What is Rain?
Rain is the physical manifestation of liquid water condensed from the atmosphere. This water is then heavy enough to fall under the force of gravity. Rain is a major component of the water cycle and is responsible for depositing the majority of Earth’s fresh water. Rain falls in four different forms: Coalescence, Relief, Frontal, and Convection. Read on to learn more. But first, what is rain? Here’s an explanation:
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In nature, coalescence is the process by which two entities merge. This process is observed in many natural processes, including the formation of raindrops. It also occurs in star and planetary formations. In rain, the process involves colliding water droplets with one another. These droplets combine and form new droplets. While coalescence is not always the case, it can make rain fall significantly more frequently. Here are some examples of coalescence in rain.
When cloud droplets collide with each other, they grow until they become large enough to fall to the ground. This is called collision coalescence. The droplets grow together and become heavier, so they fall to the Earth more rapidly. When a droplet grows too large, it becomes unstable and breaks up when it falls to the ground. It can also produce many smaller droplets that are separated by an ice-cold surface.
Frontal rain occurs when two types of air meet at a front and converge at the same time. This process causes condensation, which turns into rain. Other types of precipitation are sleet, snow, or hail. This rain occurs at the cold and warm fronts of a depression. A cold front moves north, and warm air flows southward. In either case, it will produce a frontal rain system. Listed below are the main types of frontal rainfall.
Frontal rainfall occurs when two different masses of air meet at a front and the warmer air rises above the cold air. This process cools the air above it to the point of dew formation, causing heavy rainfall. This type of rain usually lasts only for a few hours, but can be heavy during tropical cyclones. Rainfall droplets move upward and down, forming small ice particles. It is important to note that frontal rainfall is one of the three major types of rain.
Relief rainfall is a type of orographic rainfall, which occurs when warm, moist air blowing over the sea rises over a high area of land. As this air cools, the water vapour condenses, forming clouds and rain. In areas of high land, relief rainfall is a common occurrence. During the summer, relief rainfall can also produce thunderstorms, which are typically cloudier and less heavy than typical summer rain.
Relief rainfall occurs when warm, moist air rising from the Atlantic Ocean reaches the mountainous terrain and cools and condenses, carrying rain. It then descends, soaking the ground and precipitating rain. Relief rainfall is a common phenomenon near the coasts. During summer, warm moist air rising from the ocean moves inland over mountains, where it cools and condenses. Once there, it begins to fall as rain.
The term convection during rain means vertical transportation of moisture and heat. It is similar to how boiling water releases steam and bubbles of hot water on the surface. As the water cools, the air rises to replace the heated water. In the summer, convection occurs more often in the mountains. And, the process is similar to that of a thunderstorm. A thunderstorm’s water-vapor mixture condenses at the base of the cloud, releasing heat and building on top of it.
The UKV model simulates organized convective rainfall over central England during the evening. As it propagates southwards at the appropriate speed, this model is able to predict maximum rainfall rates for the right area and region, but at the risk of being 10 to 30 km too far east. Nonetheless, this model may improve our ability to predict the exact phase of precipitation, although further development is required to improve it. In the meantime, this technique holds promise for improving the precision of rainfall forecasts.
Impacts of climate change on precipitation
Most models project a significant increase in global precipitation by the end of the century, especially along the equator. Changes will also be large in the Arctic and Antarctic, where the cold limits the water vapour capacity of the air. The Mediterranean region, however, is projected to experience a 20% reduction in precipitation by 2100, with similar reductions in southern Africa and western Australia. The Mediterranean region will also likely become 10% drier in the RCP8.5 world. And while there is no clear pattern yet, all these changes tend to increase with global warming and the extent of change.
Scientists believe that the overall impacts of climate change will be determined by changes in precipitation. However, this aspect is more difficult to predict than temperature. Researchers believe that an increase in temperature will increase the amount of water vapour in the atmosphere by 7% per degree centigrade. The resulting increase in water vapour will then be reflected in changes in global precipitation. By 2050, this total volume of precipitation is expected to increase anywhere from 1-2% per degree of warming, depending on the area of the world.
Origins of raindrops
A new study shows that the size of raindrops is caused by breaking up of individual droplets rather than complex interactions. This finding is a surprise, because raindrops are widely distributed in size as they fall to the ground. Previous studies have suggested that this large variability results from the complicated interaction of individual droplets. But the new study by Benjamin Bossa and Emmanuel Villermaux shows that raindrop size is caused by the breaking up of individual, non-interacting droplets.
This study uses data from the Tropical Ocean Global Atmosphere Couple Ocean-Atmosphere Experiment to study rainfall. It shows that the N0 parameter dramatically decreases during rainfall events with little change in rainfall rate. This suggests that a transition from convective to stratiform rain occurs. These observations also support the existence of an empirical stratiform-convective classification method. Its methods are based on well-known physical equations.