Transcript Anticyclones

Anticyclones
Year 13
How Anticyclones Develop
• An anticyclone is a large mass of subsiding
(descending) air which produces high pressure
on the Earth’s surface.
• As the air descends, it warms and water
evaporates, so dry conditions prevail.
• Pressure gradients are gentle so winds are
weak or calm.
• Anticyclones may be 3000km in diameter
(compared with about 1000km for a depression)
Characteristics of anticyclones
• Stable air with limited cloud formation and
precipitation.
• Circulation is in a clockwise
• Light wind speeds or calm
• Warm, dry days and mild nights in
summer.
• Cool, dry days and frost and/or fog and
mist at night in winter.
Summer
• Day
• Night
Winter
British anticyclone weather
• In Britain in summer an anticyclone will
mean heat waves during the day. At night,
however, as there are no clouds, heat will
be quickly lost. The ground will cool
sufficiently to cause condensation of water
vapour in the descending warm air and
mist or heavy dew may form.
• In winter the longer nights combined with
clear skies leads to intense cooling of the
land. There is an increased risk of dew,
frost and thicker, more extensive fog
patches which may be slow to clear or
even persist.