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Philippe Gachon & Vicky Slonosky CCIS - OURANOS

Key atmospheric and oceanic factors responsible for climate variability and extreme events in Canada. Philippe Gachon & Vicky Slonosky CCIS - OURANOS. National Scenarios workshop – Victoria, 16-17 Oct. 2003. Key factors for climate variability & extremes.

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Philippe Gachon & Vicky Slonosky CCIS - OURANOS

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  1. Key atmospheric and oceanic factors responsible for climate variability and extreme events in Canada Philippe Gachon & Vicky Slonosky CCIS - OURANOS National Scenarios workshop – Victoria, 16-17 Oct. 2003

  2. Key factors for climate variability & extremes • Geographic & climatic context of Canada • Large scale influences :oceanic & atmospheric (ENSO, NAO, PDO), circulation variability • Regional scale influences : orographic, oceanic & ice sheets • Temporal & spatial climate variability & extremes across Canada • Conclusion : tools & scenarios National Scenarios workshop – Victoria, 16-17 Oct. 2003

  3. 2.17 × 106 km2 COOLEST REGION in ARCTIC BASIN (Overland et al., 1997) 1.22 × 106 km2 Beginning and end of Quaternary Glaciation (COHMAP, 1988) • Land surface • 9.97 × 106 km2 More than 50% of equivalent land area is covered by sea ice (North, Northeast, East) 6-8 months per year Majority of the country with Tann< 0°C

  4. Large scale influences (from Pacific Ocean) : El-Niño Temperature departure from normal (in percent above average, extreme cold or warm) See http://www.msc-smc.ec.gc.ca/education/elnino/canadian/…

  5. Regional vs Hemispheric Circulation Indicators: Canada /Greenland and NAO, January NAO 1950 - 1998 period (Slonosky & Yiou, 2002) Canada/Greenland(Halifax+Sydney) - (Godthaab+ Jacobshavan) National Scenarios workshop – Victoria, 16-17 Oct. 2003

  6. NAO variability & effects during time, January

  7. Surface cyclones (11 month running mean) from NCEP reanalyses NH Changes in surface cyclone frequency 76-99 minus 53-75After Sinclair (2003)

  8. System density for strong MSL cyclones, 53-99(most intense5%) Strong cyclones – surface (Sinclair, 2003) NH

  9. Changes in intensification rate (MSL cyclones, 76-99 minus 53-75) (Sinclair, 2003) Changes in strong MSL cyclones76-99 minus 53-75

  10. Regional scale influences Ex. of Hudson Bay in early winter Sensitivity to sea ice cover in December Differences in 1000 hPa temperature Free-Ice Gachon (1999) CRCM - 30 km National Scenarios workshop – Victoria, 16-17 Oct. 2003

  11. Climate variability & extremes Slonosky & Graham, submit. J. Clim., 2003 Trends in atmospheric circulation indices (century scale) National Scenarios workshop – Victoria, 16-17 Oct. 2003

  12. Natural variability: mid-18th century vs 20thQuébec City (Slonosky, 2003) Winters milder than most of 20th century, summers warmer. Springs and autumns cooler => milder but longer winter season

  13. Climate Trends and Variability1950-1998 • Maximum and minimum temperatures have increased at similar rate • Warming in the south and west, and cooling in the northeast (winter & spring) Trends in Winter Mean Temp (°C / 49 years) Trends in Spring Mean Temp (°C / 49 years) Trends in Summer Mean Temp (°C / 49 years) Trends in Fall Mean Temp (°C / 49 years) X. Zhang, L. Vincent, B. Hogg and A. Niitsoo, Atmosphere-Ocean, 2000 National Scenarios workshop – Victoria, 16-17 Oct. 2003

  14. Location & type of Extremes in Canada droughts, heat spells large tides, storms & snow events Saguenay (1996), 26 millions m3 of water and 9 millions tons of debris The Great Ice Storm (1998),1,5 millions customers without electricity for up to 30 days Tornadoe Flood Hurricane

  15. Thaw, Frost-severe, Frost-free days “… for the entire cold season the annual severity (number of days with negative T°C) of the cold season has decreased everywhere except in Eastern Canada, BUT with an increase in the frost-free period over the year (> 0°C, by 8% per 50 yrs)” From Groisman et al. (AMS - 2003) Trends in the frequency of winter cold and warm spells 1950-1998 (Shabbar & Bonsal, 2003) Decrease in cold spells and increase in warm spells Increase in duration/frequency of cold spells and decrease in duration warm spells

  16. TOOLS TO DEVELOP SCENARIOS OF EXTREMES & CLIM. VAR.Dynamical downscaling at high resolution (15 km CRCM runs) Gachon & Saucier (2003) CONTROL ICE_FREE ICE_FULL °C Hours of integration (1 - 8 January 1990) National Scenarios workshop – Victoria, 16-17 Oct. 2003

  17. Québec Temperature (°C, 2 m) Île Rouge 1-8 Janv. 1990 ____ Obs.  60 km ---- 30 km ____ Control ____Libre ____Englacé ÎLE ROUGE SAGUENAY Polynya of Tadoussac (Winter) ESTUARY OF St. LAWRENCE National Scenarios workshop – Victoria, 16-17 Oct. 2003

  18. Climate mean, validation & variability in model runs Ex. in Gulf of St. Lawrence 49.5°N-65.7°W) (August 1996) SST at 0.5 m depth Wind speed (10 m) Temperature (2 m) Obs.EFR (35km)MRC(old) MRC(new) Mean 15.18 16.614.715.9 St. Deviation 2.36 2.461.482.13 RMS error 2.512.092.17 Obs.EFR (35km)MRC(old) MRC(new) 4.76 5.431.515.44 2.9 2.72.864.02 2.024.483.59 National Scenarios workshop – Victoria, 16-17 Oct. 2003

  19. Conclusion • Large scale influences on climate variability : • . ENSO : western & central part of Canada; • . NAO : eastern and northeastern Canada with strong influences of regional circulation changes  positive NAO is strongly associated with winter cooling over eastern Canada. • . Links with atmospheric circulation changes : increase in the surface cyclone frequency (mean & extreme), especially in the last two decades (during +NAO). • - Regional scale influences : Inland seas (Hudson Bay), cold sink of Greenland, sea ice, deep water formation in Labrador sea (global/regional effect ?). • Climate variability & extremes trends and decadal/long term timescale : not a uniform signal across the country, eastern # rest of the country (historical-paleo timeframe), more variable in the beginning of the century with perhaps more persistence in the last few decades (+NAO).

  20. Questions – Suggestions for scenariosof extremes & climate variability • Increases in cold spell frequency and duration over the east is or not consistent with a warming world ?  a manifestation of a regional response to global warming as suggested by Shabbar & Bonsal (2003) ? • Coupled GCMs runs do not suggest cooling over eastern Canada (smaller temperature increases in the north Atlantic sector) & trends toward increased frequencies and durations of cold spells ? • Downscaling tools requirement : dynamical & statistical (both) for a large range of climate conditions & problems. • High resolution RCMs : compromise between time consuming & type of extremes simulated according to regions and VIA studies… • MUST BE VIEW/THINK IN AN INTEGRATED APPROACH  SEE PRUDENCE/STARDEX/MICE PROJECTS ? • REQUIRE CLOSE COLLABORATION BETWEEN MODELLERS/DATA/STATISTICIAN/VIA COMMUNITIES….

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