How To Use ============ Basic Usage ---------------- .. _diagnostic-usage: Computing Diagnostic Variables ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The primary use for the :meth:`wrf.getvar` function is to return diagnostic variables that require a calculation, since WRF does not produce these variables natively. These diagnostics include CAPE, storm relative helicity, omega, sea level pressure, etc. A table of all available diagnostics can be found here: :ref:`diagnostic-table`. In the example below, sea level pressure is calculated and printed. .. code-block:: python from __future__ import (absolute_import, division, print_function, unicode_literals) from netCDF4 import Dataset from wrf import getvar ncfile = Dataset("wrfout_d01_2016-10-07_00_00_00") # Get the Sea Level Pressure slp = getvar(ncfile, "slp") print(slp) Result: .. code-block:: none array([[ 1012.22033691, 1012.29815674, 1012.24786377, ..., 1010.13201904, 1009.93231201, 1010.06707764], [ 1012.43286133, 1012.44476318, 1012.33666992, ..., 1010.1072998 , 1010.10845947, 1010.04760742], [ 1012.39544678, 1012.38085938, 1012.41705322, ..., 1010.22937012, 1010.05596924, 1010.02679443], ..., [ 1009.0423584 , 1009.06921387, 1008.98779297, ..., 1019.19281006, 1019.14434814, 1019.1105957 ], [ 1009.22485352, 1009.07513428, 1008.98638916, ..., 1019.07189941, 1019.04266357, 1019.0612793 ], [ 1009.18896484, 1009.1071167 , 1008.97979736, ..., 1018.91778564, 1018.95684814, 1019.04748535]], dtype=float32) Coordinates: XLONG (south_north, west_east) float32 -122.72 -122.693 -122.666 ... XLAT (south_north, west_east) float32 21.1381 21.1451 21.1521 ... Time datetime64[ns] 2016-10-07 * south_north (south_north) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ... * west_east (west_east) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 ... Attributes: FieldType: 104 MemoryOrder: XY description: sea level pressure units: hPa stagger: coordinates: XLONG XLAT projection: LambertConformal(bottom_left=(21.138123, -122.71953), top_right=(47.843636, -60.901367), stand_lon=-97.5, moad_cen_lat=38.5000038147, truelat1=38.5, truelat2=38.5, pole_lat=90.0, pole_lon=0.0) .. _extract_ncvars: Extracting WRF NetCDF Variables ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ In addition to computing diagnostic variables (see :ref:`diagnostic-usage`), the :meth:`wrf.getvar` function can be used to extract regular WRF-ARW output NetCDF variables. .. code-block:: python from __future__ import (absolute_import, division, print_function, unicode_literals) from netCDF4 import Dataset from wrf import getvar ncfile = Dataset("wrfout_d01_2016-10-07_00_00_00") p = getvar(ncfile, "P") print(p) Result: .. code-block:: none array([[[ 1.21753906e+03, 1.22532031e+03, 1.22030469e+03, ..., 1.00760156e+03, 9.87640625e+02, 1.00111719e+03], [ 1.23877344e+03, 1.24004688e+03, 1.22926562e+03, ..., 1.00519531e+03, 1.00529688e+03, 9.99171875e+02], [ 1.23503906e+03, 1.23367188e+03, 1.23731250e+03, ..., 1.01739844e+03, 1.00005469e+03, 9.97093750e+02], ..., [ 1.77978516e+00, 1.77050781e+00, 1.79003906e+00, ..., 4.22949219e+00, 4.25659180e+00, 4.13647461e+00], [ 1.73291016e+00, 1.76879883e+00, 1.77978516e+00, ..., 4.24047852e+00, 4.24707031e+00, 4.13549805e+00], [ 1.71533203e+00, 1.65722656e+00, 1.67480469e+00, ..., 4.06884766e+00, 4.03637695e+00, 4.04785156e+00]]], dtype=float32) Coordinates: XLONG (south_north, west_east) float32 -122.72 -122.693 -122.666 ... XLAT (south_north, west_east) float32 21.1381 21.1451 21.1521 ... Time datetime64[ns] 2016-10-07 * bottom_top (bottom_top) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 ... * south_north (south_north) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ... * west_east (west_east) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 ... Attributes: FieldType: 104 MemoryOrder: XYZ description: perturbation pressure units: Pa stagger: coordinates: XLONG XLAT projection: LambertConformal(bottom_left=(21.138123, -122.71953), top_right=(47.843636, -60.901367), stand_lon=-97.5, moad_cen_lat=38.5000038147, truelat1=38.5, truelat2=38.5, pole_lat=90.0, pole_lon=0.0) Disabling xarray and metadata ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Sometimes you just want a regular numpy array and don't care about metadata. This is often the case when you are working with compiled extensions. Metadata can be disabled in one of two ways. #. disable xarray completely #. set the *meta* function parameter to False. The example below illustrates both. .. code-block:: python from __future__ import (absolute_import, division, print_function, unicode_literals) from netCDF4 import Dataset from wrf import getvar, disable_xarray ncfile = Dataset("wrfout_d01_2016-10-07_00_00_00") # Disable xarray completely disable_xarray() p_no_meta = getvar(ncfile, "P") print (type(p_no_meta)) enable_xarray() # Disable by using the meta parameter p_no_meta = getvar(ncfile, "P", meta=False) print (type(p_no_meta)) Result: .. code-block:: none Extracting a Numpy Array from a DataArray ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ If you need to convert an :class:`xarray.DataArray` to a :class:`numpy.ndarray`, wrf-python provides the :meth:`wrf.npvalues` function for this purpose. Although an :class:`xarray.DataArary` object already contains the :attr:`xarray.DataArray.values` attribute to extract the Numpy array, there is a problem when working with compiled extensions. The behavior for xarray (and pandas) is to convert missing/fill values to NaN, which may cause crashes when working with compiled extensions. Also, some existing code may be designed to work with :class:`numpy.ma.MaskedArray`, and numpy arrays with NaN may not work with it. The :meth:`wrf.npvalues` function does the following: #. If no missing/fill values are used, :meth:`wrf.npvalues` simply returns the :attr:`xarray.DataArray.values` attribute. #. If missing/fill values are used, then :meth:`wrf.npvalues` replaces the NaN values with the _FillValue found in the :attr:`xarray.DataArray.attrs` attribute (required) and a :class:`numpy.ma.MaskedArray` is returned. .. code-block:: python from __future__ import (absolute_import, division, print_function, unicode_literals) from netCDF4 import Dataset from wrf import getvar ncfile = Dataset("wrfout_d01_2016-10-07_00_00_00") # Get the Sea Level Pressure cape_3d = getvar(ncfile, "cape_3d") cape_3d_ndarray = npvalues(cape_3d) print(type(cape_3d_ndarray)) Result: .. code-block:: none Sequences of Files ---------------------- Combining Multiple Files Using the 'cat' Method ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The 'cat' (concatenate) method aggregates all files in the sequence along the 'Time' dimension, which will be the leftmost dimension for the output array. To include all of the times, in all of the files, in the output array, set the *timeidx* parameter to :data:`wrf.ALL_TIMES` (an alias for None). If a single value is specified for *timeidx*, then the time index is assumed to be taken from the concatenation of all times for all files. It is import to note that no sorting is performed in the :meth:`wrf.getvar` routine, so all files in the sequence must be sorted prior to calling this function. .. code-block:: python from __future__ import (absolute_import, division, print_function, unicode_literals) from netCDF4 import Dataset from wrf import getvar, ALL_TIMES # Creating a simple test list with three timesteps wrflist = [Dataset("wrfout_d01_2016-10-07_00_00_00"), Dataset("wrfout_d01_2016-10-07_01_00_00"), Dataset("wrfout_d01_2016-10-07_02_00_00")] # Extract the 'P' variable for all times p_cat = getvar(wrflist, "P", timeidx=ALL_TIMES, method="cat") print(p_cat) Result: .. code-block:: none array([[[[ 1.21753906e+03, 1.22532031e+03, 1.22030469e+03, ..., 1.00760156e+03, 9.87640625e+02, 1.00111719e+03], [ 1.23877344e+03, 1.24004688e+03, 1.22926562e+03, ..., 1.00519531e+03, 1.00529688e+03, 9.99171875e+02], [ 1.23503906e+03, 1.23367188e+03, 1.23731250e+03, ..., 1.01739844e+03, 1.00005469e+03, 9.97093750e+02], ..., [ 1.77978516e+00, 1.77050781e+00, 1.79003906e+00, ..., 4.22949219e+00, 4.25659180e+00, 4.13647461e+00], [ 1.73291016e+00, 1.76879883e+00, 1.77978516e+00, ..., 4.24047852e+00, 4.24707031e+00, 4.13549805e+00], [ 1.71533203e+00, 1.65722656e+00, 1.67480469e+00, ..., 4.06884766e+00, 4.03637695e+00, 4.04785156e+00]]]], dtype=float32) Coordinates: XLONG (south_north, west_east) float32 -122.72 -122.693 -122.666 ... XLAT (south_north, west_east) float32 21.1381 21.1451 21.1521 ... * Time (Time) datetime64[ns] 2016-10-07 2016-10-07 2016-10-07 * bottom_top (bottom_top) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 ... * south_north (south_north) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ... * west_east (west_east) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 ... datetime (Time) datetime64[ns] 2016-10-07T00:00:00 ... Attributes: FieldType: 104 MemoryOrder: XYZ description: perturbation pressure units: Pa stagger: coordinates: XLONG XLAT projection: