OC3570

1
OC3570 Operational Oceanography Summer Cruise
Project An Examination of Three Cruise
Locations with the ICON Tide Prediction Model By
Charles Allen September 19, 2005
2
Objective
What are we trying to do here? -Look at three
distinct points (of definite time and space) of
the cruise. -Look at the temperature, salinity,
and density graphs for two of those points for
basic trends. -Look at the Sea Level Heights for
Monterey Bay for overall tidal information. -Look
at the Sea Current information (from ADCP data)
at those points. -Look at the effect of wind on
the surface currents at those locations. -Run
the ICON Tidal Prediction model for theoretical
results. -Compare the Model Prediction to the
Actual Current Information.
3
Points of Interest

• On the first leg of the cruise, we will look at
  the location of the 13-hour time series.
• 36 - 41.50 N
• 122- 00.00 W
• July 20, 2005, from
• 0100Z to 1300Z

4
Points of Interest

• On the second leg of the cruise, we will look at
  the location of the 13-hour time series.
• 36 - 46.33 N
• 121- 57.70 W
• July 23, 2005, from
• 0200Z to 1500Z

• We will also take the location of the TRBM ADCP
  mooring.
• 36 41.94 N
• 121 56.22 W
• - July 19 to August 21, 2005

5
The CTDs
-Shallower water during this time series
200m -Evidence of Internal Wave -Strong
thermocline around 10m down.
6
The CTDs
-Fresher water toward the surface. -Again,
evidence of internal wave.
7
The CTDs
-Density tracks with both salinity and
temperature. More temperature effects near the
surface, more salinity effects deeper down.
8
The CTDs
-Deeper water at this location 750m -Less
dynamic than the first time series
9
The CTDs
10
The CTDs
11
Sea Level Heights
-Received from NOAA/NOS -For the week of the
cruise, Sea Level Heights ranged from 1.200m
above MSL to 1.300m below MSL -Time Series
Times are highlighted.
12
Sea Level Heights
Time Series 1 -Highest water at 0400Z -Lowest
water at 1200Z -Strongest shoreward tidal
current at 0100 -Strongest seaward tidal
current at 0730 -One-half of diurnal cycle
13
Sea Level Heights
Time Series 2 -Highest water at 0700Z -Lowest
water at 1400Z -Strongest shoreward tidal
current at 0400 -Strongest seaward tidal
current at 1030
14
ADCP Data
-ADCP data from both Time Series locations are
from the hull-mounted ADCP under the Point
Sur. -ADCP data from the TRBM comes directly
from the device.
15
ADCP Data
300kHz ADCP
Time Series 1 -U (North-South) current is
generally positive (northward) over the time
period but decreases and finally becomes
southward after the Low Water mark. -V(East-West)
current is generally eastward until the max
seaward flow, at which point it becomes slightly
westward.
16
ADCP Data
-Depth-averaged. -Generally northward
flow. -Generally eastward flow until max seaward
flow time.
17
ADCP Data
-Strip plot Each line is a different depth bin
of the ADCP -Bad or incomplete data is blanked
out. -Notice the shift in U from north to south
in the thermocline and halocline depths.
18
ADCP Data
-Again, notice the change in V with the changes
in depth. -Could be a result of the CUC or
simply summertime eddies or upwelling filaments.
19
ADCP Data
75kHz ADCP
Time Series 2 -U seems to start out southward
and then seem to approach zero after the High
Water mark. -V seems to start slightly west then
become east after the High Water mark. By the
max seaward flow time, it seems to be around zero.
20
ADCP Data
-Depth-averaged -This is a little clearer. -U
is generally north-flowing after the max
shoreward flow time. -V is generally westward
until the High Water mark, at which point it is
an easterly flow until the max seaward flow.
21
ADCP Data
-Not a whole lot of distinctive areas in this
strip plot
22
ADCP Data
-Ditto here for V
23
ADCP Data
TRBM (Trawl Resistant Bottom Mounted
mooring) -Pattern is indicative of the tidal
signal over both the month and the cruise week.
24
ADCP Data
TRBM (Trawl Resistant Bottom Mounted
mooring) -Pattern is indicative of the tidal
signal over both the month and the cruise
week. -V seems to vary more than U.
25
HF Current Data
-HF Radar measures the amount of current at the
surface (primarily due to winds). -Calculated
from the returns of four different radar stations
around Monterey Bay
26
HF Current Data
Around Max Shoreward Flow
Type Text Here
27
HF Current Data
Type Text Here
High Water Time
Around Max Seaward Flow Time
28
HF Current Data
-Early on, the surface currents flow southward
while the ADCP indicates a northward flow. -At
the end of the time period, however, the surface
and subsurface flows both indicate a south and
western flow.
Low Water Time
29
HF Current Data
At Max Shoreward Flow
30
HF Current Data
Type Text Here
After Max Seaward Flow
Near High Water Mark
31
HF Current Data
-At the Max Shoreward Flow time, the surface
currents show a strong south-southeastern flow,
while the ADCP shows a slight southwestern
flow. -At the High Water mark, the surface has a
western flow. According to the ADCP, the flow is
northern. -The northeastern flow around the max
seaward flow time corrolates to both the surface
and depth-averaged ADCP.
32
ICON Model
What is it? -Innovative Coastal-ocean Observing
Network -Developed by Leslie Rosenfeld, Igor
Shulman, Mike Cook, Lev Shulman and Jeff Paduan
as a way to model tidal currents in the MB
littoral region. -The ICON modelis a 3-D,
free-surface, sigma-coordinate version of the
Princeton hydrographic model. The orthogonal,
curvilinear grid has variable resolution in the
horizontal, ranging from 1-4 km. The model has
30 vertical sigma levels. Dissipation is through
quadratic bottom friction using the Charnock
formulation to determine the drag coefficient.
33
ICON Model
Cmon, what is it really? -Basically, it is a
clever computer program designed to theoretically
estimate tidal currents in an entire region
(Monterey Bay). It takes eight tidal
constituents to formulate values in 30 curving
3-D surfaces (because the surfaces curve, that is
why there is varying resolution in the
horizontal). -The model was originally run for
56 days starting August 1, 2000. After the model
was run, data past that time can be extrapolated
from the data in the model (the tidal
constituents do not change over time)
34
ICON Model
Inputs to the ICON Model The eight tidal
constituents used in the model are as follows
M2, S2, N2, K2, K1, O1, P1, and Q1 -While
there are many more components to tidal forcing,
those 8 are by far the largest contributors.
Hence, fairly accurate measurements can be made
throughout the model run and into the
future. -In this instance, I utilized the model
with the assumption of of no stratification in
the water column (it simplifies the math without
significantly changing the results).
35
ICON Model Predictions
Time Series 1 -Prediction shows continual
southern flow throughout the time
period. -Prediction shows a western flow until
the High Water mark, then it becomes eastern.
36
Model vs. Actual
U Comparison The depth-averaged U from the
ADCPdata shows a fairly consistent northern flow.
ICON predicted a consistently southern flow. V
Comparison The ADCP data indicates a change of
east to west flow over the course of the time
period. ICON predicted a change of west to
east. Notice the magnitude of the velocities for
each. The ICON model has much lower velocities
than the ADCP data.
37
ICON Model Predictions
Time Series 2 -Predicted northern flow
decreasing until the High Water mark, then
southern flow. -Eastern flow is predicted
throughout the time period.
38
Model vs. Actual
U Comparison The depth-averaged ADCP and ICON
graphs are almost inverse in nature V Comparison
The ADCP data indicates a change of east to west
flow over the course of the time period. ICON
predicted a change of west to east. Again notice
the magnitude of the velocities for each. In
this case, the ICON model more closely
approximates the magnitude of the tidal currents
shown by the ADCP data, though the ICON model
still has smaller magnitudes.
39
ICON Model Predictions
TRBM -Months worth of prediction here. Notice
the generally southern and western flow for the
first two weeks and the subsequent northern and
eastern flow for the following week. The final
week has predicted southern and western flow.
40
Model vs. Actual
U Comparison Again, this is for the whole
month. The TRBM ADCP data shows a consistent
diurnal wave pattern roughly balanced around
zero. The ICON model predicted a much more
erratic wave pattern with a tendency for the
first two weeks being southern flow, the third
week being northern flow, and the final week
again being southern flow. Notice the ICON model
predicts a maximum magnitude of roughly 3 cm/s,
while the TRBM data indicates maximum magnitudes
of rough /- 11 cm.s.
41
Model vs. Actual
V Comparison This is very similar to U. The
TRBM ADCP data shows a consistent diurnal wave
pattern roughly balanced around zero. The ICON
model predicted a much more erratic wave pattern
with a tendency for the first two weeks being
western flow, the third week being eastern flow,
and the final week again being western
flow. Notice the ICON model predicts a maximum
magnitude of roughly 3 cm/s, while the TRBM data
indicates maximum magnitudes of rough /- 11 cm.s.
42
Data Explained by Tides
Type Text Here
TIME SERIES 1 U Percent Var Predicted / Var
Original 32.5 V Percent Var Predicted / Var
Original 25.0 TIME SERIES 2 U Percent
Var Predicted / Var Original 54.7 V Percent
Var Predicted / Var Original 79.2 TRBM U
Percent Var Predicted / Var Original 47.8 V
Percent Var Predicted / Var Original 16.5
Clearly there are other forces at work here.
43
Conclusions

