1. 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. N 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. N W
July 23, 2005, from
0200Z to 1500Z
We will also take the location of the TRBM ADCP mooring.
36 – N
121 – W
- July 19 to August 21, 2005

5. The CTD’s -Shallower water during this time series: ~200m
-Evidence of Internal Wave
-Strong thermocline around 10m down.

6. The CTD’s -Fresher water toward the surface.
-Again, evidence of internal wave.

7. The CTD’s
-Density tracks with both salinity and temperature. More temperature effects near the surface, more salinity effects deeper down.

8. The CTD’s -Deeper water at this location: ~750m
-Less dynamic than the first time series

9. The CTD’s

10. The CTD’s

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.
Solid line is HW, Dashed line is LW, Square Dot line is max shoreward flow, Circle Dot line is max seaward flow.

16. ADCP Data -Depth-averaged. -Generally northward flow.
-Generally eastward flow until max seaward flow time.

17. 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.

18. 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.

19. ADCP Data TRBM (Trawl Resistant Bottom Mounted mooring)
-Pattern is indicative of the tidal signal over both the month and the cruise week.

20. 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.

21. 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

22. HF Current Data Around Max Shoreward Flow Type Text Here
Southeastward flow
Around Max Shoreward Flow
Type Text Here

23. HF Current Data Type Text Here High Water Time
Around Max Seaward Flow Time

24. 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

25. HF Current Data
At Max Shoreward Flow

26. HF Current Data Type Text Here Near High Water Mark
After Max Seaward Flow

27. 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.

28. 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 model…is 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.”

29. ICON Model C’mon, 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, 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)

30. 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).

31. 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.

32. 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.

33. 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.

34. 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.

35. ICON Model Predictions
TRBM
-Month’s 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.

36. 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.

37. 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.

38. 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.

39. 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.

40. 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.

41. 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)

42. Questions?
Concerns?