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

Key atmospheric and oceanic factors Key atmospheric and oceanic factors responsible for climate variability and responsible for climate variability and

extreme events in Canadaextreme events in Canada

Philippe Gachon

&

Vicky Slonosky

CCIS - OURANOS

National Scenarios workshop – Victoria, 16-17 Oct. 2003

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

Land surfaceLand surface9.97 9.97 × × 101066 km km22

COOLEST REGION in COOLEST REGION in ARCTIC BASINARCTIC BASIN

(Overland et al., 1997)(Overland et al., 1997)

Beginning and end of Beginning and end of QuaternaryQuaternaryGlaciationGlaciation

(COHMAP, 1988)(COHMAP, 1988)

1.22 1.22 × ×

101066 km km22

2.17 2.17 × × 101066 km km22

More than 50% of equivalent land areaMore than 50% of equivalent land area

is covered by sea ice (North, Northeast, East)is covered by sea ice (North, Northeast, East)

6-8 months per year6-8 months per year

Majority of the country with TMajority of the country with Tannann< 0< 0°°CC

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)

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)

NAO variability & effects during time, January

Surface cyclones (11 month running mean) from NCEP reanalyses

Changes in surface cyclone frequency 76-99 minus 53-75

After Sinclair (2003)

NH

System density for strong MSL cyclones, 53-99

(most intense 5%)NH

Strong cyclones – surface (Sinclair, 2003)

Changes in intensification rate (MSL cyclones, 76-99 minus 53-

75)

(Sinclair, 2003)

Changes in strong MSL cyclones

76-99 minus 53-75

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

Slonosky & Graham, submit. J. Clim., 2003Climate variability & extremes

Trends in atmospheric circulation indices (century scale)

Trends 1901-1995 (per decade *100)

NAO -1.4

C/G 1.6

P-L 0.4

Trends 1951-1995

(per decade*100)

NAO 29.2

C/G 18.6

P-L 18.4

National Scenarios workshop – Victoria, 16-17 Oct. 2003

Natural variability: mid-18th century vs 20th Québec City (Slonosky, 2003)

Winters milder than most of 20th century, summers warmer. Springs and autumns cooler => milder but longer winter season

Climate Trends and VariabilityClimate Trends and Variability1950-19981950-1998

Maximum and minimum temperatures have increased at similar rate Warming in the south and west, and cooling in the northeast (winter & spring)

Trends inFall

Mean Temp(°C / 49 years)

Trends inSpring

Mean Temp(°C / 49 years)

Trends inWinter

Mean Temp(°C / 49 years)

Trends inSummer

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

Location & type of Extremes in Canada

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

large tides, storms & snow events

droughts, heat spells

Flood Hurricane Tornadoe

Thaw, Frost-severe, Frost-free daysThaw, 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)

-11

-10

-9

-8

-7

-6

-5

-4

-3

-2

-1

0

1 21 41 61 81 101 121 141 161

CONTROLICE_FREEICE_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

-30

-26

-22

-18

-14

-10

-6

-2

2

1 21 41 61 81 101 121 141 161

____ Obs. 60 km---- 30 km____ Control____ Libre____ Englacé

Temperature (°C, 2 m) Île Rouge1-8 Janv. 1990

Polynya of Tadoussac(Winter)

ÎLE ROUGE SAGUENAY

ESTUARYESTUARYOF St. LAWRENCEOF St. LAWRENCE

Québec

National Scenarios workshop – Victoria, 16-17 Oct. 2003

8

10

12

14

16

18

20

22

24

1 21 41 61 81 101 121 141 161 181 201 221 241

Every 3 hours (from 1-08-1996 to 31-08-1996)

0

2

4

6

8

10

12

14

16

18

1 21 41 61 81 101 121 141 161 181 201 221 241

Every 3 hours (from 1-08-1996 to 31-08-1996)

Climate mean, validation Climate mean, validation & variability in model runs& variability in model runs

Ex. in Gulf of St. LawrenceEx. in Gulf of St. Lawrence 49.5°N-65.7°W)49.5°N-65.7°W)(August 1996)(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 2.13RMS 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

ConclusionConclusion- 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).

-

- 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 scenariosQuestions – Suggestions for scenariosof extremes & climate variabilityof extremes & climate variability