weather theme 5

• cold front

  • steep gradient
  • cumulonimbus clouds
  • spikey symbol
  • the colder air in the cold front meets the warm air in the warm sector at a steep gradient, causing evaporation, condensation and precipitation
• TWO THINGS that drives the earths climate system

  • the way energy from the sun moves in and out of atmosphere
  • the way heat moves around the atmosphere and oceans
• the main driver for our climate is the sun
• if greenhouse gases did not absorb and re emnit heat we wouldnt be able to live on earth because it would be too cold
• the suns energy is distributed unevenly because the earth is at a tilt of 23.5 so different areas get different amount of suns energy
• when air rises thunderstorms and clouds
• when air falls down high pressure and no rain
• ocean currents are important because they mirror the redistribution of heat through water particles
• tri cellular model of atmospheric circulation

  • polar; creates a dry desert climate further north, its a cold polar desert with high pressure
  • uk; at a point between two cells, a jet stream, air falls and rises, mix of low and high pressure
  • near equator; hot dry desert climate, high pressure
  • equator; tropical equatorial climate, maximum heat, low pressure
• low pressure forms when the polar front jet stream heads north, causing air to rise which then evaporates cools and condenses forming clouds that bring precipitation
• MILANKOVITCH CYCLE

  describe how the earths orbit changes meaning the earth is sometimes closer or further away from the sun
• solar output is the amount of energy given off by the sun, often determined by the amount of sunspots
• glacial and interglacial perioa are periods of colder and warmer global temperatures
• quaternary period is the most recent geological timeframe covering last 2.6 million years
• Aerosol is suspension of fine particles of dust and liquid droplets in the air
• stores are where carbon is kept and collected
• flows are where carbons is moved from one place to anothee
• fossil fuels are a store of carbon made from the remains of living organisms coal oil natural gas
• Over the latter part of the Quaternary period, our planet’s climate has formed a cyclical pattern of glacial and inter-glacial periods caused by natural factors such as the Milankovitch Cycles, volcanic eruptions and solar output.
• Large volcanic eruptions have enough power to propel ash and SO2 aerosol particles into the stratosphere, above the rain clouds so they aren’t washed back to earth.

  High winds spread these particles, blanketing the planet, which block the suns rays and send them back into space causing a fall in global temperatures.
• The enhanced greenhouse effect describes the process where increasingly large volumes of greenhouse gasses in the atmosphere (such as CO2) caused by human activities (such as burning fossil fuels) absorb even more of the escaping long wave energy and cause our atmosphere to warm up. This heat is re-radiated back to the planet causing global warming
• The carbon cycle is a series of stores and flows that lock carbon and move it between living things, land, sea and our atmosphere.

  Human activities such as deforestation and the burning of fossil fuels affect the carbon cycle by releasing carbon quickly from these stores and adding huge amounts of CO2 into the atmosphere.
• we have evidence from chemicals and trapped gasses in ice cores. Thousands of years of snowfall at our poles have built up into ice sheets thousands of metres thick. We can drill down into these sheets to collect evidence of climatic changes over the last 420,000 years.
• ICE CORE SAMPLES

  They show that both temperatures and CO2 levels have gone up and down as part of a natural cycle which can be clearly seen due to the large period of time we can measure over.
• As tropical storms are powered by warm oceans, global warming is likely to mean these storms will…

  1. Become more powerful (warmer temperatures = more evaporation)
  2. Become more frequent (oceans will be over 26⁰C for longer so storm seasons will be longer) and
  3. Occur in more places (larger areas of ocean will be over 26⁰C).
• At the Equator the suns energy is concentrated on a smaller area causing it to be hotter.

  Hot, less dense air at the equator rises causing a low-pressure band called the Intertropical Convergence Zone (ITCZ).

  This air then gradually cools higher in the atmosphere, becomes denser, and falls back down at the tropics causing a high-pressure band around 30 degrees north and south of the Equator
• A storm surge is a secondary effect caused by many tropical storms. They cause sea levels to rise due to the strong winds of tropical storms pushing water into the shore and low pressure causing a bulge of water to rise in the storm centre
• The Earth’s seasons means ocean temperatures reach above 26⁰C at different times of the year creating tropical storm seasons around the world.

  These storms form over the oceans between 5⁰ and 30⁰ north and south of the Equator, never on it

  quickly lose strength over land and as they travel further north or south over cooler waters
• • Tropical storms form over warm oceans (above 26⁰C).
  • Huge amounts of water vapour evaporate and rise causing very low pressure systems.
  • As it rises it cools, condenses and forms huge cumulonimbus clouds which produce vast amounts of rain.
  • Air rushes in to fill the low pressure, creating strong winds.
  • The Coriolis effect deflects these winds, causing them to spin around the eye, the calm centre of a tropical storm surrounded by the eye wall where wind speeds and rainfall are highest.
• AQUIFER;An underground layer of permeable rock containing water that can be extracted using a well/ pump.
• Global Atmospheric Circulation Model

  Describes the movement of air around the planet powered by the hot equator.
• Jet stream

  Areas of high winds caused by the temperature differences in the atmosphere. Global warming reduces these temperature differences and so slows down the jet stream.
• Droughts affect areas where there is:

  1. Little rainfall
  2. A shortage of water stored in rivers, lakes and aquifers
  3. Human impacts such as deforestation and intensive agriculture. Examples include Sub Sahara Africa but also more developed areas such as California and Australia.
• Global drought patterns are influenced by global warming.
• Global warming is also thought to be affecting the jet stream.

  When the jet stream slows or stalls, the pressure systems it moves from west to east also slow or stall, blocking other pressure systems.

  If a high pressure system stalls above you, the one or two dry days it would normally bring may turn into weeks and cause a drought.
• The high pressure belt around 30⁰ north and south of the Equator caused by the Global Atmospheric Circulation Model produces low rainfall and means that these areas often suffer from droughts.
• Heatwaves are often linked with droughts because the high pressure systems that can cause them produce extended periods of clear skies which raise temperatures as well as reducing rainfall
• Although high pressure systems can be linked to heatwaves, in winter the clear skies can bring freezing temperatures at night and affect transport routes, burst water pipes and create fog.
• In summer, heatwaves and droughts can lead to wildfires.

  These are a common secondary effect of droughts and heatwaves which often have a greater impact than the drought itself.

  Wildfires lead to loss of property, crops, resources, animals and people. They disrupt transportation and destroy communications, power and gas services. Ash leads to poor air quality and possible health problems
• Climate – the average weather for a place over 30 years.