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Purpose
• Perform Harmonic Analysis on 7 Tide Stations (Each Person Assigned 1 Station)– Run T_Tide to extract the Harmonic
Constituents– Compare the Predicted Tides to Original
Tides– Extract and Explain the Residuals– Compare the Residuals from each Station
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SW Bay of Fundy
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Station Selection
Station NameSt. John, NB Rui
Eastport, ME Lei
Cutler, ME Paul
Yarmouth, NS Tyson
North Head, NB Clark
Digby, NS Auke
Brier Island, NS Faisal 7
T_Tide
• T_Tide Harmonic Analysis Toolbox– http://www.eos.ubc.ca/~rich/#T_Tide
• Set of Matlab routines that can be used to perform classical harmonic analysis
• Read the reference: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.
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Steps:
1. Download T_Tide– See Lab Webpage for Link
2. Open Matlab and Change your “Current Directory” to T_Tide Directory
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Using T_Tide
Explanation of each subroutine
How to Run t_tide
Demo of t_tide program
Same as Example from Class
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Using T_Tide
• Save Tide Time Series Data from Lab Webpage
– For input: Only Need One Column of Tide Data
– Need to know Sampling Interval– Hours? Minutes?
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Using T_Tide
Input
• Tide Data• Flags
– Interval– Start Time– Latitude
Output
• Structure– Constituent Names– Frequency– Amplitude, Amp Error,
Phase, Phase Error
• Predicted Time Series from Constituents
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Run T_Tide
[Tide_Struct, Pred_Out] = t_tide(TideData,'interval',1/6, 'start time', StartTime,'latitude',44+38/60);
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Run T_Tide
• Tide_Struct – Structure (Constituent Names, Frequency, Amplitude, Amp Error,
Phase, Phase Error)
• Pred_Out– Predicted Tide Time Series– Same interval as input tide time series
[Tide_Struct, Pred_Out] = t_tide(TideData,'interval',1/6, 'start time', StartTime,'latitude',44+38/60);
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Run T_Tide
• TideData– One Column of Water Level Observations
loaded into Matlab– >> TideData = load('North_Head15min.txt');
– Must know the time between observations for next step
[Tide_Struct, Pred_Out] = t_tide(TideData,'interval',1/6, 'start time', StartTime,'latitude',44+38/60);
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• ‘interval’ is a fixed option in t_tide– See >>help t_tide for explanation– 1/6 is the interval between observations (units = hours)
• 15 minutes = 1/4• 10 minutes = 1/6• 6 minutes = 1/10
Run T_Tide
[Tide_Struct, Pred_Out] = t_tide(TideData,'interval',1/6, 'start time', StartTime,'latitude',44+38/60);
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• ‘start time’ is a fixed option in t_tide– See >>help t_tide for explanation
• StartTime is the start time of the tidal data series• StartTime Matlab Serial Date Number
– Ex: StartTime = datenum(2006,6,22,0,0,0)• help datenum
Run T_Tide
[Tide_Struct, Pred_Out] = t_tide(TideData,'interval',1/6,
'start time',StartTime,'latitude‘,44+38/60);
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Start Time
• Need to be working in correct time zone• Ensure that the time zone associated
with the observations is the same as the one associated with the published harmonic constituents (Bluefile of NOAA website)
• Bluefile: +4 hours• NOAA: GMT
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• For Nodal Corrections– Helps resolve satellite constituents
– See Slide 34 from Nov 2nd lecture
– See T_Tide reference from lab webpage
• Latitude in Decimal Degrees for Station Location
• Ex: 44 degrees 38 minutes 44+38/60 degrees
Run T_Tide
[Tide_Struct, Pred_Out] = t_tide(TideData,'interval',1/6, 'start time', StartTime,'latitude',44+38/60);
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Deliverables(See Lab Webpage)
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