Sandburg Center for Sky Awareness
A Fairfax County Public Schools Planetarium
- Snowflakes are six-sided! Dendritic snowflakes (more ornate
snowflakes) form when the air temperature is between 10°F and 3°F
(-12°C to -16°C) [refer to air temperature versus
ice crystal shape, courtesy USA TODAY Weather, or the Make
Snow Java applet (reset by clicking below cloud)]. So, where is it
cold enough for dendritic snowflakes to form? High in the atmosphere
(usually air temperature decreases with increasing altitude). Access the
Text Data for Selected Cities in the US. [Note: IAD = Dulles, VA.
Upper air temperatures are reported in degrees Celsius; convert Celsius
temperatures to Fahrenheit using the Weather
Calculator, courtesy Sterling, VA NWS Forecast Office).]
- Did you know that most precipitation (including rain) starts as snow?
See how the three-dimensional structure of the atmosphere determines the
type of precipitation that reaches the Earth's surface: How winter storms bring
rain, ice and snow, courtesy USA TODAY Weather. Experiment with
Type Java applet.
- Estimate the fall speed of snowflakes. Watch snowflakes as they fall
past an object of known height, e.g., a building. Speed = Distance/Time.
If a building is made of 2.75" thick bricks with 1/2" of mortar between
rows of bricks, then every 10 rows of bricks equals approximately three
feet (32.5" to be exact). On average, snowflakes fall at a speed of
approximately 3 feet per second, or 10 rows of bricks every second. [Idea
courtesy Marcia Politovich, Atmospheric Scientist, National Center for
Atmospheric Research, Boulder, CO.] Activity Extension: Calculate how long it takes snowflakes to fall to
the ground from cloud base.
- Capture snowflakes on chilled glass microscope slides; preserve
using artist's spray fixative (e.g., Krylon® "Crystal Clear"). Use a
low-power binocular microscope to examine preserved
specimens. Unless the air at the Earth's surface is very cold and dry,
most snowflakes will be partially melted.
- Make a rain/snow gauge. Cut off the top of a clear plastic two-liter
soda bottle. Use a permanent marker to mark the outside of the bottle in
centimeters or inches (measuring from bottom-to-top). Put the bottle
outside in a place where it can collect falling snow. Measure and record
the depth of snow in the container. Let the snow melt, then measure and
record the depth of water in the container. Determine the snow/water
ratio. [A typical ratio is 10:1, i.e., 10 inches of snow is equivalent to
one (1) inch of liquid precipitation. In theory, the snow/water ratio
should be higher when the air temperature is colder, and lower when the
temperature is closer to the freezing point.] Activity Extension:
Fill a plastic 12- or 20-fl. oz. soda bottle with water to the
point of overflow; tightly cap bottle and place outside (if air
temperature is below freezing) or in a refrigerator freezer. Observe that
the bottle bursts when the water freezes. Relate this observation to
snow/water ratio. Caution: DO NOT use a glass bottle!
- Research the chemistry & physics of ice crystals. A good starting
point: USA TODAY Weather's Resources: Winter
weather. See also, SnowCrystals.com,
created by Kenneth G. Libbrecht, Professor of Physics at Caltech. Dr.
Libbrecht is the co-author of a wonderful new book entitled, The
Snowflake - Winter's Secret Beauty. (Middle- or High School)
- Explore the mysterious beauty of ice crystal atmospheric optical
phenomena by visiting the Atmospheric
Halos Web site; look at the real sky for sundogs (or parhelia),
- Study the science of winter weather:
- Primary Grades: Explore snowflake symmetry. Print & photocopy a
variety of snowflake
photographs; challenge students to fold snowflakes along lines of
symmetry. (Grade Level 3, FCPS Program of Studies)
- The geometry of snowflakes--snowflakes are six-sided hexagons: (Grade
Level 5, FCPS POS)
- On an 8 1/2" x 11" sheet of white paper, use a drawing compass (such
as the Safe-T
Compass) to draw a circle 6" in diameter that is perfectly centered
on the page (to find the exact center of the page, lightly sketch an "X"
- From the center point of the circle, use a protractor to divide the
circle into six equal slices (of pie); draw six triangles (360/6 = 60
- Fold the circle in half, forming a semi-circle with three 60-degree
angles (180/3 = 60 degrees); fold paper into thirds (along lines between
pie slices). Now students should understand how you fold paper to make six-sided
- Probability - Discuss probability (for background information, visit
Access a map of the United States showing the Probability of
a White Christmas (1" of snow or more) to determine the probability of
a white Christmas for your location. The NCDC map shows that the
chance of a white Christmas in the nation's capital is slightly more than
10%! Play song, White Christmas by Irving
Berlin (Bing Crosby's rendition is a classic!).
