kinetic energy in the atmosphere kinetic energy is the energy of motion heat - the total kinetic...
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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
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