    East coast.

7
Weather People
  • Any weather will have an effect on economy of a
    country and society in general e.g. hours worked,
    communication systems, migration life itself.
  • Effects on people
  • HEALTH ISSUES
  • Disease - most likely in Spring Autumn due to
    change in temp e.g. measles colds are common
    during this period.
  • Psychological issues people get depressed
    during long dark winters, increased suicides in
    spring as others celebrate new life, more crime
    in summer as people get aggravated.
  • Elderly cannot afford to heat their homes
    properly in winter (homeless people)
    hypothermia.
  • Heat stroke and sun burn in summer.
  • Respiratory problems brought on by smog.
  • Very cold weather helps to kill germ.

8
Weather People
  • 2. SOCIAL ISSUES
  • Amount of hours spent at work very long hours
    for some outdoor jobs in summer
  • Working conditions increased heat in building
    due to double glazing, central heating people
    more irritable
  • Quicker spread of disease in air conditioned
    buildings
  • More social life style in summer eating,
    drinking out doors, more relaxation
  • Canopies or heaters can be used outdoors e.g.
    parasols and patio heaters in summer
  • Fetes, festivals held in summer months winter
    less eventful, less to look forward to.
  • Seasonal change in our diet fruit veg. in
    season, more cold food (salad) eaten in summer,
    more soups and hot drinks in winter, ice cream
    sales
  • Different clothing worn in different seasons
    retail driven by the weather
  • Long school holiday taken in summer because
    weather better and every one finds it more
    difficult to work and concentrate in the heat
  • Hose pipe bans affect gardeners, swimming pool
    owners
  • Coastal damages due to waves during storms
  • Filling of reservoirs and groundwater storage
    good for home owners and farmers
  • Loss of electricity due to winds

9
Weather People
  • 3. AGRICULTURE
  • - Weather dictates choice of crops
  • Several months of year when nothing grows
  • Aspect (S facing slopes) influences what crops
    are planted where fragile plants would not be
    grown on valley floor as frost hollows are
    created there
  • Green houses used to counterbalance weather
  • Crops covered in plastic to encourage germination
    and early growth, portable heaters
  • - Wind breaks planted to protect crops
  • Canopies or heaters can be used outdoors e.g.
    parasols and patio heaters in summer
  • Intense r.f. or hail can destroy crops (flatten,
    flood)
  • Animals brought inside in winter, out in fields
    in summer
  • Number of farms and farmers in decline due to
    long hours of work out in the elements
  • Crop failure due to drought if prolonged summer
    anticyclone
  • Need for irrigation

10
Weather People
  • 4. TRANSPORT
  • -black ice on roads very dangerous
  • -Glare from sun accounts for 25 of all road
    accidents
  • -strong winds mean bridges may be closed due to
    risk to high sided vehicles, roads closed due to
    fallen trees
  • -heavy snow fall roads (chains on tyres, people
    by 4 wheel drive, heated roads to hospitals),
    airports closed, weight on roofs buildings
    collapse, skiing, sledging
  • -sea travel storms dangerous, calm weather
    slows sailors
  • -flights to USA use jet stream (return journey
    quicker, less fuel needed)
  • -rail travel freeze-thaw cycles can buckle
    tracks, metal also corrodes

11
Exam questions
  • You need to identify the disadvantages and
    advantages of the weather associated with each
    weather system - depressions and anticyclones.
  • You need to be able to clearly describe the
    sequence of weather associated with each and then
    how each affects human environment.
  • Good to use examples of each such as Great Storm
    of 1987 (depression) and Great UK Drought of 1976
    (anticyclone).

12
Essay questions past papers (12 marks)
  • Describe and explain how the weather experienced
    during both winter and summer anticyclones in
    mid-latitudes affects the human environment. June
    2005
  • Discuss how low pressure systems in mid-latitudes
    interact with human environment. Jan 2004
  • Describe and explain the weather changes
    associated with the passage of a frontal
    depression in the mid-latitudes. May 2003
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