science unit 9.4

• Weather


  Short-term behavior of the atmosphere
• Weather


  • Temperature
  • Pressure
  • Precipitation
• Climate

  LONG-term averages of weather depending on location, latitude, altitude, water availability, etc.
• Weather changes on a daily basis


  Climate changes over long periods of time (averaged over about 30 years)
• The climate of the earth is not staying the same, nor has it over Earth's history
• Air masses


  Identified by meteorologists according to where they form over Earth, which determines their properties
• Types of air masses

  • Arctic (A): Very cold
  • Tropical (T): Moderately warm
  • Polar (P): Fairly cold
  • Equatorial (E): Very warm
• Air mass formation


  • Maritime (m): Form over the ocean, higher moisture
  • Continental (c): Form over land, lower moisture
• Air mass


  • Northern Canada air mass → continental polar
• Convection


  Hot air rises and cold air sinks
• Constant hot air rising along the equator and sinking at the poles
• Coriolis effect


  The earth rotates beneath the air masses, and the masses of air take time to "catch up"
• Air pressure


  A measure of the force that air is exerting on a square meter of land
• Hot air rises


  Lowers the pressure you experience
• Cold air sinks


  Raises the pressure you experience
• Air pressure


  The force experienced on an area from air, the denser the air the more air pressure
• Differential heating


  The difference in temperature fluctuations between day and night over land vs water, which can impact weather in coastal areas
• Coriolis effect


  Due to convection and the rotation of the earth, low pressure systems in the northern hemisphere rotate counterclockwise and spirals inwards and high pressure rotate clockwise and spirals outwards. The opposite is the case in the southern hemisphere.
• The Coriolis effect has a dramatic influence on atmospheric circulation and the movement of ocean currents.
• Water cycle and weather

  1. Evapotranspiration

  2. Advection

  3. Condensation

  4. Precipitation
• Heat transfer


  • Conduction
  • Convection
  • Radiation
• Condensation nuclei


  Solid particles in the air where water droplets can condense around, without these no clouds would form
• Isobars


  Connect areas with equal air pressure
• Pressure gradient


  The distance between the isobars
• Closer isobar lines


  Greater change in air pressure, greater/faster the winds speeds
• High pressure systems


  Bring clear/sunny weather and wind flows out and clockwise (right) in the Northern Hemisphere
• Low pressure systems


  Bring overcast/stormy weather and wind flows in and counter-clockwise (left) in the Northern Hemisphere