Displacement artifact?

[TraziBatine]

Hi. I was wondering if this shown here on the plot is an artefact or am I doing something wrong... I calculated displacement with:

pt.predict(lat, lon, startdate, duration, samprate, tidalpoten, tidalcompo=3, statazimut=0)

As you can see, there is a horizontal line at around -35, +35.

Thanks for the info!

[trichter]

Hi. Interesting! Which observable did you plot? Can you share the code to generate this plot? A guess: Maybe +-35° is the latitude for which diurnal and semidiurnal constituents have equal strength? For the region including the equator semidiurnal tides dominate, for the regions including the poles diurnal tides dominate. There has to be a region in which the transition might produce such effects.

[TraziBatine]

Hi. Thanks for the answer. Here I plot N (statazimut=0) component displacement. On the E component (statazimut=90) such lines are not present, thats why I thought it to be an artefact.

Calculations are done on hourly basis.

Later I will test statazimut=1 to see if it is still present.

Code for plot:

`step = 2.0 grid_lat = np.arange(-90.0, 90.0 + step, step) grid_lon = np.arange(-180.0, 180.0 + step, step)

Construct a dense grid of lon/lat points.

inds_lon, inds_lat = np.meshgrid(grid_lon, grid_lat)

Create an empty array of correct size.

all_vals = np.empty((grid_lat.shape[0], grid_lon.shape[0])) all_vals.fill(np.nan)

iextent = (-180, 180, -90, 90)

inorm = Normalize(vmin=tides_min, vmax=tides_max)

land_color = '#f5f5f3' water_color = '#cdd2d4'

all_invals = list(zip(lons, lats, tides))

Fill empty array with values from input data.

for inval in all_invals: ilon = np.where(inds_lon == inval[0])[1][0] ilat = np.where(inds_lat == inval[1])[0][0] all_vals[ilat, ilon] = inval[2]

fig = plt.figure(figsize=(16,9))

ax = fig.add_subplot(1,1,1, projection=crs.PlateCarree())

ax.add_feature(cfeature.OCEAN, color=water_color, linewidth=1) ax.add_feature(cfeature.LAND, color=land_color, linewidth=1) ax.add_feature(cfeature.COASTLINE, color='black', linewidth=1) ax.gridlines() ax.set_global()

im = ax.imshow(all_vals, extent=iextent, origin='lower', alpha=0.75, interpolation='bilinear', aspect='equal', resample=False, cmap='jet')

fig.tight_layout() plt.show()`

Cheers

[hydrogeoscience]

This seems to be a bug within the Fortran code. I will need some time to dig into this issue ...

[hydrogeoscience]

Just saw that the Fortran code has a comment "Attention: this component has never been tested" - which speaks to this possibly being buggy.