ANUSPLIN-gridded Adjusted Precipitation (ANUSPLIN-AdjP) datasets for Canada

The suite of gridded precipitation datasets includes the ANUSPLIN-gridded datasets of daily precipitation since 1900 (ANUSPLIN-AdjPdly), pentad average precipitation rates since 1950 (ANUSPLIN-AdjP5d), and monthly total precipitation since 1872 (ANUSPLIN-AdjPmly), on a 0.083333ºx 0.083333º latitude-longitude grid over Canada. For version 1 of these datasets, the daily precipitation data were generated from the ANUSPLIN surfaces fitted to the Adjusted Daily Rainfall and Snowfall (AdjDlyRS) dataset version 2016, which includes 3346 stations of manual observations (Wang et al. 2017; available at https://open.canada.ca/data/en/dataset/d8616c52-a812-44ad-8754-7bcc0d8de305). The monthly and pentad gridded data were generated from the ANUSPLIN surfaces fitted respectively to the monthly and pentad station data that were derived from the corresponding daily station data. When deriving the monthly station data from the daily station data, the monthly total precipitation was set to missing if there was one or more missing daily value in the month (zero tolerance for missing). The same zero tolerance for missing observations was applied in the calculation of the pentad average precipitation rates.

Details of the ANUSPLIN modelling of these three gridded precipitation datasets are provided in MacDonald et al. (2020), along with comparison to the unadjusted ANUSPLIN-gridded daily precipitation dataset (Hutchinson et al. 2009). Note that the unadjusted precipitation data significantly underestimate both the precipitation amount and the regional mean long-term trend therein (MacDonald et al. 2020).

It is important to point out that these ANUSPLIN-AdjP datasets are not homogenized and thus should not be used to assess climate trends/changes before ensuring the temporal homogeneity of the data.

Considering there were no or few stations in the North in the early period, the gridded values in the period before 1930 were set to missing (missing code -999.00) for all gridpoints north of 65ºN and west of 110ºW (including 110ºW) and for all gridpoints north of 55ºN and east of 110ºW. The gridded values in the period of 1930-1949 were also set to missing for all gridpoints north of 70ºN. For the period from 1950 onwards, the grid covers the whole land mass of Canada.

References: (1) MacDonald, H., D.W. McKenney, X.L. Wang, J. Pedlar, P. Papadopol, K. Lawrence, and M.F. Hutchinson, 2021: Spatial models of adjusted precipitation for Canada at varying time scales. J. Appl. Meteor. Climatol., 60, 291-304. doi: 10.1175/JAMC-D-20-0041.1. (2) Wang, X.L., H. Xu, B. Qian, Y. Feng, and E. Mekis, 2017: Adjusted daily rainfall and snowfall data for Canada. Atmos.-Ocean, 55, 155–168, doi:10.1080/07055900.2017.1342163. (3) Hutchinson, M.F.,D.W. McKenney, K. Lawrence, J.H. Pedlar, R. F.Hopkinson, E.Milewska, and P. Papadopol, 2009: Development and testing of Canada-wide interpolated spatial models of daily minimum–maximum temperature and precipitation for 1961–2003. J. Appl. Meteorol. Climatol., 48, 725-741. doi:10.1175/2008JAMC1979.1.