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Droughts in Canada: An Overview

Droughts in Canada: An Overview. Barrie Bonsal Environment Canada Saskatoon, SK, Canada. Outline. Background Past drought occurrence Large-scale atmospheric causes Current monitoring & prediction Future droughts Research requirements. Droughts in Canada. Drought Impacts. Agriculture.

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Droughts in Canada: An Overview

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  1. Droughts in Canada: An Overview Barrie Bonsal Environment Canada Saskatoon, SK, Canada

  2. Outline • Background • Past drought occurrence • Large-scale atmospheric causes • Current monitoring & prediction • Future droughts • Research requirements

  3. Droughts in Canada

  4. Drought Impacts Agriculture

  5. Drought Impacts Water Resources

  6. Drought Impacts

  7. Drought Research in Canada • Fragmented – spatially and temporally • Based on severe drought occurrence (e.g., 1999-2005) • Majority for Canadian Prairies • Historical comparisons difficult due to short and variable climate station records • Canadian droughts unique – both cold and warm season phenomenon

  8. Drought Occurrence Annual PDSI

  9. Summer (JJA) Drought Change 1925 - 1990 Mean Summer Temperature Summer Precipitation

  10. Drought Occurrence – Southern Prairies (1915-2002) SPI PDSI

  11. R e c o n s t r u c t e d R e g i o n a l J u l y 2 0 -2 1700 1800 1900 2000 2 0 -2 1600 1700 1800 1900 2000 Palmer Drought Severity Index (Sauchyn et al. 2001) SouthwesternSaskatchewan frequentdrought decadaldrought North-centralMontana

  12. Warm, Dry Winters Over Canada 500mb Flow 500mb Anomalies • El Niño, +PNA, +PDO, Deep Aleutian Low

  13. Hot, Dry Summers Over Western Canada 500mb Flow 500mb Anomalies • +PNA, Meridional Flow, +PDO?

  14. Coupled SVD pattern between Global Winter SSTs and Summer PDSI (1940-2002) Winter Interannual and interdecadal ENSO-like pattern is associated with dry summer conditions in western and central Canada. Squared Covariance Fraction = 28%, Correlation between time expansion = 0.5 (Shabbar and Skinner, 2004)

  15. Circulation Differences Sep-Aug 1988 Sep-Aug 1961 Sep-Aug 2001 Sep-Aug 2002

  16. Drought Monitoring • Real-time information on drought conditions over agricultural regions of Canada • National map illustrating current and historical temperature, precipitation, and drought index maps (SPI, PDSI) at various time steps • Reports of lake and reservoir levels, stream flows, snowpack accumulations, water-supply volume forecasts, dugout water levels, pasture conditions (for the Prairies) • The North American Drought Monitor

  17. Drought Monitoring • Satellite and radar measurements can provide solutions to spatial-scale problems associated with drought monitoring • MSC currently uses Special Sensor Microwave Imager (SSMI) to produce SWE maps for the Prairies that are made available to water resource agencies • Time series extends from 1978 through the present, using the brightness temperature standardization of Derksen and Walker (2003).

  18. Drought Prediction • Drought prediction involves anticipating climatic anomalies that produce unusually hot, dry conditions for extended periods • EC currently produces monthly and seasonal forecasts for T & P for lead times of 3, 6, 9, and 12 months • 0 to 3 month forecasts are made using NWP models • Longer lead times use a statistical (CCA) model using SST anomalies over the previous 12 months • Skill higher for cold season and for temperature

  19. Central North America Today 60 40 ~2070 Return Period (years) 20 0 10 15 20 25 30 Length of Dry Spell (days) The frequency and severity of droughts are likely to increase in southern Canada

  20. Future Droughts SPI PDSI

  21. Research Needs 1. A better understanding of the physical causes of drought initiation, persistence, and termination at a variety of spatial and temporal scales • Large-scale atmospheric and oceanic oscillations • Soil moisture anomalies • Moisture sources • Physical causes of multi-year droughts • Drought migration

  22. Research Needs 2. Quantification and assessment of past drought occurrences • Past trends and variability • Drought indices • Paleo-drought studies 3. Better knowledge regarding future drought occurrence • More reliable GCM/RCM output • Improved downscaling methods • Future changes to large-scale circulation patterns

  23. Research Needs 4. Ability to more accurately predict drought onset, intensity, and termination • Improvements in modelling and monitoring of current drought conditions • More reliable short term (seasonal) climate forecast 5. More effective short and long-term adaptation strategies to defend against future droughts

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