Rain is liquid precipitation that forms droplets that have condensed from the atmospheric water and bump into each other to be heavy enough to fall under the gravity.
Water covers a large percentage of the earth, which also evaporates into the atmosphere and condenses to form droplets that come back to earth in the form of rain.
It can provide favorable conditions for ecosystems. The causes of rain are moisture and also partially temperature. The precipitation formed falls from the thunderclouds that construct to rainbands.
In mountains, to the windward side, the elevation of the terrain pushes moist air to condense and falls out as rain. While on the leeward side, there is too much drying and heating of the air mass that causes monsoon troughs to bring the rainy seasons.
Let us look into a deeper understanding of the formation of rain.
There are different types of rainfall
It occurs when the solar energy heats the earth’s surface, causing evaporation of water to form water vapor. When the earth’s surface heats up, the air gets warm and causes the air to expand and rise.
Studies reveal that when hot air rises, it also cools and condenses at the same time. Condensation of air causes cumulonimbus clouds to form, and continuous process makes the rainfall to occur.
The unstable conditions of thunder and lightning are created by the electrical charge. This type of rainfall mostly occurs between tropical of Capricorn and tropic of cancer.
It is also called orographic rainfall, and it occurs in areas where land increases in height. In these areas, rain is formed when the air cools and rises over the relief areas.
Rising air cools, and condenses and falls as rain. On the leeward side, it experiences a small amount of this kind of rainfall. Research reveals that this rainfall has a total of over 1600 mm per year in the United Kingdom.
This type of rain occurs when an area of warm air meets an area of cold air. Since warm air is less dense than cold is air, it is forced over the cold air.
Warm air is cooled by the air, and water vapor is condensed. However, high clouds are formed, and precipitations occur.
It is one of the rains that lasts longer. During summer, the land is warmer than the ocean. This causes the air to rise over the land, and the air from the ocean blows in to fill the space left by the air that rose.
The warm rising air causes the formation of clouds that leads to precipitation and fall in as rain. The heavy rains last longer because the land stays warmer than the ocean, which is the source of moisture. In India, it is one of the rainiest places on earth experiencing this kind of rainfall.
It is most likely to be convectional rainfall that occurs on a large scale. Most of the time, the precipitation here in a tropical cyclone is conventional.
Mostly, air contains water vapor that has an amount of moisture in the air that can be defined as relative humidity. The relative humidity is the ratio of the amount of water vapor present in the air that is expressed as a percentage of the amount needed to saturate at the same temperature.
Cool air has less water vapor than warm air before becoming saturated. There are four ways to cool the air. Conductive cooling occurs when air gets in touch with a colder surface.
Evaporative cooling forms when there is an addition of moisture to air through a process of evaporation for cooling to occur to its wet-bulb temperature. The other way to cool is radiation cooling that occurs from the emission of infrared radiation by the surface underneath.
The water vapor can be added to the atmospheric air through dry air moving over warm water, sun heating evaporating water from the surface of the wet areas like oceans, swamps and lakes, transpiration from plants, and wind convergence to areas of upward motion.
Clouds are formed from the condensation of water vapor on condensation nuclei. The formation of stratus occurs when the cool air mass is confined underneath warm air mass.
Coalescence and Fragmentation
Water droplets can burst and fuse to form large water droplets through the coalescence process. The air turbulence causes the air to collide and fuse to form large water droplets.
The reason why the water droplets remain stationary is because of the air resistance. Descending of the larger water droplets makes coalescence to gradually continue that makes the droplets to be larger enough to overcome air resistance and fall as rain. Research has shown that coalescence can only happen if the droplets of opposite electrical charges.
For the droplets to fall to the surface, it has to be large and heavy enough to overcome the uprising air resistance that causes the formation of clouds. When a collision of water droplets occurs, the droplets fuse into a larger droplet. The more force of the collision, the droplets gain enough energy to fall to the surface.
Ladders of Precipitation.
The initial stage begins with water vapor and dirty air. Air moving vertically is crucial in weather formation, such as clouds and precipitation. Ascending air has four processes.
It starts with convergence, where the horizontal air moves towards each other and meets in a commonplace. When they meet, it is forced to rise. Convection occurs when air is heated on the land surface until it becomes less dense than the above air. The heated air rises until it is cooled to the surrounding air temperature.
Frontal lifting -it is where warm air mass meets the cold air masses. Since warm air mass is less dense than warm air, it causes it to rise above the cold air mass. In physical lifting, the air is forced to rise above topographical areas like hills and mountains.
When air ascends, it also expands. Expansion of air makes it warm to cool, and the higher it rises, the more it cools. Clouds are formed when there is the condensation of air.
Humidification increases when the air cools. If clouds are to form, the humidification brings the air to saturation. Supersaturated air makes the water vapor condense out. Clean air makes supersaturated air to produce water droplets.
Clouds are attached to particles and begin to form clouds. Clouds can be ice crystals or a large number of cloud droplets, and they remain suspended in the air because of the air resistance.
The next ladder is cloudiness which the cloud water content should be increased to experience precipitation. The cloud droplets can be increased in three ways; continuous condensation of water vapor into cloud droplets; secondly, by growing collision and coalescence of cloud droplets. The process repeats itself and forms a larger one.
Drop growth occurs when ice crystals exist in the cloud. Liquid water must be cooled below 0c before freezing. Water molecules movement occurs when the ice crystal and supercooled droplets are near each other.
The precipitation process occurs when water droplets are large enough to fall without evaporation.
Future impact activities on rain
Human density- in urban areas, mostly, they experience heavy rain on weekends than on weekdays. The urban heat the island that brings thunder.
Cities experience low rainfall due to less warm air to rise above the cold air.
Benefits of rain
Plantlife– rain is the lifeblood of most of the trees. Prolong lack of rain can cause effects to the plain and bring drought.
Water quality- irrigation needs water and mostly depends on the rain. When it is clean water, it can be used by human beings.
Man-made systems– agriculture requires rain to bring food production. In dry areas where it experiences low rain, irrigation is needed to ensure the continuous flow of rainwater.
Disadvantage of rain
Power blackouts-transformers can be blown by lightning. This causes power black in homes and industries.
Flooding streets, sewerage systems – in areas with poor drainage systems causes floods. Research reveals that Africa cities and towns have poor drainage and sewerage systems that they flood in case of heavy rainfall. Roads are submerged into rainwater
Flooding farm crops-excess rainfall causes floods in farms thus destroying crops. This causes low production of food in the farms and can cause hunger. I can personally advise farmers to construct houses in raised lands and cultivate lands.