Weather and ClimatePlease ensure that you have the glossary sheet each lesson and that you add to it when necessary.

Learning objectives:Major Climatic Controls1) Know the structure of the atmosphere and its heat budget2) Understand atmospheric circulation and surface winds3) Know how latitude, altitude and ocean circulation affect

climate.

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.

• 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.

RadiationAll 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 waveEnergy 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 waveOnce 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. Albedoand InsolationIn the Geography A-Z look up the meanings of these terms and write them in your own words.

See my lovely diagram!

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?

Global energySolar energy affects:

What controls the amount of incoming solar radiation?

• sunspot activity• elliptical earth’s orbit • latitude • day and night

• Temperature• Climate• Atmospheric motion• Precipitation• Ocean currents

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).

The effect of latitude

Incoming radiation is more diffused at higher latitudes because of angle of curvature

X

Y

X > Y

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

Global energy

Aver

age

net r

adia

tion

(w/m

²)

0

25

25

50

50

100

100

125

125

020 2040 4060 6080 80degrees from equator

Radiation balance at Earth’s surface

How is the positive heat balance (net gain in heat radiation from the Sun) within the Tropics transferred?1. Horizontally

2. VerticallyAir movements, including winds, cyclones, depressions and ocean currents.

Conduction, convection and radiation.

positive balance

negative balance

Global energy

Explain why the surface temperature varies.

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.

What factors affect insolation and heating of

the atmosphere?

Long-term effects

Altitude of the land

Page 43 A2 AQAMake your own notes.

Altitude of the sun

Proportion of sea and land

Prevailing winds

Ocean Currents

Ocean Conveyor belt

Diurnal range

Local effects

AspectCloud cover

Urbanisation

Wild weather DVD

Annotate a world map to show areas where these factors play a part in temperature.

PICTONARY

If the answer is…What is the question?

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.

Rossby wave propagation

Understand atmospheric circulation and surface winds

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.

Atmospheric circulation

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.

due to the Earth’s rotation

UK

Equator

Low pressure High pressure

low

high

high

low

low

60

60

Atmospheric circulation – Tri-cellular model

North Pole Equator

Hadley

cell

30o

High pressure

Divergence zone

Low pressure

Convergence zone

60o

Low pressure

Convergence zone

High pressure

Divergence zone

North-east trade winds

Heat from the Sun most intense at the Equator

ITCZ

Heavy convection rainfall

Air cools and sinks

Air gets deflected northwards

Warm air rises and becomes unstable

South-westerlies (winds)Easterlies (winds)

Ferrel

cell

Warm air rises

Warm air from the tropics meets cold air from the pole at the POLAR FRONT causing depressions

Polar

cell

Cold air sinks

Dry and stable

Dry and stable

Atmospheric circulation – Rossby wavesBands 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.

In N.America, what triggers the Rossby waves?

The Rocky Mountains, and to a much more limited extent, the Appalachians.

High pressure ridge

Low pressure trough

Cold air

Warm airThe 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).

Appalachian mountains

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 EarthCommercial airlines often make use of them to reduce fuel consumption.

Atmospheric circulation-Jet streams

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)

Jet stream clouds south of Cape Blanc, north Atlantic coast of Africa Courtesy NASA

Warm current Cold current

Global energy - Major ocean currentsAtmospheric 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.

Know how latitude, altitude and ocean circulation affect climate.