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Weather systems in mid-latitudes and their interaction with human environments. Winter & summer anticyclones and associated weather. Anticyclones. Definition: An anticyclone is a large mass of subsiding air which produces an area of high pressure on the earth’s surface.
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Winter & summer anticyclones and associated weather
Hot sunny days (up to 30C in S)
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
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 conditionsSummer Anticyclone
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.Winter Anticyclone
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.
2. SOCIAL ISSUES:
- Weather dictates choice of crops
- Wind breaks planted to protect crops
-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