Heating Earth's Surface and Heating Earth's Surface and

AtmosphereAtmosphere

Dr. R. B. Schultz

Motion of the EarthMotion of the Earth

• Earth has two principal motions—rotation and revolution.

• Rotation is the spinning of Earth about its axis.

• Revolution refers to the movement of Earth in its orbit around the Sun.

Solar Radiation - initial source of energy to the Earth. It can be absorbed, reflected and reradiated. The redistribution of this energy controls the structure and dynamics of the Atmosphere and Oceans.

Chapter 8 Circulation of the Atmosphere

Variations in Solar Energy and Variations in Solar Energy and SeasonsSeasons

• The two most important reasons for the variation in solar energy reaching a particular location are:The seasonal changes in the angle at which the Sun's

rays strike the surface and The length of daylight.

• The seasonal variation in the angle of the Sun affects where on Earth the solar rays are most concentrated and the thickness of atmosphere the rays must penetrate.

Heat and TemperatureHeat and Temperature• Heat is a form of energy. By contrast,

temperature refers to intensity—that is, the degree of "hotness."

• Temperature is a measure of the average kinetic energy of the individual atoms or molecules in a substance.

• Energy is the ability to do work. The two major categories of energy are:• (1) kinetic energy, which can be thought of as

energy of motion, and • (2) potential energy, energy that has the

capability to do work.

Heat TransferHeat Transfer

The three mechanisms of heat transfer are:(1) conduction, the transfer of heat

through matter by molecular activity, (2) convection, the transfer of heat by

mass movement or circulation within a substance, and

(3) radiation, the heat-transfer mechanism by which solar energy reached our planet.

•Radiation or electromagnetic radiation, whether x-rays, visible light, heat waves, or radio, travels as various size waves through the vacuum of space at 300,000 kilometers per hour.

•Shorter wavelengths of radiation are associated with greater energy. The wavelength of visible light ranges from 0.4 micrometer (violet) to 0.7 micrometer (red).

Electromagnetic RadiationElectromagnetic Radiation

The Sun’s RadiationThe Sun’s Radiation

• Although the Sun emits many forms of radiation, most of the energy is concentrated in the visible and near visible (infraredinfrared and ultravioletultraviolet) parts of the spectrum.

• The basic laws of radiation are:• (1) all objects above -273° Celsius emit radiant energy, • (2) hotter objects radiate more total energy per unit area

than colder objects, • (3) the hotter the radiating body, the shorter the

wavelength of maximum radiation, and

• (4) objects that are good absorbers of radiation are also

good emitters.

Where does the sun’s radiation go?Where does the sun’s radiation go?

•Approximately 50 percent of all radiant energy from the Sun reaches Earth's surface.

•About 30 percent is reflected back to space by the atmosphere.

•The remaining 20 percent of the energy is absorbed by clouds and the atmosphere's gases.

•The wavelength of the energy being transmitted, as well as the size and nature of the absorbing or reflecting substance, determines whether solar radiation will be scattered, reflected back to space, or absorbed.

Heat BudgetHeat Budget

AlbedoAlbedo• The fraction of radiation reflected by a surface is

called its albedoalbedo.

• Radiation absorbed by Earth's surface is reradiated skyward.

• Because Earth has a much lower surface

temperature, terrestrial radiation is primarily in the form of longwave infrared radiation.

• Because the atmospheric gases, primarily water

vapor and carbon dioxide, are more efficient absorbers of terrestrial (longwave) radiation, the atmosphere is heated from the ground up.

The Greenhouse EffectThe Greenhouse Effect

• The general drop in temperature with increased altitude in the troposphere (about 6.5°C/kilometer, a figure called the normal lapse rate) supports the fact that the atmosphere is heated from below.

• The transmission of shortwave solar radiation by the atmosphere coupled with the selective absorption of terrestrial radiation by atmospheric gases that results in the warming of the atmosphere is referred to as the greenhouse effectgreenhouse effect.

Earth’s Heat BudgetEarth’s Heat Budget

• Because of the annual balance that exists between incoming and outgoing radiation, called Earth's heat budgetheat budget, Earth's average temperature remains relatively constant, despite seasonal cold spells and heat waves.

• Although the balance of incoming and outgoing radiation holds for the entire planet, it is not maintained at each latitude.

• Averaged over the entire year, a zone around Earth between 36°N and 36°S receives more solar radiation than is lost to space.

• The opposite is true for higher latitudes, where more heat is lost through longwave terrestrial radiation than is received.

• It is this energy imbalance between the low and high latitudes that:• drives the global winds and ocean currents, • which in turn, transfers surplus heat from the

tropics poleward.

Radiation Balance Radiation Balance FluctuationsFluctuations

• Furthermore, the radiation balance of a given place fluctuates with changes in:

• cloud cover, • atmospheric composition, and most importantly, • Sun angle and length of daylight.

