The atmosphere

• Atmosphere: a blanket of air that surrounds the earth and is made up of various gases
• Atmosphere is made of

  • 78% nitrogen
  • 21% oxygen
  • 1% others including argon
• Benefits

  • provides us with air we breathe
  • thin gaseous later insulates the earth from extreme temperature
• Troposphere: bottom layer of the atmosphere, layer in which forms wind, rain
• 50% of the solar energy that reaches earth is absorbed by its surface
• Ireland is in mid latitudes
• • Seasons are caused by: the tilt in earths axis
• • 50% of energy earth receives reaches the ground
  • 25% is reflected to space by clouds, dust
  • 25% is trapped by the atmosphere in a process called greenhouse gases
• How wind forms:

  • wind forms because earth is heated unevenly
  • when air is heated, it expands and rises which creates low pressure
  • when air is cooled it becomes heavier and contracts. it presses down on the earth, created high pressure
• Winds are named:

  • by the direction in which they flow
  • the wind that’s most frequent in an area is called a prevailing wind
  • irelands prevailing wind: south westerly
• Coriolis effect

  • earth rotates on its axis from west to east
  • this causes winds in northern hemisphere to move to the right and winds in the southern hemisphere to move to the left
• Ocean currents occurs from:

  1. prevailing winds
  2. unequal heating
  3. rotation of earth from west to east
• North Atlantic drift

  • warm current that flows from the equator
  • starts in Gulf of Mexico and flows north easterly
  • keeps irelands coasts free of ice
• Labrador current

  • cold current that flows from high latitudes towards the equator
  • flows south
  • results in freezing
• Air mass: a body of air with its temperature, pressure and humidity level
• Polar air mass: cold wet winter
• Continental air mass: hot and dry summer, dry and cold winter
• Tropical air mass: warm and dry
• Maritime air mass: wet and cold
• Fronts

  • occurs when two air masses meet
  • types= cold, warm and occulded
• Warm fronts

  • formed when warm air rises over cold air
  • warm air lifts and expands
  • warm air cools, condenses and forms rain
  • forms dark, rainy clouds
• Cold fronts

  • formed when cold air moves in towards warm air
  • cold air forces the light warm air to rise
  • as the warm air rises it cools and condensation occurs
  • clouds are formed, heavy rainfall
• Isobars

  • lines on a weather chart, join places with equal pressure
  • lines close together: wind is strong
• Depressions

  • an area with low atmospheric pressure, also known as cyclones
  • bring wet and windy weather
• Anticyclones

  • also known as high pressure, descending air results in high pressure
  • bring clear, sunny weather