Slide 1

What am I describing?

Some people love this, others hate it.

40,000 people died in Europe because of it in 2003

It always occurs in summer

Usually associated with high pressure, sunny, dry weather.Heat wave!

Anticyclones, depressions, hot & drought, cold & snow

Learning Objectives:To describe and explain the weather associated with high and low pressure systems Link them to extreme weather, list the hazards associated with this extreme weather and assess their impacts on various sectors of the community.The Global Circulation:Weather is driven by the unequal heating of the Earths surface. Air heated strongly at the equator becomes less dense and rises, reaching the top of the troposphere (10-15km) and then it spreads outwards to both poles. When it reaches the Polar Regions, it sinks and through continuity flows back to the equator. This closed cell of circulation creates a low pressure at the surface where air is rising (i.e. at the equator) and a high pressure where air is sinking (Polar Regions).

The Global Circulation Continued:However, due to the Earths rotation, the circulation is more complex and actually results in three separate circulations .Adding further to the complexity is the non-uniform nature of the Earths surface (sea, land, mountains, ice etc). Video explanationAnimationNASA - 1AnticyclonesA large area of high atmospheric pressure, characterised by outward-spiralling winds - a "high". Winds are clockwise in the Northern Hemisphere and anticlockwise in the Southern (Source: BBC). H 1034Isobars Lines of equal pressureDirection of surface windsHigh pressure with pressure in millibarsThis animation shows the affect of the Coriolis force. Although the air moves from high to low pressure, the rotation of the Earth makes it appear deflect to the right from the point of view of an observer on the Earth.HCoriolis Effect AnimationAnticyclones continuedAnticyclones are masses of sinking air creating a high pressure (>1013mbars) at the surface. Horizontal pressure gradients (how much pressure changes with distance) are often small and so the surface wind speed is usually low. The sinking air inhibits convection and therefore cloud formation, so hot, dry days usually accompany high pressure systems in summer and cold, dry days in winter.CyclonesA large area of low atmospheric pressure, characterised by inward-spiralling winds - a "low" - also called a "depression". Winds are anticlockwise in the Northern Hemisphere and clockwise in the Southern (Source: BBC). Cyclones consist of rising air, creating the low pressure (40,000 people dead across Europe due to the heat wave38.5oC (101.3oF) recorded in Brogdale in Kent, UK48oC (118.4oF) recorded in Amareleja, PortugalFrance lost 20% of its wheat crops due to droughtUK rail transport severely disrupted by speed limits imposed on railways as the heat caused some rails to buckle.215,000 hectares of forest destroyed in Portuguese fires an area the size of Luxembourg!Europe 2003 Heat waveThe river Danube in Serbia fell to its lowest level in 100 years exposing world war two relics.Two nuclear power stations were forces to close due to cooling issues.Cost to European farming estimated at 13.1billion Euros.The London Eye closed for a day after cabin temperatures became unbearable.UNEP United Nation Environment Programme European heat wave review

% of expected rainfall totals in the UK for Feb Oct 2003.

Orange areas Substantially below average

Red areas exceptionally low rainfall

Source: UK Met Office - 6

Satellite image of forest fires in Portugal Source: UK Met Office 7Following this heat wave, the Met Office set up a warning system to prepare the public and health service etc in advance of an imminent heat wave.Met Office Heat-Health Watch (only available 1st June to 15th September)Cold Spells (Cold waves)On your map of Europe, draw in pencil the position of an anticyclone which could lead to cold weather in the UK.Hint: Think of the direction the air coming into the UK should be from.Answer Anticyclone to the west of the UK. This gives Northerly winds bringing cold, Arctic air into the UK. A cyclone in the North Sea would also likely occur (called a Polar Low), causing weather fronts bringing snow and high winds. OR High to NE of UK and low to S bringing in strong, cold Easterly winds from the continent.FrostDuring anticyclonic weather in winter, skies are often clear at night. The ground then radiates heat straight out to space. The ground therefore cools rapidly and causes the air around it to also cool.The air may reach temperatures below 0oC and below its dew point. This means ice will form onto surfaces (such as grass) i.e. frost.

Frost on a windscreen - 8Blizzard Definition (Met Office):30mph windsModerate or heavy snowVisibility below 200m

South Dakota Blizzard 2008A cyclone brings weather fronts with moist air, precipitation and strong winds. If these move into cold air or the cyclone comes from a cold region then snow will fall. Often the criteria above are reached and a blizzard therefore formed.

NASA - 9A satellite image showing the UK almost entirely covered in snow 07-01-10What social, economic and environmental issues are associated with cold spells?Social:DeathHypothermiaTravelling difficult for elderly and disabledOutdoor activities cancelled or postponedIncrease in admittance to A&E+Parents may spend more time with their children if schools are closed

Economic:Workers stuck at homeChildcare costs when schools are closedDamage to infrastructure e.g. Road surfaces, downed power lines. Airports, railways & roads closed.Extra winter fuel payments to elderly costs the government.Cost of road gritting/saltingPipes freeze and crackDamage or death to less cold-tolerant crops such as citrus fruitsIncrease in warm weather clothes salesGas and electricity companies increases profits as demand increases

Environmental:Increased road gritting/salting pollutes the environmentWidespread death of animals due to lack of food.Extra greenhouse gases emitted as people try to stay warm by burning fossil fuels.UK Cold Spell 2010ITN News ReportThe coldest winter for England and Wales since 1978-1979Mean winter temperature was 1.6oC (2.1oC) below the 1971-2000 average.Grit supplies ran out in some council areas. 60,000 tonnes of salt were being used per day.A gas supply alert was made to ensure supplies in the UK were maintained. This meant turning the supply off to major industrial users who had signed up to interruptible contracts.UK Cold Spell 2010The temperature fell to -22.3oC at Altnaharra, Highland.1000 vehicles were stuck on the A3(M) as over 12inches of snow fell on 6th January.Over 8000 schools were closed on the same day and 5000 homes in Sussex were left without electricity.Hampshire council called on 120 farmers to help clear roadsAll outpatient appointments and non-urgent operations at hospitals covered by the Oxford Radcliffe Hospitals Trust were postponed.

UK Cold Spell 2010The Royal Berkshire Hospital in Reading sent midwives out in 4x4s to help women in labour.Football, horseracing and many other sporting fixtures were postponed.100s of flights were cancelled to and from UK airports including Heathrow and Gatwick.

Met Office chart showing all of the UK with negative temperature anomalies for the 2009-2010 winter compared to the 1971-2000 average.10Fill in the table describing the impacts of the weather we have discussed.BINGO!AnticycloneCycloneCoriolisCold frontWarm frontOccluded frontHyperthermiaHypothermiaFrostBlizzardClockwiseAnticlockwiseSources:NASA - http://sealevel.jpl.nasa.gov/overview/images/6-cell-model.jpgNOAA - http://aviationweather.gov/adds/progs/NASA - http://rst.gsfc.nasa.gov/Sect14/Sect14_1c.htmlNASA - http://rst.gsfc.nasa.gov/Sect14/Sect14_1c.htmlNWS - http://www.srh.weather.gov/srh/jetstream/synoptic/cyclone.htmUK Met Office - http://www.nerc-wallingford.ac.uk/ih/nrfa/yb/yb2003/drought2003/fig4.htmlUK Met Office - http://www.metoffice.gov.uk/education/teens/casestudy_heatwave.html

Sources:Authors own photoNASA - http://rapidfire.sci.gsfc.nasa.gov/gallery/?2010007-0107/GreatBritain.A2010007.1150.1km.jpgUK Met Office - http://www.metoffice.gov.uk/climate/uk/2010/winter.html