This lab will use the T_Tide Harmonic Analysis Toolbox for Matlab developed by Rich Pawlowicz at UBC. The program takes a raw tidal time series as input and outputs the amplitude and phase of the harmonic constituents for the time series, along with error estimates.

• Lab Presentation
  

The objectives for this lab are as follows.

1. Input a tidal time series into the T_Tide function.

• Read the T_Tide reference listed below (Pawlowicz et al., 2002)
• See the lab presentation for how to run t_tide
• The example script "t_demo" included with the t_tide package shows an example of the capabilities of t_tide.
• Choose a Tide Station where you can download at least 3 months of observed water level information and have access to the harmonic constituents. Ex: Any NOAA gauge data
  If you choose a Canadian tide gauge email me and I will send you the harmonic constituents.

2. Compare the derived harmonics (t_tide analysis from the 3 months of water level data at your choosen station) to the published harmonics for the source data. (Make sure that you are using the correct time zone)

• Comment on differences in the harmonic constituents. (Ex. Which constituents are missing between the two lists and why? How different are the amplitudes and phases? and any other observations you can think of)
• Are the differences in Amplitude and Phase between the predicted (t_tide) and published constituents within the predicted confidence inteval (from t_tide) for that constituent (M2,K1,...) ?

3. Characterize what type of tide you are dealing with (see Form Number in notes)

4. From examining the geographic location of your tide station, what are the Non-Tidal effects which could be important in your area. (The "Non-tidal sea-level variations")

5. Plot the original tidal time series and the new predicted times series output from T_Tide.

• Determine the residuals between the predicted tides and the original tidal series (make sure they are in the same time zone) 

6. Examine the residual tidal time series and explain the residuals based on meteorological data from the same time period and location. (Ex. Pressure, Wind, River Discharge, Precipitation, etc.) 

7. Present your tidal residuals in class (very short presentation) along with an explanation of why they exist (from Question 6).

Resources:

• R. Pawlowicz, B. Beardsley, and S. Lentz, "Classical tidal harmonic analysis including error estimates in MATLAB using T_TIDE", Computers and Geosciences 28 (2002), 929-937.




• Foreman, M.G.G., 1977. Manual for Tidal Heights Analysis and Prediction. Pacific Marine Science Report 77-10, Institute of Ocean Sciences, Patricia Bay, Sidney, B.C., 58 pp. (2004 revision).

   

Last Updated November 16th, 2008