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