water evaporates from the oceans, rivers, plants, trees, humans, etc and goes up into the air as water vapor aka clouds. clouds travel around the world collecting this vapor and when they get enough, rain falls.
if its cold where it is when it falls, it becomes snow, or in places like the desert, it evaporates again before it even gets to the surface cause its so hot.
each rain drop has a piece of dust in the center, the dust in the air is what the vapor attaches itself too. as it collects more and more it becomes a water droplet and falls due to weight.
hail is the same thing but is rain that was up much higher in the air where its very cold. as it fell it hit other rain drops that were almost frozen and they collected together and form a large piece of ice that falls as hail.
2006-10-18 02:10:25
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answer #2
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answered by Anonymous
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Rain is a form of precipitation, other forms of which include snow, sleet, hail, and dew. Rain forms when separate drops of water fall to the Earth's surface from clouds. Not all rain reaches the surface, however; some evaporates while falling through dry air. When none of it reaches the ground, it is called virga, a phenomenon often seen in hot, dry desert regions. The scientific explanation of how rain forms and falls is called the Bergeron process.
Rain plays a major role in the hydrologic cycle in which moisture from the oceans evaporates, condenses into clouds, precipitates back to earth, and eventually returns to the ocean via streams and rivers to repeat the cycle again. There is also a small amount of water vapor that respires from plants and evaporates to join other water molecules in condensing into clouds.
The amount of rainfall is measured using a rain gauge. It is expressed as the depth of water that collects on a flat surface, and can be measured to the nearest 0.27 mm or 0.01 in. It is sometimes expressed in litres per square metre (1 liter/m² = 1 mm).
Falling raindrops are often depicted in cartoons or anime as "teardrop-shaped" — round at the bottom and narrowing towards the top — but this is incorrect. Only drops of water dripping from some sources are tear-shaped at the moment of formation. Small raindrops are nearly spherical. Larger ones become increasingly flattened on the bottom, like hamburger buns; very large ones are shaped like parachutes.[1]The shape of raindrops was studied by Philipp Lenard in 1898. He found that small raindrops (less than about 2 mm diameter) are approximately spherical. As they get larger (to about 5 mm diameter) they become more doughnut-shaped. Beyond about 5 mm they become unstable and fragment. On average, raindrops are 1 to 2 mm in diameter. The biggest raindrops on Earth were recorded over Brazil and the Marshall Islands in 2004 — some of them were as large as 10 mm. The large size is explained by condensation on large smoke particles or by collisions between drops in small regions with particularly high content of liquid water.
RaindropsRaindrops impact at their terminal velocity, which is greater for larger drops. At sea level and without wind, 0.5 mm drizzle impacts at about 2 m/s, while large 5 mm drops impact at around 9 m/s [2].
Generally, rain has a pH slightly under 6. This is because atmospheric carbon dioxide dissolves in the droplet to form minute quantities of carbonic acid, which then partially dissociates, lowering the pH. In some desert areas, airborne dust contains enough calcium carbonate to counter the natural acidity of precipitation, and rainfall can be neutral or even alkaline. Rain below pH 5.6 is considered acid rain.
Rain is said to be heavier immediately after a bolt of lightning. The cause of this phenomenon is traceable to the bipolar aspect of the water molecule. The intense electric and magnetic field generated by a lightning bolt forces many of the water molecules in the air surrounding the stroke to line up. These molecules then spontaneously create localized chains of water (similar to nylon or other "poly" molecules). These chains then form water droplets when the electric/magnetic field is removed. These drops then fall as intensified rain.
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Effect on agriculture
Precipitation, especially rain, has a dramatic effect on agriculture. All but perhaps a couple of plants need at least some water to survive, therefore rain (being the most effective means of watering) is important to agriculture. While a regular rain pattern is usually vital to healthy plants, too much or too little rainfall can be harmful, even devastating to crops. Drought can kill crops in massive numbers, while overly wet weather can cause disease and harmful fungus. Plants need varying amounts of rainfall to survive. For example, cacti need small amounts of water while tropical plants may need up to hundreds of inches of rain to survive.
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Human influence
The fine particulate matter produced by car exhaust and other human sources of pollution form cloud condensation nuclei, leading to the production of clouds and increasing the likelihood of rain. As commuters and commercial traffic cause pollution to build up over the course of the week, the likelihood of rain increases: it peaks by Saturday, after five days of weekday pollution has been built up. In heavily populated areas that are near the coast, such as the United States' Eastern Seaboard, the effect can be dramatic: there is a 22% higher chance of rain on Saturdays than on Mondays.[3]
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Artificial rain
There is controversy over whether it is possible to induce artificial rain, a technique known as cloud seeding. According to this theory, when chemicals such as silver iodide or dry ice are shot into clouds they freeze individual droplets of moisture, which fall down to earth, melting as they near and so creating rain.
2006-10-18 02:10:37
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answer #3
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answered by mallimalar_2000 7
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wow sori ur pretty dumb....... i learn this in grade 2.... with like lil pictures...... hmm wat grade r u in? do u kno wat earth science & geology means? i doubt it cuz ur question doesnt belong to this catagory......... and if ur higher than grade 2.... than u dont belong there either
2006-10-18 02:14:35
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answer #4
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answered by Anonymous
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