Tide, Buoyancyand WindInduced Circulation in the Narragansett Bay

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Tide-, Buoyancy-and Wind-Induced Circulation in
the Narragansett Bay
Changsheng Chen Graduate School for Marine
Science and Technology University of
Massachusetts New Bedford, MA 02744-1221 Phone
508-910-6388 Fax [phone] E-mail
c1chen_at_umassd.edu Website http//codfish.smast.
umassd.edu

• Contributors
• Liuzhi Zhao, Research Scientist, SMAST/UMASSD
• Robert C. Beardsley, Senior Scientist, Woods Hole
  Oceanographic Institution

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Main questions

• How much do we know about the circulation in the
  Narragansett Bay? Tides? River-discharge? Wind?
• How much have we learned from previous and
  on-going modeling efforts? Finite-difference (ASA
  non-orthogonal coordinate model) and
  finite-volume model (FVCOM)?
• What should be done to improve our understandings
  of the ecosystem dynamics and build up a
  practical coastal managements in the Narragansett
  Bay? An integrated coastal management model
  system with a regional cooperative monitoring
  network?

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Areas 380 km2 Volume 3.1?109 m3 Average
depth 7.8 m Deepest depth 56 m Largest
Rivers Pawtuxet, Blackstone Taunton
Station BUZM3
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M2 Co-tidal Chart
Propagate northeastward with small co-tidal range
between the entrance and up-end. Amplitudes
50-60 cm (range 10 cm) Phase 2-8
(range 12 minutes) M2 tide account for 70-80
of total energy, while
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Rannual 14 m3/s
Rannual 22 m3/s
Rannual 10 m3/s
Flushing time T Volume/Discharge 3.1?109
m3/46 m3/s 780 days !
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Key point Good coherence in the along-coastal
direction but not in the cross-coastal direction.
Seabreeze is important for local wind variation
u
v
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Monthly scatter plots of the wind velocity for
2001
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The field of the surface wind stress interpolated
from measurement data available in the Bay and
over shelf.
Period March 10- April 10, 2001
Time interval 0ne hour
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Hicks (1959) (Limnol. Oceanogr)
Aug-Sept, 51 Feb-Mar, 52 Aug-Sept, 52 Feb,
56 Apr, 56 June, 56 Aug, 56
T4
T3
ASA company Aug-Sept, 97 Sept, 98 Feb-Mar, 99
T2
T1
Chris Kincaid ADCP transect Aug, 1996
Dan McDonald ADCP/CTD survey, July, 2004 in MHB
SMAST Mooring (Brian Howes)
Weisburg-1972 mooring
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Surface
Aug, 56
Surface
Temperature
Salinity
Bottom
Bottom
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Nov, 54-Oct, 55
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Impact of the Power Station
Discharge Flow
Peak in the year
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Aircraft
ASA Measurement
9/11/98 220 PM
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Aircraft
ASA Measurement
9/11/98 600 AM
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Key points based on the long-term tidal, river,
and wind measurements

• Tidal motions are dominated by semi-diurnal M2
  tidal constituents, but other semi-diurnal (S2
  and N2) and diurnal (O1 and K1) can not ignored
  for the fortnightly and monthly variations
• Freshwater discharges has significant impact on
  the Bay in late winter through spring. Not only
  total discharge rate but also significant
  interannual variability
• Wind fields are characterized with strong
  temporal variability in all seasons. Therefore,
  monthly climatologic fields would not represent
  the realistic world of the wind-induced
  circulation in the Bay. The short-term (daily to
  week) variability of the wind field must be taken
  into account.
• It is surprised that there is no sufficient time
  and spatial coverage of hydrographic survey data
  (water temperature and salinity) in the Bay. We
  even can not build a monthly climatologic field
  of water temperature and salinity in that area.
• Hot-water from the Power Plant might change the
  stratification in the HMB and thus has an impact
  on the Narragansett Bay

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Narragansett/Mount Hope Bay Model System
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Meso-Scale Meteorological Model (MM5) Domain
NB Domain
Large Domain
9 km
3 km
27 km
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FVCOM Domain
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Phase (Degree)
Amplitude (m)
Maximum Error Amplitude 5 cm Phase 5o
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Flood Tidal Period
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Ebb tidal period
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Residual Current Comparison with different
horizontal resolution
Fine Resolution 50-70 (m)
Coarse Resolution 200-250 (m)
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Select moment for the resolution effect comparison
April 8, 2001 at 1900 GMT
Kincaid (URI) ADCP Data Clear Showed Tide pumping
Coarse Resolution
Fine Resolution
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Select moment for the resolution effect comparison
April 8, 2001 at 2300 GMT
Kincaid (URI) ADCP Data Clear Showed a persistent
outflow along the west boundary of the East
Passage
Fine Resolution
Coarse Resolution
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Show a movie for temperature plume by power plan
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Tide only
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Tide Rivers
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TideRiversWinds
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To under the tide-, river-discharge, and
wind-induced circulation in the Narragansett Bay,
we need

• Develop the high-resolution coupled
  atmosphere-ocean model system
• Develop a regional monitoring network to measure
  the currents, water temperature and salinity.

Needs for developing the coastal management
system for Narragansett Bay

• Develop the high-resolution water quality model
  driven by realistic meteorological forcing and
  high-resolution model-derived circulation and
  mixing
• Increases the coverage of nutrients and DO
  measurements in both space and times.

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THE COUPLED Proposed Ecosystem Model System
Assimilation
Forcings
NCAR-ETA Weather Model

• Real-time tidal forcing (M2, S2, N2, O1, and K1)
• River discharges
• Other open boundary forcings

Buoys Satellite
MM5 (WRF)
Winds Heat flux
SST CTD Currents
FVCOM
Water Quality Model
Sediment Model