LambertConformal(bottom_left=(21.138123, -122.71953), top_right=(47.843636, -60.901367), stand_lon=-97.5, moad_cen_lat=38.5000038147, truelat1=38.5, truelat2=38.5, pole_lat=90.0, pole_lon=0.0) Combining Multiple Files Using the 'join' Method ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The 'join' method combines a sequence of files by adding a new leftmost dimension for the file/sequence index. In situations where there are multiple files with multiple times, and the last file contains less times than the previous files, the remaining arrays will be arrays filled with missing values. There are checks in place within the wrf-python algorithms to look for these missing arrays, but be careful when calling compiled routines outside of wrf-python. In most cases, *timeidx* parameter should be set to :data:`wrf.ALL_TIMES`. If a *timeidx* value is specified, then this time index is used when extracting the variable from each file. In cases where there are multiple files with multiple time steps, this is probably nonsensical, since the nth time index for each file represents a different time. In general, join is rarely used, so the concatenate method should be used for most cases. .. code-block:: python from __future__ import (absolute_import, division, print_function, unicode_literals) from netCDF4 import Dataset from wrf import getvar, ALL_TIMES # Creating a simple test list with three timesteps wrflist = [Dataset("wrfout_d01_2016-10-07_00_00_00"), Dataset("wrfout_d01_2016-10-07_01_00_00"), Dataset("wrfout_d01_2016-10-07_02_00_00")] # Extract the 'P' variable for all times p_join = getvar(wrflist, "P", timeidx=ALL_TIMES, method="join") print(p_join) Result: .. code-block:: none array([[[[ 1.21753906e+03, 1.22532031e+03, 1.22030469e+03, ..., 1.00760156e+03, 9.87640625e+02, 1.00111719e+03], [ 1.23877344e+03, 1.24004688e+03, 1.22926562e+03, ..., 1.00519531e+03, 1.00529688e+03, 9.99171875e+02], [ 1.23503906e+03, 1.23367188e+03, 1.23731250e+03, ..., 1.01739844e+03, 1.00005469e+03, 9.97093750e+02], ..., [ 1.77978516e+00, 1.77050781e+00, 1.79003906e+00, ..., 4.22949219e+00, 4.25659180e+00, 4.13647461e+00], [ 1.73291016e+00, 1.76879883e+00, 1.77978516e+00, ..., 4.24047852e+00, 4.24707031e+00, 4.13549805e+00], [ 1.71533203e+00, 1.65722656e+00, 1.67480469e+00, ..., 4.06884766e+00, 4.03637695e+00, 4.04785156e+00]]]], dtype=float32) Coordinates: XLONG (south_north, west_east) float32 -122.72 -122.693 -122.666 ... XLAT (south_north, west_east) float32 21.1381 21.1451 21.1521 ... * bottom_top (bottom_top) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 ... * south_north (south_north) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ... * west_east (west_east) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 ... * file (file) int64 0 1 2 datetime (file) datetime64[ns] 2016-10-07T00:00:00 ... Time int64 0 Attributes: FieldType: 104 MemoryOrder: XYZ description: perturbation pressure units: Pa stagger: coordinates: XLONG XLAT projection: LambertConformal(bottom_left=(21.138123, -122.71953), top_right=(47.843636, -60.901367), stand_lon=-97.5, moad_cen_lat=38.5000038147, truelat1=38.5, truelat2=38.5, pole_lat=90.0, pole_lon=0.0) Note how the 'Time' dimension was replaced with the 'file' dimension, due to the numpy's automatic squeezing of the single 'Time' dimension. To maintain the 'Time' dimension, set the *squeeze* parameter to False. .. code-block:: python from __future__ import (absolute_import, division, print_function, unicode_literals) from netCDF4 import Dataset from wrf import getvar, ALL_TIMES # Creating a simple test list with three timesteps wrflist = [Dataset("wrfout_d01_2016-10-07_00_00_00"), Dataset("wrfout_d01_2016-10-07_01_00_00"), Dataset("wrfout_d01_2016-10-07_02_00_00")] # Extract the 'P' variable for all times p_join = getvar(wrflist, "P", timeidx=ALL_TIMES, method="join", squeeze=False) print(p_join) Result .. code-block:: none array([[[[[ 1.21753906e+03, 1.22532031e+03, 1.22030469e+03, ..., 1.00760156e+03, 9.87640625e+02, 1.00111719e+03], [ 1.23877344e+03, 1.24004688e+03, 1.22926562e+03, ..., 1.00519531e+03, 1.00529688e+03, 9.99171875e+02], [ 1.23503906e+03, 1.23367188e+03, 1.23731250e+03, ..., 1.01739844e+03, 1.00005469e+03, 9.97093750e+02], ..., [ 1.77978516e+00, 1.77050781e+00, 1.79003906e+00, ..., 4.22949219e+00, 4.25659180e+00, 4.13647461e+00], [ 1.73291016e+00, 1.76879883e+00, 1.77978516e+00, ..., 4.24047852e+00, 4.24707031e+00, 4.13549805e+00], [ 1.71533203e+00, 1.65722656e+00, 1.67480469e+00, ..., 4.06884766e+00, 4.03637695e+00, 4.04785156e+00]]]]], dtype=float32) Coordinates: XLONG (south_north, west_east) float32 -122.72 -122.693 -122.666 ... XLAT (south_north, west_east) float32 21.1381 21.1451 21.1521 ... * bottom_top (bottom_top) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 ... * south_north (south_north) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ... * west_east (west_east) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 ... * file (file) int64 0 1 2 datetime (file, Time) datetime64[ns] 2016-10-07T00:00:00 ... * Time (Time) int64 0 Attributes: FieldType: 104 MemoryOrder: XYZ description: perturbation pressure units: Pa stagger: coordinates: XLONG XLAT projection: LambertConformal(bottom_left=(21.138123, -122.71953), top_right=(47.843636, -60.901367), stand_lon=-97.5, moad_cen_lat=38.5000038147, truelat1=38.5, truelat2=38.5, pole_lat=90.0, pole_lon=0.0) Dictionaries of WRF File Sequences ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Dictionaries can also be used as input to the :meth:`wrf.getvar` functions. This can be useful when working with ensembles. However, all WRF files in the dictionary must have the same dimensions. The result is an array where the leftmost dimension is the keys from the dictionary. Nested dictionaries are allowed. The *method* argument is used to describe how each sequence in the dictionary will be combined. .. code-block:: python from __future__ import (absolute_import, division, print_function, unicode_literals) from netCDF4 import Dataset from wrf import getvar, ALL_TIMES wrf_dict = {"ens1" : [Dataset("ens1/wrfout_d01_2016-10-07_00_00_00"), Dataset("ens1/wrfout_d01_2016-10-07_01_00_00"), Dataset("ens1/wrfout_d01_2016-10-07_02_00_00")], "ens2" : [Dataset("ens2/wrfout_d01_2016-10-07_00_00_00"), Dataset("ens2/wrfout_d01_2016-10-07_01_00_00"), Dataset("ens2/wrfout_d01_2016-10-07_02_00_00")] } p = getvar(wrf_dict, "P", timeidx=ALL_TIMES) print(p) Result: .. code-block:: none array([[[[[ 1.21753906e+03, 1.22532031e+03, 1.22030469e+03, ..., 1.00760156e+03, 9.87640625e+02, 1.00111719e+03], [ 1.23877344e+03, 1.24004688e+03, 1.22926562e+03, ..., 1.00519531e+03, 1.00529688e+03, 9.99171875e+02], [ 1.23503906e+03, 1.23367188e+03, 1.23731250e+03, ..., 1.01739844e+03, 1.00005469e+03, 9.97093750e+02], ..., [ 1.77978516e+00, 1.77050781e+00, 1.79003906e+00, ..., 4.22949219e+00, 4.25659180e+00, 4.13647461e+00], [ 1.73291016e+00, 1.76879883e+00, 1.77978516e+00, ..., 4.24047852e+00, 4.24707031e+00, 4.13549805e+00], [ 1.71533203e+00, 1.65722656e+00, 1.67480469e+00, ..., 4.06884766e+00, 4.03637695e+00, 4.04785156e+00]]]]], dtype=float32) Coordinates: XLONG (south_north, west_east) float32 -122.72 -122.693 -122.666 ... XLAT (south_north, west_east) float32 21.1381 21.1451 21.1521 ... * Time (Time) datetime64[ns] 2016-10-07T00:00:00 ... * bottom_top (bottom_top) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 ... * south_north (south_north) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ... * west_east (west_east) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 ... datetime (Time) datetime64[ns] 2016-10-07T00:00:00 ... * key_0 (key_0) array([[ 5882.16992188, 5881.87939453, 5881.81005859, ..., 5890.14501953, 5890.23583984, 5890.33349609], [ 5882.71777344, 5882.17529297, 5882.1171875 , ..., 5890.37695312, 5890.38525391, 5890.27978516], [ 5883.32177734, 5882.47119141, 5882.34130859, ..., 5890.48339844, 5890.42871094, 5890.17724609], ..., [ 5581.45800781, 5580.46826172, 5579.32617188, ..., 5788.93554688, 5788.70507812, 5788.64453125], [ 5580.32714844, 5579.51611328, 5578.34863281, ..., 5788.15869141, 5787.87304688, 5787.65527344], [ 5579.64404297, 5578.30957031, 5576.98632812, ..., 5787.19384766, 5787.10888672, 5787.06933594]], dtype=float32) Coordinates: XLONG (south_north, west_east) float32 -122.72 -122.693 -122.666 ... XLAT (south_north, west_east) float32 21.1381 21.1451 21.1521 ... Time datetime64[ns] 2016-10-07 * south_north (south_north) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ... * west_east (west_east) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 ... Attributes: FieldType: 104 units: m stagger: coordinates: XLONG XLAT projection: LambertConformal(bottom_left=(21.138123, -122.71953), top_right=(47.843636, -60.901367), stand_lon=-97.5, moad_cen_lat=38.5000038147, truelat1=38.5, truelat2=38.5, pole_lat=90.0, pole_lon=0.0) level: 500 hPa missing_value: 9.96920996839e+36 _FillValue: 9.96920996839e+36 .. _vert_cross_interp: Vertical Cross Sections ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The :meth:`wrf.vertcross` function is used to create vertical cross sections. To define a