AnticyclonesAnticyclones

The calm and stillThe calm and still onesones

Characteristics of Characteristics of anticyclonesanticyclones

You know the routine – pens and the You know the routine – pens and the whiteboardwhiteboard

Just think opposite of depressionsJust think opposite of depressions

Characteristics of Characteristics of anticyclonesanticyclones

Relatively high pressureRelatively high pressure On weather maps they are closed isobars On weather maps they are closed isobars

with pressure increasing towards the centre.with pressure increasing towards the centre. Anticyclones move slowly and remain Anticyclones move slowly and remain

stationary over an area for several days or stationary over an area for several days or weeksweeks

The air subsides (sinks). It warms which The air subsides (sinks). It warms which leads to a decrease in relative humidity = leads to a decrease in relative humidity = lack of cloud & dry conditions.lack of cloud & dry conditions.

AnticyclonesAnticyclones

Anticyclones which establish themselves Anticyclones which establish themselves over UK & Western Europe are called over UK & Western Europe are called blocking anticyclonesblocking anticyclones

They deflect depressions away from UK & They deflect depressions away from UK & Western EuropeWestern Europe

Extreme conditions are then produced – dry Extreme conditions are then produced – dry and freezing in winter and heat waves in and freezing in winter and heat waves in summer.summer.

AnticyclonesAnticyclones

Anticyclone

summer winter

Unlike depressions there are two distinct types of anticyclone

There are some similarities but in other ways are very different

AnticyclonesAnticyclones

WinterWinter Cold day time Cold day time

temps, from below temps, from below 00ooc to c 5c to c 5oocc

Very cold night time Very cold night time temps – frosts temps – frosts below 0below 0ooc c

Generally clear Generally clear skies by day & nightskies by day & night

SummerSummer Hot day time temp, Hot day time temp,

over 25over 25ooc c Warm night time Warm night time

tempstemps

May not fall below May not fall below 1515oocc

Generally clear Generally clear skies by day & nightskies by day & night

WinterWinter SummerSummer

AnticyclonesAnticyclones

WinterWinter low level cloud may low level cloud may

linger and radiation fog linger and radiation fog may remain in low lying may remain in low lying areasareas

Causes high levels of Causes high levels of air pollution in urban air pollution in urban areas as pollutants are areas as pollutants are trapped by 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 or haars (onshore winds)winds)

Thunder storms can Thunder storms can occur when RH is highoccur when RH is high