This fourth generation homogenized daily (CanHomT dlyV4), and monthly (CanHomT mlyV4) surface air temperature dataset provides daily maximum, minimum and mean temperatures as well as monthly, seasonal, and annual means of these variables, for 651 long-term stations across Canada. The procedures used to produce the dataset and to estimate long-term trends over the 1948-2023 period are detailed in Wan et al. (2025). The fourth generation of CanHomT includes two main improvements over the third generation (Vincent et al., 2020): First, an adjustment for the cold bias in daily minimum temperatures, caused by an inadequate observing window defined by the climatological day since July 1, 1961, is now applied to all stations with both daily and hourly temperature observations, including all automatic stations. Second, missing daily and monthly values, including longer gaps, were filled using the ANUSPLIN surface temperature estimates. Station data records that began later than 1948 were infilled back to 1948 for monthly data, and 1949 for daily data. In addition to these main improvements, the original data were quality controlled using more comprehensive procedures than in previous generations. To form long-term series, most station records were joined with data from nearby stations, and all 651 stations are active as of 2023. An inhomogeneity test procedure, both with and without the use of reference series methods, was applied to detect non-climatic shifts in the monthly series. A quantile-matching procedure was then used to adjust the identified inhomogeneities in the daily and monthly series. This dataset enhances the reliability and the temporal and spatial continuity of observed temperature records in Canada, enabling more precise assessments of long-term climate trends.
References:
Vincent, L. A., M. M. Hartwell, and X. L. Wang, 2020: A third generation of homogenized temperature for trend analysis and monitoring changes in Canada’s climate. Atmosphere-Ocean., 58:3, 173-191, doi:10.1080/07055900.2020.1765728.
Wan, H., A. C., Spassiani & L. A. Vincent, 2025: Canada’s fourth generation of homogenized surface air temperature and its trends for 1948-2023. Atmosphere-Ocean, DOI: 10.1080/07055900.2025.2516796.