cross section, a start point and an end point needs to be specified. Alternatively, a pivot point and an angle may be used. The start point, end point, and pivot point are specified using a :class:`wrf.CoordPair` object, and coordinates can either be in grid (x,y) coordinates or (latitude,longitude) coordinates. When using (latitude,longitude) coordinates, a NetCDF file object or a :class:`wrf.WrfProj` object must be provided. The vertical levels can also be specified using the *levels* parameter. If not specified, then approximately 100 levels will be chosen in 1% increments. Example Using Start Point and End Point ***************************************** .. code-block:: python from __future__ import (absolute_import, division, print_function, unicode_literals) from netCDF4 import Dataset from wrf import getvar, vertcross, CoordPair ncfile = Dataset("wrfout_d01_2016-10-07_00_00_00") # Get the geopotential height (m) and pressure (hPa). z = getvar(ncfile, "z") p = getvar(ncfile, "pressure") # Define a start point and end point in grid coordinates start_point = CoordPair(x=0, y=(z.shape[-2]-1)//2) end_point = CoordPair(x=-1, y=(z.shape[-2]-1)//2) # Calculate the vertical cross section. By setting latlon to True, this # also calculates the latitude and longitude coordinates along the cross # section line and adds them to the 'xy_loc' metadata to help with plotting. p_vert = vertcross(p, z, start_point=start_point, end_point=end_point, latlon=True) print(p_vert) Result: .. code-block:: none array([[ nan, nan, nan, ..., nan, nan, nan], [ 989.66168213, 989.66802979, 989.66351318, ..., 988.05737305, 987.99151611, 987.96917725], [ 959.49450684, 959.50109863, 959.50030518, ..., 958.96948242, 958.92980957, 958.89294434], ..., [ 24.28092003, 24.27359581, 24.27034378, ..., 24.24800491, 24.2486496 , 24.24947357], [ 23.2868309 , 23.27933884, 23.27607918, ..., 23.25231361, 23.2530098 , 23.25384521], [ nan, nan, nan, ..., nan, nan, nan]], dtype=float32) Coordinates: Time datetime64[ns] 2016-10-07 xy_loc (idx) object CoordPair(x=0.0, y=529.0, lat=34.5279502869, lon=-127.398925781) ... * vertical (vertical) float32 0.0 261.828 523.656 785.484 1047.31 1309.14 ... * idx (idx) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 ... Attributes: FieldType: 104 description: pressure units: hPa stagger: coordinates: XLONG XLAT projection: LambertConformal(bottom_left=(21.138123, -122.71953), top_right=(47.843636, -60.901367), stand_lon=-97.5, moad_cen_lat=38.5000038147, truelat1=38.5, truelat2=38.5, pole_lat=90.0, pole_lon=0.0) orientation: (0.0, 529.0) to (1797.0, 529.0) missing_value: 9.96920996839e+36 _FillValue: 9.96920996839e+36 Example Using Pivot Point and Angle ************************************* .. code-block:: python from __future__ import (absolute_import, division, print_function, unicode_literals) from netCDF4 import Dataset from wrf import getvar, vertcross, CoordPair ncfile = Dataset("wrfout_d01_2016-10-07_00_00_00") # Get the geopotential height (m) and pressure (hPa). z = getvar(ncfile, "z") p = getvar(ncfile, "pressure") # Define a pivot point and angle in grid coordinates, with the # pivot point being the center of the grid. pivot_point = CoordPair(x=(z.shape[-1]-1)//2, y=(z.shape[-2]-1)//2) angle = 90.0 # Calculate the vertical cross section. By setting latlon to True, this # also calculates the latitude and longitude coordinates along the line # and adds them to the metadata to help with plotting labels. p_vert = vertcross(p, z, pivot_point=pivot_point, angle=angle, latlon=True) print (p_vert) Result: .. code-block:: none array([[ nan, nan, nan, ..., nan, nan, nan], [ 989.66168213, 989.66802979, 989.66351318, ..., 988.05737305, 987.99151611, 987.96917725], [ 959.49450684, 959.50109863, 959.50030518, ..., 958.96948242, 958.92980957, 958.89294434], ..., [ 24.28092003, 24.27359581, 24.27034378, ..., 24.24800491, 24.2486496 , 24.24947357], [ 23.2868309 , 23.27933884, 23.27607918, ..., 23.25231361, 23.2530098 , 23.25384521], [ nan, nan, nan, ..., nan, nan, nan]], dtype=float32) Coordinates: Time datetime64[ns] 2016-10-07 xy_loc (idx) object CoordPair(x=0.0, y=529.0, lat=34.5279502869, lon=-127.398925781) ... * vertical (vertical) float32 0.0 261.828 523.656 785.484 1047.31 1309.14 ... * idx (idx) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 ... Attributes: FieldType: 104 description: pressure units: hPa stagger: coordinates: XLONG XLAT projection: LambertConformal(bottom_left=(21.138123, -122.71953), top_right=(47.843636, -60.901367), stand_lon=-97.5, moad_cen_lat=38.5000038147, truelat1=38.5, truelat2=38.5, pole_lat=90.0, pole_lon=0.0) orientation: (0.0, 529.0) to (1797.0, 529.0) ; center=CoordPair(x=899.0, y=529.0) ; angle=90.0 missing_value: 9.96920996839e+36 _FillValue: 9.96920996839e+36 Example Using Lat/Lon Coordinates ************************************* .. code-block:: python from __future__ import (absolute_import, division, print_function, unicode_literals) from netCDF4 import Dataset from wrf import getvar, vertcross, CoordPair ncfile = Dataset("wrfout_d01_2016-10-07_00_00_00") # Get the geopotential height (m) and pressure (hPa). z = getvar(ncfile, "z") p = getvar(ncfile, "pressure") lats = getvar(ncfile, "lat") lons = getvar(ncfile, "lon") # Making the same horizontal line, but with lats/lons start_lat = lats[(lats.shape[-2]-1)//2, 0] end_lat = lats[(lats.shape[-2]-1)//2, -1] start_lon = lons[(lats.shape[-2]-1)//2, 0] end_lon = lons[(lats.shape[-2]-1)//2, -1] # Cross section line using start_point and end_point. start_point = CoordPair(lat=start_lat, lon=start_lon) end_point = CoordPair(lat=end_lat, lon=end_lon) # When using lat/lon coordinates, you must supply a netcdf file object, or a # projection object. p_vert = vertcross(p, z, wrfin=ncfile, start_point=start_point, end_point=end_point, latlon=True) print(p_vert) Result: .. code-block:: none array([[ nan, nan, nan, ..., nan, nan, nan], [ 989.66168213, 989.66802979, 989.66351318, ..., 988.05737305, 987.99151611, 987.96917725], [ 959.49450684, 959.50109863, 959.50030518, ..., 958.96948242, 958.92980957, 958.89294434], ..., [ 24.28092003, 24.27359581, 24.27034378, ..., 24.24800491, 24.2486496 , 24.24947357], [ 23.2868309 , 23.27933884, 23.27607918, ..., 23.25231361, 23.2530098 , 23.25384521], [ nan, nan, nan, ..., nan, nan, nan]], dtype=float32) Coordinates: Time datetime64[ns] 2016-10-07 xy_loc (idx) object CoordPair(x=0.0, y=529.0, lat=34.5279502869, lon=-127.398925781) ... * vertical (vertical) float32 0.0 261.828 523.656 785.484 1047.31 1309.14 ... * idx (idx) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 ... Attributes: FieldType: 104 description: pressure units: hPa stagger: coordinates: XLONG XLAT projection: LambertConformal(bottom_left=(21.138123, -122.71953), top_right=(47.843636, -60.901367), stand_lon=-97.5, moad_cen_lat=38.5000038147, truelat1=38.5, truelat2=38.5, pole_lat=90.0, pole_lon=0.0) orientation: (0.0, 529.0) to (1797.0, 529.0) missing_value: 9.96920996839e+36 _FillValue: 9.96920996839e+36 Example Using Specified Vertical Levels ***************************************** .. code-block:: python from __future__ import (absolute_import, division, print_function, unicode_literals) from netCDF4 import Dataset from wrf import getvar, vertcross, CoordPair ncfile = Dataset("wrfout_d01_2016-10-07_00_00_00") # Get the geopotential height (m) and pressure (hPa). z = getvar(ncfile, "z") p = getvar(ncfile, "pressure") lats = getvar(ncfile, "lat") lons = getvar(ncfile, "lon") # Making the same horizontal line, but with lats/lons start_lat = lats[(lats.shape[-2]-1)//2, 0] end_lat = lats[(lats.shape[-2]-1)//2, -1] start_lon = lons[(lats.shape[-2]-1)//2, 0] end_lon = lons[(lats.shape[-2]-1)//2, -1] # Pressure using start_point and end_point. These were obtained using start_point = CoordPair(lat=start_lat, lon=start_lon) end_point = CoordPair(lat=end_lat, lon=end_lon) # Specify vertical levels levels = [1000., 2000., 3000.] # Calculate the cross section p_vert = vertcross(p, z, wrfin=ncfile, levels=levels, start_point=start_point, end_point=end_point, latlon=True) print(p_vert) Result: .. code-block:: none array([[ 906.375 , 906.38043213, 906.39367676, ..., 907.6661377 , 907.63006592, 907.59191895], [ 804.24737549, 804.26885986, 804.28076172, ..., 806.98632812, 806.95556641, 806.92608643], [ 713.24578857, 713.2722168 , 713.27886963, ..., 716.09594727, 716.06610107, 716.03503418]], dtype=float32) Coordinates: Time datetime64[ns] 2016-10-07 xy_loc (idx) object CoordPair(x=0.0, y=529.0, lat=34.5279502869, lon=-127.398925781) ... * vertical (vertical) float32 1000.0 2000.0 3000.0 * idx (idx) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 ... Attributes: FieldType: 104 description: pressure units: hPa stagger: coordinates: XLONG XLAT projection: LambertConformal(bottom_left=(21.138123, -122.71953), top_right=(47.843636, -60.901367), stand_lon=-97.5, moad_cen_lat=38.5000038147, truelat1=38.5, truelat2=38.5, pole_lat=90.0, pole_lon=0.0) orientation: (0.0, 529.0) to (1797.0, 529.0) missing_value: 9.96920996839e+36 _FillValue: 9.96920996839e+36 