Canadian Gridded Homogenized Monthly Temperature (CanGridT mly)

The gridded dataset of homogenized monthly mean values of daily maximum, minimum and mean surface air temperatures, CanGridT, was produced using a kriging-based gridding scheme, i.e., the KGNGA scheme of Abbasnezhadi and Wang (2024), to grid an updated version of the Third Generation of Homogenized Temperature dataset (see details below). More specifically, ordinary kriging was used to grid the 1961-1990 climate normal values and the anomalies, separately; the resulting gridded datasets were used to produce the gridded dataset of monthly mean values of daily maximum, minimum and mean temperatures. Here, daily mean temperature is the average of daily maximum and minimum temperatures. 

As detailed in Vincent et al. (2020), the Third Generation of Homogenized Temperature dataset (available at Climate data: homogenized surface air temperature data - Canada.ca) was prepared for use in climate trend analysis in Canada. Daily observations from nearby sites were often joined to create a long data series. This includes the observations taken at Reference Climate Stations and from some of the NavCan sites which are used to extend past climate observations into recent times. This dataset contains long data series of daily maximum, minimum and mean temperatures for 780 locations across Canada. The data were quality controlled. The daily minimum temperatures from 1961 to recent years were adjusted to diminish the effects of the change in observing time (climatological day definition) in 1961 at principal stations (Vincent et al. 2009). In cases of station joining, parallel daily data, when available, were used to detect and diminish non-climatic shifts (Vincent et al. 2018), as using parallel observations is the most reliable way to do data homogenization. Series of annual and seasonal mean temperatures were tested for homogeneity and homogenized when necessary. Daily temperatures were adjusted using a Quantile-Matching procedure (Wang et al. 2010) to remove non-climatic shifts if needed. 

The Third Generation of Homogenized Temperature dataset has been updated to the end of 2023, in which around 500 out of the 780 stations are active (reporting some data). The gridded version of the updated dataset is this CanGridT mlyV3.1 dataset, which has been used to assess warming in Canada. This dataset differs from the CanGRD data in two aspects: CanGridT contains gridded temperatures on a 10-km EASE grid, while CanGRD contains gridded anomalies of temperatures on a 50-km EASE grid. 


References

Abbasnezhadi, K. and X. L. Wang, 2024: Comparison of gridding methods for precipitation over Canada and assessment of station/data density effects on gridding results. Atmos.-Ocean, 62:4, 320-346, https://doi.org/10.1080/07055900.2024.2394829.

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. https://doi.org/10.1080/07055900.2020.1765728. 

Vincent, L.A., E.J. Milewska, X. L. Wang, and M. M. Hartwell, 2018. Uncertainty in homogenized daily temperatures and derived indices of extremes illustrated using parallel observations in Canada, Intl. J. Climatol., 38:2, 692-707. DOI: 10.1002/JOC.5203. 

Vincent, L.A., E.J. Milewska, R. Hopkinson and L. Malone, 2009: Bias in minimum temperature introduced by a redefinition of the climatological day at the Canadian synoptic stations. Journal of Applied Meteorology and Climatology, 48, 2160-2168. DOI: 10.1175/2009JAMC2191.1. 

Wang, X. L., H. Chen, Y. Wu, Y. Feng, and Q. Pu, 2010: New techniques for detection and adjustment of shifts in daily precipitation data series. J. Appl. Meteor. Climatol., 49, 2416-2436. DOI: 10.1175/2010JAMC2376.1.

Organization: Environment and Climate Change Canada | Environnement et Changement climatique Canada