Glossary


Anomaly:   The difference of a value over a specified period from the long-term average value (1949-2005) over the same period.

Average Maximum Temperature: The average of all daily maximum temperatures over a given time period.

Average Mean Temperature: The mean value of the average maximum temperature and the average minimum temperature over a given time period.

Average Minimum Temperature: The average of all daily minimum temperatures over a given time period.

Calendar Year (to date): The interval between January and December (or to present month), inclusive.

COOP station:    Cooperative Observer Network (COOP), managed by the National Weather Service, consist of up to 12,000 weather stations across the United States that report daily measurements of  precipitation and/or temperature.   

Inhomogeneities:  Variations in data that are not attributed to climate variations.  Non-climatic influences on the dataset can include abrupt changes due to changes in instrumentation or station location, as well as gradual changes due to growth of nearby vegetation or urban centers. 

Linear Trend: A simple method that fits a line (linear trend) to observations of a given variable over some time period. Beside each linear trend given on this set of pages is a 95% confidence interval that provides a measure as to how likely a trend is significant. For example, a trend of +2 F/100 years with an uncertainty interval of + or - 1 F/100 years says that with 95% confidence there is a positive linear trend, with a range between +1 and +3 F/100 years. On the other hand, a linear trend of + 2 F/100 years with an uncertainty interval of +/- 5 F/100 years does not provide conclusive evidence of a linear trend, as the range is between -3 to + 7 F/100 years. Confidence Intervals are calculated according to Santer et al 2000.

PRISM:   A model that incorporates point measurements and topographic database to create a high resolution gridded climate database.  More information on PRISM is available from Oregon Climate Service.

Percentile Ranking: The ranking of a variable (e.g., temperature) over a given time period versus comparable time periods over all years of record, normalized to a 0 (coldest)  to 100 (warmest) scale.

Precipitation: The accumulation of water (in liquid form) that is deposited to the surface over a given time period.

Water Year (to date): The interval between October and September (or to present month).  For example the water year 2007 refers to the interval between October 2006 and September 2007.



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