1 / 16

24 January 2011 10 th Symposium on the Coastal Environment

U.S. IOOS Coastal Ocean Modeling Testbed. 3D & 2D Storm Surge Simulations for Hurricane Ike. L. Zheng, R. Weisberg & Y. Huang Univ. of South Florida R. Luettich Univ. of North Carolina at Chapel Hill J. Westerink, P. Kerr, & A. Donahue Univ. of Notre Dame. 24 January 2011

olesia
Download Presentation

24 January 2011 10 th Symposium on the Coastal Environment

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. U.S. IOOS Coastal Ocean Modeling Testbed 3D & 2D Storm Surge Simulations for Hurricane Ike L. Zheng, R. Weisberg & Y. Huang Univ. of South Florida R. Luettich Univ. of North Carolina at Chapel Hill J. Westerink, P. Kerr, & A. Donahue Univ. of Notre Dame 24 January 2011 10th Symposium on the Coastal Environment 92nd Annual American Meteorological Society Meeting

  2. Model: FVCOM (Chen et al., 2003) Domain: The entire Gulf of Mexico Simulations: 2D and 3D Ike storm surges Forcing: Tides, surface winds and waves

  3. Bottom Stress Parameterizations: Bottom stress: 2D, Cd=g*n2/h1/3 (1) where n: Manning coefficient : Depth-averaged velocity. 3D, Cd=ĸ2/(log(zab/z0))2 (2) where ĸ: von Karman constant (=0.4) zab: half thickness of last σ-layer z0: bottom roughness : near bottom current velocity.

  4. Example of the 2D and 3D drag coefficients: Background values in advance of the storm. 2D Cd with spatially-varying n provided by UND andEq. (1). 3D Cd with constant z0=0.01m andEq. (2). The minimum is 2.5x10-3 and the maximum is capped at 1.5x10-2.

  5. FVCOM & ADCIRC 2D and 3D simulated IKE surges

  6. FVCOM 2D & 3Dsimulated IKE surges (w/o and w/ waves)

  7. 2D and 3D simulated elevations, depth-mean current and bottom current on 09/13 00:00, 6 hrs before Ike landfall

  8. Wind and bottom stress (2D & 3D) at 09/13 00:00, 6 hrs before Ike landfall Note: Units are N/m2 x 10-3

  9. PG and (τw- τb) for2D & 3D at 09/13 00:00, 6 hrs before Ike landfall

  10. 2D and 3D simulated elevations, depth-mean current and bottom current on 09/13 6:00, around Ike landfall

  11. Wind and bottom stress (2D & 3D) at 09/13 06:00, around Ike landfall

  12. PG and (τw- τb) for2D & 3Dat 09/13 06:00, around Ike landfall

  13. Sabine Pass Cross-Section Stresses & Elevations ~6hr before landfall ~ landfall offshore coast ~6hr after landfall

  14. Sabine Pass Cross-Section Momentum Balances PG balanced by CF & (τw- τb) Note: stress direction difference between 2D & 3D. Before PG balanced by (τw- τb) + LA & CF Landfall PG balanced by (τw- τb) + LA After

  15. Summary • 2D and 3D IKE surge simulations are reasonably accurate for both FVCOM & ADCIRC. However, these results depend on bottom stress parameterizations for which Cd may be quite different. • FVCOM shows larger surges in 3D, whereas ADCIRC shows larger surges in 2D. Compared with observations, FVCOM is better in 3D than in 2D. • FVCOM 2D and 3D differences result from bottom stress. Before landfall, the 2D stress > 3D stress, and direction differences show that the 2D stress more effectively counters the wind stress, leading to the smaller 2D surge. • Momentum balances evolve as the storm approaches. Before landfall, an Ekman-geostrophic balance prevails (PG, CF & net stress (τw- τb). At landfall, the PG is balanced by the net stress and L + C accelerations. The 3D PG exceeds the 2D PG; hence the larger 3D surge.

  16. Next Steps Results depend on stress parameterizations. For 2D we used spatially varying Manning coefficients, whereas for 3D we used uniform bottom roughness. Hence the comparisons are somewhat arbitrary. In a former experiment (WZ2008) we compared 2D & 3D with similar bottom stress parameterizations and found similar results: 3D>2D surges. Further investigations are required to ascertain the relative surge magnitudes given similar bottom (and surface) stress parameterizations.

More Related