Heat from the Sun turns moisture water from plants and leaves, as well as oceans, lakes, and rivers, into water vapour gas , which disappears into the air. This vapour rises, cools, and changes into tiny water droplets, which form clouds. The water droplets in the clouds join together to form bigger drops. When the water droplets get too large and heavy, they fall as rain. This lists the logos of programs or partners of NG Education which have provided or contributed the content on this page.
Powered by. Rain is liquid precipitation : water falling from the sky. Raindrop s fall to Earth when cloud s become saturate d, or filled, with water droplets. Millions of water droplets bump into each other as they gather in a cloud.
When a small water droplet bumps into a bigger one, it condense s, or combines, with the larger one. As this continues to happen, the droplet gets heavier and heavier. When the water droplet becomes too heavy to continue floating around in the cloud, it falls to the ground.
Human life depends on rain. Rain is the source of freshwater for many cultures where river s, lake s, or aquifer s are not easily accessible. Rain makes modern life possible by providing water for agriculture , industry , hygiene , and electrical energy.
Governments, groups, and individuals collect rain for personal and public use. Raindrops condense around microscopic pieces of material called cloud condensation nuclei CCN. CCN can be particles of dust , salt , smoke , or pollution. Brightly colored CCN, such as red dust or green algae, can cause colored rain. Because CCN are so tiny, however, color is rarely visible. When rain forms around certain types of pollutants, such as sulfur dioxide and nitrogen oxide , the CCN react with water to make the rain acidic.
This is called acid rain. Acid can harm plants, aquatic animals like fish and frogs, and the soil. Sulfur dioxide and nitrogen oxide can be released into the atmosphere naturally, such as through a volcanic eruption. These pollutants can also be released by human activity, such as the burning of fossil fuel s. Burning fossil fuels can influence rain patterns.
In urban area s, where many vehicles are on the road at once, rainfall is more likely during the weekend than during the week. This is because during the week, millions of cars release exhaust into the atmosphere, creating billions of CCN in the clouds. By the end of the week, clouds are much more likely to be saturated with moisture and CCN. VAT reg no Main menu. Subjects Shop Courses Live Jobs board. View shopping cart. View mytutor2u. Account Shopping cart Logout. Explore Geography Geography Search.
Variability is a basic feature of rainfall that makes it complex to measure. Meteorologists people who study weather and researchers have developed numerous measurement devices that enable them to study the extreme variability of rainfall. We will explain the functioning of the three most commonly used devices. The most common rainfall measurement is the total rainfall depth during a given period, expressed in millimeters mm. For instance, we might want to know how many millimeters of rain fell over the course of 1 h, 1 day, 1 month, or 1 year.
You can easily get a rough measurement of rainfall depth at home. Just follow these steps: 1 Take a bottle with smooth sides, cut off the upper part and turn it upside down on the top of the bottle, to create a sort of funnel see Figure 1A.
The bumps would otherwise affect the measurement. If you plan to take your measurements during the summer, some of the water inside the bottle will evaporate up to few mm a day and this will affect your measurements. To avoid this, you can add a thin layer of oil to the water. Since it is lighter than water, the oil will float on the top of the water and prevent evaporation.
The measurements you get from your rain gauge will tell you how much rainfall occurred over a certain period of time. Professionals use more complicated devices called tipping bucket rain gauges and you can see one in Figure 1B. This rain gauge looks like your homemade device, except that there are two buckets beneath the funnel. The water falling into the rain gauge will be routed to one bucket by the funnel.
Once that bucket is filled, usually after 0. The process starts all over again with this other bucket, until it is filled and tips. The rain gauge records the time of all the bucket tips, which will give the researcher data about how quickly the rain falls over time. Figure 1C shows an example of the data that can be obtained using a tipping bucket rain gauge.
These observations were made on 27 June The rainfall depth in mm quickly increased between and , meaning that it rained a lot during that period. During a period of light rain, this device is not very precise. For example, between and , all you can tell is that 0. If there is a lot of wind, that can also affect the accuracy of the device. What is rainfall made of?
Rain drops, obviously!
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