Modeling of Large-Scale Edge Waves Generated by the Hurricane Landfall

Modeling of Large-Scale Edge Waves Generated by the Hurricane Landfall

Alexander Yankovsky

Marine Science Program and Department of Geological Sciences

University of South Carolina, USA

Alexander Yankovsky

Marine Science Program and Department of Geological Sciences

University of South Carolina, USA

2008 ROMS/TOMS European Workshop2008 ROMS/TOMS European Workshop

Acknowledgements:

-National Science Foundation

-US Geological Survey, Florida Integrated Science Center

-Drs. Eduardo Patino, Burl Goree (USGS)

Acknowledgements:

-National Science Foundation

-US Geological Survey, Florida Integrated Science Center

-Drs. Eduardo Patino, Burl Goree (USGS)

15

20

25

30

35

40

45

-85 -80 -75 -70 -65 -60 -55 -50 -45

Hurricane Wilma15-25 October 2005

Hurricane

Tropical Storm

Tropical Dep.

Extratropical

Subtr. Storm

Subtr. Dep.

00 UTC Pos/Date

12 UTC Position

Low / Wave

PPP Min. press (mb)

25

24

23

22

21

20

1918

26

1617

882 mb

from: Pasch et al. (2005)

Wilma’s track

Time series of storm surge

Wilma’s landfall

Long waves trapped in the coastal ocean:

- Subinertial coastal trapped waves (σ≤f); propagate with the coast on their right in NH, the effects of Earth’s rotation are crucial.

- Edge waves (σ>f); refraction of long gravity waves, propagate in both directions

ROMS, 2D configurationbc: radiation

bc:

Cha

pman

bc: radiationbc

: w

all

Atmospheric vortex in gradient wind balance

Standard Case:

- Pressure anomaly in the cyclone’s center is 3 hPa (wind is ~ 12 m/s)

- Translation speed of the storm system is 10 m/s eastward

- Quadratic bottom stress, C =10-3;

- f =6.3×10-5 s-1 (26 °N);

- Spatial resolution: Δx = Δy = 2.5 km

Standard case: phase diagram

Temporal and alongshore evolution of free surface at the coast

0)( 222

kgh

f

h

hkf

h

h yyyyy

Linear shallow water equations on f-plane

Boundary conditions:

kfy

0 )( y

)0)0(,0( hy

0yv )( Ly Assume: Q =kf/ω

22

22

2

)]([ kgh

f

h

hQ

h

h

fghQ

ghQ yyyyy

(y=0) (y=L) Qy yyy Q AX=μX

MATLAB EIG routine

Standard case, dispersion diagram of the edge wave modes propagating downstream (solid line) and upstream (dashed line)

Across-shelf structure of edge wave modes

From ROMS

Case B

Us = 5 m/s

Case C

Us = 3 m/s

Us=10 m/s Us=5 m/s Us=3 m/s

Case D

Us = 8.66 m/s

Vs = -5 m/s

Case E

Us = 8.66 m/s

Vs = 5 m/s

Case F: strong wind

ΔP = -20 hPa (max wind ≈ 34 m/s); C = 3×10-3

· Hurricane Wilma’s landfall generated a long-wave pulse traveling downstream (northwestward) along the coast. This wave pulse lasted ~6 hrs and its height was ~1.5 m in the detided sea level.

· Zero-mode edge waves dominate the response. Their structure in the model is very close to the theoretical estimates.

· The wave pulse is identified as an edge wave of large spatial and temporal scales. Numerical calculations show that such waves can be generated by a fast-moving storm crossing the continental shelf at the close-to-normal angle.

Conclusions