Lab C 2007 Tidal Analysis Lab Ian Church

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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 5

SW Bay of Fundy 6

Station Selection StationName St. John, NBRui Eastport, MELei Cutler, MEPaul Yarmouth, NSTyson North Head, NBClark Digby, NSAuke Brier Island, NSFaisal 7

T_Tide T_Tide Harmonic Analysis Toolbox – 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),

Steps: 1.Download T_Tide –See Lab Webpage for Link 2.Open Matlab and Change your “Current Directory” to T_Tide Directory 9

Using T_Tide Explanation of each subroutine How to Run t_tide Demo of t_tide program Same as Example from Class 10

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? 11

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 12

Run T_Tide [Tide_Struct, Pred_Out] = t_tide(TideData,'interval',1/6, 'start time', StartTime,'latitude',44+38/60); 13

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); 14

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); 15

‘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); 16

‘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); 17

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 18

For Nodal Corrections –Helps resolve satellite constituents –See Slide 34 from Nov 2 nd 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); 19

Deliverables (See Lab Webpage) 20