A comprehensive presentation of subchapter 2.2 The Global Energy Budget, from the second chapter of Physical Geography, AS Cambridge, Atmosphere and Weather.

1. ASGEOGRAPHYREVISION
ATMOSPHEREANDWEATHER
2.2 THEGLOBALENERGYBUDGET

2. KEYTERMSANDDEFINITIONS
Anticyclone is a high-pressure system.
Aspect is the direction in which a slope faces. In the northern
hemisphere a slope with a southerly aspect receives more sunshine
than other slopes and is therefore better suited for growing crops.
Continentality is a climate characteristic of a continental area (i.e. a
long way from the sea), having very hot summers, very cold winters
and low rainfall.
Coriolis effect is an effect that causes any body that moves freely with
respect to the rotating Earth to veer to the right in the northern
hemisphere and to the left in the southern hemisphere.

3. KEYTERMSANDDEFINITIONS
El Niño is an anomalous warming of surface waters in the eastern
equatorial Pacific Ocean linked with climatic disturbances throughout
the world.
Frontal rainfall is the rain formed when warm air is forced to rise over
denser cold air when two different air masses meet at a front.

4. KEYTERMSANDDEFINITIONS
General Circulation Model is a model of the general circulation of
atmosphere based on convection. In the most simple case, cells of
warm air rise at the equator and descend at the poles. In fact, there are
three such cells in each hemisphere. The first two of these consist of air
that rises at the equator and sinks at the tropics; the second two exist
at the mid-latitudes where the air from the sub-tropics flows towards
the cold air masses of the third pair of cells circulating from the two
polar regions.

6. KEYTERMSANDDEFINITIONS
Insolation is the amount of incoming solar radiation (heat energy from
the Sun) that reaches the Earth’s surface. Insolation varies with season
and latitude, being greatest at the equator and least at the poles.
Jet streams are narrow, fast-flowing currents of air found near the
tropopause. The major jet streams are meandering westerly winds. The
main jet streams in each hemisphere are the polar jets, which are
associated with the polar front, at around 8–11 km above sea level, and
the higher and weaker subtropical jets at around 11–16 km height.

7. KEYTERMSANDDEFINITIONS
Pressure (air) refers to the pressure at any point on the Earth’s surface
that is due to the weight of the air above it; it decreases as altitude
increases. At sea level the average pressure is 1013 millibars. Areas of
relatively high pressure are called anticyclones; areas of low pressure
are called depressions.
Prevailing wind is the direction from which the wind most commonly
blows in a locality. In north-western Europe, for example, the prevailing
wind is south-westerly, blowing from the Atlantic Ocean in the south
west and bringing moist conditions.

9. KEYTERMSANDDEFINITIONS
Thermohaline circulation (THC) is also known as the ocean conveyor
belt, and is a deep water ocean convection current that moves cold
water at depth from polar areas towards the equator, while at the
same time transferring warm waters from tropical and sub-tropical
areas to the mid latitudes. The North Atlantic Drift is part of the
thermohaline circulation.

10. TOPICSUMMARY
The atmosphere is an open energy system receiving energy from both
Sun and Earth. Incoming solar radiation is referred to as insolation.
Radiation is the emission of electromagnetic waves such as X-ray,
short- and long-wave.
Convection is the transfer of heat by the movement of a gas or liquid.
Conduction is the transfer of heat by contact.
Very hot bodies such as the Sun emit short-wave radiation, whereas
cold bodies such as the Earth emit long-wave radiation.

11. TOPICSUMMARY
The atmosphere is largely heated from below. Most of the incoming
short-wave radiation is let through, but the outgoing long-wave
radiation is trapped by CO2. This is known as the greenhouse effect.
There are important large-scale east–west temperature zones. These
patterns reflect the general decrease of insolation from the equator to
the poles.
Sea-level pressure conditions show marked differences between the
hemispheres. In the northern hemisphere (NH) there are greater
seasonal contrasts, whereas in the southern hemisphere (SH) much
simpler average conditions exist.
On a global scale, latitude is the most important factor determining
temperature.

12. TOPICSUMMARY
The specific heat capacity is the amount of heat needed to raise the
temperature of a body by 1 °C. There are important differences
between the heating and cooling of water. The effect of ocean currents
on temperatures depends upon whether the current is cold or warm.
Vertical air motion is important on a local scale, whereas horizontal
motion (wind) is important at many scales, from small-scale eddies to
global wind systems.
The driving force is the pressure gradient, i.e. the difference in
pressure between any two points. Air blows from high pressure to low
pressure.
The general circulation model is a model that links low latitude and
high latitude circulation of winds.

14. ADDITIONALWORK
1. Describe and explain seasonal variations in surface pressure belts.
2. Outline the main factors that affect global temperature patterns.
3. Describe and explain the factors affecting air movement.
4. Briefly explain the general circulation model.

15. SUGGESTEDWEBSITES
http://earthguide.ucsd.edu/earthguide/diagrams/energybalance/ind
ex.html for an animated diagram of the global energy budget.
www.ace.mmu.ac.uk/resources/gcc/1-2-4.html for the energy budget
of the atmosphere.
www.cgd.ucar.edu/cas/Trenberth/trenberth.papers/TrenberthScienc
ePerspectives-1.pdf for an article on recent changes to the Earth’s
energy budget.
http://openlearn.open.ac.uk/mod/oucontent/view.php?id=397952&s
ection=1.1.4 provides an overview of the Earth’s energy budget.