Week 10

• Atmosphere


  Troposphere, stratosphere, mesosphere and thermosphere
• As you move up the atmosphere

  The temperature decreases due to the decreasing density
• Stratosphere


  The warmest zone and is where the ozone layer is
• Speed of particles is greater in the stratosphere


  There is lots of collisions and energy produced
• Atmospheric stability and instability

  1. Parcels of hot air rise, expand and cool, becoming less dense

  2. Rate of cooling is less if water vapour in the air mass starts to condense

  3. If the air parcel is warm enough there are a high number of collisions, and the water remains in gas form

  4. As the air mass expands and the number of collisions reduces the amount of heat reduces, and water vapour drops back into water form

  5. Each time a change occurs, such as gas to solid there is energy produced
• Absolutely unstable


  Hot air rises (to some extent as there are usually lower temps than the parcel higher up)
• Conditionally unstable


  In between absolutely unstable and absolutely stable
• Absolutely stable


  The air is cooler and does not rise
• If the airmass is unstable and goes up


  It expands and cools off, resulting in moisture and rainfall
• If the air mass is stable


  It rises and there is no rainfall
• Inversion


  Occurs when there is significant cooling close to the ground level, however warmer air above. Thus, the air does not rise and the pollution/smoke within it remains trapped beneath the overlayer
• Pollutants trapped in inversion

  • Photochemical smog
  • Carbon dioxide
  • Particulates like ash, dust
• PM 2.5


  Can be extremely dangerous as it can clog lungs
• PM 10


  Another main measurement of particulates
• World health organisation has a warning measurement system for PM emissions
• Christchurch used to have some of the worst air pollution in New Zealand, primary source was coal and wood burning
• Positive implication of the earthquakes

  Air pollution is reducing due to getting rid of chimneys and transitioning to other heating methods
• Air pollution is more common in winter


  There is cool air at ground level, particularly during the mornings, as the sun's rays warm the surface above it
• Cool air at ground level, warmer air above

  Results in an inversion effect
• Airmass tries to rise and cools a bit as it goes up


  1. There is still air at the surface and circulation aloft, different airmass above the level of the city, which is warmer as it has come from the West Coast

  2. This acts as a barrier for anything coming out of the bottom layer
• Understanding wind patterns is important in determining where the pollution is coming from/how it can spread
• Pollution can travel thousands of kilometres and China is the biggest contributor of pollution on the planet
• Key atmosphere points


  • All climate is ultimately driven by pressure (temperature) contrast of the poles and equator, which is vital for the redistribution of heat
  • There is a fluid envelope around the planet (oceans + atmosphere), critical for moving heat through convective processes
  • Warmer at the equator due to the angle of incidence of sun radiation
• There is excess energy at the equator and a deficit at the poles
• Earth's rotation


  • High speed rotation- results in a 3-cell circulation system, the Hadley cell, Ferrel cell and Polar cell
  • Warm air rises at the equator (Hadley) then cools and circles to the tropics, Ferrell cell moves in opposite direction and Polar cell carries cool air

  
• Coriolis effect


  Created by the earth's rotation causing the deflection of fluids (ocean and wind currents) to the right in the Northern Hemisphere and to the left in the Southern Hemisphere

  
• Atmospheric circulation


  Drives surface ocean circulation
• Thermal structure of the oceans

  • Solar energy enters from the top, surface waters are warmed and sit above cold water (does not easily mix)
  • Circulation is necessary, this takes 1000 or 1500 years in the ocean, thus carbon is stored for a long time
  • Circulation of the ocean is density driven, circulating deep water up is difficult
• Ekman Drift


  1. Coriolis effect enacts force causing the water to be deflected to the sides

  2. This also pushes it down and results in upwelling (water rising up)

  3. Brings up cold, nutrient rich water which is good for fishing

  4. More likely to occur along coasts e.g off Chile and Peru
• Thermohaline circulation


  • Process driven by density differences in water due to temperature (thermo) and salinity (haline) variations in different parts of the ocean
  • Pacific Ocean is cool and fresh
  • Atlantic Ocean is warm and salty
• Sinking water


  1. North Atlantic Deep-Water production (NADW)- north Atlantic drift brings warm water to high latitude where it sinks and produces NADW

  2. Antarctic Bottom water production (AABW)- coldest and most saline water on the planet, which forms under ice shelves. Produced at -1.8 degrees C
• These processes are extremely important, however due to climate change and other factors it could reorganise global climates
• Important as oceans have absorbed 75% of energy and 50% of expected temp change and CO2. However, these circulations are changing which could impact their ability to store excess CO2 and heat.