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Introduction
Soil Temperature
Alaska
Russia
Snow Cover
Snow Off Day
Sea Ice Index
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Derivation
Interpretation
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Snow Cover: Snow
Off Day
Snow Off Day (SOD) gives the day of the year (to within about five to ten days) when snow last covers a location. The data are derived from satellite passive microwave data. See the documentation for more information.
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Average SOD The mean SOD value obtained over the period 1979 - 2000. From the Pathfinder data set.
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Current SOD Last day of snow for the most recent season.
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SOD Anomalies (Relative to 1979-2000 Mean)
SOD Anomaly, First Five Years Passive Microwave Data Minus Mean
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SOD Anomaly, Last Five Years Passive Microwave Data Minus Mean
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Notes: The images show that while SOD has, on average, been coming earlier (note that the image on the right has more blue than orange grid cells), there is a considerable amount of regional variability. The North Slope of Alaska, for example, is less blue than is the Russian coast.
Time Series of Average Regional Values for SOD
Notes: Time series of SOD values (left) and anomalies from the 1979-2000 mean (right) for 250 square km areas of Russia, Canada, and Alaska show a general trend toward earlier snow melt, but with large temporal variability. When linear regression is used to find the trends, all three areas have a negative trend in SOD. However the trend is only significant (at a 95% confidence level) for the Canadian site, where it is minus 3.7 days per decade. (For a quick overview of linear regression see Linear Regression for Trend Analysis: Assumptions and Limitations in the Sea Ice Index indicator documentation.)
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