Weather & Climate

Weather: the short term atmospheric conditions of a particular place. E.g. Temperature, precipitation, cloud cover, wind speed etc. (hours, days, weeks).

Climate: the long term atmospheric conditions of a particular place. Average measurements of temperature, precipitation etc. over a long period of time (years, decades, centuries).

The Earth receives energy from the sun through solar radiation but as the Earth is a sphere most of this is concentrated on the equator (the same amount of energy is spread over a larger area at the poles).

This energy is re-distributed throughout the world through winds and oceans. 

Winds:

• The sun warms air at the equator causing it to rise and thus creates an area of low pressure. The area of low pressure is the Inter Tropical Convergence Zone (ITCZ).
• The air cools as it rises and moves away from the equator before sinking at 30degrees north and south. The sinking creates an area of high pressure.
• The air then moves as surface winds back to the equator or out towards the poles.
• Winds travelling towards the equator are Trade Winds.
• Winds travelling towards the poles are Westerlies.
• The winds moving towards the poles collide with cold air from the poles at 60degrees N&S.
• Warm air rises over the cold air and so there is low pressure. The air either continues moving towards the poles or travels back to 30degrees N&S. 
• When cold air sinks at the poles it creates an area of high pressure. 

There are 3 main types of global atmospheric circulation cells.

• Between the equator and 30degrees = Hadley Cell.
• Between 30 and 60degrees = Ferrel Cell.
• Between 60degrees and the Pole = Polar Cell.

Ocean Currents

Ocean currents are large scale movements of water caused by differences in water density.

The density of water is dependent on the temperature and salinity.

Affected by surface winds mainly but also by the position of land masses and other currents.

Ocean currents form huge loops travelling clockwise (Northern Hemisphere) and anti-clockwise (Southern Hemisphere). 

A well known ocean current is the Gulf Stream which originates in the Gulf of Mexico and brings warm water to the UK. The Canary Current takes cold water from the UK back to the equator.

The UK is a temperate climate - warm but wet summers and cold, wet winters. 

Temperature ranges from an average of 5 degrees in January to 20 degrees in August.

Rainfall is high all year however there is less in spring and summer than autumn and winter. 

UK climate is the result of:

Latitude: Sun never gets very high in the sky so it doesnt get hot but theres several hours of daylight even in winter so it doesnt get very cold.

Location (in relation to atmospheric cells): Northern edge of the Ferrel cell. Warm surface winds from the south rise to create an area of low pressure and allowing depressions to form. 

Location (maritime): Water gains and loses energy slower than land which leads to cooler summers but warmer winters than places on the same latitude.

Gulf Stream: the warm water helps keep the UK temperature warmer than places of similar latitude within a continent. 

There are 5 air masses which affect the UK. The main two are Tropical Maritime (Tm) and Polar Maritime (Pm). Air masses are classified by the region they form over. Maritime = Moist, Continental = Dry etc.

Depressions: 

• Warm air from the south brought in by the Tm air mass interacts with colder air from the north brought by the Pm air mass. 
• The point at which these two masses meet is called the Polar Front.
• The warm air rises above the cool air as it is less dense and gets twisted about by jet streams as well the coreolis affect of the Earth's natural rotation. 
• The warm and cold fronts now rotate in an anti-clockwise direction however gradually the warm front is caught up by the faster-moving cold front and an occluded front is formed.The warm air is therefore lifted away from the ground entirely.

Anticyclones:

• Areas of high atmospheric pressure caused by a large mass of falling air.
• The air heats up as it falls and thus humidity is reduced as air masses can hold more moisture when warmer. 
• Clouds dont develop and conditions a dry. 

Winter Weather:

• Low temperatures (below freezing to 5 degreesC)
• Extremely cold nights - no clouds allows heat to escape.
• Low level clouds and radiation fogs in the mornings.
• High levels of atmospheric pollution - trapped by temperature inversions and no wind to disperse pollutant particles.

Summer Weather:

• Hot (over 20 degreesC at midday), Sunny, no rain.
• Temperature inversions caused by rapid radiation. Coastal areas may receive fog. 
• Risk of thunderstorms after several days due to large amounts of rapidly rising warm air.

