ANTICYCLONES
10
Anticyclones Anticyclones
-
Upload
alex-c-g-cooper -
Category
Documents
-
view
150 -
download
3
Transcript of ANTICYCLONES
AnticyclonesAnticyclones
Remember anticyclones form as a result of air pil ing up aloft.
This encourages air to subside / sink down.
As the air sinks, it warms, this increases the amount of water the air can hold, and thus keeps the sky relatively cloud free.
Leading edge
Anticyclones, HighsAnticyclones, Highs Anticyclones over the British Isles occur Anticyclones over the British Isles occur
frequently, but are frequently, but are less commonless common than than depressions. depressions.
Anticyclones give rise to Anticyclones give rise to differentdifferent weather weather conditions, depending upon the time of year.conditions, depending upon the time of year.
Anticyclones move slowly and are stable Anticyclones move slowly and are stable features.features.
They can be 3000km wide – much bigger than They can be 3000km wide – much bigger than depressionsdepressions
High pressure systems tend to be longer lasting High pressure systems tend to be longer lasting than depressions, once ‘than depressions, once ‘blockedblocked’ they can last ’ they can last up 10 days. up 10 days. They deflect depressions away from They deflect depressions away from UK & Western Europe.UK & Western Europe.
Anticyclones are characterised by:Anticyclones are characterised by: High pressure readings in the middle.High pressure readings in the middle. Far apart isobars = calm wind.Far apart isobars = calm wind. The air subsides (sinks). It warms adiabatically The air subsides (sinks). It warms adiabatically
which leads to a decrease in relative humidity = lack which leads to a decrease in relative humidity = lack of cloud & dry conditions.of cloud & dry conditions.
Air moving away from the centre of the high.Air moving away from the centre of the high. Air spins clockwise around from the high.Air spins clockwise around from the high. They normally travel to the British Isles from They normally travel to the British Isles from
mainland Europe.mainland Europe. High pressure systems form commonly over the High pressure systems form commonly over the
Azores – ‘Azores High’.Azores – ‘Azores High’.
Anticyclones give rise to different Anticyclones give rise to different conditions, depending on the time of conditions, depending on the time of
year.year.WinterWinter Cold day time temps, Cold day time temps,
from below 0from below 0ooc to 5c to 5oocc Very cold night time Very cold night time
temps – frosts below temps – frosts below 00ooc c
Thick morning fogs are Thick morning fogs are often presentoften present
SummerSummer Hot day time temp, Hot day time temp,
over 25over 25ooc c Warm night time tempsWarm night time temps May not fall below 15May not fall below 15oocc Generally clear skies Generally clear skies
by day & nightby day & night
WinterWinter Low level cloud may Low level cloud may
linger and radiation linger and radiation fog may remain in low fog may remain in low lying areaslying areas
Causes high levels of Causes high levels of air pollution in urban air pollution in urban areas as pollutants areas as pollutants are trapped by are trapped by temperature inversiontemperature inversion
SummerSummer Hazy sunshine in some Hazy sunshine in some
areasareas Early morning mists Early morning mists
which disperse quicklywhich disperse quickly Heavy dew in the Heavy dew in the
morningsmornings East coast has sea frets East coast has sea frets
or haars (onshore winds)or haars (onshore winds) Thunder storms can Thunder storms can
occur when RH is high occur when RH is high (Spanish Plume)(Spanish Plume)
Anticyclones give rise to different condit ions, Anticyclones give rise to different condit ions, depending on the time of year.depending on the time of year.
