Energy and Earth - Fundamentals of the Physical Environment - page 39

In total, the processes of energy transfer maintain a
steady-state equilibrium within the global system; they
replenish energy losses in areas where outputs exceed
inputs (the higher latitudes) and they remove energy from
areas where inputs are in excess (the lower latitudes).

Sun

Emission of
radiant energy

Sensible and
latent heat

Absorption

LOCAL AND REGIONAL ENERGY
TRANSFERS

Radiant
energy

While these atmospheric and oceanic processes account
for the spatial redistribution of energy at a global scale,
they are not the only means of energy transfer in the global
system. At a more local level, numerous other transfers are
taking place.

Absorption

Atmospheric transfers
Within the atmosphere, local and regional winds, convec-
tion currents and air masses carry energy as sensible
heat and as latent heat. The uplift of air and the water
contained within it transform some of this energy into
potential energy, which is released when the air sinks or
the water condenses. Small, local transfers of energy to
Earth's surface occur owing to friction, while the kinetic
energy of the wind is transmitted to soil and rock particles
as these are picked up and blown along. Heat energy from
the atmosphere is also transferred to soils and plants
through conduction and radiation ( Figure 2.17 ).

Conduction Conduction

Soil Soil

Bedrock

Bedrock

Figure 2.17 Energy transfers at the surface.

Rainfall
Potential energy
+
Kinetic energy

Hydrological transfers

Water similarly takes part in a variety of transfer processes
( Figure 2.18 ). Water condensing in the atmosphere
releases latent heat; this warms the surrounding atmos-
phere. Potential energy derived from the initial uplift of
water vapour into the atmosphere is transformed into
kinetic energy as raindrops fall, and some of this kinetic
energy is transmitted to Earth's surface as rock and soil
particles are splashed into motion. Further potential
energy is expended and converted to kinetic energy as the
water percolates through the soil, runs into streams and
flows to the sea. The flowing water again imparts some of
its kinetic energy to material that it picks up and carries
along.
The water also takes part in chemical processes of
weathering and thus chemical energy is transferred to heat
energy, given off during the chemical reactions. In the sea,
the currents transfer energy laterally, while the upwelling
and sinking of water masses leads to vertical transfers.
Finally the evaporation of water from the sea, from rivers

Rainsplash Surface storage Weathering

Heat energy
+
Chemical energy

Kinetic
energy

Potential
energy

Kinetic
energy

Erosion Friction

Kinetic
energy

Kinetic
energy

Figure 2.18 Energy transfers involving water.