Rain may be the most essential weather phenomenon in order for life to exist on Earth. Without it, lakes, rivers, oceans and the availability of drinking water would cease to exist. It is the final phase of the water cycle, in which water returns to the Earth.
Facts about Rain
- Raindrops form in clouds where temperatures are lower and water vapor begins to cool and condense. With liquid water's unique adhesion properties, water droplets adhere to and gather around particles in the air.
- Drops are not shaped like teardrops as they fall, as is commonly depicted - they are actually dome shaped.
- According to the USGS, a single inch of rain that falls on a single acre is equal to approximately 27,000 gallons of water.
- The place that receives the most annual rainfall on average is a village in India called Mawsynram, Meghalaya, India. They receive about 467 inches each year, most of which falls during monsoon season.
- Conversely, the village that receives the least rainfall on average is Yungay, Chile. It receives .004 inches each year. That is a tremendous difference!
- Some regions of the world get rain nearly every day or every other day. Galway, Ireland gets this weather about 220 - 230 days or more each year. Similarly, parts of Hawaii and other tropical areas receive brief spurts of rain on an almost daily basis.
How does rain form?
As a critical piece of the water cycle, rain supplies the Earth with life sustaining water. The water cycle 'begins' when water begins to evaporate due to heat from the Sun. This step in the water cycle is known as Evaporation where water is changed from a liquid to a gas. Water vapor weighs less than dry air, which is composed mostly of nitrogen and oxygen.
The next step in the water cycle is Condensation. As water vapor continues to rise above dry air, the temperature of the surrounding air begins to cool at higher altitudes. As the temperature cools, water vapor again begins to condense from a gas back into a liquid, and small water droplets begin to form. Liquid water has unique adhesion and binding properties, allowing the water droplets to begin to adhere to small particles present in the atmosphere. When more and more water droplets collect around these particles, raindrops begin to form.
The final step in the cycle is Precipitation. Precipitation occurs when enough water vapor has condensed and collected, and liquid raindrops are heavier than the surrounding air. The raindrops fall back to Earth, where the water cycle 'ends' and can begin again. This process occurs thousands if not millions of times in a single rain shower.
It should be noted that instead of rain, the water cycle can result in sleet, snow, hail and ice as well. The resulting precipitation is determined by the air temperature and altitude at which the precipitation formed, and the temperature of the surrounding air as it fell.
What do raindrops really look like?
Scientists have determined that raindrops do not actually look like the teardrop shape that has long been associated with them (as they are shown on this site's menu!). They are actually dome-shaped, and the bottom is flat because of air resistance.
Acid Rain forms when pollutant compounds such as sulfur dioxide and nitrogen oxide exist or are released into the atmosphere and bind with water vapor in the atmosphere. These pollutants can come from natural events such as lightning strikes or volcanic eruptions, or man-made events such as burning of fossil fuels like oil and coal. Acid rain can damage life in natural biomes like ponds, streams and rivers. Much of this type of rain in the United States falls in the east and northeast, as pollutants from the industrial regions of Ohio, Indiana, Michigan and Pennsylvania are carried eastward by weather systems.
Perhaps one of the biggest threats associated with heavy rain is the potential for flash floods. One of the best precautions people can make when heavy rain is expected is to stay tuned to local forecasts and be aware of flash flood watches and warnings. If these indicators are present, it would be highly advisable for people to avoid walking, biking and driving in the alert area. Low elevation areas and areas near existing bodies of water are particularly susceptible to flash floods.
Another danger, known as hydroplaning, occurs when rainwater gathers on roadways and cars drive through the accumulated water. If tires of the automobiles lose contact with the road and/or traction, the driver can quickly lose control of the car. To avoid hydroplaning while driving, it is advisable to reduce speed and areas of standing water.
Rain in Literature, Film and Culture
- A very famous song and dance was performed by Gene Kelly in the 1952 movie "Singin' in the Rain".
- Another famous song is "Raindrops keep fallin' on my head", performed by B.J. Thomas for the movie "Butch Cassidy and the Sundance Kid".