The Various Forms of Precipitation

Weather affects our lives daily, so it would enrich us to learn more about it. While there are only a few basic types of weather, people in the mountains in Vail, Colorado experience the snow differently than those living in New York City, and those living on the coastline experience rain a different way than people living on the prairie.

Rain

Rain is the form of precipitation seen most frequently in the world, and densely populated areas with much urban development and vehicle traffic receive a majority of the rainfall. The reason for this is because raindrops are formed around particles that were released into the air by vehicle exhausts. Although many people who grew up watching cartoons believe that raindrops are shaped like a teardrop, small ones are actually round and they become hamburger bun shaped and then more doughnut shaped as they get larger.

• A Network of volunteers measuring the rainfall across the nation

• The ELC discusses acid rain

• Science Daily has news, articles and videos about rain

Hail

Little balls of ice raining down from the sky during a storm are known as hail. Hail is formed when a thunderhead cloud with powerful, upward air movement moves raindrops around inside of it. As a raindrop begins to fall, it is caught by the updraft in the cloud and taken to the upper levels where it freezes. It then becomes too heavy to remain at the top so it falls to the bottom of the cloud where the updraft catches it again and the cycle starts all over again. Hailstones can be little pellets or a few inches in diameter, and many have interesting stripes caused when a new layer of ice was added each time it went to the top of the cloud.

• Hail.org is all about hail and includes news, maps and warnings

• Science Mag talks about hail detection with radar

• WAAESD This link is to the paper on managing and utilizing precipitation observations

Freezing Rain

Freezing Rain differs from hail in that hail is little balls of ice and freezing rain is supercooled water droplets. This occurs when rain falls in an area where the temperature of surfaces on the ground is below freezing. When the droplets hit objects on the ground, everything becomes glazed with ice.

• HPS discusses freezing rain in conjunction with health

• Natural Hazards talks about different aspects of ice storms

Sleet

Sleet is fine rain droplets that have frozen in the cloud. When they hit the ground they do not melt but rather bounce off of the surface they hit. Sleet is almost always spherical, and it only forms when the weather conditions are perfect to produce it. When a cloud forms snow but the snow has to travel through a warm layer of atmosphere to get to the ground, it melts. When it reaches the layer above the ground which is still below freezing, the melted snow refreezes into the perfect little ball known as sleet.

• WW2010 The University of Illinois offers a comprehensive weather site here.

• Weather Channel can answer any question about the weather

Snow

Snow is water in crystal form that falls to the ground and blows around if it is very cold or packs down if there is a cycle of freezing and thawing. It is formed when water particles are frozen and remain in a supersaturated cloud to continue growing. Snow can cause major commuting problems but it is the only type of precipitation that can be used for recreation.

• NSIDC is the National Snow and Ice Data Center

• University of Illinois offers this complete winter storm resource center

• Snow and a variety of its causes and effects.

• Thinkquest offers a variety of activities to teach about snow

• Avalanches are a hazard where snowfall is heavy

Additional Resources

• Teacher's Domain offers video and lesson plans for precipitation

• Storm 2K is a forum dedicated to weather related issues

• NOAA Is the National Oceanic and Atmospheric Administration with in depth weather coverage

• Weather.org offers some insight into how weather is forecasted

• Wunderground is a citizen contributed weather site