“Clouds come floating into my life, no longer to carry rain or usher storm, but to add color to my sunset sky.”— Rabindranath Tagore
Rain is liquid water in the form of droplets that have condensed from atmospheric water vapor and then precipitated. It becomes heavy enough to fall under gravity. Rain is a major component of the water cycle and responsible for depositing most of the fresh water on earth. It provides suitable conditions for many types of ecosystems, as well as water for hydroelectric power plants and crop irrigation. Everybody loves the monsoon season as it brings relief after the hot summers. However, it also causes traffic jams, floods, and landslides much to our dismay, but that is part of nature. India primarily relies on rainfalls owing to its agricultural economy. Maybe some of us might have pondered hard over how the rain forms, but most of us aren’t aware of the facts. So, let us come back to the main question—why does it rain?
To put it in simple words, when water becomes warm enough, it evaporates as vapor into the air. The water vapor condenses into clusters of tiny water droplets and frozen water crystals when a mass of air quickly cools to its saturation point. We call these clusters clouds. Over time, the droplets and crystals that make clouds can attract more water to themselves. When water droplets grow heavy enough, gravity pulls them down as raindrops. If the air is cold enough, the ice crystals remain frozen and grow large enough to fall as snow, sleet, freezing rain or hail.
If we dig deeper into science, rain can be classified into the frontal, orographic 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 over the cold dense air, creating the ‘front’. As a result, much like when the air is forced up over mountains, the warm, less dense air cools, and the water vapor condenses into water and falls as raindrops.
- Orographic rain is produced as a result of the clouds formed from topography, which is the shape of the land. On high grounds or surfaces, moist air is forced upwards to produce cloud and potentially, precipitation.
- Convective rain is a result of convective clouds, which are formed in vertical motions that result from the instability of the atmosphere. The atmosphere becomes unstable only by the heat 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 vapor rises, it cools and condenses into clouds and eventually, it rains.
If you are curious enough to experience the process of water cycle and rainfall at home, you can follow these steps. Remember to take help from your mom, dad or teacher as it could be unsafe to try it alone.
- Boil water until steam rises.
- Hold a tray of ice about 5 inches above the steam. Use potholders to protect your hands from the hot steam.
- Continue holding the tray until drops form at the bottom surface, get heavy and it starts raining!
There is always a rise in the numbers of people falling sick during the monsoon season. Read about why it happens, here.