Extreme Storm Surge and Wind-storm Climatology in the South coast of British Columbia
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Extreme Storm Surge and Wind-storm Climatology in the South coast of British Columbia RESULTS SUMMARY. Dilumie Abeysirigunawardena Climate Impact Researcher BC Ministry of Environment Ph.D. Candidate University of Victoria [email protected] or [email protected]

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Extreme Storm Surge and Wind-storm Climatology in the South coast of British ColumbiaRESULTS SUMMARY

Dilumie Abeysirigunawardena

Climate Impact Researcher BC Ministry of Environment

Ph.D. Candidate University of Victoria

[email protected]

or

[email protected]

CIG Seminar Series, 29th May 2008, University of Washington, USA


The Objective

Study the response of Extreme Sealevels and Windstorms to

Natural Climate Variability


Data

  • (1) Pacific Region tide gauge stations

    Total Water level data (TWL) = Tide + Residuals

List of Tide Gauge Stations

(1) 7120-Victoria Harbour

(2) 7277- Patricia Bay

(3) 7735-Vancouver

(4) 7795-Point Atkinson

(5) 8074-Campbell River

(6) 8408-Port Hardy

(7) 8545-Bamfield

(8) 8615-Tofino

(9) 8735-Winter Harbour

(10) 8976-Bella Bella

(11) 9354-Prince Rupert

(12) 9850-Queen Charlotte City


Data

A typical Tidal constituent table & Residual Time-series


Data.

Total Water level Data:al

Pt. Atkinson - (1949-2006) (51yrs)

  • Directional Wind Data:

  • YVR - (1953-2006)

    (53-Years)

  • Sandhead - (1993-2006)

    (14-Years)

  • Saturna- (1993-2006)

    (14-Years)


Methodology ..

Extreme Value Analysis Statistical Technique (Coles, 2001).

TWL Extremes

(i) Annual Maxima (GEV)

Wind Extremes

(ii) Peak over Threshold (GPD)

μ = Location

σ = Scale

ξ = Shape

Parameter Estimation

For a given set of maxima the parameters are estimated via the Maximum Likelihood Estimation (MLE) method.

The Extremes Toolkit (Gilleland and Katz (2005)


Methodology

Generalised Extreme Value Distribution (GEV).

Step 1 :Application of GEV to project Return Levels without Climate considerations:

Project Return Levels based on the Annual Maxima Residuals.


Extreme Value Analysis in the presence of Climate Variability Covariates (X)

Methodology.

Effect of Natural Climate Variability on Extremes.

(μ, σ, ξ ) = f( X = MEI, PDO, NOI, ALPI, PNA)

Location Parameter

Scale Parameter

Shape Parameter

  • Step 1: Identify the CV indices that shows significant improvement in the model fit with respect to the no-covariate case.

Add each CV variable as Covariates in the Location(µ) , Scale (σ) and shape ( ξ)parameter and test for significant model improvements through a Likelihood ratio test.


Methodology

Generalised Extreme Value Distribution (GEV).

Step 2 : Investigate the influence of Cyclic Climate Variability Phenomena on return level projections:

Station 7120 : Victoria Harbour


Methodology

Effect of Natural Climate Variability on Extremes.

  • Most climate indices are closely related

  • Redundancy test was performed

  • Step 2: Systematically add each variable isolated in step (1) in to the model and eliminate the ones that does not improve the model fit significantly with respect to the former.


Methodology

Effect of Natural Climate Variability on Storm surge recurrences.

  • Redundancy test

Station 7120 : Victoria Harbour

NOI

NOI + PNA


Methodology

Effect of Natural Climate Variability on Storm surge recurrences.

  • Final Model Consideration with CV effects after the redundancy test

Station 7120 : Victoria Harbour

μ (x) = 57.5 + 7.04(PNA)-2.28(NOI)

σ (x) = 10.5

ξ(x) = -0.368


Methodology.

Effect of Natural Climate Variability on Extremes.

Step 3: Climate Indices Conditional on 3-dominant Climate State

(i) Warm ENSO

(ii) Neutral

(iii) Cold ENSO

  • The definitions are based on the Environment Canada classification scheme.


Results


Results Sensitivity of Storm Surges to Climate Covariates

Climatic patterns governed by PNA, NOI and MEI has a significant influence on storm surge occurrences in the region.


Results

Effect of Natural Climate Variability on Storm surge recurrences.

Station 7120 : Victoria Harbour

Estimated return levels and 95% confidence intervals under ENSO conditions. Results for no climate consideration are included for comparison purposes


ResultsStorm Surges with 1% exceedance in each year with CV effects

4

7

10

11

5

3

2

1

9

6

8

All stations indicate higher residual water-levels during warm ENSO episodes.


Results.

Extreme Directional Wind recurrences with climate Covariates.


Results.

Directional Wind Recurrences at YVR with climate covariates.


Case Studies (i) December 16th 1982 Extreme Event (ii) February 4th 2006 Extreme Event


December 16th 1982 Storm Event examples of impacts…

Damage to Mud Bay during 1982 flooding

Damage to Westham Island

Damage along King George HWY in Surrey

Serpentine Dike Damage


December 16th 1982 Storm Event


Results.

Extreme TWL Recurrences With CV effects at Pt. Atkinson

(1)

(2)

(3)

(4)

(5)

(6)


February 4th 2006 Storm Event examples of impacts…


February 4th 2006 Storm Event : TWL Event


February 4th 2006 Storm Event : Wind Direction


February 4th 2006 Storm Event : Wind Speed


2006 event Recurrences viewed under Climate Variability

  • Extreme TWL Recurrences and Extreme Storm Recurrences are not in phase

    • Warm ENSO phase favors extreme TWL & Residuals

    • Cold ENSO phase favors extreme windstorms


Conclusions..

  • Climate Variability has significant effects on extreme sea levels and windstorm recurrences in Southern BC.

  • All stations in coastal BC indicate an increase in the Residuals during warm ENSO episodes.

  • Climatic patterns represented by PNA, NOI and MEI climate indices has a significant influence on storm surge occurrences in the region

  • A Cold ENSO phase could result in more frequent windstorms in the study region

  • Extreme TWL Recurrences and Extreme Wind-Storm Recurrences are not in phase in Southern BC.


Policy decisions are mainly driven by potential societal impacts resulting from climate variability and change, and not the climate change itselfChanging extremes due to CC and CV effects are the most damaging Therefore it is strongly recommended to account for the effects of CC and CV in the analysis of Extremes leading to new policy decision for adaptation and design criteria.

“February 04th 2006 Storm Impact at Boundary bay “

Picture provided by the Fraser Delta’s Engineering Department

photo courtesy of Michael Brown


Acknowledgements

  • Ben Kangasniemi , BC Ministry of Environment.

  • Rick Thompson, Bill Crawford , Scott Tinis, IOS Sidney BC

  • Eric Gilleland NCAR,Boulder CO, USA

  • Bill Taylor and Mark Barton Environment Canada

  • Trevor Murdock & Pacific Climate Impact Consortium

  • Research Support & Contributions

    • BC Ministry of Environment

    • Environment Canada

    • DFO & IOS Sidney BC

    • Pacific Climate Impact Consortium (PCIC)

    • National Center for Atmospheric Research (NCAR), USA

    • Co-op Social Science University of Victoria

    • BC Ministry of Labour and Citizens’ Services


Thank you… feedback?


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