Climate Basics

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  • Created by: 8cburton
  • Created on: 21-05-15 14:19

Global energy budget

Solar energy is not evenly distributed across the earths surface. The equator has an energy surplus while the poles have energy deficit. Energy is transferred by wind and ocean currents. There are 3 factor affecting climate...

1) Seasonality

2) Curviture of the earth- Equator gets max sunlight due to energy being concentrated on small 

3) Angle to the sun

(http://maps.unomaha.edu/Peterson/geog1000/Notes/Notes_Exam1/Seasons&Climate_files/image003.jpg)Inter-Tropical convergence zone

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Climate prinicples

Warm air rises- creating low pressure- as it loses energy the air spreads out, cooling- this causes it to sink. More water vapour condenses to rain clouds. 

Cold air descends- Creating high pressure (concentrating of air molecules)- which causes the air to warm and become more humid (can carry more water when warmer)- gains energy

Coriolis effect- Winds travelling across the earth's surface are deflected to the right in the northern hemispere and left in the southern hemisphere due to the spin of the earth on it's axis

Albeo- The reflectivity of the earth's surface. Described in percentages

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Troposphere

  • The layer extending 8-17km upwards from earths surface
  • Temperature decreases with altitude (-60 degrees)
  • Lots of turbulance as warm air rises and cool air sinks
  • Lots of clouds and water vapour
  • Jet stream are found just bellow the tropopause.
  • -60 degrees
  • The tropopause acts as a temperature inversion, forming an effective ceiing to convection in the troposphere, providing an upper limit to earths weather systems 
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Statosphere

  • Layer above the troposphere
  • Temperature increases with altitude because the ozone layer in the lower stratosphere aborbs UV radiation which warms the upper atmosphere (-20 degrees)
  • Extends 12-50km
  • Free from cloud and dust
  • Warming is greater in the poles than the tropics causing strong horizontal air movements at great heights.
  • Global warming is linked to changes it this layer
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Mesophere

  • Layer above stratosphere
  • 50-80km
  • Temperature decreases as altitude increases as the stratosphere warms it (-90 degrees)
  • Boundary is the menopause(http://scied.ucar.edu/sites/default/files/images/large_image_for_image_content/mesosphere_diagram_720x440.jpg)
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Thermosphere

  • Outermost layer of the earth's atmosphere
  • 80-1000km
  • Temperature increases because small amounts of oxygen in this layer absord UV radiation. >1500 degrees

(http://scied.ucar.edu/sites/default/files/images/large_image_for_image_content/aurora_iss_wheelock_25july2010_900x500.jpg)

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Atmospheric heat budget

  • We get energy from the sun in the form of short wave solar radiation, insolation
  • 50% is absorbed by the surface and released as long wave radiation which heats troposphere
  • 25% reflected back to space by air + clouds
  • 20% absorbed by air + clouds
  • 5% reflected back into space by earths surface
  • Overall the surface has a net gain of energy except in the poles
  • The atmosphere has a net loss in energy (because of this difference heat is transferre from the surface to the atmosphere by radiation, conduction and by the release of latent heat.

4 main factors affecting how much solar radiation the atmosphere receives

1) Solar constant- sun's activity varies slightly

2) Distance from the sun

3) Height of the sun in the sky varies with latitude (equator it is high + spread over small area)

4) Length of day and night- changes with the seasons are more pronounced at higher latitudes

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Atmospheric pressure and planetary winds

Wind= Air moving to different air pressures. Pressure differences occur due to global+ local temperature variations.

As air temp increases- air expands and rises- reduces air pressure

As air temp decreases- air becomes denser and sinks- increasing air pressure

Gradual temp changes- gradual pressure change- pressure gradient created

The temperature of a wind is influences by area of origin and by the surface is has travelled over.

Atmospheric pressure= pressure exerted by the weight of air in the atmosphere at the surface of the earth measured in millibar (mb) by a Barometer. Points of equal atmospheric pressure are joined on a weather map by isobars.

The difference in air pressure are caused by differences in atmospheric heating between the poles and equator create a pattern of pressure cells. The movement within these cells is usually circular and responisble for the transfer of surplus energy from the equator regions to other parts of the world. 

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Hadley cell

  • Basis of tropical
  • between the 2 hadley cells is a region of low pressure called the ITCZ
  • sun is always high- ground rapidly heated- lots of surface evaporation- hot air rises in convection current- area of low pressure develops- heavy rainfall
  • Air masses move polewards but due to deflection from the coriolis effect the air moves westerly
  • At 30N/30S cold air sinks and as it warms any reidual moisture is evaporated+ jet streams
  • At the surface high pressure is created with cloudless skies known as subtropical anticyclones
  • when reaching the ground some air moves towards the equator known as trade winds
  • Polarward side of the cell is the subtropical jet stream

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Ferrel cell

  • Occurs as higher latitudes (30-60N/S). 
  • As air on the surface is pulled towards the poles it forms the south westerly winds in the N hemisphere and north westerlies in the S hemisphere.
  • These winds pick up moisture as they travel over oceans
  • At 60S/N they meet the colder air from the poles so the warmer, lighter air from the equator rises as the 2 air masses meet. this uplift causes low pressure and the unstable climate resulting in mid-latitude depressions (cool temperate western maritime (CTWM climate)(http://www.cmmap.org/images/learn/climate/ferrel.jpg)
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Polar cell

  • Desccending air at the poles results in dry weather at the pole 
  • Winds are pulled from the poles to the mid- latitude low pressure belt (60N/S)
  • This addresses energy deficit
  • The winds are easterly due to the coriolis effect
  • Polar front jet stream marks the division of the polar and ferrel cell

(http://www.huronwind.com/edu/images/edu1.3-image.jpg)

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Oceanic circulation

  • 20% of the energy budget is tranferred by currents caused by differences in water densities. Density depends on water temp and salinity
  • each ocean has its pattern of currents called a gyre
  • Currents are affected by surface winds, poistion of land masses, other currents and the coriolis effect
  • Warm ocean- raises air temp- warms land nearby
  • Cold ocean- lowers air tem- cools land nearby
  • Ocean currents form gaint loops that travel clockwise in the N hemisphere and anticlockwise in the S hemisphere
  • The Gulf Stream keeps western Europe much warmer than it would otherwisr be- cools in the north- becomes thicker+ more dense- sinks and carried south by the Canary current(http://americasfirstentrepreneur.com/wp-content/uploads/2011/12/Gulf-Stream.gif)
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Latitude

Insolation varies with latitude due to...

1) length of daylight hours

2) Angle of incidence- If the sun raise is lower it must travel a greater distance through the earths atmosphere away from the equator losing energy as it does. When it hits the surface the ray must heat up a larger area the further away from the equator and therefore is less concentrated.

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