========
Spectrum
========

Compute spectrum and spectrum ratio on some area
************************************************

Load data

.. code-block:: python

    raw = RegularGridDataset(grid_name, lon_name, lat_name)
    filtered = RegularGridDataset(grid_name, lon_name, lat_name)
    filtered.bessel_low_filter("adt", 150, order=3)

    areas = dict(
        sud_pacific=dict(llcrnrlon=188, urcrnrlon=280, llcrnrlat=-64, urcrnrlat=-7),
        atlantic_nord=dict(llcrnrlon=290, urcrnrlon=340, llcrnrlat=19.5, urcrnrlat=43),
        indien_sud=dict(llcrnrlon=35, urcrnrlon=110, llcrnrlat=-49, urcrnrlat=-26),
    )

Compute and display spectrum

.. code-block:: python

    fig = plt.figure(figsize=(10, 6))
    ax = fig.add_subplot(111)
    ax.set_title("Spectrum")
    ax.set_xlabel("km")
    for name_area, area in areas.items():
        lon_spec, lat_spec = raw.spectrum_lonlat("adt", area=area)
        mappable = ax.loglog(*lat_spec, label="lat %s raw" % name_area)[0]
        ax.loglog(
            *lon_spec,
            label="lon %s raw" % name_area,
            color=mappable.get_color(),
            linestyle="--"
        )

        lon_spec, lat_spec = filtered.spectrum_lonlat("adt", area=area)
        mappable = ax.loglog(*lat_spec, label="lat %s high" % name_area)[0]
        ax.loglog(
            *lon_spec,
            label="lon %s high" % name_area,
            color=mappable.get_color(),
            linestyle="--"
        )

    ax.set_xscale("log")
    ax.legend()
    ax.grid()
    fig.savefig("share/png/spectrum.png")


.. image:: ../share/png/spectrum.png

Compute and display spectrum ratio

.. code-block:: python

    fig = plt.figure(figsize=(10, 6))
    ax = fig.add_subplot(111)
    ax.set_title("Spectrum ratio")
    ax.set_xlabel("km")
    for name_area, area in areas.items():
        lon_spec, lat_spec = filtered.spectrum_lonlat("adt", area=area, ref=raw)
        mappable = ax.plot(*lat_spec, label="lat %s high" % name_area)[0]
        ax.plot(
            *lon_spec,
            label="lon %s high" % name_area,
            color=mappable.get_color(),
            linestyle="--"
        )

    ax.set_xscale("log")
    ax.legend()
    ax.grid()
    fig.savefig("share/png/spectrum_ratio.png")

.. image:: ../share/png/spectrum_ratio.png