WEEK 4

• Weather occurs in the troposphere because this layer contains most of the water vapor or Earth's clouds
• When air is heated

  1. It expands (meaning the volume increases)

  2. It rises
• As warm air rises


  The air in the surroundings will move towards the place where warm air is rising
• The moving air


  Is called WIND
• Convection


  • A type of transfer of heat between two bodies by currents of moving gas or fluid
• Free convection

  • Air or water moves away from the heated body as the warm air or water rises and is replaced by a cooler parcel of air or water
• What happens when air is heated

  • The hotter the air, the faster the molecules move
  • They are moving apart as they are heated
  • Air expands when heated
  • The hot air is less dense than the surrounding matter and the hot air floats upward
• What happens when the air is cooled down

  • The colder the air, the slower molecules move
  • Air contracts when cooled
  • The cold air is denser than the surrounding matter and the cold air sinks
• Solar heating of the Earth's surface is uneven because land heats faster than water, and this causes air to warm, expand and rise over land while it cools and sinks over the cooler water surfaces
• The land or soil absorbs more heat than the water during daytime while water absorbs less heat. When the sun goes down, the land cools faster and emits more heat energy than the water. The land gains and loses heat energy faster while water gains and loses heat energy slower
• Local winds


  The result of the movement of air between low and high-pressure systems within small regions
• Local winds occur because the land and sea heat up and cool at different temperatures and this produces wind due to low and high-pressure areas
• The most common example of local wind

  A breeze
• Two common types of breezes

  • Land Breeze
  • Sea Breeze
• During the day

  1. The land heats up faster than the water in the sea

  2. The air above land will then become warm ahead of the air above the sea
• Sea breeze


  • Occurs during daytime
  • Cool air comes from the sea moving towards the warm air from the land
• During nighttime


  1. The land and sea will both cool down

  2. But the land will lose heat faster than the water in the sea and the sea will stay warm

  3. The air above the sea will be warmer than the air above the land
• Land breeze


  • Occurs during nighttime
  • Cool air comes from the land moving towards the warm air from the sea