Presenting in the form of drizzles and showers, rain is the most frequent form of precipitation. Defined as the falling of water in liquid form, rain results when grouping of water droplets occurs or through the melting of ice crystals. Raindrops vary in size, at times growing in diameter up to four to five millimeters before splitting into smaller droplets. Students can analyze the different sizes of rain through a multi-step activity using a strainer, cake pan, flour, bowl and water. Sift flour into a cake pan and spray it with water using a spray bottle. Place the moist flour in the strainer and shake it to push the excess flour through the holes and into a bowl. Remove the remaining flour balls from the strainer and repeat the same steps until you have strained all of the flour. Students then measure the flour balls using a ruler and record their results. Use a magnifying lens to provide a closer look at the size of each “raindrop.”
Factors such as temperature and atmospheric conditions can affect the level of different forms of precipitation in various regions across the United States. Comparing and predicting precipitation levels can be adapted for rain, snow, sleet, hail, and freezing rain. Using Internet or print resources, students gather information on precipitation levels for specific regions or states. For example, regional categories would include Northeast, Southeast, Midwest, Southwest and Northwest. Students may also look at specific states or areas within states. Students in California might compare precipitation levels for southern, central and northern California regions. Note specific precipitation trends and compare them, such as the difference in snow fall between Maine and Florida. Based on these trends, students make predictions for each region or state being studied and compare professional data to evaluate the results.
The rate of descent for different forms of precipitation is density, size, velocity and size. Best suited for older students, a comparative activity based on the relationship of these factors to descent requires students to consult a table on size and speed factors for precipitation types ranging from fog to cloudbursts. Students answer questions based on this information. For example, students may be asked to provide the difference in speed, recorded as feet per second, of drizzle and a heavy rain shower. The speed of drizzle is 13.5 feet per second while a heavy rain has a speed of 22 feet per second. The answer to the question would be 8.5 feet per second difference between drizzle and heavy rain speed. As students complete the activity, encourage them to notice trends related to precipitation types and variations in intensity, average diameter of precipitation and drops per second, per square feet.
Almost all forms of precipitation begin their descent from the atmosphere as snow. Students can study the composition of snow crystals through activities designed to capture and preserve specimens. Use super glue to achieve this goal in just a few steps. Students place a cardboard collection box outside while it is snowing to collect the snow crystals. Place suitable specimens on chilled glass microscope slides using a paintbrush. Add super glue over the snow crystal and place the slide cover over top. Place slides in a freezer or outside to allow the glue to set without damage to the snow crystal. After the slides have dried, students can study the different formations of the preserved snow crystals.