Case Study: Great Storm, 1987.

Impact:    Social                              Economic                                 Environmental

    18 people died.   1million buildings damaged.Insurance - £1.4b 15million trees blown down. 

Power/Phone lines broken.      Transport disrupted (blocked roads).    Loss of animal habitats.

(150,000 homes without power).         Gatwick Airport closed.

Response:

• Emergency authorities (Fire, Ambulance, Police, & Coastguard) dealt with calls.
• Recovery and clean-up operation began after storm had passed. Round the clock repair of damaged infrastructure (power/phone lines).
• Road, railway etc. clearance began.
• Met Office criticised. Changes made - more observations and improved computer models.
• Government established the national severe weather warning service to improve warnings issued in the case of similar, future storms.
• MoD warned military assistance might be needed.

Tropical Savanna Climates are found between latitudes 5 and 20 degrees North and South, the areas between the ITCZ and zones of subtropical high pressure. 

Characteristics:

• Hot temperatures (18-30 degreesC) all year as the sun is always overhead.
• Daytime temperature variation: 2-4 degreesC.
• Nightime temperatures are around 10-15 degreesC lower.
• Seasonal rainfall with a wet season and dry season. 500-1700mm/year.
• Amount of rain depends on location of ITCZ.

For the Northern Hemisphere: Dry Season - January & Wet Season - July

Dry - ITCZ moves south of the equator in January meaning the area of high pressure also moves south and lies above the African Savannah meaning dry conditions. 

Wet - ITCZ moves north of the equator in July and sits on top of the Northern Hemisphere African Savannah bringing an area of low pressure and therefore heavy rainfall. 

The African Savannah lies south of the Sahara desert and in the Northern Hemisphere stretches from Senegal (Atlantic Ocean) to Somalia (Indian Ocean).

Tropical Revolving Storms are slow moving systems of extremely low pressure. What they are called depends on the region in which they occur. 

North America: Hurricanes. South Asia/Oceania: Cyclones. Japan: Typhoons.

Several conditions are needed for a storm to form.

These are:

• Disturbance near the sea-surface e.g. area of low pressure.
• Warm sea water (26.5 degrees C up to 50m below the sea-surface). So there's lots of evaporating water.
• Convergence of air in lower atmosphere. E.g. along the boundary of warm and cold air masses.
• For all of the above to occur further that 5 degrees from the equator where the Coriolis effect is enough to make them spin. 
• For a revolving storm to remain powerful it needs the source of heat from the ocean and this is why many lose lots of energy when they make landfall. 

Social

• People drown and can be injured or killed by flying debris.
• Infrastructure destroyed. Roads blocked, power supplies cut off etc. Can hinder communication, aid and rescue efforts 
• Contaminated water supplies as sewage overflows.
• Shortage of clean water/lack of sanitation. 
• Shortage of food in poorer countries - no aid, livestock killed and farms ruined.
• Unemployment increases as businesses are destroyed.

Economic

• Huge amount of money to rebuild roads, airports, schools etc. that are damaged/destroyed
• Damage to crops and businesses means they can't trade their goods. 

Environmental

• Beaches eroded and coastal habitats (E.g. coral reefs) destroyed.
• Salt water, oil, chemicals etc pollute environments and water supplies.

Impacts of storms are usually greater in poorer countries for many reasons.

• Don't have the money to respond - No flood defences, no trained emergency teams etc.
• Buildings are of poorer quality and so are more easily damaged.
• Evacuation harder to organise - limited access to communications and transport.
• Poor healthcare and can't cope with influx of injured.
• Emergency services take longer to reach the affected area as there's poor infrastructure. 

However the economic cost is usually much less in poorer countries as buildings/infrastructure aren't worth as much.

Example:

Economic impact of Katrina was $300billion.

Economic impact of Nargis was $4billion.

Evacuation:

• Fairly accurate predictions can be made on when and where a storm will hit and a predicted path can be mapped allowing people in the areas most likely to be hit can evacuate. 
• Can use time to lessen impact on homes and businesses - sandbags/boarding windows.

