Science applications of high resolution water level observations

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Science applications of high resolution water
level observations
Water level is a key remotely sensed observation
of the momentum equation
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Science applications of high resolution water
level observations
Mesoscale energy Tide and wind-driven
inundation River effects on optical
properties Surface wave dissipation
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Sea Surface Height (SSH) and abyssal
currents Superimposed on SSH variability

• Mesoscale instabilities pump energy into the
  abyssal layer
• Bottom topography constrains flow to roughly f/H
• Bottom mean flow advects thermocline
  displacements
• Strong coupling between mesoscale variability and
  mean circulation

Abyssal currents superimposed on the bottom
topography
From Hurlburt, Wallcraft, Schmitz, Hogan and
Metzger (1996 JGR-O) Hurlburt et al., Reviews of
Geophysics, submitted 2006.
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Do we have sufficient observations to determine
energy exchange between the surface and deep
water?

• 1/25 resolution Gulf of Mexico
• Assimilated Jason-1, ENVISAT, GFO
• Color is surface height
• Vectors are 500m currents
• Baroclinic shear exchanges potential and kinetic
  energy between deep and surface waters
• 14 Acoustic doppler current profilers deployed
  May 2004 March 2005

(cm)
-40
40
Hogan and Zamudio, work under way
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Correlation of along-shelfbreak currents
NOGAPS, Assim NOGAPS, Assim 2
Hogan and Zamudio, work under way
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Correlation of along-shelfbreak currents
NOGAPS, Assim NOGAPS, Assim 2 A1/A2
Hogan and Zamudio, work under way
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Science applications of high resolution water
level observations
Mesoscale energy Tide and wind-driven
inundation River effects on biology and optical
properties Surface wave dissipation
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Are there sufficient observations to understand
inundation physics?
Hurricane Katrina Strom Surge/Inundation Along
The Mississippi Gulf Coast
Bay St. Louis
feet
Several months of work to get this. Why?
Blain and Massey, Marine Tech., submitted 2006
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Many physical processes influence results

• Wind forcing
• Bottom drag (flat land, grass, shrubs, trees,
  houses, )
• Morphological changes

Comparison to 27 USGS High Water Mark Locations
Topography (Land , Water -) in feet
Blain and Massey, Marine Tech., submitted 2006
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Observations through tide cycles are required to
understand and test the relevant physics
Water line observed from visible imagery
Ebb Tide
Flood Tide
Dry areas appear gray
MODIS (250 m)
White lines show coastline from a global
database.
Massey, work under way, 2006
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Massey, work under way, 2006
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Science applications of high resolution water
level observations
Mesoscale energy Tide and wind-driven
inundation River effects on biology and optical
properties Surface wave dissipation
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Correlation between optical absorption and
Mississippi River discharge
Chlorophyll absorption
CDOM absorption

• Monthly composite images over 2000-2004
• Monthly averaged observed river outflow

Green et al., Montreal, 2006
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Discharge event, March 17-23, 2004
Blain et al., RSCME meeting, Hallifax, 2006
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River discharge and local circulation are
required to predict particle fate
MAR 17
MAR 19
MAR 21
Current Magnitude (Tides Winds River
Forcing) 1 particle every hour
Blain et al., RSCME meeting, Hallifax, 2006
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Science applications of high resolution water
level observations
Mesoscale energy Tide and wind-driven
inundation River effects on biology and optical
properties Surface wave dissipation
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Do we have sufficient observations to determine
wave energy dissipation mechanisms nearshore?
P4 P3 P2 P1

• Pressure gauges along transect to beach
• Wave rider buoy for boundary conditions

Rogers et al., work under way, 2006
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Pressure gauge spectra at p4 with and without
fluid mud layer dissipation (Ng, 1974 formulation)
Wave rider buoy wavenumber spectrum
Energy spectrum at P4, near shore
Rogers et al., work under way, 2006
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Wave rider buoy wavenumber spectrum

• Possible dissipation
• Fluid mud layer
• Form drag from sand ripples
• Wave energy matches observations with two
  possible mechanisms, though insufficient
  information to separate the two
• Additional areas must be observed and theory
  tested

Bathymetry along transect
Integrated spectral energy
Integrated spectral energy
Distance from shore (km)
Rogers et al., work under way, 2006
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Science applications of high resolution water
level observations
Mesoscale energy Tide and wind-driven
inundation River effects on biology and optical
properties Surface wave dissipation