def _regularise_shape(grib_message):
"""
Calculate the regularised shape of the reduced message and push
dummy regularised values into the message to force the gribapi
to update the message grid type from reduced to regular.
"""
# Make sure to read any missing values as NaN.
gribapi.grib_set_double(grib_message, "missingValue", np.nan)
# Get full longitude values, these describe the longitude value of
# *every* point in the grid, they are not 1d monotonic coordinates.
lons = gribapi.grib_get_double_array(grib_message, "longitudes")
# Compute the new longitude coordinate for the regular grid.
new_nx = max(gribapi.grib_get_long_array(grib_message, "pl"))
new_x_step = (max(lons) - min(lons)) / (new_nx - 1)
if gribapi.grib_get_long(grib_message, "iScansNegatively"):
new_x_step *= -1
gribapi.grib_set_long(grib_message, "Nx", int(new_nx))
gribapi.grib_set_double(grib_message, "iDirectionIncrementInDegrees",
float(new_x_step))
# Spoof gribapi with false regularised values.
nj = gribapi.grib_get_long(grib_message, 'Nj')
temp = np.zeros((nj * new_nx,), dtype=np.float)
gribapi.grib_set_double_array(grib_message, 'values', temp)
gribapi.grib_set_long(grib_message, "jPointsAreConsecutive", 0)
gribapi.grib_set_long(grib_message, "PLPresent", 0)
def _regularise_shape(grib_message):
"""
Calculate the regularised shape of the reduced message and push
dummy regularised values into the message to force the gribapi
to update the message grid type from reduced to regular.
"""
# Make sure to read any missing values as NaN.
gribapi.grib_set_double(grib_message, "missingValue", np.nan)
# Get full longitude values, these describe the longitude value of
# *every* point in the grid, they are not 1d monotonic coordinates.
lons = gribapi.grib_get_double_array(grib_message, "longitudes")
# Compute the new longitude coordinate for the regular grid.
new_nx = max(gribapi.grib_get_long_array(grib_message, "pl"))
new_x_step = (max(lons) - min(lons)) / (new_nx - 1)
if gribapi.grib_get_long(grib_message, "iScansNegatively"):
new_x_step *= -1
gribapi.grib_set_long(grib_message, "Nx", int(new_nx))
gribapi.grib_set_double(grib_message, "iDirectionIncrementInDegrees",
float(new_x_step))
# Spoof gribapi with false regularised values.
nj = gribapi.grib_get_long(grib_message, 'Nj')
temp = np.zeros((nj * new_nx,), dtype=np.float)
gribapi.grib_set_double_array(grib_message, 'values', temp)
gribapi.grib_set_long(grib_message, "jPointsAreConsecutive", 0)
gribapi.grib_set_long(grib_message, "PLPresent", 0)
def _regularise(grib_message):
"""
Transform a reduced grid to a regular grid using interpolation.
Uses 1d linear interpolation at constant latitude to make the grid
regular. If the longitude dimension is circular then this is taken
into account by the interpolation. If the longitude dimension is not
circular then extrapolation is allowed to make sure all end regular
grid points get a value. In practice this extrapolation is likely to
be minimal.
"""
# Make sure to read any missing values as NaN.
gribapi.grib_set_double(grib_message, "missingValue", np.nan)
# Get full longitude values, these describe the longitude value of
# *every* point in the grid, they are not 1d monotonic coordinates.
lons = gribapi.grib_get_double_array(grib_message, "longitudes")
# Compute the new longitude coordinate for the regular grid.
new_nx = max(gribapi.grib_get_long_array(grib_message, "pl"))
new_x_step = (max(lons) - min(lons)) / (new_nx - 1)
if gribapi.grib_get_long(grib_message, "iScansNegatively"):
new_x_step *= -1
new_lons = np.arange(new_nx) * new_x_step + lons[0]
# Get full latitude and data values, these describe the latitude and
# data values of *every* point in the grid, they are not 1d monotonic
# coordinates.
lats = gribapi.grib_get_double_array(grib_message, "latitudes")
values = gribapi.grib_get_double_array(grib_message, "values")
# Retrieve the distinct latitudes from the GRIB message. GRIBAPI docs
# don't specify if these points are guaranteed to be oriented correctly so
# the safe option is to sort them into ascending (south-to-north) order
# and then reverse the order if necessary.
new_lats = gribapi.grib_get_double_array(grib_message, "distinctLatitudes")
new_lats.sort()
if not gribapi.grib_get_long(grib_message, "jScansPositively"):
new_lats = new_lats[::-1]
ny = new_lats.shape[0]
# Use 1d linear interpolation along latitude circles to regularise the
# reduced data.
cyclic = _longitude_is_cyclic(new_lons)
new_values = np.empty([ny, new_nx], dtype=values.dtype)
for ilat, lat in enumerate(new_lats):
idx = np.where(lats == lat)
llons = lons[idx]
vvalues = values[idx]
if cyclic:
# For cyclic data we insert dummy points at each end to ensure
# we can interpolate to all output longitudes using pure
# interpolation.
cgap = (360 - llons[-1] - llons[0])
llons = np.concatenate(
(llons[0:1] - cgap, llons, llons[-1:] + cgap))
vvalues = np.concatenate(
(vvalues[-1:], vvalues, vvalues[0:1]))
fixed_latitude_interpolator = scipy.interpolate.interp1d(
llons, vvalues)
else:
# Allow extrapolation for non-cyclic data sets to ensure we can
# interpolate to all output longitudes.
fixed_latitude_interpolator = Linear1dExtrapolator(
scipy.interpolate.interp1d(llons, vvalues))
new_values[ilat] = fixed_latitude_interpolator(new_lons)
new_values = new_values.flatten()
# Set flags for the regularised data.
if np.isnan(new_values).any():
# Account for any missing data.
gribapi.grib_set_double(grib_message, "missingValue", np.inf)
gribapi.grib_set(grib_message, "bitmapPresent", 1)
new_values = np.where(np.isnan(new_values), np.inf, new_values)
gribapi.grib_set_long(grib_message, "Nx", int(new_nx))
gribapi.grib_set_double(grib_message,
"iDirectionIncrementInDegrees", float(new_x_step))
gribapi.grib_set_double_array(grib_message, "values", new_values)
gribapi.grib_set_long(grib_message, "jPointsAreConsecutive", 0)
gribapi.grib_set_long(grib_message, "PLPresent", 0)
def _regularise(grib_message):
"""
Transform a reduced grid to a regular grid using interpolation.
Uses 1d linear interpolation at constant latitude to make the grid
regular. If the longitude dimension is circular then this is taken
into account by the interpolation. If the longitude dimension is not
circular then extrapolation is allowed to make sure all end regular
grid points get a value. In practice this extrapolation is likely to
be minimal.
"""
# Make sure to read any missing values as NaN.
gribapi.grib_set_double(grib_message, "missingValue", np.nan)
# Get full longitude values, these describe the longitude value of
# *every* point in the grid, they are not 1d monotonic coordinates.
lons = gribapi.grib_get_double_array(grib_message, "longitudes")
# Compute the new longitude coordinate for the regular grid.
new_nx = max(gribapi.grib_get_long_array(grib_message, "pl"))
new_x_step = (max(lons) - min(lons)) / (new_nx - 1)
if gribapi.grib_get_long(grib_message, "iScansNegatively"):
new_x_step *= -1
new_lons = np.arange(new_nx) * new_x_step + lons[0]
# Get full latitude and data values, these describe the latitude and
# data values of *every* point in the grid, they are not 1d monotonic
# coordinates.
lats = gribapi.grib_get_double_array(grib_message, "latitudes")
values = gribapi.grib_get_double_array(grib_message, "values")
# Retrieve the distinct latitudes from the GRIB message. GRIBAPI docs
# don't specify if these points are guaranteed to be oriented correctly so
# the safe option is to sort them into ascending (south-to-north) order
# and then reverse the order if necessary.
new_lats = gribapi.grib_get_double_array(grib_message, "distinctLatitudes")
new_lats.sort()
if not gribapi.grib_get_long(grib_message, "jScansPositively"):
new_lats = new_lats[::-1]
ny = new_lats.shape[0]
# Use 1d linear interpolation along latitude circles to regularise the
# reduced data.
cyclic = _longitude_is_cyclic(new_lons)
new_values = np.empty([ny, new_nx], dtype=values.dtype)
for ilat, lat in enumerate(new_lats):
idx = np.where(lats == lat)
llons = lons[idx]
vvalues = values[idx]
if cyclic:
# For cyclic data we insert dummy points at each end to ensure
# we can interpolate to all output longitudes using pure
# interpolation.
cgap = (360 - llons[-1] - llons[0])
llons = np.concatenate(
(llons[0:1] - cgap, llons, llons[-1:] + cgap))
vvalues = np.concatenate(
(vvalues[-1:], vvalues, vvalues[0:1]))
fixed_latitude_interpolator = scipy.interpolate.interp1d(
llons, vvalues)
else:
# Allow extrapolation for non-cyclic data sets to ensure we can
# interpolate to all output longitudes.
fixed_latitude_interpolator = Linear1dExtrapolator(
scipy.interpolate.interp1d(llons, vvalues))
new_values[ilat] = fixed_latitude_interpolator(new_lons)
new_values = new_values.flatten()
# Set flags for the regularised data.
if np.isnan(new_values).any():
# Account for any missing data.
gribapi.grib_set_double(grib_message, "missingValue", np.inf)
gribapi.grib_set(grib_message, "bitmapPresent", 1)
new_values = np.where(np.isnan(new_values), np.inf, new_values)
gribapi.grib_set_long(grib_message, "Nx", int(new_nx))
gribapi.grib_set_double(grib_message,
"iDirectionIncrementInDegrees", float(new_x_step))
gribapi.grib_set_double_array(grib_message, "values", new_values)
gribapi.grib_set_long(grib_message, "jPointsAreConsecutive", 0)
gribapi.grib_set_long(grib_message, "PLPresent", 0)