Planning and Education:

• Future developments can be planned to avoid most at-risk areas e.g. the coast.
• Emergency agencies can prepare on what to do. Example: FEMA in the USA.
• Governments can plan evacuation routes and educate on how best to prepare for the storm.

Building Techniques

• Stilts, reinforced concrete and secured roofs can mitigate the effects of a storm.
• Flood defences can protect against storm surge. Levees (rivers) and sea walls (coasts)

Aid

• Aid sent by governments and world organisations can be very effective at helping the region.

The Urban Heat Island effect is a phenomenom of urban areas being warmer than the surrounding countryside. The CBD and other densley built-up areas of the city are the warmest.                

This 'microclimate' may occur because:

• Buildings can absorb heat and store it before slowly releasing it - most noticeably at night.
• Air Pollution from cars and factories increases cloud cover which traps heat trying to escape.
• Human Activities release heat. Cars, factories, central heating, and people etc.
• Evapotranspiration uses heat energy however water quickly drains and there isn't as much vegetation and so, in a city, evapotranspiration is reduced. 

UHI effect varies diurnally (between day and night) and seasonally

Urban area is 0.6 degrees warmer (day) and 3-4 degrees warmer (night).

More solar radiation in the summer means urban areas are 5 degrees warmer than rural but in the winter they're only 2 degrees warmer. 

Stronger when there's an anticyclone (more solar radiation reaches the ground, no wind). 

• Winds are affected by the buildings in urban areas. 
• The friction created by tall buildings lowers the average wind speed and in some areas wind speeds are 0 as the buildings block it. 
• Turbulence can be created around a building when wind that has had to part (to pass by the building) and rejoin - the wind coming from different directions (sides and above) creates vortices. 
• Powerful gusts of wind can be channelled down long streets with tall buildings either side and cause complications with building design. This is the canyon effect. 

Precipitation, Fog and Thunderstorms occur more frequently in UHI. 

• UHI effect means air is warm in urban areas so it can hold more moisture. As the air rises it cools, the air can no longer store the moisture and it rains. Called Convectional Rainfall.
• Pollution and dust created by cities act as condensation nuclei which encourages clouds to form and it to rain rather than allowing warm moist air to disperse. 
• Higher concentration of condensation nuclei increases frequency of fog. 

There's more particulate pollution in cities than the countryside due to the higher number of pollutants. The source of the particulates can be vehicle exhausts, burning (of refuse, cigarettes, coal etc.), construction (brick fragments, cement dust etc.), and plants/mould (pollen/spores).

Photochemical Smog is from other types of pollution such as burning fossil fuels.

• Burning fossil fuels - releases nitrogen oxides, sulfur oxides etc. 
• These pollutants come into contact with sunlight and the UV light breaks them down into harmful chemicals (ozone) which form photochemical smog. 
• Problem for many cities but more common in hot/sunny climates where there's more UV light.
• Temperature Inversions in these cities where warm air is trapped beneath cooler air means the pollution remains fairly close to the ground.
• Can lead to breathing difficulties (coughing), respiratory disorders (asthma) and headaches. 

Reducing Traffic

Congestion Charging. E.g. London.

Pedestrianisation. E.g. Briggate, Leeds.

Public Transport Improvements. E.g. London (extending Tube). Manchester (Trams). If people can travel on public transport cheaply and it is fast (separated from the road) more will use it and number of cars on the road will decrease. 2.6million cars off road thanks to Bury-Altrincham tram.

No Car Days. E.g. Mexico City - bans cars 1 day of the week depending on number plate.

Bike Schemes. E.g. London ('Boris Bikes') - cheap bike hire at many points in the city.

Car-Sharing Initiatives such as multiple-occupancy lanes. 

Legislation (Laws)

UK clean air acts (1956 and 1968) reduced domestic pollution - smoke control areas introduced where only smokeless fuel could be burned. 

Road Vehicles Regulations reduce exhaust emissions by ensuring cars pass emissions test in MOT.

Fines can be issued to those who leave their engine running unnecessarily.

Alternative Fuel

Biofuels produced from plants can directly replace petrol/diesel and lower particulate emissions.

