Kinetic Energy In The Atmosphere• Kinetic Energy is the energy of motion• Heat - the total kinetic energy of the

atoms composing a substance (atmospheric components)• Temperature - a measure of the average

kinetic energy of the atoms• Scales:− Fahrenheit−Celsius−Kelvin

Transport of Heat Energy • A Temperature Gradient shows the

change in temperature over distance

• Heat flows from locations of higher temperatures toward locations of lower temperatures (2nd Law of Thermodynamics)

Methods of Heat Flow •Conduction - heat transfer through collisions between neighboring atoms; requires direct contact• Solids are better conductors of heat

energy than liquids• Liquids are better conductors of heat

energy than gases

•Convection - heat transfer within a fluid (liquids & gases)

• Warm fluids are less dense than cold fluids

• Denser fluids descend & push warmer, less dense fluids upward

• Is the main method of transferring heat vertically in the troposphere

• Sensible heating - the combined processes of conduction and convection

•Radiation - the transfer of heat energy through electromagnetic waves

• Is the primary method of atmospheric heating from the sun

• Is primary method of heat escape into space• Energy can travel through vacuum

Heat Imbalance vs. Equilibrium • Heat Imbalance refers to the variations

in radiational heating and cooling throughout the Earth’s atmosphere

• Result of heat imbalance is temperature gradients

• Although there are variations of heat energy within the atmosphere, Earth is in radiational equilibrium

Heat Imbalance & Latitude • Incoming solar radiation strikes lower

latitudes more directly than higher latitudes

• High latitudes have lower solar intensity• Latitudes poleward of 30 degrees North

or South experience net cooling• Latitudes within 30 degrees of the

equator experience net heating

• Heat is transported from lower latitudes to higher latitudes by way of three mechanisms:• Air mass exchange

− Types of air masses (based on their origin)− Cold / Humid− Cold / Dry− Warm / Humid− Warm / Dry

•Storms−At lower latitudes, water evaporates

from surface water and is drawn into storm circulation−As storm travels to higher latitudes,

water vapor condenses to form clouds and precipitation, releasing latent heat into the atmosphere

•Ocean Circulation−Water currents carry warm water at

lower latitudes toward higher latitudes−Example - Gulf Stream

Latent Heating • Equilibrium within the atmosphere is

maintained through latent heating.• Latent Heating is the transfer of heat

energy from place to place as a consequence of changes in the phase of water• During phase changes, heat energy is either

absorbed or released• Condensation & freezing release latent heat

into the environment• Melting & evaporation absorb heat from the

environment

Specific Heat • Specific Heat is the amount of heat

required to change the temperature of one gram of a substance 1 degree Celsius• A substance with low specific heat warms

up more than a substance with a higher specific heat

• Water has the greatest specific heat of all natural substances

•Specific heat differences is the main reason land surface temperatures vary more than lakes & oceans• Land heats up more during day/summer

and cools down more at night/winter• Water has greater resistance to

temperature change - Thermal Inertia• Locations close to large bodies of water

exhibit smaller seasonal temperature variations than inland locations

Temperature Related Indexes

•Heating & Cooling Degree Days•Heating Degree Days are a measure of the number of days needed to heat buildings

• Cooling Degree Days are a measure of the number of days needed to cool buildings

• The daily average temperature is compared to 65F• Temp. averages less than 65F require heating• Temp. averages greater than 65F require cooling

•Windchill Equivalent Temperature (WET)

• A temperature determination due to the combined effects of cold temperature and wind speed

• A layer of still air surrounds the skin due to heat being conducted from the skin to the cold air (temperature gradient) - Boundary layer

• Air is a poor conductor of heat; thus the boundary layer helps insulate the body from heat loss

• As wind speed increases, the boundary layer thickness diminishes

• The body experiences an increase in heat loss

• Wind speeds greater than 35 mph have minimal increased effect

•Heat Index (Apparent Temperature)

• A combination of temperature and humidity influence the rate of surface skin water evaporation

• Higher humidity reduces the evaporative process; surface skin temperature increases

• Other factors influencing apparent temperature include:

• Cloud cover• Air pressure• Wind speed