Colocate looper with eddy from altimetry

All loopers data used in this example are a subset from the dataset described in this article [Lumpkin, R. : Global characteristics of coherent vortices from surface drifter trajectories](https://doi.org/10.1002/2015JC011435)

import re

from matplotlib import pyplot as plt
from matplotlib.animation import FuncAnimation
import numpy as np
import py_eddy_tracker_sample

from py_eddy_tracker import data
from py_eddy_tracker.appli.gui import Anim
from py_eddy_tracker.observations.tracking import TrackEddiesObservations

class VideoAnimation(FuncAnimation):
    def _repr_html_(self, *args, **kwargs):
        """To get video in html and have a player"""
        content = self.to_html5_video()
        return re.sub(
            r'width="[0-9]*"\sheight="[0-9]*"', 'width="100%" height="100%"', content
        )

    def save(self, *args, **kwargs):
        if args[0].endswith("gif"):
            # In this case gif is used to create thumbnail which is not used but consume same time than video
            # So we create an empty file, to save time
            with open(args[0], "w") as _:
                pass
            return
        return super().save(*args, **kwargs)


def start_axes(title):
    fig = plt.figure(figsize=(13, 5))
    ax = fig.add_axes([0.03, 0.03, 0.90, 0.94], aspect="equal")
    ax.set_xlim(-6, 36.5), ax.set_ylim(30, 46)
    ax.set_title(title, weight="bold")
    return ax


def update_axes(ax, mappable=None):
    ax.grid()
    if mappable:
        plt.colorbar(mappable, cax=ax.figure.add_axes([0.94, 0.05, 0.01, 0.9]))

Load eddies dataset

cyclonic_eddies = TrackEddiesObservations.load_file(
    py_eddy_tracker_sample.get_demo_path("eddies_med_adt_allsat_dt2018/Cyclonic.zarr")
)
anticyclonic_eddies = TrackEddiesObservations.load_file(
    py_eddy_tracker_sample.get_demo_path(
        "eddies_med_adt_allsat_dt2018/Anticyclonic.zarr"
    )
)

Load loopers dataset

loopers_med = TrackEddiesObservations.load_file(
    data.get_demo_path("loopers_lumpkin_med.nc")
)

Global view

ax = start_axes("All drifters available in Med from Lumpkin dataset")
loopers_med.plot(ax, lw=0.5, color="r", ref=-10)
update_axes(ax)

One segment of drifter

Get a drifter segment (the indexes used have no correspondance with the original dataset).

looper = loopers_med.extract_ids((3588,))
fig = plt.figure(figsize=(16, 6))
ax = fig.add_subplot(111, aspect="equal")
looper.plot(ax, lw=0.5, label="Original position of drifter")
looper_filtered = looper.copy()
looper_filtered.position_filter(1, 13)
s = looper_filtered.scatter(
    ax,
    "time",
    cmap=plt.get_cmap("Spectral_r", 20),
    label="Filtered position of drifter",
)
plt.colorbar(s).set_label("time (days from 1/1/1950)")
ax.legend()
ax.grid()

Try to find a detected eddies with adt at same place. We used filtered track to simulate an eddy center

match = looper_filtered.close_tracks(
    anticyclonic_eddies, method="close_center", delta=0.1, nb_obs_min=50
)
fig = plt.figure(figsize=(16, 6))
ax = fig.add_subplot(111, aspect="equal")
looper.plot(ax, lw=0.5, label="Original position of drifter")
looper_filtered.plot(ax, lw=1.5, label="Filtered position of drifter")
match.plot(ax, lw=1.5, label="Matched eddy")
ax.legend()
ax.grid()

Display radius of this 2 datasets.

fig = plt.figure(figsize=(20, 8))
ax = fig.add_subplot(111)
ax.plot(looper.time, looper.radius_s / 1e3, label="loopers")
looper_radius = looper.copy()
looper_radius.median_filter(1, "time", "radius_s", inplace=True)
looper_radius.loess_filter(13, "time", "radius_s", inplace=True)
ax.plot(
    looper_radius.time,
    looper_radius.radius_s / 1e3,
    label="loopers (filtered half window 13 days)",
)
ax.plot(match.time, match.radius_s / 1e3, label="altimetry")
match_radius = match.copy()
match_radius.median_filter(1, "time", "radius_s", inplace=True)
match_radius.loess_filter(13, "time", "radius_s", inplace=True)
ax.plot(
    match_radius.time,
    match_radius.radius_s / 1e3,
    label="altimetry (filtered half window 13 days)",
)
ax.set_ylabel("radius(km)"), ax.set_ylim(0, 100)
ax.legend()
ax.set_title("Radius from loopers and altimeter")
ax.grid()

Animation of a drifter and its colocated eddy

def update(frame):
    # We display last 5 days of loopers trajectory
    m = (looper.time < frame) * (looper.time > (frame - 5))
    anim.func_animation(frame)
    line.set_data(looper.lon[m], looper.lat[m])


anim = Anim(match, intern=True, figsize=(8, 8), cmap="magma_r", nb_step=10, dpi=75)
# mappable to show drifter in red
line = anim.ax.plot([], [], "r", lw=4, zorder=100)[0]
anim.fig.suptitle("")
_ = VideoAnimation(anim.fig, update, frames=np.arange(*anim.period, 1), interval=125)