Droughts in Canada: An OverviewDroughts in Canada: An Overview

Barrie Bonsal

Environment Canada

Saskatoon, SK, Canada

OutlineOutline

• BackgroundBackground• Past drought occurrencePast drought occurrence• Large-scale atmospheric causesLarge-scale atmospheric causes• Current monitoring & predictionCurrent monitoring & prediction• Future droughtsFuture droughts• Research requirementsResearch requirements

Droughts in CanadaDroughts in Canada

Drought ImpactsDrought ImpactsAgriculture

Drought ImpactsDrought ImpactsWater Resources

Drought ImpactsDrought Impacts

Drought Research in CanadaDrought Research in Canada• Fragmented – spatially and Fragmented – spatially and

temporallytemporally• Based on severe drought Based on severe drought

occurrence (e.g., 1999-2005)occurrence (e.g., 1999-2005)• Majority for Canadian Prairies Majority for Canadian Prairies • Historical comparisons difficult Historical comparisons difficult

due to short and variable climate due to short and variable climate station recordsstation records

• Canadian droughts unique – both Canadian droughts unique – both cold and warm season cold and warm season phenomenonphenomenon

a) Kamloops, BC

-6

-4

-2

0

2

4

6

1900

1905

1910

1915

1920

1925

1930

1935

1940

1945

1950

1955

1960

1965

1970

1975

1980

1985

1990

1995

2000

b) Saskatoon, SK

-6

-4

-2

0

2

4

6

1900

1905

1910

1915

1920

1925

1930

1935

1940

1945

1950

1955

1960

1965

1970

1975

1980

1985

1990

1995

2000

c) Sherbrooke, QC

-6

-4

-2

0

2

4

6

1900

1905

1910

1915

1920

1925

1930

1935

1940

1945

1950

1955

1960

1965

1970

1975

1980

1985

1990

1995

2000

d) Yarmouth, NS

-6

-4

-2

0

2

4

6

1900

1905

1910

1915

1920

1925

1930

1935

1940

1945

1950

1955

1960

1965

1970

1975

1980

1985

1990

1995

2000

Annual PDSI Annual PDSI

Drought OccurrenceDrought Occurrence

Summer (JJA) Drought Change Summer (JJA) Drought Change 1925 - 19901925 - 1990

- 3

- 2

- 1

0

1

2

3

4

5

95°

PD SIMean Summer Temperature

Summer Precipitation

Drought Occurrence – Southern Prairies (1915-2002)Drought Occurrence – Southern Prairies (1915-2002)

SPI PDSI

1600 1700 1800 1900 2000

-2

0

2

1700 1800 1900 2000

-2

0

2

Reconstructed Regional July Palmer Drought Severity Index (Sauchyn et al. 2001)

SouthwesternSaskatchewan

North-centralMontana

frequentdrought

decadaldrought

Warm, Dry Winters Over CanadaWarm, Dry Winters Over Canada500mb Flow 500mb Anomalies

El Niño, +PNA, +PDO, Deep Aleutian Low

Hot, Dry Summers Over Western CanadaHot, Dry Summers Over Western Canada

500mb Flow 500mb Anomalies

+PNA, Meridional Flow, +PDO?

Coupled SVD pattern between Coupled SVD pattern between Global Winter SSTs and Summer Global Winter SSTs and Summer

PDSI (1940-2002)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)

Circulation DifferencesCirculation Differences

Sep-Aug 1961

Sep-Aug 2001 Sep-Aug 2002

Sep-Aug 1988

Drought MonitoringDrought 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

Drought MonitoringDrought 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).

Drought PredictionDrought 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

The frequency and severity of droughts are The frequency and severity of droughts are likely to increase in southern Canadalikely to increase in southern Canada

020

40

60

Retu

rn P

eri

od (

years

)

10 15 20 25 30

Length of Dry Spell (days)

Central North America

Today

~2070

Future DroughtsFuture Droughts

SPI PDSI

Research NeedsResearch Needs

1. A better understanding of the physical causes of drought 1. A better understanding of the physical causes of drought initiation, persistence, and termination at a variety of spatial and initiation, persistence, and termination at a variety of spatial and temporal scalestemporal scales

• Large-scale atmospheric and oceanic oscillationsLarge-scale atmospheric and oceanic oscillations• Soil moisture anomaliesSoil moisture anomalies• Moisture sourcesMoisture sources• Physical causes of multi-year droughtsPhysical causes of multi-year droughts• Drought migrationDrought migration

Research NeedsResearch Needs

2. Quantification and assessment of past drought occurrences2. Quantification and assessment of past drought occurrences• Past trends and variabilityPast trends and variability• Drought indicesDrought indices• Paleo-drought studiesPaleo-drought studies

3. Better knowledge regarding future drought occurrence3. Better knowledge regarding future drought occurrence• More reliable GCM/RCM outputMore reliable GCM/RCM output• Improved downscaling methodsImproved downscaling methods• Future changes to large-scale circulation patternsFuture changes to large-scale circulation patterns

Research NeedsResearch Needs

4. Ability to more accurately predict drought onset, intensity, and 4. Ability to more accurately predict drought onset, intensity, and terminationtermination

• Improvements in modelling and monitoring of current drought Improvements in modelling and monitoring of current drought conditionsconditions

• More reliable short term (seasonal) climate forecastMore reliable short term (seasonal) climate forecast

5. More effective short and long-term adaptation strategies to 5. More effective short and long-term adaptation strategies to defend against future droughtsdefend against future droughts