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A collection of diagnostic and interpolation routines for use with output from the Weather Research and Forecasting (WRF-ARW) Model.
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wrf-python/src/wrf/projection.py

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from __future__ import (absolute_import, division, print_function)
import numpy as np
import math
from decimal import Decimal, Context, ROUND_HALF_UP
from .config import basemap_enabled, cartopy_enabled, pyngl_enabled
from .constants import Constants, ProjectionTypes
from .projutils import dict_keys_to_upper
from .py3compat import viewitems
if cartopy_enabled():
from cartopy import crs
if basemap_enabled():
from mpl_toolkits.basemap import Basemap
if pyngl_enabled():
from Ngl import Resources
if cartopy_enabled():
class MercatorWithLatTS(crs.Mercator):
"""A :class:`cartopy.crs.Mercator` subclass that adds support for
a latitude of true scale parameter.
See Also:
:class:`cartopy.crs.Mercator`
"""
def __init__(self, central_longitude=0.0,
latitude_true_scale=0.0,
min_latitude=-80.0,
max_latitude=84.0,
globe=None):
"""Initialize a :class:`wrf.MercatorWithLatTS` object.
Args:
central_longitude (:obj:`float`, optional): The central
longitude. Default is 0.0.
latitude_true_scale (:obj:`float`, optional): The latitude
of true scale. Default is 0.0.
min_latitude (:obj:`float`, optional): The maximum southerly
extent of the projection. Default is -80.0.
max_latitude (:obj:`float`, optional): The maximum northerly
extent of the projection. Default is 84.0.
globe (:class:`cartopy.crs.Globe`, optional): A globe object.
If omitted, a default globe is created.
"""
proj4_params = [("proj", "merc"),
("lon_0", central_longitude),
("lat_ts", latitude_true_scale),
("k", 1),
("units", "m")]
super(crs.Mercator, self).__init__(proj4_params, globe=globe)
# Calculate limits.
limits = self.transform_points(
crs.Geodetic(),
np.array([-180, 180]) + central_longitude,
np.array([min_latitude, max_latitude]))
# When using a latitude of true scale, the min/max x-limits get set
# to the same value, so make sure the left one is negative
xlimits = limits[..., 0]
if math.fabs(xlimits[0] - xlimits[1]) < 1e-6:
if xlimits[0] < 0:
xlimits[1] = -xlimits[1]
else:
xlimits[0] = -xlimits[0]
self._xlimits = tuple(xlimits)
self._ylimits = tuple(limits[..., 1])
# Compatibility with cartopy >= 0.17
self._x_limits = self._xlimits
self._y_limits = self._ylimits
self._threshold = np.diff(self.x_limits)[0] / 720
def _ismissing(val, islat=True):
"""Return True if a value is None or out of bounds.
This function is used to check for invalid latitude/longitude values.
Args:
val (numeric): A numeric value.
islat (:obj:`bool`): Set to False if checking for longitude values.
Returns:
:obj:`bool`: True if the value is None, or an out of bounds value.
"""
if islat:
if val is None:
return True
if math.fabs(val) > 90.:
return True
else:
if val is None:
return True
if math.fabs(val) > 360.:
return True
return False
class WrfProj(object):
"""A base class for storing map projection information from WRF data.
Subclasses of this type will be stored in the 'projection' attribute
entry within a :attr:`xarray.DataArray.attrs` dictionary. This base class
contains the methods required to extract the appropriate projection class
for PyNGL, matplotlib basemap, and cartopy.
Attributes:
map_proj (:obj:`int`): Model projection integer id.
truelat1 (:obj:`float`): True latitude 1.
truelat2 (:obj:`float`): True latitude 2.
moad_cen_lat (:obj:`float`): Mother of all domains center latitude.
stand_lon (:obj:`float`): Standard longitude.
pole_lat (:obj:`float`): The pole latitude.
pole_lon (:obj:`float`): The pole longitude.
dx (:obj:`float`): The x grid spacing.
dy (:obj:`float`): The y grid spacing.
"""
def __init__(self, **proj_params):
"""Initialize a :class:`wrf.WrfProj` object.
Args:
**proj_params: Map projection optional keyword arguments, that
have the same names as found in WRF output NetCDF global
attributes (case insensitive):
- 'MAP_PROJ': The map projection type as an integer.
- 'TRUELAT1': True latitude 1.
- 'TRUELAT2': True latitude 2.
- 'MOAD_CEN_LAT': Mother of all domains center latitude.
- 'STAND_LON': Standard longitude.
- 'POLE_LAT': Pole latitude.
- 'POLE_LON': Pole longitude.
