Time series of freeze-free season anomalies

Developed for the 2014 NCA. New reports and images will be added as they become available.

Wed, 01/09/2013 - 00:09 -- mbp

General Information

Freeze-free season anomalies shown as number of days per year. Length of the freeze-free season is defined as the period between the last occurrence of 32F in the spring and first occurrence of 32F in the fall. The dashed line is a linear fit. Based on daily COOP data from long-term stations in the National Climatic Data Centers Global Historical Climate Network data set. Only stations with less than 10% missing daily temperature data for the period 1895-2010 are used in this analysis. Freeze events are first identified for each individual station. Then, event dates for each year are averaged for 1x1 degree grid boxes. Finally, a regional average is determined by averaging the values for the individual grid boxes. There has been a statistically significant increase in freeze-free season length over the entire time period.
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Source Information

Image Source: 
Laura Stevens