from __future__ import (absolute_import, division, print_function, unicode_literals) import numpy as np import numpy.ma as ma from .constants import Constants, default_fill from .extension import _tk, _rh, _cloudfrac from .metadecorators import set_cloudfrac_metadata from .util import extract_vars from .g_geoht import _get_geoht @set_cloudfrac_metadata() def get_cloudfrac(wrfin, timeidx=0, method="cat", squeeze=True, cache=None, meta=True, _key=None, vert_type="height_agl", low_thresh=None, mid_thresh=None, high_thresh=None, missing=default_fill(np.float64)): """Return the cloud fraction for low, mid, and high level clouds. The leftmost dimension of the returned array represents three different quantities: - return_val[0,...] will contain LOW level cloud fraction - return_val[1,...] will contain MID level cloud fraction - return_val[2,...] will contain HIGH level cloud fraction If the vertical coordinate type is 'height_agl' or 'height_msl', the default cloud levels are defined as: 300 m <= low_cloud < 2000 m 2000 m <= mid_cloud < 6000 m 6000 m <= high_cloud For 'pressure', the default cloud levels are defined as: 97000 Pa <= low_cloud < 80000 Pa 80000 Pa <= mid_cloud < 45000 Pa 45000 Pa <= high_cloud Note that the default low cloud levels are chosen to exclude clouds near the surface (fog). If you want fog included, set *low_thresh* to ~99500 Pa if *vert_type* is set to 'pressure', or 15 m if using 'height_msl' or 'height_agl'. Keep in mind that the lowest mass grid points are slightly above the ground, and in order to find clouds, the *low_thresh* needs to be set to values that are slightly greater than (less than) the lowest height (pressure) values. When using 'pressure' or 'height_agl' for *vert_type*, there is a possibility that the lowest WRF level will be higher than the low_cloud or mid_cloud threshold, particularly for mountainous regions. When this happens, a fill value will be used in the output. This functions extracts the necessary variables from the NetCDF file object in order to perform the calculation. Args: wrfin (:class:`netCDF4.Dataset`, :class:`Nio.NioFile`, or an \ iterable): WRF-ARW NetCDF data as a :class:`netCDF4.Dataset`, :class:`Nio.NioFile` or an iterable sequence of the aforementioned types. timeidx (:obj:`int` or :data:`wrf.ALL_TIMES`, optional): The desired time index. This value can be a positive integer, negative integer, or :data:`wrf.ALL_TIMES` (an alias for None) to return all times in the file or sequence. The default is 0. method (:obj:`str`, optional): The aggregation method to use for sequences. Must be either 'cat' or 'join'. 'cat' combines the data along the Time dimension. 'join' creates a new dimension for the file index. The default is 'cat'. squeeze (:obj:`bool`, optional): Set to False to prevent dimensions with a size of 1 from being automatically removed from the shape of the output. Default is True. cache (:obj:`dict`, optional): A dictionary of (varname, ndarray) that can be used to supply pre-extracted NetCDF variables to the computational routines. It is primarily used for internal purposes, but can also be used to improve performance by eliminating the need to repeatedly extract the same variables used in multiple diagnostics calculations, particularly when using large sequences of files. Default is None. meta (:obj:`bool`, optional): Set to False to disable metadata and return :class:`numpy.ndarray` instead of :class:`xarray.DataArray`. Default is True. _key (:obj:`int`, optional): A caching key. This is used for internal purposes only. Default is None. vert_type (:obj:`str`, optional): The type of vertical coordinate used to determine cloud type thresholds. Must be 'height_agl', 'height_msl', or 'pres'. The default is 'height_agl'. low_thresh (:obj:`float`, optional): The lower bound for what is considered a low cloud. If *vert_type* is 'pres', the default is 97000 Pa. If *vert_type* is 'height_agl' or 'height_msl', then the default is 300 m. mid_thresh (:obj:`float`, optional): The lower bound for what is considered a mid level cloud. If *vert_type* is 'pres', the default is 80000 Pa. If *vert_type* is 'height_agl' or 'height_msl', then the default is 2000 m. high_thresh (:obj:`float`, optional): The lower bound for what is considered a high level cloud. If *vert_type* is 'pres', the default is 45000 Pa. If *vert_type* is 'height_agl' or 'height_msl', then the default is 6000 m. Returns: :class:`xarray.DataArray` or :class:`numpy.ndarray`: The cloud fraction array whose leftmost dimension is 3 (LOW=0, MID=1, HIGH=2). If xarray is enabled and the *meta* parameter is True, then the result will be a :class:`xarray.DataArray` object. Otherwise, the result will be a :class:`numpy.ndarray` object with no metadata. """ ncvars = extract_vars(wrfin, timeidx, ("P", "PB", "QVAPOR", "T"), method, squeeze, cache, meta=False, _key=_key) p = ncvars["P"] pb = ncvars["PB"] qv = ncvars["QVAPOR"] t = ncvars["T"] full_p = p + pb full_t = t + Constants.T_BASE tk = _tk(full_p, full_t) rh = _rh(qv, full_p, tk) if vert_type.lower() == "pres" or vert_type.lower() == "pressure": v_coord = full_p _low_thresh = 97000. if low_thresh is None else low_thresh _mid_thresh = 80000. if mid_thresh is None else mid_thresh _high_thresh = 45000. if high_thresh is None else high_thresh vert_inc_w_height = 0 elif (vert_type.lower() == "height_msl" or vert_type.lower() == "height_agl"): is_msl = vert_type.lower() == "height_msl" v_coord = _get_geoht(wrfin, timeidx, method, squeeze, cache, meta=False, _key=_key, height=True, msl=is_msl) _low_thresh = 300. if low_thresh is None else low_thresh _mid_thresh = 2000. if mid_thresh is None else mid_thresh _high_thresh = 6000. if high_thresh is None else high_thresh vert_inc_w_height = 1 else: raise ValueError("'vert_type' must be 'pres', 'height_msl', " "or 'height_agl'") cfrac = _cloudfrac(v_coord, rh, vert_inc_w_height, _low_thresh, _mid_thresh, _high_thresh, missing) return ma.masked_values(cfrac, missing)