"""
up_proj_params = dict_keys_to_upper(proj_params)
self.map_proj = up_proj_params.get("MAP_PROJ", None)
# These indicate the center of the nest/domain, not necessarily the
# center of the projection
self._cen_lat = up_proj_params.get("CEN_LAT", None)
self._cen_lon = up_proj_params.get("CEN_LON", None)
self.truelat1 = up_proj_params.get("TRUELAT1", None)
self.truelat2 = (up_proj_params.get("TRUELAT2", None)
if not _ismissing(up_proj_params.get("TRUELAT2",
None))
else None)
self.moad_cen_lat = up_proj_params.get("MOAD_CEN_LAT", None)
self.stand_lon = up_proj_params.get("STAND_LON", None)
self.pole_lat = up_proj_params.get("POLE_LAT", None)
self.pole_lon = up_proj_params.get("POLE_LON", None)
self.dx = up_proj_params.get("DX", None)
self.dy = up_proj_params.get("DY", None)
# Just in case...
if self.moad_cen_lat is None:
self.moad_cen_lat = self._cen_lat
if self.stand_lon is None:
self.stand_lon = self._cen_lon
@staticmethod
def _context_equal(x, y, ctx):
"""Return True if both objects are equal based on the provided context.
Args:
x (numeric): A numeric value.
y (numeric): A numeric value.
ctx (:class:`decimal.Context`): A decimal Context object.
Returns:
:obj:`bool`: True if the values are equal based on the provided
context, False otherwise.
"""
if x is not None:
if y is None:
return False
# Note: The float conversion is because these may come in as
# numpy.float32 or numpy.float64, which Decimal does not know
# how to handle.
if (Decimal(float(x)).normalize(ctx) !=
Decimal(float(y)).normalize(ctx)):
return False
else:
if y is not None:
return False
return True
def __eq__(self, other):
"""Return True if this projection object is the same as *other*.
Note: WRF can use either floats or doubles, so only going to
guarantee floating point precision equivalence, in case the different
types are ever compared (or a projection is hand constructed). For WRF
domains, 7-digit equivalence should be good enough.
"""
if self.map_proj is not None:
if self.map_proj != other.map_proj:
return False
else:
if other.map_proj is not None:
return False
# Only checking for floating point equal.
ctx = Context(prec=7, rounding=ROUND_HALF_UP)
return (WrfProj._context_equal(self.truelat1, other.truelat1, ctx) and
WrfProj._context_equal(self.truelat2, other.truelat2, ctx) and
WrfProj._context_equal(self.moad_cen_lat, other.moad_cen_lat,
ctx) and
WrfProj._context_equal(self.stand_lon, other.stand_lon,
ctx) and
WrfProj._context_equal(self.pole_lat, other.pole_lat, ctx) and
WrfProj._context_equal(self.pole_lon, other.pole_lon, ctx) and
WrfProj._context_equal(self.dx, other.dx, ctx) and
WrfProj._context_equal(self.dy, other.dy, ctx))
def _basemap(self, geobounds, **kwargs):
return None
def _cf_params(self):
return None
def _cartopy(self):
return None
def _calc_extents(self, geobounds):
# Need to modify the extents for the new projection
pc = crs.PlateCarree()
xs, ys, _ = self._cartopy().transform_points(
pc,
np.array([geobounds.bottom_left.lon, geobounds.top_right.lon]),
np.array([geobounds.bottom_left.lat, geobounds.top_right.lat])).T
_xlimits = xs.tolist()
_ylimits = ys.tolist()
return (_xlimits, _ylimits)
def _cart_extents(self, geobounds):
try:
_ = len(geobounds)
except TypeError: # Only a single object
extents = self._calc_extents(geobounds)
else:
extents = np.empty(geobounds.shape, np.object)
for idxs, geobnd_val in np.ndenumerate(geobounds):
extents[idxs] = self._calc_extents(geobnd_val)
return extents
def _pyngl(self, geobounds):
return None
def _proj4(self):
return None
def _globe(self):
return (None if not cartopy_enabled()
else crs.Globe(ellipse=None,
semimajor_axis=Constants.WRF_EARTH_RADIUS,
semiminor_axis=Constants.WRF_EARTH_RADIUS,
nadgrids="@null"))
def cartopy_xlim(self, geobounds):
"""Return the x extents in projected coordinates for cartopy.
Returns:
:obj:`list`: A pair of [xmin, xmax].
