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85 lines
3.4 KiB
85 lines
3.4 KiB
from __future__ import (absolute_import, division, print_function, |
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unicode_literals) |
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from .constants import Constants |
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from .destag import destagger |
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from .extension import _omega, _tk |
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from .util import extract_vars |
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from .metadecorators import copy_and_set_metadata |
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@copy_and_set_metadata(copy_varname="T", name="omega", |
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description="omega", |
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units="Pa s-1") |
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def get_omega(wrfin, timeidx=0, method="cat", squeeze=True, cache=None, |
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meta=True, _key=None): |
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"""Return Omega. |
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This functions extracts the necessary variables from the NetCDF file |
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object in order to perform the calculation. |
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Args: |
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wrfin (:class:`netCDF4.Dataset`, :class:`Nio.NioFile`, or an \ |
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iterable): Input WRF ARW NetCDF |
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data as a :class:`netCDF4.Dataset`, :class:`Nio.NioFile` |
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or an iterable sequence of the aforementioned types. |
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timeidx (:obj:`int` or :data:`wrf.ALL_TIMES`, optional): The |
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desired time index. This value can be a positive integer, |
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negative integer, or |
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:data:`wrf.ALL_TIMES` (an alias for None) to return |
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all times in the file or sequence. The default is 0. |
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method (:obj:`str`, optional): The aggregation method to use for |
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sequences. Must be either 'cat' or 'join'. |
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'cat' combines the data along the Time dimension. |
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'join' creates a new dimension for the file index. |
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The default is 'cat'. |
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squeeze (:obj:`bool`, optional): Set to False to prevent dimensions |
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with a size of 1 from being automatically removed from the shape |
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of the output. Default is True. |
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cache (:obj:`dict`, optional): A dictionary of (varname, ndarray) |
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that can be used to supply pre-extracted NetCDF variables to the |
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computational routines. It is primarily used for internal |
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purposes, but can also be used to improve performance by |
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eliminating the need to repeatedly extract the same variables |
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used in multiple diagnostics calculations, particularly when using |
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large sequences of files. |
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Default is None. |
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meta (:obj:`bool`, optional): Set to False to disable metadata and |
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return :class:`numpy.ndarray` instead of |
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:class:`xarray.DataArray`. Default is True. |
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_key (:obj:`int`, optional): A caching key. This is used for internal |
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purposes only. Default is None. |
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Returns: |
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:class:`xarray.DataArray` or :class:`numpy.ndarray`: Omega. |
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If xarray is |
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enabled and the *meta* parameter is True, then the result will be a |
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:class:`xarray.DataArray` object. Otherwise, the result will be a |
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:class:`numpy.ndarray` object with no metadata. |
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""" |
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varnames=("T", "P", "W", "PB", "QVAPOR") |
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ncvars = extract_vars(wrfin, timeidx, varnames, method, squeeze, cache, |
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meta=False, _key=_key) |
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t = ncvars["T"] |
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p = ncvars["P"] |
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w = ncvars["W"] |
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pb = ncvars["PB"] |
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qv = ncvars["QVAPOR"] |
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wa = destagger(w, -3) |
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full_t = t + Constants.T_BASE |
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full_p = p + pb |
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tk = _tk(full_p, full_t) |
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omega = _omega(qv, tk, wa, full_p) |
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return omega |
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