Unit 2

• What is precipitation formed from?


  Water vapour condensing around small particles in the atmosphere.
• What is the dew point?


  The temperature at which condensation occurs.
• What is the lapse rate?


  The change in temperature with altitude.
• How much does temperature decrease for every 1000m increase in altitude?


  1. 6.5 - 9.8 degrees Celsius.
• What are the types of precipitation?

  • Orographic / Relief
  • Convectional
  • Frontal
• How is orographic precipitation formed?


  Warm and moist air is forced to rise over high ground, cooling and reaching the dew point.
• What effect does orographic precipitation have on the air?

  It reduces moisture in the air and creates a rain shadow.
• What causes convectional precipitation?


  Radiation from the sun heats the ground, causing the air to rise and reach the dew point.
• What is the characteristic of rainfall from convectional precipitation?


  It results in short, intense rainfall.
• How does frontal precipitation occur?


  Warm air is forced up over cool air, reaching the dew point and causing prolonged rainfall.
• When does frontal precipitation typically occur?


  When tropical air meets polar air.
• What percentage of Haiti was originally covered by forest?


  60%
• What is the consequence of deforestation in Haiti regarding soil?


  It causes rain to remove the top layer of soil, making farmland less fertile
• How does deforestation affect flooding in Haiti?


  It leads to increased flooding due to less protection from trees
• What is one effect of urbanization on surface runoff?


  It creates more impermeable surfaces that exacerbate surface runoff
• What happens to infiltration and soil storage due to urbanization?


  There is less infiltration and soil storage
• What is the result of reduced infiltration and soil storage in urban areas?

  It leads to more rapid runoff flow into rivers
• What is the Bergeron—Findeisen theory related to?


  Ice crystal growth
• Where does the Bergeron—Findeisen theory primarily apply?


  Higher altitudes and latitudes where temperatures are below 0 degrees Celsius
• What happens to pure water vapor droplets in the Bergeron—Findeisen theory?


  They stay liquid until they contact condensation nuclei
• What causes the droplets to freeze in the Bergeron—Findeisen theory?


  Contact with condensation nuclei, such as dust particles
• What happens to the frozen droplets as temperatures increase in the Bergeron—Findeisen theory?

  They melt and cause rain
• What is the Collision Mechanism theory related to?


  Formation of large water droplets in the tropics
• In which regions does the Collision Mechanism occur?

  In the tropics where ice crystals cannot form
• How do large water droplets form in the Collision Mechanism?

  They form around large nuclei and absorb smaller droplets upon collision
• What type of rainfall is caused by the Collision Mechanism?

  Convectional rainfall
• What can result from the Collision Mechanism in tropical regions?

  Flash flooding
• What was notable about the winter of February 2020 in the UK?


  It was the 5th wettest winter on record.
• What caused the severity of flooding during the February 2020 rainfall in the UK?


  High soil saturation worsened the severity of flooding.
• How many properties were damaged due to flooding in February 2020 in the UK?

  3130 properties were damaged.
• What were the main factors contributing to the Boscastle floods in 2004?

  • Flash flooding from infiltration
  • Excess overland flow
  • 75mm of rain fell in 2 hours
  • Caused by frontal rainfall in a convergence zone
• How many buildings were destroyed and damaged during the Boscastle floods in 2004?


  5 buildings were destroyed and 60 were damaged.
• How many people were rescued during the Boscastle floods in 2004?


  100 people were rescued.
• What were the main causes of the Red River flood of Fargo in 2009?


  • Rapid snowmelt on frozen soil
  • High rainfall
  • Low infiltration
  • Floods reached 40 ft high in March
• In which states did the Red River flood occur in 2009?


  The flood occurred in Minnesota and North Dakota, USA.
• What was the height of the floods during the Red River flood of Fargo in 2009?


  The floods reached 40 ft high.