Depressions and Anticyclones – A Revision Sheet

DEPRESSIONS ANTICYCLONES

From: http://www.stacey.peak-media.co.uk Source: http://www.metoffice.gov.uk

Pre

ssu

re

Low Pressure, Isobars (lines joining areas of equal pressure) close together

High Pressure, isobars far apart

Cau

se Cold and Warm air masses meet and don’t

mix easily. The cold air pushes the warm air upwards creating an area of unstable weather.

Cool, dry air sinks creating an area of high pressure, and stable weather conditions for a longer period of time (days-weeks).

Win

d Anticlockwise direction. High wind speeds– the closer together the isobars are, the higher the wind speed.

Clockwise, light or no wind

Weath

er

Strong winds, occasionally gale force, rainfall and cloud, thunderstorms can occur over cold front.

Source: http://www.bbc.co.uk/schools/gcsebitesize/geography/images/g_depression.gif

Settled weather lasting for a number of days, clear skies, no rainfall due to little chance for air/water vapour to evaporate:Summer – clear skies, warm temperatures, heat wave possible.Winter – clear skies, very cold due to no cloud cover and sun is lower in the sky in winter, no rainfall/no snow, but... frosts and fog due to air warming at surface as it sinks.

Eff

ects

on

peop

le

Rainfall – can cause flooding i.e. damage to homes, possessions lost, businesses, transport routes cut off.High winds – structural damage to buildings e.g. chimneys blown off roofs, transport affected by fallen trees, bridges such as Severn Bridge closed affecting transport, lorries can be blown over in very high winds.Snow in winter – schools closed, elderly people trapped in homes, transport: roads closed due to snow, trains cancelled, economic losses to businesses due to people not going into work.

Summer – dehydration (particularly elderly and children) due to not drinking enough water, heat stroke, sunburn, increased sales of ice-cream etc, water shortages if no rainfall over longer period of time and possibly even droughts, hosepipe bans.Winter – football and other sports games called off due to frost, elderly people and children slipping on ice = broken bones, more traffic accidents due to icy roads, hypothermia in elderly people.