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<FONT SIZE=4><P ALIGN="CENTER"><A NAME="QuickMark"></A>A WINTER DAY</P>
</FONT><P>PURPOSE: To measure winter weather conditions and describe snow in the air and on the ground.</P>
<P>MATERIALS: Field -- suitable winter clothing, thermometers, wind gauge, windchill equivalent temperature chart, snow layer chart, snow shovel, snow core sampler, hand lenses, snow scoop, four 1000 ml plastic beakers or plastic bags (30 x 30 cm), 3 watch glasses, narrow range pH paper, water hardness indicator paper, meter stick, snowflake kit, clipboard or other firm writing surface. Lab -- platform balance, microscope. Optional: prepared snowflake slides </P>
<P>INTRODUCTION: One of the most outstanding characteristics of the winter environment is the presence of snow. Snow is ecologically important because its characteristics often set the limits for the survival of living things.</P>
<P>In this activity, you will observe and record the abiotic (nonliving) factors for a winter day. You will take measurements of the weather, investigate the physical and chemical properties of snow, and speculate on the winter activities of animals.</P>
<P>PROCEDURE: Divide the tasks below among groups of students. One student should act as class recorder to make sure that all the needed data is collected and shared among all students. Select a study site near school where the snowpack is undisturbed. </P>
<P>A. <U>Weather Conditions</U>: Using the weather instruments, record the weather factors listed on the data sheet. Use the chart to determine the wind chill equivalent temperature.</P>
<P>B. <U>Snowpack Structure</U>: Dig into the snow with the shovel to expose a vertical face.</P><DIR>
<P>(1) Measure and record the depth of the snow on the ground in centimeters.</P>
<P>(2) Notice the layered structure of the snowpack. Identify, count, and record the number of distinct layers in the snowpack. Note any crust or ice layers. Measure the temperature of the top, middle, and bottom layers by inserting the thermometers horizontally into the snow, and allowing them to remain there for at least one minute.</P>
<P>(3) Insert the snow core sampler vertically into the snowpack, then remove with a twisting motion. Examine the crystalline structure of the sample with the aid of a hand lens. Using descriptive or comparative terms record any observable differences in the texture or appearance of the snow in the top, middle, and bottom layers.</P></DIR>
<P>C. <U>Snow Density:</U> Dig into the snow with the shovel to expose a vertical face. To calculate snow density, you must determine the weight of a known volume of snow as follows: </P><DIR>
<P>(1) Collect a snow sample from the top, middle, and bottom layers using the snow scoop. Insert the snow scoop horizontally into each layer. Use your hands or the shovel to remove and trim the scoop full of snow. Each sample should be the same size. Transfer the samples to the labeled plastic beakers or bags. </P>
<P>(2) Collect a fourth snow sample, but this time compact the snow into the snow scoop as tightly as possible. </P>
<P>(3) When you return to the lab, weigh each sample. Calculate snow density in g/cm<SUP>3</SUP>. For example, if 300 cm<SUP>3</SUP> (300 ml) of snow weighs 100 g, the snow density is 0.33 g/cm3. Record your results.</P></DIR>
<P>D. <U>Snow pH</U>. Using 3 separate watch glasses, pick up a small amount of snow from the top, middle and bottom snow layers. Warm the bottom of each watch glass with your hand to speed melting, and then test the melt water for pH and water hardness using the indicator paper strips. Record the results.</P>
<P>E. <U>Animal Signs</U>: Look for any evidence of animal activity, such as tracks in the snow, scats, air shafts from the bottom snow layer, and so on. Be sure to look in the depressions around trees, and close to the building.</P>
<P>F. <U>Snowflakes</U>: If it is snowing, you may want to try to preserve snowflakes. Follow the directions that are found in the snowflake kit. </P>
<P>CLASS DATA:</P>
<P>WEATHER FACTORS: Cloud cover:______% Air temperature:_____<SUP>o</SUP>F _____<SUP>o</SUP>C</P>
<P>Wind speed:_____mi/hr Wind chill temperature:_____<SUP>o</SUP>F _____<SUP>o</SUP>C</P>
<P>SNOW CHARACTERISTICS: Depth:_____cm</P>
<P>Number of distinct layers:_____ Number of crust or ice layers:_____</P>
<TABLE BORDER CELLSPACING=1 CELLPADDING=7 WIDTH=571>
<TR><TD WIDTH="17%" VALIGN="TOP">
<P> </TD>
<TD WIDTH="28%" VALIGN="TOP">
<P ALIGN="CENTER">Top Layer</TD>
<TD WIDTH="27%" VALIGN="TOP">
<P ALIGN="CENTER">Middle Layer</TD>
<TD WIDTH="27%" VALIGN="TOP">
<P ALIGN="CENTER">Bottom Layer</TD>
</TR>
<TR><TD WIDTH="17%" VALIGN="TOP">
<P>Temperature</TD>
<TD WIDTH="28%" VALIGN="TOP">
<P> </TD>
<TD WIDTH="27%" VALIGN="TOP">
<P> </TD>
<TD WIDTH="27%" VALIGN="TOP">
<P> </TD>
</TR>
<TR><TD WIDTH="17%" VALIGN="TOP">
<P>Texture</TD>
<TD WIDTH="28%" VALIGN="TOP">
<P> </TD>
<TD WIDTH="27%" VALIGN="TOP">
<P> </TD>
<TD WIDTH="27%" VALIGN="TOP">
<P> </TD>
</TR>
<TR><TD WIDTH="17%" VALIGN="TOP">
<P>pH</TD>
<TD WIDTH="28%" VALIGN="TOP">
<P> </TD>
<TD WIDTH="27%" VALIGN="TOP">
<P> </TD>
<TD WIDTH="27%" VALIGN="TOP">
<P> </TD>
