Global Snow Cover Changes
This lesson allows students to use online mapping tools to investigate global snow cover changes. Students develop a problem statement about global snow cover and then use mapping tools to investigate their problem or question.
Students will become familiar with the data and tools used to analyze snow cover changes in order to answer questions pertaining to snow data.
Students should have a basic understanding of meteorology and climatology concepts before starting this exploration. Refer to http://climate.rutgers.edu/snowcover/ for more information. See Resources section for a list of terms to know.
Background information: Since the dawn of the satellite era in the 1960's, Northern Hemispheric snow cover has been monitored by NOAA (National Oceanic and Atmospheric Administration). Studying snow cover from satellite imagery has its benefits over ground measurements since there are numerous inherent issues with surface observations related to topography, instrumentation, etc. Initially there were errors in the identification of land and water in the satellite images, which meant that the amount of snow in the northern hemisphere was miscalculated. With the development of software by the Rutgers University Global Snow Lab, these errors were corrected and new maps are generated on a regular basis. The team at the Global Snow Lab has since created an accurate grid cell product which details Northern Hemisphere snow cover data over the last 42 years. The cell resolution of these maps ranges from 16,000 to 42,000 square kilometers, and where a cell is 50% or more snow covered, the entire cell is considered snow covered; whereas if the cell is less than 50% snow covered, it is considered snow free. The North America Blended Charts contain charts that are higher resolution incorporating visible light, microwave remote sensing data, and station data. The "3-way" Pentads (pentad = five day) provides a comparison of the data sources.
Students will access the Global Snow Lab website: http://climate.rutgers.edu/snowcover/index.php and answer the questions on the attached worksheet.
Terms: Satellite Imagery – view of the Earth from above. Satellites vary in their orbits above the Earth's surface, thus providing varying degrees of resolution in their imagery. The imagery used for this application has a resolution of 1.1km x 1.1 km.
Monthly Departure – the colors in the maps demonstrate snow cover changes from the previous time period you are currently viewing (day, month or year). Colors show the percentage of time each cell is considered snow covered in a given month over the period of record 1966-1999.
Monthly Climatology – Colors show the percentage of time each cell is considered snow covered in a given month over the period of record 1966-1999.
Anomaly – When analyzing the data, there may be differences from the mean values from one time period to another. These differences (departures) are called anomalies.
Pentad – Refers to a 5 day interval and the charts are five-day snow charts were generated by examining the snow depth in each 1° x 1° cell for each day. A pentad cell was considered snow covered if three or more days in the pentad had a snow depth of more than 1.27 cm (one half inch).
89x89 grid cell – The maps are digitized by overlaying a grid on the polar stereographic maps. The cells number 89 by 89 with the corners of the square touching the equator.
N.H. – Northern Hemisphere
The completed worksheet questions can be used for assessment.
Missy Holzer, mholzer [at] monmouth [dot] com