ElecScie 7 - Q4

• Radiant energy


  Solar heat energy in the form of short waves transmitted through space
• Atmosphere


  • Almost transparent to solar radiation
  • Absorbs very little short-wave radiation
  • Solar heating of the atmosphere is minimal
• Terrestrial radiation


  Long waves reradiated back to the atmosphere from the earth's surface
• Atmosphere heated


  From below rather than above by radiation
• Convection


  1. Rising of air parcels under the action of buoyancy

  2. Condensation of water vapor releases latent heat

  3. Heating of the atmosphere
• Convection currents


  • Warm air expands, becomes less dense, and rises
  • Cooler air contacts, then becomes dense and sinks
• Conduction


  • Minor heat source
  • Provides initial buoyant force to air parcel in convection
• Land is a better absorber of heat energy than water
• Good heat absorbers are also good emitters
• Air is warmed


  • Air molecules move faster and occupy a bigger space
  • Fewer molecules exerting force per unit area
  • Decrease in air pressure
• Air loses heat


  • Air molecules come closer together
  • More molecules exerting force per unit area
  • Increase in air pressure
• Breeze


  Local circulation of horizontal movement of air
• Types of breeze


  • Land and sea breeze
  • Mountain and valley breeze
• Effect of Coriolis force on local winds is very minor
• Land and sea breeze


  Caused by difference in heat-absorbing and heat-emitting capacities between land and water
• Mountain and valley breeze

  1. During day, air above mountain slopes heats up and rises

  2. Air from valley rises up slopes to replace rising warm air (valley breeze)

  3. At night, air above mountainside cooled by conduction, flows down to valley (mountain breeze)
• Differences in air density

  Cause differences in air pressure
• Differences in air pressure

  Cause air to move parallel to earth's surface (wind) and in vertical circular patterns (convection cells/currents)
• Increase in air temperature

  Air expands, density and pressure decrease
• Increase in water vapor content

  Air density and pressure decrease
• Increase in altitude


  Atmospheric density and pressure decrease
• Humidity


  Refers to amount of water vapor in air compared to air's capacity to hold water vapor, expressed as percentage (relative humidity)
• Cloud types by altitude


  • Low clouds (300-6,500 ft)
  • Middle clouds (6,500-20,000 ft)
  • High clouds (20,000 ft+)
• Low clouds


  • Stratus - low, gray, uniform, sheet-like
  • Indicate no turbulence
  • Produce light drizzle or snow grains
• Middle clouds


  • Altostratus - gray/blue veil, may produce very light precipitation
  • Associated with poor visibility, smooth air, moderate winds
• High clouds


  • Cirrus - white, thin, feathery
  • Don't produce precipitation
  • Sign of approaching bad weather
• Wind


  Horizontal movement of air parallel to earth's surface, caused by differences in air pressure
• Pressure gradient


  Difference in air pressure over a specific distance
• Factors affecting wind flow


  • Coriolis force
  • Centrifugal force
  • Frictional force
• General circulation of atmosphere

  Average flow of air over entire globe, caused by uneven heating of earth's surface
• Coriolis force


  Apparent force that deflects air motion to the right in Northern hemisphere and left in Southern hemisphere
• Land vs water


  Land has lower heat capacity, heats/cools faster than water
• Air mass


  Large body of air with generally uniform temperature and moisture content
• Temperature classifications of air masses


  • Continental polar cold (cPc)
  • Maritime tropical warm (mTw)
• Front


  Boundary between two air masses with different temperatures
• Types of fronts


  • Cold
  • Warm
  • Occluded
  • Stationary
• Global wind system


  Average flow of air over entire globe, caused by uneven heating of earth's surface and modified by earth's rotation and land/water distribution
• Stationary


  When two adjacent air masses of different characteristics remain in the same positions
• Global wind system


  1. Air rises at the equator and flows towards the poles

  2. Air cools and sinks at the poles, inducing equatorward transport of air at the surface

  3. Greatly modified by the earth's rotation and the non-uniform properties of the surface
• Coriolis force


  Apparent force that tends to deflect the motion of an air parcel to the right in the Northern hemisphere and to the left in the southern hemisphere