Homogenization of Daily Temperatures over Canada

• Published in: Journal of climate Vol. 15; no. 11; pp. 1322 - 1334
• Main Authors: Vincent, Lucie A., Zhang, X., Bonsal, B. R., Hogg, W. D.
• Format: Journal Article
• Language: English
• Published: Boston, MA American Meteorological Society 01-06-2002
• Subjects: Climate change; Climate change adaptation; Datasets; Earth, ocean, space; Error rates; Exact sciences and technology; External geophysics; High temperature; Homogenization; Inhomogeneity; Meteorology; Seasons; Temperature; Temperature distribution; Time series; Weather analysis and prediction; Canada; North America; America; Homogenization; Minimum temperature; Linear interpolation; Maximum temperature; Atmospheric temperature
• ISSN: 0894-8755; 1520-0442
• DOI: 10.1175/1520-0442(2002)015<1322:HODTOC>2.0.CO;2

A method to homogenize daily maximum and minimum temperatures over Canada is presented. The procedure is based on previously defined monthly adjustments derived from step changes identified in annual Canadian temperature series. Daily temperatures are adjusted by incorporating a linear interpolation scheme that preserves these monthly adjustments. The temperature trends and variations present in the homogenized monthly and annual datasets are therefore preserved. Comparisons between unadjusted and adjusted daily temperatures at collocated sites show that the greatest impact of the adjustments is on the annual mean of the daily maximum and minimum temperatures with little effect on the standard deviation. The frequency and distribution of the extremes are much closer to those provided by the target observations after adjustments. Furthermore, the adjusted daily temperatures produced by this procedure greatly improve the spatial pattern of the observed twentieth century extreme temperature trends across the country.