Precipitation Uncertainty Across Canadian Watersheds

Precipitation is a vital element of the water and energy cycles and a key forcing variable in driving hydrological models. The availability of accurate precipitation measurements are useful in many applications, such as climate change and/or land use changes, natural hazards, agricultural and environmental studies, and hydrological and water resource planning. A number of global and regional gridded climate products incorporating multiple sources of data have recently been developed with the aim of providing better and more reliable measurements for climate and hydrological studies. However, research into the accuracy of these products for various regions has been limited and in many cases non-existent. This research aims to understand and quantify the spatial and temporal variability of the errors associated with several observational, reanalysis, and satellite-based precipitation products over Canada and develops a systematic analysis framework to assess the characteristics of errors associated with the different products, using the best available precipitation-gauge data as a benchmark. We look at, for example, Multi-satellitE Retrievals for Global Precipitation Measurement (GPM) – IMERG, Canadian Precipitation Analysis (CaPA), European Union Water and Global Change (WATCH) Forcing Data, and North American Regional Reanalysis (NARR).

Fifteen terrestrial ecozones of Canada with numerical codes indicating Region from 1 Arctic Cordillera to 15 Hudson Plain. The white dots represent precipitation-gauge stations from the Canadian adjusted and homogenized precipitation datasets. The black dots are major cities in Canada.

Example evaluation of different precipitation products. The bar charts show the annual accuracy (PBias) (first row) and magnitude of the errors (RMSE) (second row) of each precipitation dataset for the period of 1979 to 2012 (left panel) and 2002 to 2012 (right panel) in different ecozones. The white bar shows the scale of the bars with number beside it indicating the value of the bar.

Spatial structure of 8-month (April – Nov 2015) mean daily precipitation (mm/day) for IMERG (Multi-satellitE Retrievals for Global Precipitation Measurement (GPM)), CaPA (Canadian Precipitation Analysis) and EC-S (Environment Canada Stations) over the study area.