Liquefied Petroleum Gas

Evidence

Physical

• Ice cores - analysing the gases trapped can tell you what the temperature was.
• Sea floor sediments - record the chemical composition of sea water when they were deposited
• Sea level change - Ice caps melt, sea levels rise. Valleys formed above sea level are submerged now.
• Retreating glaciers - terminal morraine can show the glacier has retreated and rocks can be dated to show how old they are.

Biological

• Pollen analysis - analysis can find out what conditions were like when pollen produced.
• Tree rings - grow thicker when conditions are warm and wet. Age known by counting rings.

Observations

• Weather records (since 1861) and historical records (pictures, agricultural reports etc.)

Human causes

Burning fossil fuels

• Carbon dioxide released when fossil fuels are burnt (CO2 is greenhouse gas).
• atmospheric CO2 levels increased from 280-380 ppm since industrial revolution. whereas they'd been stable for around 10,000 years before that.

Deforestation

• Plants absorb CO2 in the atmosphere and therefore when they are cut down these 'carbon sinks' are lost. 
• CO2 is released into the atmosphere when trees are chopped or burnt.

Farming

• Nitrogen-based fertilizer increases nitrous oxide emissions.
• Livestock farms produce a lot of methane.
• Rice paddies - flooded fields emit methane.

Impacts

Changes to precipitation patterns. - Wet areas get wetter, precipitation decrease 5-20% in dry areas due to changes to ocean circulation and wind patterns. 

Glaciers, sea ice and ice caps would melt - sea level rises. 10-15% less arctic ice since 1950s.

More extreme weather events. - Storms, floods and drought expected to be more severe and happen more regularly. LEDCs would suffer the most.

Increase in incidences of disease. - Breathing problems (Smog increase), heat-stroke, malarial moquitos move to areas where they currently arent.

Conflict over water could increase. - Would become much more valuable resource.

Agricultural patterns could change. - Where crops grown, time of year etc. Productivity may alter.

Decrease in biodiversity. - Species distribution might change and some species may become extinct due to loss of habitat. 

• Likely to get hotter resulting in higher evapotranspiration and drought. 
• Rainfall likely to increase closer to the equator bringing flooding and water-borne diseases (cholera etc.) but may also mean increased agricultural productivity. 
• Further from the equator the rainfall would decrease leading to drought and likely extinction of species. 
• Rainfall would become more variable - more storms in wet season.
• Flooding of low-lying areas, increased coastal erosion, and damage to coral reefs through increased sea temperatures. 

International 

Kyoto Protocol (1997-2012)

• Developed countries agreed to cut their emissions (by 5% at 1990 levels).
• Developing countries didn't need to cut emissions but monitor and report them instead. 
• Incentives used to promote this was carbon credits. Countries given limits on how much emissions they produce, stay within this target and credits can be sold, go over and more need to be bought.
• Credits also gained through helping reduce emissions in developing countries. Helping them to develop in a sustainable way. 

Problems with Kyoto

• USA, India, China and Australia didn't sign up for original agreement and all have high emissions.
• Countries haven't met their targets and some thing the targets need to be higher.
• Copenhagen Accord discussed in 2009 where countries set their own targets to meet however it's not legally binding and no penalties for missing targets. 

National

Changing the energy mix.

Replacing fossil fuels with nuclear and renewable power. 

Using new technologies to cut emissions from power stations. 

Carbon capture and storage designed to reduce emissions by storing it safely underground. Technology for this is at a development stage only at the moment. 

Encouraging domestic energy conservation.

15% of emissions reductions by 2020 will be achieved this way. Government providing efficiency grants to those who produce their own electricity etc.

Reducing transport emissions.

Encouraging people to use less polluting cars (electric/hybrid) through financial incentives. 

Local

Recycling waste.

Reduces amount in landfill and requires less energy to recycle than make product from scratch. In the UK recycling prevents 10-15million tonnes of CO2 emission each year (equal to 3.5m cars).

Using cars less.

Walking, cycling or using public transport reduces transport emissions as average car produces 2.7 tonnes of CO2/year.

Buying local.

Reduces transport emissions as food doesn't need to travel as far. Eating seasonally reduces our need for heated greenhouses or our need to fly food across the world.

Choosing energy efficient appliances.

Many modern appliances 50% more efficient than older models.