See Also:
:mod:`cartopy`, :mod:`matplotlib`
"""
try:
_ = len(geobounds)
except TypeError:
x_extents = self._cart_extents(geobounds)[0]
else:
extents = self._cart_extents(geobounds)
x_extents = np.empty(extents.shape, np.object)
for idxs, extent in np.ndenumerate(extents):
x_extents[idxs] = extent[0]
return x_extents
def cartopy_ylim(self, geobounds):
"""Return the y extents in projected coordinates for cartopy.
Returns:
:obj:`list`: A pair of [ymin, ymax].
See Also:
:mod:`cartopy`, :mod:`matplotlib`
"""
try:
_ = len(geobounds)
except TypeError:
y_extents = self._cart_extents(geobounds)[1]
else:
extents = self._cart_extents(geobounds)
y_extents = np.empty(extents.shape, np.object)
for idxs, extent in np.ndenumerate(extents):
y_extents[idxs] = extent[1]
return y_extents
def __repr__(self):
args = ("stand_lon={}, moad_cen_lat={}, "
"truelat1={}, truelat2={}, "
"pole_lat={}, pole_lon={}".format(self.stand_lon,
self.moad_cen_lat,
self.truelat1,
self.truelat2,
self.pole_lat,
self.pole_lon))
return "{}({})".format(self.__class__.__name__, args)
def basemap(self, geobounds, **kwargs):
"""Return a :class:`matplotlib.mpl_toolkits.basemap.Basemap` object
for the map projection.
Args:
geobounds (:class:`wrf.GeoBounds`, optional): The geobounds to
get the extents. If set to None and using the *var* parameter,
the geobounds will be taken from the variable. If using a
file, then the geobounds will be taken from the native grid.
**kwargs: Keyword arguments for creating a
:class:`matplotlib.mpl_toolkits.basemap.Basemap`. By default,
the domain bounds will be set to the native projection, the
resolution will be set to 'l', and the other projection
parameters will be set by the information in the file.
Returns:
:class:`matplotlib.mpl_toolkits.basemap.Basemap`: A Basemap
object for the projection.
See Also:
:class:`matplotlib.mpl_toolkits.basemap.Basemap`
"""
if not basemap_enabled():
raise RuntimeError("'mpl_toolkits.basemap' is not "
"installed or is disabled")
return self._basemap(geobounds, **kwargs)
def cartopy(self):
"""Return a :class:`cartopy.crs.Projection` subclass for the
map projection.
Returns:
:class:`cartopy.crs.Projection`: A Projection subclass for the
map projection.
See Also:
:class:`cartopy.crs.Projection`
"""
if not cartopy_enabled():
raise RuntimeError("'cartopy' is not "
"installed or is disabled")
return self._cartopy()
def pyngl(self, geobounds, **kwargs):
"""Return a :class:`Ngl.Resources` object for the map projection.
Args:
geobounds (:class:`wrf.GeoBounds`, optional): The geobounds to
get the extents. If set to None and using the *var* parameter,
the geobounds will be taken from the variable. If using a
file, then the geobounds will be taken from the native grid.
**kwargs: Additional PyNGL resources to set while creating the
:class:`Ngl.Resources` object.
Returns:
:class:`Ngl.Resources`: A dict-like object that contains the
PyNGL resources for the map projection.
See Also:
`PyNGL <https://www.pyngl.ucar.edu/>`_
"""
if not pyngl_enabled():
raise RuntimeError("'pyngl' is not "
"installed or is disabled")
return self._pyngl(geobounds, **kwargs)
def proj4(self):
"""Return the PROJ.4 string for the map projection.
Returns:
:obj:`str`: A string suitable for use with the PROJ.4 library.
See Also:
PROJ.4 <https://trac.osgeo.org/proj/>`_
"""
return self._proj4()
def cf(self):
"""Return a dictionary with the NetCDF CF parameters for the
projection.
Returns:
:obj:`dict`: A dictionary with the NetCDF CF parameter names and
projection parameter values.
"""
return self._cf_params()
# Used for 'missing' projection values during the 'join' method
class NullProjection(WrfProj):
"""A :class:`wrf.WrfProj` subclass for empty projections.
The :class:`NullProjection` is primarily used for creating missing
projections when using the 'join' method.
"""
def __init__(self):
"""Initialize a :class:`wrf.NullProjection` object."""
pass
def __repr__(self):
return "{}()".format(self.__class__.__name__)
class LambertConformal(WrfProj):
"""A :class:`wrf.WrfProj` subclass for Lambert Conformal Conic projections.
See Also:
:class:`wrf.WrfProj`, :class:`wrf.LatLon`,
:class:`wrf.PolarStereographic`,
:class:`Mercator`, :class:`RotatedLatLon`
"""
def __init__(self, **proj_params):
"""Initialize a :class:`wrf.LambertConformal` object.
