Global influences of the 18.61 year Global influences of the 18.61 year lunar nodal cycle and 8.85 year cycle lunar nodal cycle and 8.85 year cycle of lunar perigee on coastal floodingof lunar perigee on coastal flooding

The School of Environmental Systems Engineering and the UWA Oceans Institute

The University of Western Australia

Ivan Haigh, Matt Eliot and Chari PattiaratchiIvan Haigh, Matt Eliot and Chari Pattiaratchi

School of Environmental Systems Engineering

New Orleans, Hurricane Katrina1. Introduction1. Introduction

Source: http://newsmediainsider.blogspot.com/2010/08/katrina-survivor-talks-about-escaping.html

1. Introduction1. Introduction

Observed Tide

Mean Sea Level

AstronomicalTide

Surge

=

+

+

1. Introduction1. Introduction

BROOME

FREMATLE

18.6 years

4.4 years

1. Introduction1. Introduction

The aim of this study is to examine The aim of this study is to examine the contribution of the 18.61 year the contribution of the 18.61 year lunar nodal cycle and 8.85 year lunar nodal cycle and 8.85 year cycle of lunar perigee to high tidal cycle of lunar perigee to high tidal levels (coastal flooding) on a global levels (coastal flooding) on a global scale;scale;

A global assessment of when these A global assessment of when these tidal modulations occur allows for tidal modulations occur allows for prediction of periods when prediction of periods when enhanced risk of coastal enhanced risk of coastal flooding/inundation is likely in flooding/inundation is likely in different coastal regions.different coastal regions.

2. Background:2. Background:

A. 18.61 year lunar nodal cycleA. 18.61 year lunar nodal cycle

Cross-section view:Cross-section view:23.5° - 5°= 18.5°

23.5°

5°

23.5° + 5°= 28.5°

23.5°

5°

2. Background2. BackgroundB. 8.85 year cycle of lunar perigeeB. 8.85 year cycle of lunar perigee

View from above:View from above:

Quasi-4.4 years cycle (of perigean influence)Quasi-4.4 years cycle (of perigean influence)

2. Background2. Background

Tidal analysis (Matlab t-tide) Tidal analysis (Matlab t-tide) performed on a year or two of tide performed on a year or two of tide gauge observations;gauge observations;

Inter-annual modulations can not be Inter-annual modulations can not be independently determined from a single independently determined from a single year of data;year of data;

Handled using small adjustment Handled using small adjustment factors:factors:

f (amplitude);f (amplitude); u (angle);u (angle);

Constituent f (factor)

M2, N2 3.7%

K2 28.6%

Q1, O1 18.7%

K1 11.5%

3. Methodology3. MethodologyBest fits the Laplace Best fits the Laplace Tidal Equations and Tidal Equations and T/P and Jason altimetry T/P and Jason altimetry data using OTIS data using OTIS ((OOregon State regon State University University TTidal idal IInversion nversion SSoftware);oftware);

8 primary and 2 long 8 primary and 2 long period const. on ¼ deg period const. on ¼ deg resolution global grid;resolution global grid;

Tidal Model Driver Tidal Model Driver (TMD) Matlab toolbox(TMD) Matlab toolbox• Infers 16 minor Infers 16 minor

const;const;• Modulation Modulation

corrections based on corrections based on equilibrium tide equilibrium tide expectations.expectations.

Egbert and Erofeeva Egbert and Erofeeva (2002)(2002)

TPXO 7.2 Global Ocean Tidal TPXO 7.2 Global Ocean Tidal ModelModel

BroomeBroome

2 cm2 cm8 cm8 cm

3. Methodology3. MethodologyFremantleFremantle

26 cm26 cm4 cm4 cm

4. Results: Range4. Results: Range

18.6 lunar nodal year18.6 lunar nodal year

0 – 80 cm 0 – 80 cm

4. Results: Range4. Results: Range

4.4 year cycle of lunar perigee4.4 year cycle of lunar perigee

0 – 50 cm 0 – 50 cm

4. Results: Range4. Results: Range

18.6 year18.6 year Form FactorForm Factor

4.4 year4.4 year Tidal RangeTidal Range

18.6 lunar nodal 18.6 lunar nodal yearyear

4. Results: Range as % of tidal range4. Results: Range as % of tidal range18.6 lunar nodal year18.6 lunar nodal year

4.4 year cycle of lunar perigee4.4 year cycle of lunar perigee

4. Results: Dominant4. Results: Dominant

FF >~ 0.6 (mixed, diurnal)FF >~ 0.6 (mixed, diurnal) FF <~ 0.6 (semi-diurnal)FF <~ 0.6 (semi-diurnal)

18.6 year cycle dominates18.6 year cycle dominates 4.4 year cycle dominates4.4 year cycle dominates

4. Results: Phase4. Results: Phase

FremantleFremantle BroomeBroome

20062006 20082008 19971997 20062006

maximise diurnal maximise diurnal at expense of semi-diurnalat expense of semi-diurnal

23.5° - 5°

23.5° + 5°

maximise semi-diurnal maximise semi-diurnal at expense of diurnalat expense of diurnal

4. Results: Phase 18.6 year cycle4. Results: Phase 18.6 year cycle

1987, 2006, 1987, 2006, 20242024 1978, 1997, 1978, 1997, 20152015

FF >~ 0.6 (mixed, diurnal)FF >~ 0.6 (mixed, diurnal) FF <~ 0.6 (semi-diurnal)FF <~ 0.6 (semi-diurnal)

5. Conclusions5. Conclusions

Haigh, I.D., Eliot, M., Pattiaratchi, C., in press. Global influences of the 18.61 year nodal cycle and 8.85 year cycle of lunar perigee on high tidal levels. Journal of Geophysical Research.

Paper in press:Paper in press:

Future work compare with measured Future work compare with measured data – GESLA (Hunter, Woodworth) data data – GESLA (Hunter, Woodworth) data set:set:

6. Future Work6. Future Work ModelModelMeasuredMeasured

Brest, FranceBrest, France

Fremantle, AustraliaFremantle, Australia

San Francisco, USASan Francisco, USA

Balboa, PanamaBalboa, Panama

Honolulu, HawaiiHonolulu, Hawaii

Any Questions

Ivan Haigh, Matt Eliot and Chari PattiaratchiIvan Haigh, Matt Eliot and Chari Pattiaratchi