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Heat & the Atmosphere:

Objectives:

    1.    Describe how energy from the sun moves through the atmosphere by radiation, conduction and convection.

    2.    Identify the characteristics of each layer of the atmosphere.

    3.    Analyze Earth's heat budget.

Key Terms:

    radiation    conduction    convection    temperature    heat    troposphere    stratosphere    ozone    mesosphere    thermosphere    ionosphere    insolation

Notes: (17.2)

How heat and energy moves

As you remember from earlier chapters Earth is a closed system in which the only thing that freely enters and leaves is energy.  This energy is obtained principally from the sun through radiation.  The Sun's energy is responsible for driving our weather and is essential to the core production of nutrients that feed all organisms on Earth.  

The energy budget refers to the energy cycle on Earth where if we retain more than we give off our Earth warms and visa-versa.  Below are the means by which energy is transfered.

Radiation

Is how we get energy from the sun

The energy is carried by eloctromagnetic waves

The UV radiation is absorbed by the ozone

Heats up the atmosphere

IR radiation is absorbed at the surface

Cannot escape atmosphere

Diagram of Earth's Radiation Budget

(www.arm.gov/general/photolibrary/ radiation.jpg)

Conduction

Energy transfer when atoms or molecules bump into one another

By direct contact

Energy transfer continues until both substances are the same temp

(kkd.ou.edu/conduction.jpg)

Convection

Is the transfer of heat in flowing currents in a liquid or gas

Currents are caused by the difference in temperatures

Hotter less dense molecules rise where they cool and condense and begin to sink

(www.ipgp.jussieu.fr/.../profondeur/ dynamique/convection.jpg)

Heat & Temperature

Energy is the term used to describe the capacity to produce heat or to do work.  There are two major forms of energy, Kinetic and Potential.  

Kinetic Energy (KE)is the energy of motion.  When an object is in motion, it carries kinetic energy in the amount of 1/2 multiplied by the mass multiplied by the velocity squared.  (1/2mv2)  Kinetic energy can also come in the form of mechanical energy (energy created by the gears of a machine) and thermal energy (heat created by the internal motion of particles of matter).

Although heat and Temperature are related they are not the same

Heat is the total kinetic energy of the particles in a substance (think friction)

Temperature is the measure of the kinetic energy in a substance

Although two items of the same composition and of different weights may have the same temperature, they have different amounts of heat

 

Structure of the Atmosphere:

Structure of the atmosphere - Arranged in layers

    Troposphere (0-10km)

Contains ~75% of the atmospheric gasses, solids and liquids

Weather and clouds occur here

Temperature decreases with altitude

Tropopause separates it from the stratosphere

    Stratosphere (10-50km)

Ozone layer & Jet stream

Temperature increases with altitude - due to absorption of radiation 

Stratopause separates it from the mesosphere

    Mesosphere middle (50-95km)

Temperature decreases with altitude 

Mesoopause separates it from the thermosphere

    Thermosphere (95-~250km)

Contains the ionosphere area of charged particles

Very few particles

Temperature increases with altitude - due to absorption of radiation 

Thermopause separates it from the exosphere

    Exosphere - Outer limit of the atmosphere (>250km above earth)

    Place of shuttle orbiting

 

(www.cimms.ou.edu/~cortinas/ 1014/A01_07.gif)

 

Heat Budget

The heat budget compares the amount of insolation (incoming solar radiation) to the amount of radiation leaving our atmosphere.  If our budget is in balance the temperature will remain fairly consistent (which is generally the case).  The retention of insolation is called the greenhouse effect.  

(blueox.uoregon.edu/.../dlivelyb/ ph161/rad_heat_budget.gif)

Absorption & Reflection of Insolation

30% reflected directly back to space
+51% absorbed by the Earth
        -6% directly released back to space
        45% into the atmosphere in the form of evaporation,         condensation, conduction and convection
+19% absorbed by the clouds
-64% eventually released to space through the atmosphere
Total insolation = total radiation

(www.oceansonline.com/ images/greeneff.jpg)

 

 

 

 

 

Last modified: December 08, 2003