Chapter 2

Weather Factors

Section 2

Heat Transfer

How Heat is Transferred

• Heat is transferred in 3 ways: radiation, conduction, and convection.

How Heat is Transferred

• Heat is the energy transferred from a hotter object to a cooler one.

Radiation

• Radiation is the direct transfer of energy by electromagnetic waves.

Radiation

• You can’t see it, but you can feel it.

Radiation

• Examples: sun’s rays, campfire.

Conduction

• Conduction is the direct transfer of heat from one substance to another substance that it is touching.

Conduction

• Solids conduct heat better than liquids or gases (molecules are closer together).

Conduction

• Examples: walking on hot sand, touching a hot pot.

Convection

• Convection is the transfer of heat by the movement of a fluid.

Convection

• Examples: steam furnace, boiling water.

Heat Transfer in the Troposphere

• Radiation, conduction, and convection work together to heat the troposphere.

Heat Transfer in the Troposphere

1. Earth’s surface absorbs solar energy and is heated by radiation.

Heat Transfer in the Troposphere

2. Earth’s surface reradiates heat and warms the lower troposphere by conduction.

Heat Transfer in the Troposphere

3. The heated air molecules move faster making the warm air rise and the cold air sink.This creates convection currents which move heat throughout the troposphere.

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Earth’s surface is heated by radiation.

Earth’s surface reradiates heat.

Lower atmosphere is heated by

conduction.

Warm gases rise, cool gases sink = convection.

HEATING THE TROPOSPHERE

The Greenhouse Effect

•When Earth’s surface is heated, it radiates some of the energy back into the atmosphere.

The Greenhouse Effect

•Most of this energy can’t travel back into space so is absorbed by gases in the atmosphere.

The Greenhouse Effect

• These heated gases form a “blanket” around Earth that holds heat in the atmosphere.

The Greenhouse Effect

• Greenhouse effect is the process by which gases hold heat in the air.

The Greenhouse Effect

• The greenhouse effect is a natural process that keeps Earth’s atmosphere at a comfortable temperature for most living things.