coriolis_param (#176)

NCAR · Feb 4, 2025 · 3008321 · 3008321
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diff --git a/ncl/ncl_entries/meteorology.ipynb b/ncl/ncl_entries/meteorology.ipynb
@@ -19,7 +19,8 @@
     "- [daylight_fao56](https://www.ncl.ucar.edu/Document/Functions/Crop/daylight_fao56.shtml)\n",
     "- [satvpr_temp_fao56](https://www.ncl.ucar.edu/Document/Functions/Crop/satvpr_temp_fao56.shtml)\n",
     "- [satvpr_tdew_fao56](https://www.ncl.ucar.edu/Document/Functions/Crop/satvpr_tdew_fao56.shtml)\n",
-    "- [satvpr_slope_fao56](https://www.ncl.ucar.edu/Document/Functions/Crop/satvpr_slope_fao56.shtml)"
+    "- [satvpr_slope_fao56](https://www.ncl.ucar.edu/Document/Functions/Crop/satvpr_slope_fao56.shtml)\n",
+    "- [coriolis_param](https://www.ncl.ucar.edu/Document/Functions/Contributed/coriolis_param.shtml)"
    ]
   },
   {
@@ -92,9 +93,9 @@
     "\n",
     "{math}`N = \\frac{24}{{\\pi}} {\\omega}_{s}`\n",
     "\n",
-    "And {math}`{\\omega}_{s}` is the sunset hour angle in radians [(Chapter 3, Equation 25)](https://www.fao.org/4/X0490E/x0490e07.htm#chapter%203%20%20%20meteorological%20data) {footcite}`allan_fao_1998` which is calculated from the latitude of the observer on Earth ({math}`\\phi`) and the sun's declination ({math}`\\delta`):\n",
+    "And {math}`{\\omega}_{s}` is the sunset hour angle in radians [(Chapter 3, Equation 25)](https://www.fao.org/4/X0490E/x0490e07.htm#chapter%203%20%20%20meteorological%20data) {footcite}`allan_fao_1998` which is calculated from the latitude of the observer on Earth ({math}`\\varphi`) and the sun's declination ({math}`\\delta`):\n",
     "\n",
-    "{math}`{\\omega}_{s} = arccos[-tan({\\phi})tan({\\delta})]`"
+    "{math}`{\\omega}_{s} = arccos[-tan({\\varphi})tan({\\delta})]`"
    ]
   },
   {
@@ -265,6 +266,53 @@
     "saturation_vapor_pressure_slope(temp)"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## coriolis_param\n",
+    "\n",
+    "NCL's `coriolis_param` calculates the Coriolis parameter at a given latitude\n",
+    "\n",
+    "The Coriolis parameter (also known as the Coriolis frequency or the Coriolis coefficient) is calculated as twice the rotation rate ({math}`{\\Omega}`) of the Earth times the sine of the latitude ({math}`{\\varphi}`){footcite}`hobbs_wallace_1997`\n",
+    "\n",
+    "{math}`f = 2{\\Omega}sin({\\varphi})`\n",
+    "\n",
+    "The rotation rate depends on the length of the rotation period of the Earth (T) which is defined as one sidereal day (23 hours and 56 minutes):\n",
+    "\n",
+    "{math}`{\\Omega} = \\frac{2 * {\\pi}}{T}  = 7.292\\text{e-5} \\frac{rad}{s}`"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# Input: Single Value\n",
+    "from metpy.calc import coriolis_parameter\n",
+    "from metpy.units import units\n",
+    "\n",
+    "latitude = 40  # degrees\n",
+    "\n",
+    "coriolis_parameter(latitude * units.degree).magnitude"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# Input: List/Array\n",
+    "from metpy.calc import coriolis_parameter\n",
+    "from metpy.units import units\n",
+    "\n",
+    "latitude = [-20, 40, 65]  # degrees\n",
+    "\n",
+    "coriolis_parameter(latitude * units.degree).magnitude"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},
@@ -283,6 +331,7 @@
     "- [GeoCAT-comp `saturation_vapor_pressure` Documentation](https://geocat-comp.readthedocs.io/en/latest/user_api/generated/geocat.comp.meteorology.saturation_vapor_pressure.html)\n",
     "- [GeoCAT-comp `actual_saturation_vapor_pressure` Documentation](https://geocat-comp.readthedocs.io/en/latest/user_api/generated/geocat.comp.meteorology.actual_saturation_vapor_pressure.html)\n",
     "- [GeoCAT-comp `saturation_vapor_pressure_slope` Documentation](https://geocat-comp.readthedocs.io/en/latest/user_api/generated/geocat.comp.meteorology.saturation_vapor_pressure_slope.html)\n",
+    "- [MetPy `coriolis_parameter` Documentation](https://unidata.github.io/MetPy/latest/api/generated/metpy.calc.coriolis_parameter.html)\n",
     "\n",
     "## Additional Reading\n",
     "- [NOAA: Dew Point vs. Humidity](https://www.weather.gov/arx/why_dewpoint_vs_humidity)"

