A Python code to extract tidal harmonic components from a hdf5 file.

Points/Cells Coordinates

The first step is to obtain the point coordinates that will be used to extract the information from the HDF5 file. Here, the coordinates are from a MOHID Land grid file, which the DTM was exported as XYZ. In GIS software, only the boundary coordinates were kept and saved into a txt file.

FES Model

The tidal model used is FES2014, and it can be downloaded here:

Tidal Extraction

The script opens the HDF file, finds close coordinates between the Points and the FES2014 coordinates, and extracts the amplitude and phase for each harmonic available. The script also saves in a text file the amplitudes and phases for each Point coordinated, as:

Harmonics, Amplitude, Phase
M2,1.6089622497558593,256.92163848876953
N2,0.3257173156738281,243.20376586914062
O1,0.09126119613647461,242.03919219970703
S2,0.49927242279052736,289.93888092041016

The second script is developed in Matlab, but it can be easily transformed into Python. Here, the tide prediction is done using the formula (Foreman and Henry, 1989):

signal = amplitude * cos((frequency * time) - phase)

The only function from t_tide used here is to find the frequency for each component (t_tide_name2freq)

Until now, you have coordinate points from the center cell, but to add a boundary value in each cell in MOHID Land, It requires one line for each cell. This script will help you to create those lines.

Don't forget to change the 'half_cell_size' variable according to your cell size. Since the coordinates are in degrees, this variable has to be in degrees.

Thus, pay attention to your coordinates.

This will save different lines for each cell, allowing you to impose different water levels for each cell in MOHID Land.

Now that the prediction and lines are made, this information needs to be passed to the MOHID Land.

First, the prediction files must be written in the MOHID time series file.

The code will process and transform for this specific format.

The final step is to join all this information in a block that MOHID Land can read:

<begin_boundary_line>
LINE_FILENAME           : D:/DOUTORAMENTO/Tide/Tide_Extractor/output_lines/tidal_line_-0.503179_-46.162969.lin
VARIABLE_WATER_LEVEL    : 1
DEFAULTVALUE            : 0
FILENAME                : D:/DOUTORAMENTO/Tide/Tide_Extractor/output_timeseries/TidePara_FES2014_-0.503179_-46.162969.txt
DATA_COLUMN             : 2
<end_boundary_line>

After this file is created, copy to the RunOff_1.dat file.

Now you are ready to run multiple tide inputs in MOHID Land!

Any questions, contact: [email protected]