- Word problems - Take the chill off a cold morning with these
challenging warm-up problems:
- If a typical snowflake falls at a rate of
descent of less than 5 feet per second, then how long would it take for
the snowflake to reach the ground from a cloud base of 10,000 feet (the
approximate height of a typical nimbostratus cloud base)? Answer:
10,000 feet / 5 feet per second = 2,000 seconds or approximately 33
- On average, Washington, D.C. receives 39.51" of precipitation
annually, including 18.3" of snow. If we assume that 1 inch of liquid
precipitation equals approximately 10 inches of snow, then what percentage
of the total annual precipitation in Washington, D.C. falls as snow?
Answer: 39.51" / 1.83" (water equivalent of average annual snowfall) x
100 = approximately 5%
- Read The Snowflake Man, an
article by Duncan C. Blanchard (Bob Ryan's 1999 Almanac and Guide for
the Weatherwise). Answer the following mini-scavenger hunt questions:
- Who was "the Snowflake Man?"
- Snow crystals are symmetrical with how many sides?
- What is the well-known expression about snowflakes coined by the
Snowflake Man (after photographing thousands of snowflakes)?
- Read the 1999 Caldecott Award winning book, Snowflake
Bentley, by Jacqueline Briggs Martin, illustrated by Mary Azarian.
(Ages 4-8. Recommended as a read-aloud for Grades 1-3; read-alone Grades
- Read Caldecott Medal winner The BIG
SNOW, by Berta and Elmer Hader (recommended as a read-aloud for
Grade 2) or The
Mitten, adapted and illustrated by Jan Brett (K-3).
- Write "snow" diamante poems. Diamantes are diamond-shaped poems with
seven (7) lines. Incorporates oral, analytical thinking, reading, and
writing skills. Great exercise for parts of speech. Mount student
poems on diamond-shaped colored paper; arrange six diamante poems into a
giant snowflake for bulletin board display. For background information and
sample diamantes, visit the following Web sites:
- Write (and illustrate) "snow" poems or short stories.
- Read Snow
Crystals, by Wilson Bentley & W. J. Humphreys, a collection of
2,453 of Bentley's best snowflake photographs (the larger
cover image displays numerous snowflakes to duplicate).
ARTS & CRAFTS
- How to fold & cut snowflakes using an 8
1/2" x 11" sheet of paper and scissors [directions courtesy Joanne Goodwin, School-Based
Technology Specialist (SBTS), Churchill Road ES, FCPS].
- How to fold & cut snowflakes using a square sheet of paper:
- Maddy & Maverick's Paper Snowflakes Web
& Jerry's Paper SnowFlakes - Simple fold-&-cut paper snowflake
templates. Use SnowFlake
#3 only. [Editorial Commentary: While fun to make, the Ben &
Jerry's "#1- & #2 Cone Flake" templates are four-fold designs that produce
eight-sided snowflakes. Don't teach Bad
Science--snowflakes are six-sided!]
- Transform your classroom into a winter wonderland! Use thread (or fishing line) to hang
paper snowflakes from the ceiling; use transparent tape to hang them on
- Illustrate snow poems or short stories, e.g., wintery skyscapes or
snowy landscapes such as the Impressionists
in Winter: Effets de Neige virtual exhibit.
- Take snow photographs (digital, Polaroid, or conventional film).
Single-use cameras are inexpensive (typically priced around $10 each) and
can be loaned to students for use when school is closed due to inclement
weather. Panorama (wide-angle) single-use cameras are great fun! Simple
writing exercise: write captions that clearly and concisely describe the
photographs. Use a sequence of photographs to tell a story (like a movie
storyboard). For tips from the pros, see two resources from Kodak: Winter Photo
Tips; and Winter
Photography - Better Pictures in the Snow.
HEALTH & PHYSICAL EDUCATION
Use a computer to play "mood" music while students work. Click
[Play] to spawn an external audio control panel:
- [Play] Let It
Frosty the Snowman
FUN & GAMES
Last update: 24 DEC 2003. Added several new hyperlinks;
all old hyperlinks verified.
Copyright © 1999-2011 by Walter Sanford. All rights
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