Args:
**proj_params: Map projection optional keyword arguments, that
have the same names as found in WRF output NetCDF global
attributes:
- 'TRUELAT1': True latitude 1.
- 'TRUELAT2': True latitude 2.
- 'MOAD_CEN_LAT': Mother of all domains center latitude.
- 'STAND_LON': Standard longitude.
- 'POLE_LAT': Pole latitude.
- 'POLE_LON': Pole longitude.
"""
super(LambertConformal, self).__init__(**proj_params)
self._std_parallels = [self.truelat1]
if self.truelat2 is not None:
self._std_parallels.append(self.truelat2)
def _cf_params(self):
_cf_params = {}
_cf_params["grid_mapping_name"] = "lambert_conformal_conic"
_cf_params["standard_parallel"] = self._std_parallels
_cf_params["longitude_of_central_meridian"] = self.stand_lon
_cf_params["latitude_of_projection_origin"] = self.moad_cen_lat
_cf_params["semi_major_axis"] = Constants.WRF_EARTH_RADIUS
return _cf_params
def _pyngl(self, geobounds, **kwargs):
if not pyngl_enabled():
return None
truelat2 = (self.truelat1 if _ismissing(self.truelat2)
else self.truelat2)
_pyngl = Resources()
_pyngl.mpProjection = "LambertConformal"
_pyngl.mpDataBaseVersion = "MediumRes"
_pyngl.mpLambertMeridianF = self.stand_lon
_pyngl.mpLambertParallel1F = self.truelat1
_pyngl.mpLambertParallel2F = truelat2
_pyngl.mpLimitMode = "Corners"
_pyngl.mpLeftCornerLonF = geobounds.bottom_left.lon
_pyngl.mpLeftCornerLatF = geobounds.bottom_left.lat
_pyngl.mpRightCornerLonF = geobounds.top_right.lon
_pyngl.mpRightCornerLatF = geobounds.top_right.lat
for key, val in viewitems(kwargs):
setattr(_pyngl, key, val)
return _pyngl
def _basemap(self, geobounds, **kwargs):
if not basemap_enabled():
return None
local_kwargs = dict(projection="lcc",
lon_0=self.stand_lon,
lat_0=self.moad_cen_lat,
lat_1=self.truelat1,
lat_2=self.truelat2,
llcrnrlat=geobounds.bottom_left.lat,
urcrnrlat=geobounds.top_right.lat,
llcrnrlon=geobounds.bottom_left.lon,
urcrnrlon=geobounds.top_right.lon,
rsphere=Constants.WRF_EARTH_RADIUS,
resolution='l')
local_kwargs.update(kwargs)
_basemap = Basemap(**local_kwargs)
return _basemap
def _cartopy(self):
if not cartopy_enabled():
return None
# Set cutoff to -30 for NH, +30.0 for SH.
cutoff = -30.0 if self.moad_cen_lat >= 0 else 30.0
_cartopy = crs.LambertConformal(
central_longitude=self.stand_lon,
central_latitude=self.moad_cen_lat,
standard_parallels=self._std_parallels,
globe=self._globe(),
cutoff=cutoff)
return _cartopy
def _proj4(self):
truelat2 = (self.truelat1
if _ismissing(self.truelat2)
else self.truelat2)
_proj4 = ("+proj=lcc +units=meters +a={} +b={} +lat_1={} "
"+lat_2={} +lat_0={} +lon_0={} +nadgrids=@null".format(
Constants.WRF_EARTH_RADIUS,
Constants.WRF_EARTH_RADIUS,
self.truelat1,
truelat2,
self.moad_cen_lat,
self.stand_lon))
return _proj4
class Mercator(WrfProj):
"""A :class:`wrf.WrfProj` subclass for Mercator projections.
See Also:
:class:`wrf.WrfProj`, :class:`wrf.LatLon`,
:class:`wrf.PolarStereographic`,
:class:`RotatedLatLon`, :class:`LambertConformal`
"""
def __init__(self, **proj_params):
"""Initialize a :class:`wrf.Mercator` object.
Args:
**proj_params: Map projection optional keyword arguments, that
have the same names as found in WRF output NetCDF global
attributes:
- 'TRUELAT1': True latitude 1.
- 'TRUELAT2': True latitude 2.
- 'MOAD_CEN_LAT': Mother of all domains center latitude.
- 'STAND_LON': Standard longitude.
- 'POLE_LAT': Pole latitude.
- 'POLE_LON': Pole longitude.
