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  {
   "cell_type": "markdown",
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   "source": [
    "# Polarized Calculations\n",
    "\n",
    "SK-DO contains the ability to model the Stokes vector inside the Earth's atmosphere.  Currently we assume that V=0, i.e., there is no circular polarization.  Therefore only the I, Q, U components of the Stoke's vector are calculated.  Every stokes component is fully linearized."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "54ccd126",
   "metadata": {},
   "outputs": [],
   "source": [
    "%matplotlib inline"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "4becaf42",
   "metadata": {},
   "outputs": [],
   "source": [
    "import sasktran as sk\n",
    "import sasktran.disco.interface as do\n",
    "import numpy as np\n",
    "import matplotlib.pyplot as plt"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "2cb2aaef",
   "metadata": {},
   "outputs": [],
   "source": [
    "geometry = sk.NadirGeometry()\n",
    "geometry.from_zeniths_and_azimuth_difference(80, 30, 45)\n",
    "\n",
    "atmosphere = sk.Atmosphere()\n",
    "\n",
    "# add our species\n",
    "atmosphere['rayleigh'] = sk.Species(sk.Rayleigh(), sk.MSIS90())\n",
    "atmosphere['o3'] = sk.Species(sk.O3OSIRISRes(), sk.Labow())\n",
    "atmosphere['no2'] = sk.Species(sk.NO2OSIRISRes(), sk.Pratmo())\n",
    "atmosphere.atmospheric_state = sk.MSIS90()\n",
    "\n",
    "# add our surface properties\n",
    "# setting to a scalar automatically sets the surface to be Lambertian\n",
    "atmosphere.brdf = 0.3"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "50aa1661",
   "metadata": {},
   "outputs": [],
   "source": [
    "atmosphere = sk.Atmosphere()\n",
    "\n",
    "# add our species\n",
    "atmosphere['rayleigh'] = sk.Species(sk.Rayleigh(), sk.MSIS90())\n",
    "atmosphere['o3'] = sk.Species(sk.O3OSIRISRes(), sk.Labow())\n",
    "atmosphere['no2'] = sk.Species(sk.NO2OSIRISRes(), sk.Pratmo())\n",
    "atmosphere.atmospheric_state = sk.MSIS90()\n",
    "\n",
    "# add our surface properties\n",
    "atmosphere.brdf = sk.Kokhanovsky()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "eba441f7",
   "metadata": {},
   "outputs": [],
   "source": [
    "wavelengths = np.linspace(340,700, 361)\n",
    "engine = do.EngineDO(geometry=geometry, atmosphere=atmosphere, wavelengths=wavelengths)\n",
    "\n",
    "engine.num_stokes = 3\n",
    "engine.num_streams = 4\n",
    "\n",
    "rad = engine.calculate_radiance()\n",
    "print(rad)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "7837dd1c",
   "metadata": {},
   "outputs": [],
   "source": [
    "# Make plot\n",
    "plt.figure()\n",
    "plt.plot(rad['wavelength'], rad['radiance'].isel(stokes=0))\n",
    "plt.plot(rad['wavelength'], rad['radiance'].isel(stokes=1))\n",
    "plt.plot(rad['wavelength'], rad['radiance'].isel(stokes=2))\n",
    "\n",
    "\n",
    "plt.xlabel('Wavelength [nm]')\n",
    "plt.ylabel('Sun Normalized Radiance [/ster]')\n",
    "\n",
    "plt.legend(['I', 'Q', 'U'])\n",
    "plt.show()"
   ]
  }
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