Where does the energy come from that drives convection on Earth and heat source drives convection currents in the atmosphere?
Next to sun radiation and human activities, there is a significant amount of heat generated by nuclear reactions within the earth.
The source of energy that drives mantle convection is heat whereas the source of energy that drives all other is solar energy. Mantle convection is how the Earth's mantle moves due to currents of convection. Mantle convection is caused by the currents carrying heat from the core of the Earth to the outer layers. The Sun also provides the energy that drives convection in the ocean and produces ocean currents. There are two main types of ocean currents: surface currents and deep currents. Surface currents are stream-like movements of water that occur at or near the surface of the ocean.Heating of earth's surface and atmosphere by the sun drives convection within the atmosphere and oceans, which produces winds and ocean currents. Convection currents are heat-driven cycles that occur in the air, ocean, and mantle. They are caused by a difference in temperature, often due to a differing proximity to a heat source. The difference in temperature relates directly to the density of the material, causing this effect. Convection is the process of thermal energy exchange in fluids via the motion of matter within them. A bulk transfer of molecules within the fluid occurs. It occurs in both gases and liquids and leads to a cyclical effect. Convection currents are heat-driven cycles that occur in the air, ocean, and mantle. They are caused by a difference in temperature, often due to a differing proximity to a heat source. The difference in temperature relates directly to the density of the material, causing this effect. The Earth's atmosphere is heated in by the transfer of energy from the Sun.
The Earth-Atmosphere Energy Balance
Share:Share to Twitter Share to Facebook Share by email PrintThe AtmosphereLayers of the Atmosphere Air Pressure The Transfer of Heat Energy Energy BalanceHydrologic Cycle Precipitation 📷How cloud cover can affect nighttime temperatures.Download ImageThe earth-atmosphere energy balance is the balance between incoming energy from the Sun and outgoing energy from the Earth. Energy released from the Sun is emitted as shortwave light and ultraviolet energy. When it reaches the Earth, some is reflected back to space by clouds, some is absorbed by the atmosphere, and some is absorbed at the Earth's surface.Learning Lesson: Canned HeatHowever, since the Earth is much cooler than the Sun, its radiating energy is much weaker (long wavelength) infrared energy. We can indirectly see this energy radiate into the atmosphere as heat, rising from a hot road, creating shimmers on hot sunny days.The earth-atmosphere energy balance is achieved as the energy received from the Sun balances the energy lost by the Earth back into space. In this way, the Earth maintains a stable average temperature and therefore a stable climate. Using 100 units of energy from the sun as a baseline the energy balance is as follows: 📷Download ImageAt the top of the atmosphere - Incoming energy from the sun is balanced with outgoing energy from the Earth. Incoming energy Outgoing energy Units Source Units Source +100Shortwave radiation from the sun.-23 Shortwave radiation reflected back to space by clouds. -7 Shortwave radiation reflected to space by the earth's surface. -49 Longwave radiation from the atmosphere into space. -9 Longwave radiation from clouds into space. -12 Longwave radiation from the earth's surface into space. +100 Total Incoming -100 Total Outgoing The atmosphere itself - Energy into the atmosphere is balanced with outgoing energy from atmosphere. Incoming energy Outgoing energy Units Source Units Source +19 Absorbed shortwave radiation by gases in the atmosphere. -9 Longwave radiation emitted to space by clouds. +4 Absorbed shortwave radiation by clouds. -49 Longwave radiation emitted to space by gases in atmosphere. +104 Absorbed longwave radiation from earth's surface. -98 Longwave radiation emitted to earth's surface by gases in atmosphere. +5 From convective currents (rising air warms the atmosphere). +24 Condensation /Deposition of water vapor (heat is released into the atmosphere by process). +156 Total Incoming -156 Total Outgoing At the Earth's surface - Energy absorbed is balanced with the energy released. Incoming energy Outgoing energy Units Source Units Source +47 Absorbed shortwave radiation from the sun. -116 Longwave radiation emitted by the surface. +98 Absorbed longwave radiation from gases in atmosphere. -5 Removal of heat by convection (rising warm air). -24 Heat required by the processes of evaporation and sublimation and therefore removed from the surface. +145 Total Incoming -145 Total OutgoingThe absorption of infrared radiation trying to escape from the Earth back to space is particularly important to the global energy balance. Energy absorption by the atmosphere stores more energy near its surface than it would if there was no atmosphere.The average surface temperature of the moon, which has no atmosphere, is 0°F (-18°C). By contrast, the average surface temperature of the Earth is 59°F (15°C). This heating effect is called the greenhouse effect.
Thermal energy is always transferred from an area with a higher temperature to an area with a lower temperature. Moving particles transfer thermal energy through a fluid by forming convection currents. Convection currents are heat-driven cycles that occur in the air, ocean, and mantle. They are caused by a difference in temperature, often due to a differing proximity to a heat source. The source of energy that drives mantle convection is heat whereas the source of energy that drives all other is solar energy. Mantle convection is how the Earth's mantle moves due to currents of convection. Mantle convection is caused by the currents carrying heat from the core of the Earth to the outer layers. The primary sources of thermal energy for mantle convection are three: (1) internal heating due to the decay of the radioactive isotopes of uranium, thorium, and potassium; (2) the long-term secular cooling of the earth; and (3) heat from the core. Convection is the transfer of thermal energy by particles moving through a fluid. The difference in temperature relates directly to the density of the material, causing this effect. Convection currents are the result of differential heating. Lighter (less dense), warm material rises while heavier (more dense) cool material sinks. It is this movement that creates circulation patterns known as convection currents in the atmosphere, in water, and in the mantle of Earth. While winds are responsible for ocean currents, the sun is the initial energy source of the currents. Since the sun heats the Earth more in some places than in others, convection currents are formed, which cause winds to blow. Earth's rotation produces a force on winds and currents. The Sun imparts a tidal force on Earth's atmosphere through radiative heating of the atmosphere and surface and latent heat release via global scale convection. One of the most important sources of energy is the sun. The energy of the sun is the original source of most of the energy found on earth. We get solar heat energy from the sun, and sunlight can also be used to produce electricity from solar (photovoltaic) cells.