"""
super(Mercator, self).__init__(**proj_params)
self._lat_ts = (
None if self.truelat1 == 0. or _ismissing(self.truelat1)
else self.truelat1)
self._stand_lon = (0. if _ismissing(self.stand_lon, islat=False)
else self.stand_lon)
def _cf_params(self):
_cf_params = {}
_cf_params["grid_mapping_name"] = "mercator"
_cf_params["longitude_of_projection_origin"] = self.stand_lon
_cf_params["standard_parallel"] = self.truelat1
return _cf_params
def _pyngl(self, geobounds, **kwargs):
if not pyngl_enabled():
return None
_pyngl = Resources()
_pyngl.mpProjection = "Mercator"
_pyngl.mpDataBaseVersion = "MediumRes"
_pyngl.mpCenterLatF = 0.0
_pyngl.mpCenterLonF = self._stand_lon
_pyngl.mpLimitMode = "Corners"
_pyngl.mpLeftCornerLonF = geobounds.bottom_left.lon
_pyngl.mpLeftCornerLatF = geobounds.bottom_left.lat
_pyngl.mpRightCornerLonF = geobounds.top_right.lon
_pyngl.mpRightCornerLatF = geobounds.top_right.lat
for key, val in viewitems(kwargs):
setattr(_pyngl, key, val)
return _pyngl
def _basemap(self, geobounds, **kwargs):
if not basemap_enabled():
return None
local_kwargs = dict(projection="merc",
lon_0=self._stand_lon,
lat_0=self.moad_cen_lat,
lat_ts=self._lat_ts,
llcrnrlat=geobounds.bottom_left.lat,
urcrnrlat=geobounds.top_right.lat,
llcrnrlon=geobounds.bottom_left.lon,
urcrnrlon=geobounds.top_right.lon,
rsphere=Constants.WRF_EARTH_RADIUS,
resolution="l")
local_kwargs.update(kwargs)
_basemap = Basemap(**local_kwargs)
return _basemap
def _cartopy(self):
if not cartopy_enabled():
return None
if self._lat_ts == 0.0:
_cartopy = crs.Mercator(central_longitude=self._stand_lon,
globe=self._globe())
else:
_cartopy = MercatorWithLatTS(central_longitude=self._stand_lon,
latitude_true_scale=self._lat_ts,
globe=self._globe())
return _cartopy
def _proj4(self):
_proj4 = ("+proj=merc +units=meters +a={} +b={} "
"+lon_0={} +lat_ts={} +nadgrids=@null".format(
Constants.WRF_EARTH_RADIUS,
Constants.WRF_EARTH_RADIUS,
self._stand_lon,
self._lat_ts))
return _proj4
class PolarStereographic(WrfProj):
"""A :class:`wrf.WrfProj` subclass for Polar Stereographic projections.
See Also:
:class:`wrf.WrfProj`, :class:`wrf.LatLon`,
:class:`wrf.RotatedLatLon`,
:class:`Mercator`, :class:`LambertConformal`
"""
def __init__(self, **proj_params):
"""Initialize a :class:`wrf.PolarStereographic` object.
Args:
**proj_params: Map projection optional keyword arguments, that
have the same names as found in WRF output NetCDF global
attributes:
- 'TRUELAT1': True latitude 1.
- 'TRUELAT2': True latitude 2.
- 'MOAD_CEN_LAT': Mother of all domains center latitude.
- 'STAND_LON': Standard longitude.
- 'POLE_LAT': Pole latitude.
- 'POLE_LON': Pole longitude.
"""
super(PolarStereographic, self).__init__(**proj_params)
self._hemi = -90. if self.truelat1 < 0 else 90.
