Rain is the most prominent weather phenomenon. Adequate amount of rain helps life to sustain on Earth however excess or shortage of rain can cause catastrophe too. For a long period the science behind the formation of rain was unknown. After the invention of weather radar it became possible to discover the stages by which rain is formed. Rain plays a very important role in the agricultural. It also brings moisture in the atmosphere. Basically rain formation takes place in 3 stages.
Formation of Rain:
Step1: Innumerable air bubbles formed by the foaming of the oceans continuously burst and thus cause water particles that ejects towards the sky. These particles are very rich in salt and carried away by winds and rise upward in the atmosphere. These particles are known as aerosols, they function as water traps, and form cloud drops by collecting around the water vapor themselves, which rises from the seas as tiny droplets. Clouds contain huge numbers of tiny droplets of moisture.
Step 2: The clouds formed from water vapor in first step condenses around the salt crystals or dust particles in the air. As the water droplets in these clouds are very small, somewhere around a diameter between 0.01 and 0.02 mm, the clouds are suspended in the air, and spread across the sky. Thus the sky is covered with clouds before rain occurs.
Step 3: Rain drops are formed by the thickening of the water particles that surround salt crystals and dust particles. The updrafts near the centre of the cloud are stronger than those near the edges. These updrafts cause the cloud body to grow vertically, so the cloud is stacked up. This vertical growth causes the cloud body to stretch into cooler regions of the atmosphere, where drops of water and hail formulate and begin to grow larger and larger. When these drops of water and hail become too heavy for the updrafts to support them, drops leave the clouds and start to fall to the ground as rain.
Rain plays a role in the hydrologic cycle in which moisture from the oceans evaporates, condenses into drops, precipitates (falls) from the sky, and eventually returns to the ocean via rivers and streams to repeat the cycle again.
Classification of Rain according to the precipitation:
When cloud particles become too heavy to remain suspended in the air, they fall to the earth as precipitation. Precipitation occurs in a variety of forms; hail, rain, freezing rain, sleet or snow.
Acid Rain: Acid rain occurs when gases react in the atmosphere with water, oxygen, and other chemicals to form various acidic compounds. Acid rain is measured using a scale called "pH." The lower a substance's pH, the more acidic it is. Acid rain causes acidification of lakes and streams and contributes to damage of trees at high elevations. To reduce acid rain:
Trees go through a process called Transpiration in which it sends out the excess water in the form of water vapor through small pores present on the leaf surface and this enables the raise in content of water vapor in the whole atmosphere leading to precipitation in form of rain. Rain is very important so we must plant more and more trees all around and should not support cutting of trees unnecessarily.
(Sources: mapsofworld.com, evidencesofcreation.com, policyalmanac.org, smh.com.au)