#!/usr/bin/env python
"""
These functions are tools used to define the ``cellWidth`` variable on
regular lat/lon grids. The ``cellWidth`` variable is a ``jigsaw`` input that
defines the mesh.
"""
from __future__ import absolute_import, division, print_function, \
unicode_literals
import numpy as np
[docs]
def mergeCellWidthVsLat(
lat,
cellWidthInSouth,
cellWidthInNorth,
latTransition,
latWidthTransition):
"""
Combine two cell width distributions using a ``tanh`` function. This is
intended as part of the workflow to make an MPAS global mesh.
Parameters
----------
lat : ndarray
vector of length n, with entries between -90 and 90, degrees
cellWidthInSouth : ndarray
vector of length n, first distribution
cellWidthInNorth : ndarray
vector of length n, second distribution
latTransition : float
lat to change from ``cellWidthInSouth`` to ``cellWidthInNorth`` in
degrees
latWidthTransition : float
width of lat transition in degrees
Returns
-------
cellWidthOut : ndarray
vector of length n, entries are cell width as a function of lat
"""
cellWidthOut = np.ones(lat.size)
if latWidthTransition == 0:
for j in range(lat.size):
if lat[j] < latTransition:
cellWidthOut[j] = cellWidthInSouth[j]
else:
cellWidthOut[j] = cellWidthInNorth[j]
else:
for j in range(lat.size):
weightNorth = 0.5 * \
(np.tanh((lat[j] - latTransition) / latWidthTransition) + 1.0)
weightSouth = 1.0 - weightNorth
cellWidthOut[j] = weightSouth * cellWidthInSouth[j] + \
weightNorth * cellWidthInNorth[j]
return cellWidthOut
[docs]
def EC_CellWidthVsLat(lat, cellWidthEq=30.0, cellWidthMidLat=60.0,
cellWidthPole=35.0, latPosEq=15.0, latPosPole=73.0,
latTransition=40.0, latWidthEq=6.0, latWidthPole=9.0):
"""
Create Eddy Closure spacing as a function of lat. This is intended as part
of the workflow to make an MPAS global mesh.
Parameters
----------
lat : ndarray
vector of length n, with entries between -90 and 90, degrees
cellWidthEq : float, optional
Cell width in km at the equator
cellWidthMidLat : float, optional
Cell width in km at mid latitudes
cellWidthPole : float, optional
Cell width in km at the poles
latPosEq : float, optional
Latitude in degrees of center of the equatorial transition region
latPosPole : float, optional
Latitude in degrees of center of the polar transition region
latTransition : float, optional
Latitude in degrees of the change from equatorial to polar function
latWidthEq : float, optional
Width in degrees latitude of the equatorial transition region
latWidthPole : float, optional
Width in degrees latitude of the polar transition region
Returns
-------
cellWidthOut : ndarray
1D array of same length as ``lat`` with entries that are cell width as
a function of lat
Examples
--------
Default
>>> EC60to30 = EC_CellWidthVsLat(lat)
Half the default resolution:
>>> EC120to60 = EC_CellWidthVsLat(lat, cellWidthEq=60., cellWidthMidLat=120., cellWidthPole=70.)
"""
minCellWidth = min(cellWidthEq, min(cellWidthMidLat, cellWidthPole))
densityEq = (minCellWidth / cellWidthEq)**4
densityMidLat = (minCellWidth / cellWidthMidLat)**4
densityPole = (minCellWidth / cellWidthPole)**4
densityEqToMid = ((densityEq - densityMidLat) * (1.0 + np.tanh(
(latPosEq - np.abs(lat)) / latWidthEq)) / 2.0) + densityMidLat
densityMidToPole = ((densityMidLat - densityPole) * (1.0 + np.tanh(
(latPosPole - np.abs(lat)) / latWidthPole)) / 2.0) + densityPole
mask = np.abs(lat) < latTransition
densityEC = np.array(densityMidToPole)
densityEC[mask] = densityEqToMid[mask]
cellWidthOut = minCellWidth / densityEC**0.25
return cellWidthOut
[docs]
def RRS_CellWidthVsLat(lat, cellWidthEq, cellWidthPole):
"""
Create Rossby Radius Scaling as a function of lat. This is intended as
part of the workflow to make an MPAS global mesh.
Parameters
----------
lat : ndarray
vector of length n, with entries between -90 and 90, degrees
cellWidthEq : float, optional
Cell width in km at the equator
cellWidthPole : float, optional
Cell width in km at the poles
Returns
-------
cellWidthOut : ndarray
1D array of same length as ``lat`` with entries that are cell width as
a function of lat
Examples
--------
>>> RRS18to6 = EC_CellWidthVsLat(lat, 18., 6.)
"""
# ratio between high and low resolution
gamma = (cellWidthPole / cellWidthEq)**4.0
densityRRS = (1.0 - gamma) * \
np.power(np.sin(np.deg2rad(np.absolute(lat))), 4.0) + gamma
cellWidthOut = cellWidthPole / np.power(densityRRS, 0.25)
return cellWidthOut
[docs]
def AtlanticPacificGrid(lat, lon, cellWidthInAtlantic, cellWidthInPacific):
"""
Combine two cell width distributions using a ``tanh`` function.
Parameters
----------
lat : ndarray
vector of length n, with entries between -90 and 90, degrees
lon : ndarray
vector of length m, with entries between -180, 180, degrees
cellWidthInAtlantic : float, optional
vector of length n, cell width in Atlantic as a function of lon, km
cellWidthInPacific : float, optional
vector of length n, cell width in Pacific as a function of lon, km
Returns
-------
cellWidthOut : ndarray
m by n array, grid cell width on globe, km
"""
cellWidthOut = np.zeros((lat.size, lon.size))
for i in range(lon.size):
for j in range(lat.size):
# set to Pacific mask as default
cellWidthOut[j, i] = cellWidthInPacific[j]
# test if in Atlantic Basin:
if lat[j] > 65.0:
if (lon[i] > -150.0) & (lon[i] < 170.0):
cellWidthOut[j, i] = cellWidthInAtlantic[j]
elif lat[j] > 20.0:
if (lon[i] > -100.0) & (lon[i] < 35.0):
cellWidthOut[j, i] = cellWidthInAtlantic[j]
elif lat[j] > 0.0:
if (lon[i] > -2.0 * lat[j] - 60.0) & (lon[i] < 35.0):
cellWidthOut[j, i] = cellWidthInAtlantic[j]
else:
if (lon[i] > -60.0) & (lon[i] < 20.0):
cellWidthOut[j, i] = cellWidthInAtlantic[j]
return cellWidthOut