DATA Series

Using data from the National Climate Data Center (NCDC) track snowfall in your area and assess historic snowfall levels from Winter Olympics host cities.

Objectives

• Explain the water cycle and processes that lead to snowflake formation.
• Recognize the variety of snowflake structures.
• Evaluate local and international snowfall levels.

Introduction
Snow, to those in the snowbelt states, may seem like no day at the beach, but in reality it’s far closer than you may think. In fact, that knee-deep snow that upstate New Yorkers are trudging through was, not so long ago, water that someone else was wading in in the ocean. All of the earth’s water is directly connected through the water cycle.

More than 97% of the world’s water is in the oceans. So how does it become snow in New York? Water near the ocean’s surface evaporates and rises in the air. Wind then carries it toward land. Once it reaches land, the evaporated water is carried even higher into the atmosphere by warm updrafts. As the evaporated water rises, it reaches cooler temperatures causing it to condense on small particles of dust. As more water drops condense, they form a cloud. When the air temperature is low enough and the air is saturated with water, snow crystals form. Water droplets are attracted to the snow crystal adhering to it and forming a snowflake (or raindrop in warmer weather).

After the snow falls, it eventually makes its way back to the ocean by becoming surface water in streams and rivers, or seeping into the ground and returning to the ocean with the groundwater. The return route the water takes determines how long it will take to reach the ocean. Residence time of water in rivers averages about 5 months, but the residence time of deep groundwater can be 10,000 years.

The formation of a snow crystal is influenced by temperature, humidity and air currents. Snow crystals can take a variety of plate-like or column formations. In general, the colder it is the more intricate the snowflake. Most snow crystals are symmetrical due to water’s hydrogen bonds creating an ordered arrangement. These hydrogen bond arrangements take on different forms as well.

Everyone has heard that no two snowflakes are exactly alike, but is that true? Snowflakes are very complicated structures, so it is quite unlikely that there would be two snowflakes that were identical down to the exact same number of water molecules and oxygen isotopes, but it is possible that two snowflakes could look identical.

Now that you know the science behind snow, consider how snow affects our lives. In our daily lives, it may not seem that snow has much of an affect other than the much anticipated school closings, but snow can have a major impact on world events. For instance, what impact is heavy snowfall having on the Eastern European country of Georgia that is currently experiencing a severe energy crisis? Or on a lighter note, what would happen if Turino, Italy had no snow for the winter Olympic games? (That almost happened at the 1960 winter Olympics near Lake Tahoe, until a blizzard at the last minute saved the day.)

Data Activity
The National Oceanic and Atmospheric Administration’s (NOAA’s) National Climate Data Center (NCDC) has an enormous amount of weather data available online. For our data activity, we will look at the NCDC’s Average Snowfall data and track the current month’s snowfall comparing it to the NCDC’s average.

First, print the Average Snowfall data. Then, go to the Unisys Weather Meteograms webpage. Scroll down to the bottom of the page and select the station nearest you. If you are in an area that does not get snow, select a location that does.

Clicking on the Meteogram will give you the weather for your station for the previous 24 hours. The first graph is temperature, and below that are snow depth (SNWDP) and precipitation (PREC) data in inches (click here for detailed information about the data from meteograms). To determine if the precipitation was rain or snow, look at the temperature graph to see if the temperature was above or below 32°F. Record the snow depth and precipitation for the day then continue to check the Meteogram each day throughout the month. At the end of the month, compare the total amount of snowfall you recorded from the Meteogram to the NCDC’s average snowfall. How did this year’s snowfall compare to the average rate?

For an additional snowfall activity, let’s look at historical snowfall for the area around Torina, Italy, site of the 2006 Winter Olympics, to predict whether or not Mother Nature will supply enough snow for the Olympics, or if the snow machines will have to be in high gear. The National Snow and Ice Data Center (NSIDC) has historical snow data for Bardonecchia, Italy (site of alpine skiing and snowboarding events) from 1925-1996. Get these data in Microsoft Excel or PDF format. What is the average snowfall for Bardonecchia for February? How does this compare to Salt Lake City, site of the 2002 Winter Olympics, where the average February snowfall is 9.9 inches? (Don’t forget to convert centimeters to inches.) Did the Olympics have ample snow?

Coming soon!

Coming soon!