A&W

• Explain how frontal precipitation occurs.

  • Interaction of warm and cold air masses
  • Uplift is caused by undercutting of warm air by cold air at the fronts
  • Moderate to light showers at warm front and heavy showers at cold front
  • Mechanism of condensation at dew point and formation of raindrops;condensation nuclei provide a surface for water vapour to condense on
  • Precipitation occurs when water droplets increase sufficiently in size(collision idea) and fall
  • Discussion of condensation and occluded fronts is also relevant
• Explain how atmospheric conditions and surface conditions affect the components shown in incoming shortwave solar radiation:

  Atmospheric and surface conditions will reflect and absorb the radiation depending on the nature of those conditions.

  Atmospheric conditions will determine particulate matter, gases and moisture (clouds) and their ability to reflect or absorb energy.

  Surface conditions will determine the albedo of various surfaces (water, ice, vegetation, etc.) and their ability to absorb energy.
• Compare the causes of precipitation shown in Fig. 2.1 and Fig. 2.2.


  Differences:

  • Uplift is caused by the fronts (with air of different densities) in Fig. 2.1 but by convection in Fig. 2.2
  • Evaporation/evapotranspiration occurs in Fig. 2.2 but not in Fig. 2.1
  • Similarities:
  • Rising of warm, moist air occurs in both causes
  • Leading to cooling and condensation and formation of clouds
• Explain how precipitation is caused by orographic uplift of air:


  • Presence of a topographic barrier such as a hill or mountain
  • Moving air/wind forced to rise up this barrier
  • Air cools as it rises and reaches condensation level; condensation nucleiprovide a surface for water vapour to condense on
  • Precipitation occurs when water droplets increase sufficiently in size(collision idea) and falls
  • On the windward side, precipitation will occur
• Explain how frontal precipitation occurs:


  • Interaction of warm and cold air masses
  • Uplift is caused by undercutting of warm air by cold air at the fronts
  • Moderate to light showers at warm front and heavy showers at cold front
  • Mechanism of condensation at dew point and formation of raindrops;condensation nuclei provide a surface for water vapour to condense on
  • Precipitation occurs when water droplets increase sufficiently in size(collision idea) and fall