{
  "cells": [
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n# Double gyre - Lagrangian Coherent Structures\n\nCalculating attracting and repelling LCS for an idealised (analytical) eddy current field.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "from datetime import datetime, timedelta\nimport matplotlib.pyplot as plt\n\nfrom opendrift.readers import reader_double_gyre\nfrom opendrift.models.oceandrift import OceanDrift\n\no = OceanDrift(loglevel=20)  # Set loglevel to 0 for debug information\n\no.set_config('environment:fallback:land_binary_mask', 0)"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "Note that Runge-Kutta here makes a difference to Euler scheme\n\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "o.set_config('drift:advection_scheme', 'runge-kutta4')\n\ndouble_gyre = reader_double_gyre.Reader(epsilon=.25, omega=0.628, A=0.1)\nprint(double_gyre)\n\no.add_reader(double_gyre)\n\nlcs = o.calculate_ftle(time=double_gyre.initial_time+timedelta(seconds=3),\n                       time_step=timedelta(seconds=.5),\n                       duration=timedelta(seconds=15),\n                       delta=.02)"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "These plots should reproduce Mov 12 on this page:\nhttps://shaddenlab.berkeley.edu/uploads/LCS-tutorial/examples.html\n\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "plt.subplot(2,1,1)\nplt.imshow(lcs['RLCS'][0,:,:], interpolation='nearest', cmap='jet', origin='lower')\nplt.colorbar()\nplt.title('Repelling LCS (forwards)')\nplt.subplot(2,1,2)\nplt.imshow(lcs['ALCS'][0,:,:], interpolation='nearest', cmap='jet', origin='lower')\nplt.colorbar()\nplt.title('Attracting LCS (backwards)')\nplt.show()"
      ]
    }
  ],
  "metadata": {
    "kernelspec": {
      "display_name": "Python 3",
      "language": "python",
      "name": "python3"
    },
    "language_info": {
      "codemirror_mode": {
        "name": "ipython",
        "version": 3
      },
      "file_extension": ".py",
      "mimetype": "text/x-python",
      "name": "python",
      "nbconvert_exporter": "python",
      "pygments_lexer": "ipython3",
      "version": "3.11.6"
    }
  },
  "nbformat": 4,
  "nbformat_minor": 0
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