diff --git a/ncl/ncl_index/ncl-index-table.csv b/ncl/ncl_index/ncl-index-table.csv
@@ -50,3 +50,4 @@ NCL Function,Description,Python Equivalent,Notes
 `satvpr_temp_fao56 <https://www.ncl.ucar.edu/Document/Functions/Crop/satvpr_temp_fao56.shtml>`__,"Compute saturation vapor pressure using temperature as described in FAO 56","``geocat.comp.saturation_vapor_pressure()``",`example notebook <../ncl_entries/meteorology.ipynb#satvpr-temp-fao56>`__
 `satvpr_tdew_fao56 <https://www.ncl.ucar.edu/Document/Functions/Crop/satvpr_tdew_fao56.shtml>`__,"Compute actual saturation vapor pressure as described in FAO 56","``geocat.comp.actual_saturation_vapor_pressure()``",`example notebook <../ncl_entries/meteorology.ipynb#satvpr-tdew-fao56>`__
 `satvpr_slope_fao56 <https://www.ncl.ucar.edu/Document/Functions/Crop/satvpr_slope_fao56.shtml>`__," Compute the slope of the saturation vapor pressure curve as described in FAO 56","``geocat.comp.saturation_vapor_pressure_slope()``",`example notebook <../ncl_entries/meteorology.ipynb#satvpr-slope-fao56>`__
+`coriolis_param <https://www.ncl.ucar.edu/Document/Functions/Contributed/coriolis_param.shtml>`__,"Calculate the Coriolis parameter","``metpy.calc.coriolis_parameter()``",`example notebook <../ncl_entries/meteorology.ipynb#coriolis-param>`__
diff --git a/ncl/ncl_raw/meteorology.ncl b/ncl/ncl_raw/meteorology.ncl
@@ -66,3 +66,13 @@ do temp=33,212
 		print (temp + "," + slope_satvpr)
 	end
 end do
+
+; coriolis_param
+; Adapted from https://www.ncl.ucar.edu/Document/Functions/Contributed/coriolis_param.shtml
+
+; ncl -n coriolis_param.ncl >> coriolis_param_output.txt
+
+print("Latitude (Degree), Coriolis Parameter")
+do lat=-90,90
+	print(lat + "," + coriolis_param(lat))
+end do
diff --git a/ncl/receipts/meteorology.ipynb b/ncl/receipts/meteorology.ipynb
@@ -28,7 +28,8 @@
     "- [daylight_fao56](https://www.ncl.ucar.edu/Document/Functions/Crop/daylight_fao56.shtml)\n",
     "- [satvpr_temp_fao56](https://www.ncl.ucar.edu/Document/Functions/Crop/satvpr_temp_fao56.shtml)\n",
     "- [satvpr_tdew_fao56](https://www.ncl.ucar.edu/Document/Functions/Crop/satvpr_tdew_fao56.shtml)\n",
-    "- [satvpr_slope_fao56](https://www.ncl.ucar.edu/Document/Functions/Crop/satvpr_slope_fao56.shtml)"
+    "- [satvpr_slope_fao56](https://www.ncl.ucar.edu/Document/Functions/Crop/satvpr_slope_fao56.shtml)\n",
+    "- [coriolis_param](https://www.ncl.ucar.edu/Document/Functions/Contributed/coriolis_param.shtml)"
    ]
   },
   {
@@ -339,6 +340,59 @@
     "    geocat_satvpr_slope_fao56[temp] = saturation_vapor_pressure_slope(temp)"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "3b9ce2e3-833a-4dbc-8d6a-35eb86397b19",
+   "metadata": {},
+   "source": [
+    "### coriolis_param"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "c2646150-8327-4faa-8979-b70e98be9631",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "#### Collect NCL values for coriolis_param from geocat-datafiles\n",
+    "import geocat.datafiles as gdf\n",
+    "import numpy as np\n",
+    "\n",
+    "coriolis_param_data = gdf.get(\n",
+    "    'applications_files/ncl_outputs/coriolis_param_output.txt'\n",
+    ")\n",
+    "coriolis_param_data = np.loadtxt(coriolis_param_data, delimiter=',', skiprows=6)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "9a699cc2-5a21-4a49-92f9-353635036d06",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "### Collect NCL `coriolis_param_data` value and associated coriolis parameter values\n",
+    "ncl_coriolis_param = dict(zip(coriolis_param_data[::, 0], coriolis_param_data[::, 1]))"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "04410fd1-3033-4c6b-812f-e6b12b3e884e",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "### Calculate MetPy \"coriolis_parameter\"\n",
+    "from metpy.calc import coriolis_parameter\n",
+    "from metpy.units import units\n",
+    "\n",
+    "metpy_coriolis_para = {}\n",
+    "\n",
+    "for lat in range(-90, 90 + 1):\n",
+    "    metpy_coriolis_para[lat] = coriolis_parameter(lat * units.degree).magnitude"
+   ]
+  },
   {
    "cell_type": "markdown",
    "id": "3237a0bffc6827fc",
@@ -469,6 +523,29 @@
     "        ncl_satvpr_slope_fao56[key], geocat_satvpr_slope_fao56[key], rel_tol=1e-05\n",
     "    )  # within 5 decimal points"
    ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "980c82cf-3860-4f46-bb98-65e4bea9f3cf",
+   "metadata": {},
+   "source": [
+    "### coriolis_param"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "1229100a-0e88-46ef-afad-d557b043a713",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "import math\n",
+    "\n",
+    "for key in ncl_coriolis_param.keys():\n",
+    "    assert math.isclose(\n",
+    "        ncl_coriolis_param[key], metpy_coriolis_para[key], rel_tol=1e-04\n",
+    "    )  # within 4 decimal points"
+   ]
   }
  ],
  "metadata": {

diff --git a/references.bib b/references.bib
@@ -128,3 +128,11 @@ @misc{usgs_1987
 	title = {Map projections: A working manual},
 	doi = {10.3133/pp1395}
 }
+
+@book{hobbs_wallace_1997,
+	author = {Hobbs, Peter V. and Wallace, John Michael},
+	title = {Atmospheric Science: An Introductory Survey},
+	year = {1977},
+	pages = {277},
+	publisher = {Academic Press}
+}