Weather and Climate

1. Weather and Climate Please ensure that you have the glossary sheet each lesson and that you add to it when necessary. Learning objectives: Major Climatic Controls Know the structure of the atmosphere and its heat budget Understand atmospheric circulation and surface winds Know how latitude, altitude and ocean circulation affect climate.

2. Know the structure of the atmosphere and its heat budget There are four vertical layers within the atmosphere, each with its own particular characteristics. The outer limit of the atmosphere is set at 1000km, but the vast majority of our weather and climate is found within the lower 12km.

3. Beginning at the earth's surface, the four layers of the atmosphere are listed below: • Troposphere - layer characteristics: • Decrease of temperature with height (6.4 degrees per 1000m). • Increase in wind speeds with height. • Fall in pressure with height. • An unstable layer due to the presence of cloud, pollution water vapour and dust. • The tropopause marks the outer edge of the troposphere and the limit to the earth's weather and climate. • Stratosphere - layer characteristics: • Temperatures increase with height in this layer, and it is here that ozone is concentrated, which absorbs UV radiation from the sun. • Winds increase with height but pressure falls. • The boundary is marked by the stratopause. • Mesosphere - layer characteristics: • A rapid fall in temperature with height, caused by a lack of water vapour, cloud and dust). • Temperatures are extremely low and winds high. • Its boundary is marked by the mesopause. • Thermosphere - layer characteristics: • The outer layer of the atmosphere. • A rapid increase in temperature with height, exceeding 1000 degrees.

4. Radiation All energy for the heating of the atmosphere comes from the sun, some energy is lost. Radiation varied with the orbit of the sun. Heating of the atmosphere takes place when the light energy from the sun reaches the ground. Short wave Energy that comes from the sun and passes through the atmosphere to earth is in the form of short wave radiation or insolation. It is responsible for the Earth's weather and climate and is converted via photosynthesis to support all forms of life. It is easy to enter the atmosphere. Long wave Once insolation has reached the surface of the Earth, it is converted into heat energy. The ground begins to warm and slowly heats the atmosphere above it, meaning that the atmosphere is warmed from ground level upwards. The amount of heating of the atmosphere that occurs depends on the surface (for example, water, ice, grass, sand) that is being heated. It is difficult for it to leave the Earth’s atmosphere. AlbedoandInsolation In the Geography A-Z look up the meanings of these terms and write them in your own words. See my lovely diagram!

6. Review • Name 4 ways short wave radiation is absorbed. • Long wave radiation is.... • If incoming radiation was 84% at point X and 30% is reflected, what is albedo? • What is the cycle for radiation to and from the Earths surface?

7. The effect of latitude Incoming radiation is more diffused at higher latitudes because of angle of curvature X X > Y Y Global energy Solar energy affects: The incoming solar radiation is short-wave. As the Earth heats up it radiates it’s own heat in the form of long-waves (infra-red). The albedo is the percentage of radiation that is reflected. This depends on the type of surface (e.g. sea, forest, ice, cloud thickness). • Temperature • Climate • Atmospheric motion • Precipitation • Ocean currents What controls the amount of incoming solar radiation? • sunspot activity • elliptical earth’s orbit • latitude • day and night

8. Exam Style Question • Explain why the poles are cooler than the equator. 8 marks Level 1 – simple statements/ description. No development/ linked thinking. 1-3 marks Level 2 – some detail and depth of processes. Development and linked thinking. 4-8 marks

9. Global energy Radiation balance at Earth’s surface 125 100 50 25 positive balance 0 Average net radiation (w/m²) 80 60 40 20 0 20 40 60 80 25 degrees from equator 50 100 negative balance 125 How is the positive heat balance (net gain in heat radiation from the Sun) within the Tropics transferred? 1. Horizontally Air movements, including winds, cyclones, depressions and ocean currents. 2. Vertically Conduction, convection and radiation.

10. Global energy Explain why the surface temperature varies.

11. How is heat transferred? • Horizontal heat transfer: About 80% of heat transferred away from the tropics is carried by winds e.g. Jet stream, hurricanes, depressions. The rest is transferred by the movement of warm ocean currents. • Vertical Heat transfer: Transferred vertically by radiation, conduction and convection. Latent heat also helps. Precipitation releases energy and warms up the atmosphere. Vertical movement can transfer heat from a positive budget and its linked to horizontal transfer.