self._lat_ts = (None if _ismissing(self.truelat1) else self.truelat1)
def _cf_params(self):
_cf_params = {}
_cf_params["grid_mapping_name"] = "polar_stereographic"
_cf_params["straight_vertical_longitude_from_pole"] = (
self.stand_lon)
_cf_params["standard_parallel"] = self.truelat1
_cf_params["latitude_of_projection_origin"] = self._hemi
return _cf_params
def _pyngl(self, geobounds, **kwargs):
if not pyngl_enabled():
return None
_pyngl = Resources()
_pyngl.mpProjection = "Stereographic"
_pyngl.mpDataBaseVersion = "MediumRes"
_pyngl.mpCenterLonF = self.stand_lon
if self._hemi > 0:
_pyngl.mpCenterLatF = 90.0
else:
_pyngl.mpCenterLatF = -90.0
_pyngl.mpLimitMode = "Corners"
_pyngl.mpLeftCornerLonF = geobounds.bottom_left.lon
_pyngl.mpLeftCornerLatF = geobounds.bottom_left.lat
_pyngl.mpRightCornerLonF = geobounds.top_right.lon
_pyngl.mpRightCornerLatF = geobounds.top_right.lat
for key, val in viewitems(kwargs):
setattr(_pyngl, key, val)
return _pyngl
def _basemap(self, geobounds, **kwargs):
if not basemap_enabled():
return None
local_kwargs = dict(projection="stere",
lon_0=self.stand_lon,
lat_0=self._hemi,
lat_ts=self._lat_ts,
llcrnrlat=geobounds.bottom_left.lat,
urcrnrlat=geobounds.top_right.lat,
llcrnrlon=geobounds.bottom_left.lon,
urcrnrlon=geobounds.top_right.lon,
rsphere=Constants.WRF_EARTH_RADIUS,
resolution="l")
local_kwargs.update(kwargs)
_basemap = Basemap(**local_kwargs)
return _basemap
def _cartopy(self):
if not cartopy_enabled():
return None
_cartopy = crs.Stereographic(central_latitude=self._hemi,
central_longitude=self.stand_lon,
true_scale_latitude=self._lat_ts,
globe=self._globe())
return _cartopy
def _proj4(self):
_proj4 = ("+proj=stere +units=meters +a={} +b={} "
"+lat0={} +lon_0={} +lat_ts={} +nadgrids=@null".format(
Constants.WRF_EARTH_RADIUS,
Constants.WRF_EARTH_RADIUS,
self._hemi,
self.stand_lon,
self._lat_ts))
return _proj4
class LatLon(WrfProj):
"""A :class:`wrf.WrfProj` subclass for Lat Lon projections.
See Also:
:class:`wrf.WrfProj`, :class:`wrf.RotatedLatLon`,
:class:`wrf.PolarStereographic`,
:class:`Mercator`, :class:`LambertConformal`
"""
def __init__(self, **proj_params):
"""Initialize a :class:`wrf.LatLon` object.
Args:
**proj_params: Map projection optional keyword arguments, that
have the same names as found in WRF output NetCDF global
attributes:
- 'TRUELAT1': True latitude 1.
- 'TRUELAT2': True latitude 2.
- 'MOAD_CEN_LAT': Mother of all domains center latitude.
- 'STAND_LON': Standard longitude.
- 'POLE_LAT': Pole latitude.
- 'POLE_LON': Pole longitude.
"""
super(LatLon, self).__init__(**proj_params)
def _cf_params(self):
_cf_params = {}
_cf_params["grid_mapping_name"] = "latitude_longitude"
return _cf_params
def _pyngl(self, geobounds, **kwargs):
if not pyngl_enabled():
return None
_pyngl = Resources()
_pyngl.mpProjection = "CylindricalEquidistant"
_pyngl.mpDataBaseVersion = "MediumRes"
_pyngl.mpCenterLonF = self.stand_lon
_pyngl.mpCenterLatF = self.moad_cen_lat
_pyngl.mpLimitMode = "Corners"
_pyngl.mpLeftCornerLonF = geobounds.bottom_left.lon
_pyngl.mpLeftCornerLatF = geobounds.bottom_left.lat
_pyngl.mpRightCornerLonF = geobounds.top_right.lon
_pyngl.mpRightCornerLatF = geobounds.top_right.lat
for key, val in viewitems(kwargs):
setattr(_pyngl, key, val)
return _pyngl
def _basemap(self, geobounds, **kwargs):
if not basemap_enabled():
return None
local_kwargs = dict(projection="cyl",
lon_0=self.stand_lon,
lat_0=self.moad_cen_lat,
llcrnrlat=geobounds.bottom_left.lat,
urcrnrlat=geobounds.top_right.lat,
llcrnrlon=geobounds.bottom_left.lon,
urcrnrlon=geobounds.top_right.lon,
rsphere=Constants.WRF_EARTH_RADIUS,
resolution="l")
local_kwargs.update(kwargs)
_basemap = Basemap(**local_kwargs)
return _basemap
def _cartopy(self):
if not cartopy_enabled():
return None
_cartopy = crs.PlateCarree(central_longitude=self.stand_lon,
globe=self._globe())
return _cartopy
def _cart_extents(self, geobounds):
return ([geobounds.bottom_left.lon, geobounds.top_right.lon],
[geobounds.bottom_left.lat, geobounds.top_right.lat])
def _proj4(self):
_proj4 = ("+proj=eqc +units=meters +a={} +b={} "
"+lon_0={} +nadgrids=@null".format(
Constants.WRF_EARTH_RADIUS,
Constants.WRF_EARTH_RADIUS,
self.stand_lon))
