Anticyclones

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Formation

  • Areas of high pressure which produce calm, settled weather with little cloud or rain
  • High pressure system brought in by anticyclone comes from south of UK
  • Tc air arrives from areas of high pressure and brings warm and dry air into the British Isles
  • As air subsides from a high altitude, condensation can't take place so no clouds
  • Anticyclonic conditions also occur in winter when Pc air develops high pressure and sinking conditions
  • Anticyclones can move into an area for a few days or longer blocking out any other weather system
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Summer and Winter Anticyclones

Summer Anticyclones

  • High pressure of up to 1000mb
  • Warm temps as Tc is over British Isles- temps can be above 24°C
  • Sinking air allows for no condensation resulting in little cloud with calm settled  during the day- at night clear skies can lead to cold nights as air escapes as no cloud is blocking it
  • Isobars are far apart- conditions are calm and any wind moves in a clockwise direction
  • Very little rain due to lack of cloud cover- if any rain, fog can form in evening or thunderstorms can develop due to convectional rainfall

Winter Anticyclones

  • High pressure of up to 1000mb
  • Much lower temps as Pc is overhead and sun is lower in sky
  • As in summer, but lack of cloud at night allows temps to go below freezing and lead to frost and ice
  • Isobars are far apart- conditons are calm and any wind moves in a clockwise direction
  • Little rain but freezing fog and frost/ice can be formed due to lack of cloud
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Impacts: Winter Anticyclones

People

+Nice days during winter with no cloud or rain and a break from depression conditions

+Very cold temps and frosts can remove disease causing organisms within soil

-People with asthma and other respiratory illnesses find it difficult to berate in cold weather

-Frost and ice can be a hazard for drivers or old people may slip and fall

Economy

-Fog can restrict transport and close airports

-Ice on roads can cause an increase in road traffic accidents, which can slow movement of goods

-People may need to use more heating in cold weather, which can cost more money

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Impacts: Summer Anticyclones

People

+Brings good weather, lifting people's spirits and encourages them to go outside and enjoy more activities

-Brings long periods of hot, dry weather increasing drought risk leading to hosepipe bans and soil erosion

-Old people and those with underlying medical conditions can be affected in dry spells, increases risk of heat exhaustion

Economy

+Ideal for crops to allow them to ripen fully increasing profit

+Tourism boosted, people take trips close to home spend money on local economy

-Brings drought, which can cause crops to die back, farmers lose money

-Irrigation can be used to artificially water land but it is expensive and can do more damage than good

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Case Study: 1976 summer anticyclone in England

  • Heat wave led to hottest summer temps in UK since records began- whole country suffered drought
  • 15 consecutive days temps stayed above 30°C
  • Parts of country went 45 days without rain in July and August
  • Number of deaths as well as forest fires, crops failed due to drought, causing over £500 million of damage
  • Food prices decreases by 15%
  • Some rivers went completely dry, some homes in Yorkshire has complete water ban
  • Government passed Drought Act to forbid water usage for non-essential uses
  • Foundations that had used dried out and crumbled houses to subside in following years
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