Elsci

• How much water is in the air over how much water can fit in the air(right before the water condenses out of the air).

  Humidity
• It is a COMPARISON of the amount of water vapor actually present in the air to the capacity of that air to hold water vapor expressed in percent. 


  Relative humidity
• Weather


  Elements of weather and their effects
• Heat transfer


  1. Convection

  2. Conduction

  3. Radiation
• Air


  What happens when it absorbs or releases heat
• Warm air


  Lower pressure
• Cool air


  Higher pressure
• Air systems and air masses

  • Differences in pressure and temperature
• The earth is heated by the radiant energy from the sun
• Some of the sun's energy is reflected back into space or scattered throughout the atmosphere
• Much of the sun's energy is absorbed by the atmosphere and by the earth's surface
• Heat transfer by radiation

  1. Solar heat energy in the form of short waves is transmitted through space

  2. Atmosphere is almost transparent to solar radiation

  3. Solar heating of the atmosphere is minimal

  4. Solar energy that reaches the surface is reradiated back to the atmosphere in the form of long waves

  5. Water vapor and carbon dioxide in the atmosphere absorb the long wave radiation, trapping the heat
• Heating of the atmosphere by convection

  1. Air parcels carrying water vapor rise, condensation occurs, releasing latent heat

  2. Convection currents form as warm air rises and cool air sinks
• Heating of the atmosphere by conduction


  Air directly in contact with a warm surface is heated through conduction
• Land is a better absorber and emitter of heat energy than water
• Warm air


  Molecules move faster, occupy bigger space, fewer molecules exerting force per unit area, resulting in lower pressure
• Cool air


  Molecules come closer together, more molecules exerting force per unit area, resulting in higher pressure
• Difference in heat-absorbing capacity of land and water areas causes differences in air pressure, resulting in air movement from high to low pressure areas
• Local circulation of horizontal air movement

  • Land and sea breeze
  • Mountain and valley breeze
• Coriolis force has a minor effect on local winds
• Land and sea breeze

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

  Caused by difference in temperature due to topography
• Differences in air density cause differences in air pressure, which cause air to move parallel to the earth's surface (wind) and in vertical circular patterns (convection cells)
• Increasing temperature


  Air expands, density and pressure decrease
• Increasing moisture content


  Air density and pressure decrease
• Increasing altitude


  Air density and pressure decrease
• Humidity


  Comparison of the amount of water vapor actually present in air to the capacity of that air to hold water vapor, expressed in percent
• Low clouds


  • Beginning at 300-6,500 feet, include stratus, stratocumulus, cumulonimbus, nimbostratus
• Middle clouds


  • Beginning at 6,500-20,000 feet, include altostratus, altocumulus
• High clouds


  • Beginning at 20,000 feet and higher, include cirrus, cirrostratus, cirrocumulus
• Wind


  Horizontal movement of air parallel to the earth's surface, caused by differences in air pressure
• Factors affecting wind flow

  • Coriolis force, centrifugal force, frictional force
• General circulation of the atmosphere

  Caused by uneven heating of the earth's surface, air rises at the equator and sinks at the poles, modified by the earth's rotation and uneven distribution of land and water
• Coriolis force


  Apparent force that deflects the motion of an air parcel to the right in the Northern hemisphere and to the left in the Southern hemisphere
• Land and water have very contrasting heat capacities, with land heating and cooling faster than water
• Air mass


  A large body of air with generally the same temperature and moisture content
• Types of air masses

  • Continental polar cold
  • Maritime tropical warm
• Front


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


  • Cold front
  • Warm front
  • Occluded front
  • Stationary front
• Forced to rise as it advances

  • Wedge of a cooler air mass
  • Cool air is heavier
  • Interface between opposing wedges of cold air masses