return _proj4
# Notes (may not be correct since this projection confuses me):
# Each projection system handles this differently.
# 1) In WRF, if following the WPS instructions, POLE_LON is mainly used to
# determine north or south hemisphere. In other words, it determines if
# the globe is tipped toward or away from you.
# 2) In WRF, POLE_LAT is always positive, but should be negative in the
# proj4 based systems when using the southern hemisphere projections.
# 3) In cartopy, pole_longitude is used to describe the dateline, which
# is 180 degrees away from the normal central (standard) longitude
# (e.g. center of the projection), according to the cartopy developer.
# 4) In basemap, lon_0 should be set to the central (standard) longitude.
# 5) In either cartopy, basemap or pyngl, I'm not sure that projections with
# a pole_lon not equal to 0 or 180 can be plotted. Hopefully people
# follow the WPS instructions, otherwise I need to see a sample file.
# 6) For items in 3 - 4, the "longitude" (lon_0 or pole_longitude) is
# determined by WRF's
# STAND_LON values, with the following calculations based on hemisphere:
# BASEMAP: NH: -STAND_LON; SH: 180.0 - STAND_LON
# CARTOPY: NH: -STAND_LON - 180.; SH: -STAND_LON
# 9) For PYNGL/NCL, you only need to set the center lat and center lon,
# Center lat is the offset of the pole from +/- 90 degrees. Center
# lon is -STAND_LON in NH and 180.0 - STAND_LON in SH.
# 10) It also appears that NetCDF CF has no clear documentation on what
# each parameter means. Going to assume it is the same as basemap, since
# basemap appears to mirror the WMO way of doing things (tilt earth, then
# spin globe).
# 11) Basemap and cartopy produce projections that differ in their extent
# calculations by either using negative values or 0-360 (basemap). For
# this reason, the proj4 string for this class will use cartopy's values
# to keep things in the -180 to 180, -90 to 90 range.
# 12) This projection makes me sad.
class RotatedLatLon(WrfProj):
"""A :class:`wrf.WrfProj` subclass for Rotated Lat Lon projections.
See Also:
:class:`wrf.WrfProj`, :class:`wrf.LatLon`,
:class:`wrf.PolarStereographic`,
:class:`Mercator`, :class:`LambertConformal`
"""
def __init__(self, **proj_params):
"""Initialize a :class:`wrf.RotatedLatLon` object.
Args:
**proj_params: Map projection optional keyword arguments, that
have the same names as found in WRF output NetCDF global
attributes:
- 'TRUELAT1': True latitude 1.
- 'TRUELAT2': True latitude 2.
- 'MOAD_CEN_LAT': Mother of all domains center latitude.
- 'STAND_LON': Standard longitude.
- 'POLE_LAT': Pole latitude.
- 'POLE_LON': Pole longitude.
"""
super(RotatedLatLon, self).__init__(**proj_params)
# Need to determine hemisphere, typically pole_lon is 0 for southern
# hemisphere, 180 for northern hemisphere. If not, going to have
# to guess based on other parameters, but hopefully people follow
# the WPS instructions and this never happens.
self._north = True
if self.pole_lon is not None:
if self.pole_lon == 0.:
self._north = False
elif self.pole_lon != 180.:
if self.moad_cen_lat is not None and self.moad_cen_lat < 0.0:
# Only probably true
self._north = False
else:
if self.moad_cen_lat is not None and self.moad_cen_lat < 0.0:
# Only probably true
self._north = False
if self.pole_lat is not None and self.stand_lon is not None:
self._pyngl_cen_lat = (90. - self.pole_lat if self._north
else self.pole_lat - 90.0)
self._pyngl_cen_lon = (-self.stand_lon if self._north
else 180.0 - self.stand_lon)
self._bm_lon_0 = (-self.stand_lon if self._north
else 180.0 - self.stand_lon)
self._bm_cart_pole_lat = (self.pole_lat if self._north
else -self.pole_lat)
