Trends of Drought in the Canadian Prairies Kit Szeto 1, Eva Mekis 1, Seung-Ki Min 1, Walter Skinner 1, Lei Wen 2, Charles Lin 1 and Stefan De Young 1 1 Environment Canada 2 McGill University
Motivations Results from recent global drought trend studies (e.g. Dai et al. 2004; Burke et al. 2006) suggest that the Canadian Prairies is one of the regions that has exhibited a significant increasing drought trend The Canadian Prairies is a major agricultural region and severe droughts in the area are amongst the most costly natural disasters for Canada Carrying out a comprehensive regional study of Prairie drought trends is warranted
Motivations.. Cont. Source: Dai et al. 2004
Methodology and Datasets Use multiple regional drought indices datasets to assess linear trends, and changes in other attributes of, Prairie droughts Associate identified drought trends with temporal behavior of regional water and energy budgets Datasets: PDSI and SPI from adjusted station data; soil moisture data from VIC model simulations forced with station data; ERA40 for water and energy budgets Focused on the 1950-2005 period and over the Canadian Prairies
Simulated Soil Moisture Data with the VIC Model 1. Reconstructing a 56-yr prairie s drought history using the Variable Infiltration Capacity (VIC) land surface macroscale hydrology model driven by observed daily maximum and minimum air temperatures and precipitation from 1 January, 1950 to 31 December, 2005 2 soil layers: 1-20 cm; 20-100 cm
Annual Prairie Drought Trend Maps 1950-2005 ( /10y) ( /10y) ( /1y) ( /1y) (mm/d/y) Dots denote data locations and Pink denotes trends that are significant at 95% level
Growing Season (Apr-Sep) Prairie Drought Trend Maps 1950-2005 ( /10y) ( /10y) ( /1y) ( /1y) (mm/d/y) Dots denote data locations and Pink denotes trends that are significant at 95% level
Growing Season (Apr-Sep) Prairie Drought Trend Maps 1950-1999 ( /10y) ( /10y) ( /1y) ( /1y) (mm/d/y) Dots denote data locations and Pink denotes trends that are significant at 95% level
Annual timeseries of drought indices averaged over Apr-Sep and over the western Prairies Correlations
Annual timeseries of CANGRID Ts averaged over Apr-Sep and over the western Prairies
Annual timeseries of ERA40 ET averaged over Apr-Sep and over the western Prairies
Seasonal Mean Drying Trends 1949-98 98 Observations (GHCN) IPCC AR4 Model (20C, 70 runs) Inter-model Agreement > 60% MAM JJA Observed and simulated patterns are not consistent Large inter-model uncertainty
Summary Quite consistent drying patterns exhibited in all indices with significant drying over the western Prairies on the annual time scale Similar spatial pattern for growing season drying trends but trends are only significant in PDSI Growing season drying trends in PDSI over the western Prairies are reflected in both the increased frequency and severity of droughts over the region but such attributes are not evident in other indices Moderate warming trends were observed during the growing season over the western Prairies but corresponding increases in ERA40 evapotranspiration is less evident -> cautions for interpretation of the PDSI trends IPCC AR4 GCM results are not good enough for regional drought trend detections
Magnitude of Correction for Precipitation Precipitation Rain Snow 1.6 1.55 1.5 1.45 1.4 1.35 1.3 1.25 1.2 1.15 1.1 1.05 1 0.95 0.9 0.85 0.8 Ratio = Corrected / Not corrected 1950 2008 period Further information: Éva Mekis, CRD, Environment Canada