Thermal Energy from the Sun

A. Energy from the Sun 1. Energy from the sun reaches the Earth through the process of radiation. 2. Radiation is the transfer of energy. 3. Not all of the sun’s energy reaches the Earth’s surface.

B. What happens to the sun’s energy when it reachers Earth? 1. Absorption: Gas and particles in the atmosphere absorb 20% of incoming radiation. 2. Reflection: Clouds and other particles in the atmosphere reflect about 25% of the sun’s radiation. 3. Snow covered, icy or rocky surfaces also reflect about 5% of incoming radiation. 4. The Earth’s surface only receives and absorbs only about 50% of incoming solar radiation.

C. Thermal Energy Transfer 1. Heat is thermal energy. 2. Thermal energy transfer occurs through radiation, conduction and convection. 3. All 3 of these occur in the atmosphere.

D. Radiation 1. Radiation is the process that transfers energy from the sun. 2. Example: heat coming from a heat source- The fire is radiating heat.

E. Conduction 1. Conduction is the transfer of thermal energy by collisions between particles of matter. 2. Example: Energy is transferred from a hot pot on the stove when you touch it. 3. Conduction occurs where the atmosphere touches the Earth.

F. Convection 1. Convection is the transfer of thermal energy by the movement of particles within matter. 2. Example: boiling water circulates and steam rises. 3. Remember convection currents- movement of molten rock in the mantle.

G. Circulating Air and Air Movement 1. Energy is transferred through the atmosphere through convection. 2. The differences in air temperature create a difference in air pressure. 3. Warm air is less dense, cool air is more dense. 4. Warm air rises and cool air sinks. The movement and circulation of the air affects weather and climate around the world.