Rainfall

• What is convectional rainfall?

  The sun heats the ground. This heat transferred to the air close to the ground and this hot air starts to rise. The process of it is called convection. As the air rises it cools and water vapour condenses to form clouds. This condensation occurs at the dew point and it is here that cumulonimbus clouds are formed. Heavy rain storm occur. These usually include lightening, thunder due to the electrical created by unstable conditions.

  
• What is frontal rainfall?

  When a cold air mass meets a warm air mass they do not mix. The warm air is forced to rise up over the cold air. The warm air rises and cools and when it reaches dew point condensation occurs. Water vapour turns into water droplets creates clouds and rain.

  
• What is relief rainfall?

  Evaporation occurs in warm air as it travels across the seas. When air reaches land it is forced upwards if it encounters large mountains. As the air cools by 1'C every 100m. Cold ai can't hold as much moister as warm air and when it reaches dew point it condenses and this cause clouds to form. Rain occurs on the windward slope. When the air has passed over the mountains it starts to warm and depend. As warmer air can hold more water vapour, evaporation occurs and the clouds disappear. The dry area on the leeward side of the mountain is called the rain shadow.