</TR>
<TR><TD WIDTH="17%" VALIGN="TOP">
<P>Hardness</TD>
<TD WIDTH="28%" VALIGN="TOP">
<P> </TD>
<TD WIDTH="27%" VALIGN="TOP">
<P> </TD>
<TD WIDTH="27%" VALIGN="TOP">
<P> </TD>
</TR>
<TR><TD WIDTH="17%" VALIGN="TOP">
<P>Density</TD>
<TD WIDTH="28%" VALIGN="TOP">
<P> </TD>
<TD WIDTH="27%" VALIGN="TOP">
<P> </TD>
<TD WIDTH="27%" VALIGN="TOP">
<P> </TD>
</TR>
</TABLE>
<P>Density of compacted snow: ______g/cm<SUP>3</P>
</SUP><P>ANIMAL OBSERVATIONS:_____________________________________________________</P>
<P>_________________________________________________________________________</P>
<P>_________________________________________________________________________</P>
<P>CONCLUSIONS:</P>
<P>1. How does the wind chill equivalent temperature compare to the air temperature? How does the air temperature compare to the temperature of the bottom snow layer?</P>
<P>2. What does the number of snow and ice layers tell you about the past weather?</P>
<P>3. What change occurs in the pH of the snow with depth?</P>
<P>4. How does the density of snow compare to the density of water? How does the density of snow change with depth? What does compaction of snow do to its density?</P>
<P>5. What is the general shape of a snowflake?</P>
<P>DISCUSSION:</P>
<P>6. Explain why there is a difference between the air temperature and the wind chill equivalent temperature.</P>
<P>7. Considering the wind chill equivalent temperature, what precautions should you take to protect yourself from the cold and wind? What can small mammals do for protection? </P>
<P>8. Explain why there is a difference between the air temperature and the temperature below the snow.</P>
<P>9. Why are there differences in the crystal structure of the snow layers with depth?</P>
<P>10. How do you account for the pH of melted snow?</P>
<P>11. What characteristics of the bottom layer provide a favorable environment for such small mammals as mice or voles? How would compaction of the snow, perhaps by snowmobiles or skis, change those characteristics? </P>
<P>12. Why can't you pack snow to make it as dense as water?</P>
<P>13. Animals that remain in your region over winter must have special adaptations for survival. Name one animal that is active in winter and describe its survival adaptations.</P>
<P> </P>
<FONT SIZE=4><P ALIGN="CENTER"><A NAME="QuickMark"></A>SNOWFLAKE KIT</P>
</FONT><P>MATERIALS: Clear plastic in spray can (Krylon #1303 or equivalent art supply product) OR formvar solution (1% polyvinyl formal in ethylene dichloride) in dropper bottle, glass microscope slides, dissection pin or toothpick, storage box for completed slides. Optional: swatch of velvet cloth, wooden spring-type clothespin. </P>
<P>PROCEDURE:</P>
<P>A. Keep slides and snowflake preservative below freezing while collecting snowflakes. Always hold slides by the edges with a clothespin or with gloved hand to prevent transfer of heat and moisture from your hand.</P>
<P>B. <U>To prepare slides using formvar solution</U>: Spread several drops of cold formvar solution on a cold slide with the eyedropper.</P>
<P> <U>To prepare slides with clear plastic spray</U>: Spray cold slide with cold plastic. Let excess plastic drain off one corner of the slide.</P>
<P>C. Collect <U>random</U> falling snow crystals as follows: Put snowflake preservative on a slide. Hold the slide out in the falling snow until several crystals fall into the solution.</P>
<P>D. Collect <U>selected</U> falling snow crystals as follows: Put snowflake preservative on a slide and on a cold pin or toothpick. Let snow fall on the sleeve of your jacket or the velvet cloth. Transfer several snow crystals with the pin or toothpick to the preservative.</P>
<P>E. Store the completed slides in a cold sheltered place for several hours until the snowflake preservative hardens.</P>
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<P> </P>
<FONT SIZE=4><P ALIGN="CENTER">SNOW LAYER CHART</P>
</FONT><U><P>Frost</U>: A thin layer of crystals which form on top of the snowpack by sublimation of water vapor from the air.</P>
<U><P>Powder snow</U>: Cloud-formed crystals or parts of broken crystals. Layer is light and fluffy and makes terrible snowballs.</P>
<U><P>Wet snow</U>: Snow with high water content, ranging from good snowball snow to slush.</P>
<U><P>Ice Pellets</U>: Sleet or hail.</P>
<U><P>Wind-blown snow (Upsik)</U>: Small snow grains, rounded by tumbling in the wind. An upsik layer usually has been packed hard by the wind.</P>
<U><P>Granular Snow (Corn Snow)</U>: Old snow in which the original crystal structure has broken down by moving water vapor, leaving rounded grains. </P>
<U><P>Crust</U>: Snow grains fused together at various spots by liquid water moving down into the snowpack and refreezing.</P>
<U><P>Ice</U>: Ice layers are formed by freezing rain or snow melting and refreezing at the surface of the snowpack. Ice or crust layers can be buried by subsequent snow storms.</P>
<U><P>Depth hoar (Pukak, Sugar Snow)</U>: Large crystals with much air space between them. This layer is formed near the ground as water vapor moves from cold snow to colder snow in the snowpack.</P>
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