Heat Energy Transfer Mechanisms

Heat Energy Transfer Mechanisms

• There are three mechanisms of heat energy transfer: radiation, conduction, and convection.

Radiation

• Radiation is the release of infrared radiation by a substance at a higher temperature than its surroundings.
• It is the only mechanism that works in a vacuum (outer space, including the space between the Earth and the Sun).

Conduction

• Conduction is the transfer of kinetic energy (the energy of motion) between particles in direct contact.
• It is most effective in solids.

Convection

• Convection is the movement of particles from one location to another: cooler, denser material will sink relative to warmer, less dense material.
• It is most effective in liquids and gases.

Solar Radiation

• Energy from the Sun arrives in the form of radiation (both visible and infrared).
• Not all energy is absorbed: some is reflected, with varying percentages reflected by different surfaces (e.g. ice and snow, vegetation and dark soil, ocean water).

Surface Temperature Responses

• Different surfaces have different temperature responses to the same heat energy input.
• Water has a high heat capacity, which means it takes more energy to change its temperature than land.

Heat Distribution

• Arriving solar radiation is not distributed evenly: equatorial regions receive more direct sunlight than polar regions.
• This uneven heating results in the transfer of heat energy from the equatorial region to the poles by convection in the atmosphere and hydrosphere.

Convection in the Atmosphere

• Warm, moist air at the Equator rises, releases its moisture, and cools, sinking down at around 30°N and 30°S latitude.
• The Coriolis Effect forces surface air moving toward the Equator from east to west, resulting in the NE and SE trade winds.

Convection in the Atmosphere of the Poles

• Similar convection cells result in prevailing westerly winds, which is why weather patterns across Canada move from west to east.

Convection in the Hydrosphere

• The patterns of ocean currents are complicated by the position of the continents.

Effects of Climate Change

• Global warming can change climate patterns, resulting in increased evaporation from the oceans, increased precipitation of snow, and increased albedo, leading to colder winters.
• The increased melting of glaciers and Arctic ice could result in increased cold ocean currents from the Arctic, possibly reversing the North Atlantic Drift that keeps Europe temperate.