Why Does It Rain Do You Really Know
Why Does It Rain Do You Really Know: Rain – and other forms of precipitation – occur when warm moist air cools and condensation occurs. Since warm air can hold more water than cool air, when the warmer air is cooled the moisture condenses to liquid – and it rains. Three types of rain that you get are- Frontal rain, Orographic rain and Convective rain.
Frontal rain occurs when two air masses meet. When a warm air mass meets a cold air mass, they don’t mix as they have different densities (a bit like oil and water). Instead, the warm less dense air is pushed up over the cold dense air creating the ‘front’. As a result, much like when air is forced up over mountains, the warm less dense air cools, and the water vapour condenses into water and falls as raindrops. This type of rain can happen anywhere in the UK or Capetown.
Orographic rain is rainfall produced as a result of clouds formed from the topography – or shape – of the land. Where there is high ground moist air is forced upwards producing cloud and potentially, precipitation. Mountainous areas close to prevailing westerly winds are most likely to experience this type of rainfall.
Convective rain is produced by convective cloud. Convective cloud is formed in vertical motions that result from instability of the atmosphere. One way that the atmosphere can become unstable is by heating from the sun. The ground warms up, causing moisture in the ground to evaporate and rise, and the hot ground also heats the air above it. As the water vapour rises, it cools and condenses into clouds and eventually rain.
When you heat the air from below like this, much like in a boiling kettle, you tend to get “bubbles” of rising air, known as updraughts. These are much smaller than the large-scale lifting of air that occurs at fronts and over mountain ranges. This tends to give us smaller areas of rain, with clear spells in between, commonly referred to in the UK as “sunshine and showers”.
Rain is responsible for most of the fresh water on Earth and it is essential to life. It is part of the water cycle, the continuous movement of water between the Earth and the atmosphere. In the water cycle, water is evaporated and transpired into the atmosphere. There it is condensed, where it falls as rain, or in the colder months, sleet or snow. The runoff and ground water is evaporated and the cycle begins again. Earth as a whole experiences precipitation and evaporation levels that are almost exactly the same. The driest place on Earth is the Atacama Desert in Chile. Parts of this desert have not had rain in 400 years and the average rainfall in the entire desert is .004 inches per year. The wettest place in the world is Mawsynram in India. Mawsynram receives an average of 467 inches of rain every year.