• Thus, areas of radiation surplus and deficit migrate seasonally as the Sun angle and length of day change.

Re-distribution of heat

• Heat gained at Equatorial latitudes• Heat lost at higher latitudes• Winds and ocean currents redistribute heat around

the Earth

Warm equatorial water flows to higher latitudes

Cool Polar water flow to lower latitudes

Earth’s Uneven Solar Heating Results in Earth’s Uneven Solar Heating Results in Large-Scale Thermal Cell type of Large-Scale Thermal Cell type of Atmospheric CirculationAtmospheric Circulation

A convection current forms in a room when air flows from a hot radiator to a cold window and back.

A convection cell is driven by density differences

The Coriolis Effect Influences the Movement of Air in The Coriolis Effect Influences the Movement of Air in Atmospheric Circulation CellsAtmospheric Circulation Cells

Uneven solar heating causes convection currents to form in the atmosphere and leads to areas of different atmospheric pressures. The direction of air flow in these currents is influenced by the rotation of Earth.

To observers on the surface, Earth's rotation causes moving air (or any moving mass) in the Northern Hemisphere to curve to the right of its initial path, and in the Southern Hemisphere to the left. This is known as the Coriolis effect.

The atmosphere responds to uneven solar heating by flowing in three great circulating cells over each hemisphere. The flow of air within these cells is influenced by Earth’s rotation (Coriolis effect). Each hemisphere has three large atmospheric circulation cells: a Hadley cell, a Ferrel cell, and a polar cell (less pronounced over the South Pole).

Large storms are spinning areas of unstable air that develop between or within air masses. Extratropical cyclones originate at the boundary between air masses.

Tropical cyclones, the most powerful of Earth's atmospheric storms, occur within a single humid air mass.

Key TerminologyKey Terminology

Rotation Revolution

Conduction Convection

Radiation Electromagnetic radiation

Albedo Longwave radiation

Shortwave radiation Greenhouse Effect

Scattering Absorption

Terrestrial heat Solar heat

The lithosphere is the solid part of the earth made up of rocks, minerals, and other elements, not including the oceans. It includes plate tectonics, also known as continental drift, which explains the shape and position of our planet's land masses, oceans, and mountain ranges

The biosphere is the part of the planet where living things can be found - from the upper reaches of the atmosphere to the bottoms of the oceans and thermal pools

The atmosphere is the thin layer of gasses that surround our planet. It gives us the many varied climates, or long-term weather conditions, around the world. Along with larger-scale factors, local features of the landscape, such as the topography, strongly shape the wind and precipitation patterns of a particular place.

The hydrosphere includes all of the water on earth, from the oceans to glaciers and underground water. The hydrological cycle, is the circulation of water throughout the world, from the sea and land into the atmosphere and back to land again. The hydrological cycle is one of the major forces shaping climate and the weather.

The cryosphere includes all of the earth's frozen water, including glaciers, permafrost, and sea ice. A significant portion of the fresh water on the planet is frozen. Glaciers and the polar ice caps play a large role in climate and weather around the world.

Origin of heat in the Earth’s interior

1. radioactive decay

2. residual heat from Earth’s formation

and to a lesser extent, heat contribution from the growth of the inner core which drives the convection in the outer core

• Earth is heated from the core due to radioactive decay generating heat energy in the solid core.

• Heat can also be provided by the core of the Earth by frictional heating as heavy particles sink to the centre of the earth

• There is also residual heat from when planet Earth was formed.

• Heavier elements undergo radioactive decay by fission in the core, which produces heat.

• Radioactive decay produces large amounts of heat energy due to the large numbers of heavy elements in the core.

• This heats the lower mantle by conduction where the particles have to touch in order to transfer energy

• Convection currents in the core transfer heat to the mantle by convection.

• The mantle is a highly viscous liquid that moves very slowly.

• As the lower mantle is heated by conduction this heat energy is transferred throughout the mantle by convection.

• This sets up a convection current, whereby as the material that is rising gets more dense, it begins to sink again.

• This material that sinks is then reheated by conduction from the radioactivity in the core and rises again.

• The convection currents in the mantle also provide the driving force behind plate tectonics.

• Under oceans the heated mantle material can become magma at divergent plate boundaries driving sea floor spreading at a plate boundary.

• This moving plate boundary can lead to a subduction zone at the other edge of the plate boundary, which can be then heated further and erupted through volcanic eruptions of lava and ash.

Putting it all togetherPutting it all togetherIn your books find a double page.Draw a circle in the middle of the

page to represent the Earth.Add in the layers of the Earths

interior.Around the outside of the Earth, note

down all different things that happen to the radiation that comes from the sun