Second generation of adjusted precipitation and homogenized temperature datasets for Canada: impact of adjustments and new challenges

The second generation of long-term and historically adjusted precipitation datasets - specifically designed for climate change analyses over Canada - consists of the best quality rainfall and snowfall measurements for over 460 locations across the country. First the station selection and adjustments for all known issues related to daily rain and snow observations were revised. When the observations of two adjacent stations were combined into one, the adjustments were obtained either from overlapping periods or standardized ratio homogeneity tests using surrounding stations. The importance of metadata (installation dates, observing programs, etc.), inconsistency in measuring trace versus small precipitation amounts, and the use of flags in the daily climate archive will be outlined.

The second generation of long term and homogenized temperature dataset contain 336 stations; more then 120 new locations are added to the original datasets. Recently, new procedures have been developed to address the redefinition of the climatological day in 1961 which generated a bias in the monthly and annual means of the daily minimum temperatures. The bias is more pronounced in the eastern regions of the country during the fall and winter. Non-climatic steps due to station relocation, change in instrument exposure, etc. were also detected using newly developed techniques and adjustment procedures.

The impact of adjusting precipitation and temperature datasets will be discussed for different locations in Canada.