Interpolating Two-Dimensional Fields to a Line ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Two-dimensional fields can be interpolated along a line, in a manner similar to the vertical cross section (see :ref:`vert_cross_interp`), using the :meth:`wrf.interpline` function. To define the line to interpolate along, a start point and an end point needs to be specified. Alternatively, a pivot point and an angle may be used. The start point, end point, and pivot point are specified using a :class:`wrf.CoordPair` object, and coordinates can either be in grid (x,y) coordinates or (latitude,longitude) coordinates. When using (latitude,longitude) coordinates, a NetCDF file object or a :class:`wrf.WrfProj` object must also be provided. Example Using Start Point and End Point ***************************************** .. code-block:: python from __future__ import (absolute_import, division, print_function, unicode_literals) from netCDF4 import Dataset from wrf import getvar, interpline, CoordPair ncfile = Dataset("wrfout_d01_2016-10-07_00_00_00") # Get the 2m temperature t2 = getvar(ncfile, "T2") # Create a south-north line in the center of the domain using # start point and end point start_point = CoordPair(x=(t2.shape[-1]-1)//2, y=0) end_point = CoordPair(x=(t2.shape[-1]-1)//2, y=-1) # Calculate the vertical cross section. By setting latlon to True, this # also calculates the latitude and longitude coordinates along the line # and adds them to the metadata to help with plotting labels. t2_line = interpline(t2, start_point=start_point, end_point=end_point, latlon=True) print(t2_line, "\n") Result: .. code-block:: none array([ 302.07214355, 302.08505249, 302.08688354, ..., 279.18557739, 279.1998291 , 279.23132324], dtype=float32) Coordinates: Time datetime64[ns] 2016-10-07 xy_loc (line_idx) object CoordPair(x=899.0, y=0.0, lat=24.3645858765, lon=-97.5) ... * line_idx (line_idx) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 ... Attributes: FieldType: 104 description: TEMP at 2 M units: K stagger: coordinates: XLONG XLAT projection: LambertConformal(bottom_left=(21.138123, -122.71953), top_right=(47.843636, -60.901367), stand_lon=-97.5, moad_cen_lat=38.5000038147, truelat1=38.5, truelat2=38.5, pole_lat=90.0, pole_lon=0.0) orientation: (899.0, 0.0) to (899.0, 1057.0) Example Using Pivot Point and Angle ***************************************** .. code-block:: python from __future__ import (absolute_import, division, print_function, unicode_literals) from netCDF4 import Dataset from wrf import getvar, interpline, CoordPair ncfile = Dataset("wrfout_d01_2016-10-07_00_00_00") # Get the 2m temperature t2 = getvar(ncfile, "T2") # Create a south-north line using pivot point and angle pivot_point = CoordPair((t2.shape[-1]-1)//2, (t2.shape[-2]-1)//2) angle = 0.0 # Calculate the vertical cross section. By setting latlon to True, this # also calculates the latitude and longitude coordinates along the line # and adds them to the metadata to help with plotting labels. t2_line = interpline(t2, start_point=start_point, end_point=end_point, latlon=True) print(t2_line, "\n") Result: .. code-block:: none array([ 302.07214355, 302.08505249, 302.08688354, ..., 279.18557739, 279.1998291 , 279.23132324], dtype=float32) Coordinates: Time datetime64[ns] 2016-10-07 xy_loc (line_idx) object CoordPair(x=899.0, y=0.0, lat=24.3645858765, lon=-97.5) ... * line_idx (line_idx) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 ... Attributes: FieldType: 104 description: TEMP at 2 M units: K stagger: coordinates: XLONG XLAT projection: LambertConformal(bottom_left=(21.138123, -122.71953), top_right=(47.843636, -60.901367), stand_lon=-97.5, moad_cen_lat=38.5000038147, truelat1=38.5, truelat2=38.5, pole_lat=90.0, pole_lon=0.0) orientation: (899.0, 0.0) to (899.0, 1057.0) ; center=CoordPair(x=899, y=529) ; angle=0.0 Example Using Lat/Lon Coordinates ************************************* .. code-block:: python from __future__ import (absolute_import, division, print_function, unicode_literals) from netCDF4 import Dataset from wrf import getvar, interpline, CoordPair ncfile = Dataset("wrfout_d01_2016-10-07_00_00_00") t2 = getvar(ncfile, "T2") lats = getvar(ncfile, "lat") lons = getvar(ncfile, "lon") # Select the latitude,longitude points for a vertical line through # the center of the domain. start_lat = lats[0, (lats.shape[-1]-1)//2] end_lat = lats[-1, (lats.shape[-1]-1)//2] start_lon = lons[0, (lons.shape[-1]-1)//2] end_lon = lons[-1, (lons.shape[-1]-1)//2] # Create the CoordPairs start_point = CoordPair(lat=start_lat, lon=start_lon) end_point = CoordPair(lat=end_lat, lon=end_lon) # Calculate the vertical cross section. By setting latlon to True, this # also calculates the latitude and longitude coordinates along the line # and adds them to the metadata to help with plotting labels. t2_line = interpline(t2, wrfin=ncfile, start_point=start_point, end_point=end_point, latlon=True) print (t2_line) Result: .. code-block:: none array([ 302.07214355, 302.08505249, 302.08688354, ..., 279.18557739, 279.1998291 , 279.23132324], dtype=float32) Coordinates: Time datetime64[ns] 2016-10-07 xy_loc (line_idx) object CoordPair(x=899.0, y=0.0, lat=24.3645858765, lon=-97.5) ... * line_idx (line_idx) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 ... Attributes: FieldType: 104 description: TEMP at 2 M units: K stagger: coordinates: XLONG XLAT projection: LambertConformal(bottom_left=(21.138123, -122.71953), top_right=(47.843636, -60.901367), stand_lon=-97.5, moad_cen_lat=38.5000038147, truelat1=38.5, truelat2=38.5, pole_lat=90.0, pole_lon=0.0) orientation: (899.0, 0.0) to (899.0, 1057.0) Interpolating a 3D Field to a Surface Type ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The :meth:`wrf.vinterp` is used to interpolate a field to a type of surface. The available surfaces are pressure, geopotential height, theta, and theta-e. The surface levels to interpolate also need to be specified. .. code-block:: python from __future__ import (absolute_import, division, print_function, unicode_literals) from netCDF4 import Dataset from wrf import getvar, interpline, CoordPair ncfile = Dataset("wrfout_d01_2016-10-07_00_00_00") # Interpolate tk to theta-e levels interp_levels = [200, 300, 500, 1000] interp_field = vinterp(ncfile, field=tk, vert_coord="eth", interp_levels=interp_levels, extrapolate=True, field_type="tk", log_p=True) print(interp_field) Result: .. code-block:: none array([[[ 296.12872314, 296.1166687 , 296.08905029, ..., 301.71026611, 301.67956543, 301.67791748], [ 296.11352539, 295.95581055, 295.91555786, ..., 301.63052368, 301.62905884, 301.65887451], [ 296.07556152, 295.91577148, 295.88214111, ..., 301.61499023, 301.60287476, 301.63961792], ..., [ 219.11134338, 219.08581543, 219.08602905, ..., 218.29879761, 218.30923462, 218.3787384 ], [ 219.09260559, 219.07765198, 219.08340454, ..., 218.2855072 , 218.30444336, 218.37931824], [ 219.07936096, 219.08181763, 219.10089111, ..., 218.31173706, 218.34288025, 218.3687439 ]]], dtype=float32) Coordinates: XLONG (south_north, west_east) float32 -122.72 -122.693 -122.666 ... XLAT (south_north, west_east) float32 21.1381 21.1451 21.1521 ... Time datetime64[ns] 2016-10-07 * south_north (south_north) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ... * west_east (west_east) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 ... * interp_level (interp_level) int64 200 300 500 1000 Attributes: FieldType: 104 MemoryOrder: XYZ description: temperature units: K stagger: coordinates: XLONG XLAT projection: LambertConformal(bottom_left=(21.138123, -122.71953), top_right=(47.843636, -60.901367), stand_lon=-97.5, moad_cen_lat=38.5000038147, truelat1=38.5, truelat2=38.5, pole_lat=90.0, pole_lon=0.0) vert_interp_type: eth Lat/Lon <-> XY Routines -------------------------- wrf-python includes a set of routines for converting back and forth between latitude,longitude space and x,y space. The methods are :meth:`wrf.xy_to_ll`, :meth:`wrf.xy_to_ll_proj`, :meth:`wrf.ll_to_xy`, :meth:`wrf.ll_to_xy_proj`. The *latitude*, *longitude*, *x*, and *y* parameters to these methods can contain sequences if multiple points are desired to be converted. Example With Single Coordinates ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ .. code-block:: python from __future__ import (absolute_import, division, print_function, unicode_literals) from netCDF4 import Dataset from wrf import getvar, interpline, CoordPair, xy_to_ll, ll_to_xy ncfile = Dataset("wrfout_d01_2016-10-07_00_00_00") lat_lon = xy_to_ll(ncfile, 400, 200) print(lat_lon) x_y = ll_to_xy(ncfile, lat_lon[0], lat_lon[1]) print (x_y) Result: .. code-block:: none array([ 28.55816408, -112.67827617]) Coordinates: * lat_lon (lat_lon) array([400, 200]) Coordinates: latlon_coord object CoordPair(lat=28.5581640822, lon=-112.678276173) * x_y (x_y) array([[ 28.55816408, 27.03835783], [-112.67827617, -121.36392174]]) Coordinates: * lat_lon (lat_lon) array([[400, 105], [200, 205]]) Coordinates: latlon_coord (idx) object CoordPair(lat=28.5581640822, lon=-112.678276173) ... * x_y (x_y)