• Monterey Bay is a dynamic littoral area in which
  many forces are at work.
• The ICON Model seems to do an acceptable job
  predicting the tidal currents within the Bay,
  however currents at specific points can be caused
  by more than just tides (wind, eddies, oceanic
  currents, etc.).
• -The currents measured at the three cruise points
  has a wide range of compatibility with the ICON
  model runs. Hence, verifying the accuracy of the
  ICON model can prove troublesome.
• -Regardless of compatibility, the ICON model
  seems to predict a lower magnitude of tidal
  current values than what is actually seen at the
  points.

44
Conclusions
-Errors in the process do not help matters any.
Errors may be caused by -Wind forcing -Only
eight tidal constituents are used in the
model -Grid points on the model are not
precisely on the cruise points. -Filaments and
eddies -The ever-extending time frame to which
one must extend the data from the original ICON
model run in 2000. -More work needs to be done
comparing the ICON model with obtained ADCP data
to determine and eliminate errors and produce
useful predictions.
45
Acknowledgements
-Mr. Mike Cook for Data Processing and MATLAB
Expertise -Mr. Tarry Rago for ADCP/TRBM data
processing -Dr. Leslie Rosenfeld et al. for ICON
Model Usage -The crew, technicians and
scientists on the MV Point Sur -Arnold
Schwarzenegger for the movie Commando (which
has nothing to do with this report)
46
Questions? Concerns?