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Key atmospheric and oceanic factors responsible for climate variability and extreme events in Canada Philippe Gachon & Vicky Slonosky CCIS - OURANOS National.

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Presentation on theme: "Key atmospheric and oceanic factors responsible for climate variability and extreme events in Canada Philippe Gachon & Vicky Slonosky CCIS - OURANOS National."— Presentation transcript:

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 Land surface 9.97 × 10 6 km 2 COOLEST REGION in ARCTIC BASIN (Overland et al., 1997) Beginning and end of QuaternaryGlaciation (COHMAP, 1988) 1.22 × 10 6 km 2 2.17 × 10 6 km 2 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 T ann < 0°C

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

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

6 NAO variability & effects during time, January

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

8 System density for strong MSL cyclones, 53-99 (most intense 5%) NH Strong cyclones – surface (Sinclair, 2003)

9 Changes in intensification rate ( MSL cyclones, 76-99 minus 53-75) (Sinclair, 2003) Changes in strong MSL cyclones 76-99 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 Slonosky & Graham, submit. J. Clim., 2003 Climate variability & extremes Trends in atmospheric circulation indices (century scale) Trends 1901-1995 (per decade *100) NAO-1.4 C/G1.6 P-L0.4 Trends 1951-1995 (per decade*100) NAO29.2 C/G18.6 P-L18.4 National Scenarios workshop – Victoria, 16-17 Oct. 2003

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

13 Climate Trends and Variability 1950-1998 Climate Trends and Variability 1950-1998 Maximum and minimum temperatures have increased at similar rate Warming in the south and west, and cooling in the northeast (winter & spring) Trends in Fall Mean Temp (°C / 49 years) Trends in Spring Mean Temp (°C / 49 years) Trends in Winter Mean Temp (°C / 49 years) Trends in Summer 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 Saguenay (1996), 26 millions m 3 of water and 9 millions tons of debris The Great Ice Storm (1998), 1,5 millions customers without electricity for up to 30 days large tides, storms & snow events droughts, heat spells Flood Hurricane Tornadoe

15 Thaw, Frost-severe, Frost-free days From Groisman et al. (AMS - 2003) … 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) Decrease in cold spells and increase in warm spells Increase in duration/frequency of cold spells and decrease in duration warm spells Trends in the frequency of winter cold and warm spells 1950-1998 (Shabbar & Bonsal, 2003)

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

17 ____ Obs. 60 km ---- 30 km ____ Control ____ Libre ____ Englacé Temperature (°C, 2 m) Île Rouge 1-8 Janv. 1990 Polynya of Tadoussac (Winter) ÎLE ROUGE SAGUENAY ESTUARY OF St. LAWRENCE Québec 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) 49.5°N-65.7°W) (August 1996) Temperature (2 m) Wind speed (10 m) SST at 0.5 m depth National Scenarios workshop – Victoria, 16-17 Oct. 2003 Obs. EFR (35km) MRC(old) MRC(new) Mean 15.18 16.6 14.7 15.9 St. Deviation 2.36 2.46 1.48 2.13 RMS error 2.51 2.09 2.17 Obs. EFR (35km) MRC(old) MRC(new) 4.76 5.43 1.51 5.44 2.9 2.7 2.86 4.02 2.02 4.48 3.59

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 - 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…. Questions – Suggestions for scenarios of extremes & climate variability


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