{
  "cells": [
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n# Convolve input\n\nDecreasing the spatial resolution of fields from a reader by convolution.\nThis may improve accuracy, see: https://doi.org/10.1016/j.rse.2019.01.001\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "from datetime import datetime, timedelta\nimport matplotlib.pyplot as plt\nfrom opendrift.readers import reader_netCDF_CF_generic\nfrom opendrift.models.oceandrift import OceanDrift\n\n\nlon = 4.9; lat = 60.0\no = OceanDrift(loglevel=20)\n\nreader_norkyst = reader_netCDF_CF_generic.Reader(o.test_data_folder() + '16Nov2015_NorKyst_z_surface/norkyst800_subset_16Nov2015.nc')\ntime = reader_norkyst.start_time\n\no.add_reader([reader_norkyst])\no.seed_elements(lon, lat, radius=1000, number=1000, time=time)\no.run(steps=20)"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "Store final field of x-component of current\n\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "original_current = reader_norkyst.var_block_after[list(reader_norkyst.var_block_after.keys())[0]].data_dict['x_sea_water_velocity'].copy()"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "For the second run, the NorKyst currents are convolved with a kernel,\neffectively lowering the spatial resolution.\n<reader>.set_convolution_kernel may also be given as an array (kernel) directly\n\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "N = 10  # Convolusion kernel size\nreader_norkyst.set_convolution_kernel(N)  # Using convolution kernel for second run\no2 = OceanDrift(loglevel=20)\no2.add_reader([reader_norkyst])\no2.seed_elements(lon, lat, radius=1000, number=1000, time=time)\no2.run(steps=20)"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "Store final field of x-component of (convolved) current\n\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "convolved_current = reader_norkyst.var_block_after[\n    \"['x_sea_water_velocity', 'y_sea_water_velocity']\"].data_dict['x_sea_water_velocity']\n\nplt.subplot(2,1,1)\nplt.imshow(original_current, interpolation='nearest')\nplt.title('Original current field (x-component)')\nclim = plt.gci().get_clim()\nplt.colorbar()\nplt.subplot(2,1,2)\nplt.imshow(convolved_current, interpolation='nearest')\nplt.clim(clim)  # Make sure plots are comparable\nplt.colorbar()\nplt.title('Final, convolved current field (x-component)')\nplt.show()"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "Print and plot results, with convolved currents as background\n\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "print(o)\no.animation(compare=o2, fast=True, legend=[\n    'Original currents', 'Current convoled with kernel of size %s' % N],\n    background=['x_sea_water_velocity', 'y_sea_water_velocity'])"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "<img src=\"file://gallery/animations/example_convolve_input_0.gif\">\n\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "o.plot(fast=True)"
      ]
    }
  ],
  "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"
    }
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  "nbformat": 4,
  "nbformat_minor": 0
}