RK Naresh: interesting question. The answer lays in the derivative of the heat transfer equations since, if you heat something uniformly, you will not have convection. When energy from the sun is applied to the air and water at a non uniform heat flux (e.g. higher energy flux at the equator and lower at the poles) convection will occur as the fluid density changes and becomes lower. lower density fluids will rise, being replaced by colder denser fluid from the north and south pole. As the earth rotates, the fluid that is moving to the equator is affected by the earth's rotation, causing the air to rotate faster as it moves farther from the poles. Thus, the earth's rotation contributes to the movement of the fluid. Again, remember that this rotation would not occur if the fluid were uniformly heated and not moving. rotation of fluids is driven by the change in tangential velocity as the air moves away from the center of rotation. "Coriolis effect".
In addition, there is a thermodynamic cycle that is enabled by the convection. Water at higher temperatures will evaporate at a logarithmically faster rate (the pressure / temperature curve of water is very strong), resulting in a strong evaporation at the equator and condensation at the colder temperatures. This drives a partial pressure gradient that drives mass transfer (convection). The colder temperatures are located in two directions. Higher elevations in the atmosphere are colder due to the lower pressure (perfect gas law), resulting in freezing particles (clouds). Colder temperatures are also located at the poles. This temperature is driven by radiative cooling to space. Outer space has a temperature of 2.7 Kelvin, minus 453.8 degrees Fahrenheit or minus 270.45 degrees Celsius and heat transfer to space is proportional to the 4th power of the temperature difference. In the absense of heating, the north and south poles would become very frozen (like the south pole of the moon). The rate of cooling increases when the air is heated due to global warming. (stabalizing negative feedback loop)
In addition, the existance of counter clockwise rotation (in the northern hemisphere) results in a reduced pressure at the center of rotation (coriolis forces). When this pressure occurs over water, the evaporation rate increases drastically, resulting in high moisture low density air that rises and pulls air in from the outer bands of a hurricane. Conservation of rotational energy results in an increase in velocity at the center (vortex).
Thank you for the question. Very few people understand the Physics behind this complicated world. Even the weather modelers have not included all of the physics in their models, only recently adding there thermal capacity of the oceans to the models, moderating the atmospheric temperatures.
Also interesting to note there earth is in a balance between the heating from the sun and the radiative cooling to space. The sun is only heating for 12 hours a day and primarily at the equator due to the angle of incidence. Space on the other hand is cooling the earth 24 hours a day and with a 99 percent solid angle to space (adjustments for the sun and moon). Both heating and cooling transfer the same amount of energy.
Rick
It is interesting to note that the heat production within the earth (nuclear reactions) is also contributing to this very complex balance.
Avraham Hirschberg: very good point ! Geothermal heating from nuclear energy in the earth is the largest contributor to heating at the south pole during the winter. The average geothermal heat flux at the Earth's surface is 0.087 watts per square meter. This contributes to melting of ice in the layer between the rock earth surface and the ice above. Water temperature in Lake Vostok is -3C
The central core of the Earth is the internal source of energy that drives convection currents within the lithosphere, which in turn drive plate movement. The sun is the external source of energy that causes convection currents, which drive the winds, ocean currents, and the water cycle. Convection currents are heat-driven cycles that occur in the air, ocean, and mantle. They are caused by a difference in temperature, often due to a differing proximity to a heat source. The difference in temperature relates directly to the density of the material, causing this effect. The Earth's atmosphere is heated in by the transfer of energy from the Sun. Earth receives its energy from the Sun. The Sun's energy travels to Earth in the form of radiation. Convection is driven by temperature differences across that fluid. When a fluid is heated, the region in closest contact with the heat source becomes less dense due to increased kinetic energy in the particles. The portion of fluid that is less dense then rises, while the denser portion of fluid sinks. Convection happens because warm air is less dense than the cold air around it, so it is lighter and rises or goes up in the atmosphere. Evidence of convection happening is seen with the formation and growth of cumulus clouds. Heating of earth's surface and atmosphere by the sun drives convection within the atmosphere and oceans, which produces winds and ocean currents. Convection currents are heat-driven cycles that occur in the air, ocean, and mantle. Convection is the transfer of thermal energy by particles moving through a fluid. Thermal energy is always transferred from an area with a higher temperature to an area with a lower temperature. Moving particles transfer thermal energy through a fluid by forming convection currents. Convection currents are the result of differential heating. Lighter (less dense), warm material rises while heavier (more dense) cool material sinks. It is this movement that creates circulation patterns known as convection currents in the atmosphere, in water, and in the mantle of Earth. While winds are responsible for ocean currents, the sun is the initial energy source of the currents. Since the sun heats the Earth more in some places than in others, convection currents are formed, which cause winds to blow. Earth's rotation produces a force on winds and currents.
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