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