Transcript Earth`s heat sources 2012

Heating Earth's Surface and
Atmosphere
Dr. R. B. Schultz
Motion 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.
Chapter 8
Circulation of the Atmosphere
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.
Variations in Solar Energy and
Seasons
•
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 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 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.
Electromagnetic Radiation
•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).
The Sun’s Radiation
•
•
Although the Sun emits many forms of radiation,
most of the energy is concentrated in the visible
and near visible (infrared and ultraviolet) 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?
•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 Budget
Albedo
•
The fraction of radiation reflected by a surface is
called its albedo.
•
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 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 effect.
Earth’s Heat Budget
•
Because of the annual balance that exists
between incoming and outgoing radiation,
called Earth's heat 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
Fluctuations
•
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 LargeScale Thermal Cell type of Atmospheric 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 Atmospheric
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 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 together
In 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