# The important point is that pole longitude is the position
# of the dateline of the new projection, not its central
# longitude (per the creator of cartopy). This is based on
# how it's handled by agencies like WMO, but not proj4.
self._cart_pole_lon = (-self.stand_lon - 180.0 if self._north
else -self.stand_lon)
else:
self._pyngl_cen_lat = self.moad_cen_lat
self._pyngl_cen_lon = self.stand_lon
self._bm_cart_pole_lat = (90.0 - self.moad_cen_lat if self._north
else -90.0 - self.moad_cen_lat)
self._bm_lon_0 = (-self.stand_lon if self._north
else 180.0 - self.stand_lon)
self._cart_pole_lon = (-self.stand_lon - 180.0 if self._north
else -self.stand_lon)
def _cf_params(self):
_cf_params = {}
# Assuming this follows the same guidelines as cartopy
_cf_params["grid_mapping_name"] = "rotated_latitude_longitude"
_cf_params["grid_north_pole_latitude"] = self._bm_cart_pole_lat
_cf_params["grid_north_pole_longitude"] = self.pole_lon
_cf_params["north_pole_grid_longitude"] = self._bm_lon_0
return _cf_params
def _pyngl(self, geobounds, **kwargs):
if not pyngl_enabled():
return None
_pyngl = Resources()
_pyngl.mpProjection = "CylindricalEquidistant"
_pyngl.mpDataBaseVersion = "MediumRes"
_pyngl.mpCenterLatF = self._pyngl_cen_lat
_pyngl.mpCenterLonF = self._pyngl_cen_lon
_pyngl.mpLimitMode = "Corners"
_pyngl.mpLeftCornerLonF = geobounds.bottom_left.lon
_pyngl.mpLeftCornerLatF = geobounds.bottom_left.lat
_pyngl.mpRightCornerLonF = geobounds.top_right.lon
_pyngl.mpRightCornerLatF = geobounds.top_right.lat
for key, val in viewitems(kwargs):
setattr(_pyngl, key, val)
return _pyngl
def _basemap(self, geobounds, **kwargs):
if not basemap_enabled():
return None
local_kwargs = dict(projection="rotpole",
o_lat_p=self._bm_cart_pole_lat,
o_lon_p=self.pole_lon,
llcrnrlat=geobounds.bottom_left.lat,
urcrnrlat=geobounds.top_right.lat,
llcrnrlon=geobounds.bottom_left.lon,
urcrnrlon=geobounds.top_right.lon,
lon_0=self._bm_lon_0,
rsphere=Constants.WRF_EARTH_RADIUS,
resolution="l")
local_kwargs.update(kwargs)
_basemap = Basemap(**local_kwargs)
return _basemap
def _cartopy(self):
if not cartopy_enabled():
return None
_cartopy = crs.RotatedPole(pole_longitude=self._cart_pole_lon,
pole_latitude=self._bm_cart_pole_lat,
central_rotated_longitude=(
180.0 - self.pole_lon), # Probably
globe=self._globe())
return _cartopy
def _proj4(self):
_proj4 = ("+proj=ob_tran +o_proj=latlon "
"+a={} +b={} +to_meter={} +o_lon_p={} +o_lat_p={} "
"+lon_0={}".format(Constants.WRF_EARTH_RADIUS,
Constants.WRF_EARTH_RADIUS,
math.radians(1),
180.0 - self.pole_lon,
self._bm_cart_pole_lat,
180.0 + self._cart_pole_lon))
return _proj4
def getproj(**proj_params):
"""Return a :class:`wrf.WrfProj` subclass.
This functions serves as a factory function for returning a
:class:`wrf.WrfProj` subclass from the specified map projection parameters.
Args:
**proj_params: Map projection optional keyword arguments, that
have the same names as found in WRF output NetCDF global
attributes:
- 'MAP_PROJ': The map projection type as an integer.
- 'TRUELAT1': True latitude 1.
- 'TRUELAT2': True latitude 2.
- 'MOAD_CEN_LAT': Mother of all domains center latitude.
- 'STAND_LON': Standard longitude.
- 'POLE_LAT': Pole latitude.
- 'POLE_LON': Pole longitude.
Returns:
:class:`wrf.WrfProj`: A :class:`wrf.WrfProj` subclass for the
specified map projection parameters.
"""
up_proj_params = dict_keys_to_upper(proj_params)
proj_type = up_proj_params.get("MAP_PROJ", 0)
if proj_type == ProjectionTypes.LAMBERT_CONFORMAL:
return LambertConformal(**proj_params)
elif proj_type == ProjectionTypes.POLAR_STEREOGRAPHIC:
return PolarStereographic(**proj_params)
elif proj_type == ProjectionTypes.MERCATOR:
return Mercator(**proj_params)
elif (proj_type == ProjectionTypes.ZERO or
proj_type == ProjectionTypes.LAT_LON):
if (up_proj_params.get("POLE_LAT", None) == 90.
and up_proj_params.get("POLE_LON", None) == 0.):
return LatLon(**proj_params)
else:
return RotatedLatLon(**proj_params)
else:
# Unknown projection
return WrfProj(**proj_params)