Energy, Radiation, and
Earth - Sun Relations

Introduction

The most important source of energy to drive environmental processes at the surface of the Earth is that received from the Sun. Heating the Earth's surface, evaporation of water, photosynthesis, heat for chemical reactions to break down rock materials use energy from the Sun. However, the amount and intensity of energy received is unequally distributed across the surface of the Earth. In this lecture we'll discuss what controls the geographical distribution of energy at the Earth's surface.

Energy

Definitions

• Energy: ability to do work as a result of motion or position.

• Types of energy:

  • Heat energy - the total energy associated with random atomic and molecular motions of a substance. (Don't confuse with temperature.)

  • Potential energy - energy of position.

  • Kinetic energy- energy of motion.

Modes of Heat Transfer

• Radiation: transfer by electromagnetic waves.

• Conduction: transfer by molecular collisions.

• Convection: transfer by circulation of a fluid.

Aspects of heat transfer

• The wavelength (distance between crests) of radiation emission depends on the temperature of the emitting body. ("Hotter the body -> shorter the wavelength")

• The amount of radiation  emitted by a body is dependent on its temperature. Hotter the body -> the more energy emitted")

• Heat energy is transferred from object or regions of more energy to those of less energy, e.g. hot surfaces to cold surfaces. ("Energy Gradient")

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