Observations of the Coastal Ocean Response to Ivan: Implications for Hurricane Intensity Change Lynn...
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![Page 1: Observations of the Coastal Ocean Response to Ivan: Implications for Hurricane Intensity Change Lynn “Nick” Shay, G. Halliwell, and W. Teague MPO, RSMAS,](https://reader036.fdocuments.net/reader036/viewer/2022062714/56649d405503460f94a19d26/html5/thumbnails/1.jpg)
Observations of the Coastal Ocean Response to Ivan: Implications for Hurricane Intensity Change
Lynn “Nick” Shay, G. Halliwell, and W. Teague
MPO, RSMAS, Univ. of MiamiOceanography Department, NRL-Stennis
http://iwave.rsmas.miami.edu/~nick
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MOTIVATION:
SHA field from GFO altimeter (left panels) and SST Image from TMI (right)Relative to Katrina’s track & intensity.
Severe Storm (Cat 3 or above) Tracks (red) relative to the posit of the LC and WCR complex based on satellite data in Aug 05.
LC
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In addition to thermal structure,measuring current and shear is central for mixing and oceanic cooling and hence feedback to the storm.(from Shay 2007)
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Ivan’s Track and Intensity Relative to OHC (left) NRL SEED Mooring Locations in Northern Gulf of Mexico Relative
to Bottom Depth (Right) (Teague et al., JPO, 2007).
14 ADCP moorings!
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NRL Mooring Specifics (Teague et al., JPO, 2007).Note ADCP provides absolute velocity (u,v,w)
Array # LatoN
LongoW
StartDate2004
EndDate2004
Δt(hr)
DepthRange
(m)
Δz(m)
BottomDepth
(m)
InstrumentType
2 29.43 88.01 05/01 10/31 0.25 4-54 2 60 TRBM
8 29.14 88.11 05/03 11/07 1.0 42-492 10 518 LR
9 29.19 87.94 05/03 11/07 1.0 40-500 10 518 LR
14 29.20 87.65 05/05 11/07 1.0 42-502 10 1029 LR/RCM9
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Ivan’s eye of over the moorings (dots) at 00 UTC on 16 Sept 04.
(a) Wind stress (Pa) with winds, (b) frictional wind velocity (m s-1), (c) wind stress divergence (s-1) (d) wind stress curl (s-1). Based on HWIND fields.
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Intense Forcing (upper) and Relaxation Stages (lower) for NRL SEED moorings 7-14
7-10 Red ~500 m
11-14 Yellow~1000 m
(Teague et al. JPO, 2007).
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Temperature time series at the bottom of each ADCP for M1-M14
A11-A14 are Aanderaa CM
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M8 (Track) and M9 (1.5 Rmax) Near-Inertial Current Response (Rmax= 32 km)
BP 22 to 29 h ; normalized by 20 cm s-1 based on (max Rmax)/(0bUh)
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M8 (Track) Observed and Near-Inertial Current Shear Response (Rmax= 32 km)
Normalized shear by 10-2 s-1 based on (max Rmax)/(0bUh)
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M9 (1.5 Rmax) Observed and Near-Inertial Current Shear Response (Rmax= 32 km)
Normalized shear by 10-2 s-1 based on (max Rmax)/(0bUh)
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Depth-Averaged Current at Mooring 8
Depth-averaged response in near-inertial wave band at 12 hours for a few days.
White-Obs, Black-OA
Color is log of the depth-averaged KE cm2 s-2.
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Oceanic Response and Intensity Impacts
Ivan a clear example of negative feedback (cooling/mixing induced by strong winds and Cold Core Ring) as opposed to positive feedback over the Loop Current and Warm Core Rings (i.e. Katrina, Rita and Wilma-the Trifecta).
To evaluate state-of-the-art coupled models, temperatures and currents needed to assess mixing schemes and evaluate initialization schemes.
We have only had 7 sets of T(z), V(z) data since 1984 from the NOAA WP-3D and USAF deployments.
Aircraft expendables (AXCP, AXCTD) conduct targeted measurements of ocean.
SST is not enough for ocean’s influence on hurricanes:
1. Implement optimal ocean sampling schemes for pre, during and post hurricanes; 2. Initialize ocean models with Loop Current and Warm/Cold Core Rings.
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Shay’s Top 5 Reasons Why We Need to Understand The LC/WCR/CCR in GOM:
1. Improve intensity predictions at Operational Centers.
2. When in phase with hurricane season…Rapid Deepening spells DISASTER.
3. Sustained air-sea fluxes (>1.5 Kw m-2) with little SST cooling and OHC change .
4. Deep warm thermal layers (>100 m) with OHC values exceeding 100 kJ cm-2.
5. Part of the natural ocean variability (gyre circulation) with strong currents (1-1.5 m s-1 ) advecting warm water (advective time scale is O(day)).
Models need good 3-D Ocean Data to evaluate the coupled models-operations.