12. Page 43 A2 AQA Make your own notes. What factors affect insolation and heating of the atmosphere? Altitude of the sun Altitude of the land Prevailing winds Long-term effects Proportion of sea and land Diurnal range Ocean Currents Local effects Ocean Conveyor belt Urbanisation Aspect Annotate a world map to show areas where these factors play a part in temperature. Cloud cover Wild weather DVD

13. PICTONARY If the answer is… What is the question?

14. Understand atmospheric circulation and surface winds Rossby wave propagation Wind speed and direction Wind speed is affected by a number of factors that operate on a variety of scales (micro to macro) e.g. the pressure gradient, Rossby waves and jet streams and local weather conditions such as sea breezes and urban winds. Pressure gradient = difference in air pressure (millibars) between two points in the atmosphere or on the Earth’s surface. The > the P difference the faster the wind. Air flows from areas of HP to LP Pressure gradient, Coriolis force and friction all combine to influence wind direction. Local weather conditions can also influence wind speed as the formation of tropical storms and hurricanes can drastically affect the velocity of the wind.

15. due to the Earth’s rotation 60 low UK high Equator low high Low pressure High pressure 60 low Atmospheric circulation As air moves from HP to LP in the N. hemisphere, it is deflected to the right by the Coriolis force. In the S. hemisphere, air moving from HP to LP is deflected to the left by the Coriolis force. All points on the Earth’s surface have the same rotational velocity (they go round once per day) An object travelling away from the equator (e.g. wind) will eventually be heading east faster than the ground below it and will seem to be moved east by some mysterious "force". This movement is eastwards in the northern hemisphere and westwards in the southern hemisphere. The diagram illustrates how it affects winds in both hemispheres and shows why the prevailing UK winds are from the SW. Pressure also helps determine direction.

16. Hadley cell Atmospheric circulation – Tri-cellular model Warm air from the tropics meets cold air from the pole at the POLAR FRONT causing depressions Air gets deflected northwards Heat from the Sun most intense at the Equator Air cools and sinks Cold air sinks Heavy convection rainfall Warm air rises Ferrel cell Polar cell Warm air rises and becomes unstable Dry and stable Dry and stable ITCZ Easterlies (winds) South-westerlies (winds) North-east trade winds North Pole 60o 30o Equator High pressure Divergence zone Low pressure Convergence zone High pressure Divergence zone Low pressure Convergence zone

17. Warm air Cold air Low pressure trough High pressure ridge Appalachian mountains Atmospheric circulation – Rossby waves Bands of strong winds blowing around the globe in the upper atmosphere (about 10km to 15km above the surface). They drive surface weather systems like depressions. A slight change in their path is what caused the very wet summer in 2007. They are produced largely because the atmosphere in motion encounters barriers to its progress, and is forced to ascend (by the changing surface level), then descends under gravity. The resultant compression and release of the air columns involved leads to alterations to the rates of "spin" of the air flow (vorticity– add to your glossary). In N.America, what triggers the Rossby waves? The Rocky Mountains, and to a much more limited extent, the Appalachians.

18. Jet stream clouds south of Cape Blanc, north Atlantic coast of Africa Courtesy NASA Atmospheric circulation-Jet streams Jet streams are bands of even faster winds (300km/hr) within the Rossby waves at about 10km above the surface. Their position and strength relate to the surface temperature contrast between warm and cold areas on Earth Commercial airlines often make use of them to reduce fuel consumption. • There are two jet streams: • The Subtropical Jet (between Ferrel and Hadley cells) which exists as a mechanism to transport moisture and energy from the tropics polewards. • The Polar Jet above the Polar Front (the boundary between polar and mid-latitude cells)

19. Warm current Cold current Know how latitude, altitude and ocean circulation affect climate. Global energy - Major ocean currents Atmospheric processes are closely linked to the oceans because they store massive amounts of heat energy (and water) which has a major influence on weather and climate. They are involved in the horizontal transfer of heat with warm currents carrying water towards the poles and cold currents towards the Equator. This has the effect of raising or cooling the surrounding sea and air temperature which affects coastal climate.