wrf.getvar

wrf.getvar(wrfin, varname, timeidx=0, method='cat', squeeze=True, cache=None, meta=True, **kwargs)

Returns basic diagnostics from the WRF ARW model output.

A table of all available diagnostics is below.

Variable Name

Description

Available Units

Additional Keyword Arguments

avo

Absolute Vorticity

10-5 s-1

eth/theta_e

Equivalent Potential Temperature

K

degC

degF

units (str) : Set to desired units. Default is ‘K’.

cape_2d

2D CAPE (MCAPE/MCIN/LCL/LFC)

J kg-1 ; J kg-1 ; m ; m

missing (float): Fill value for output only

cape_3d

3D CAPE and CIN

J kg-1

missing (float): Fill value for output only

ctt

Cloud Top Temperature

degC

K

degF

fill_nocloud (boolean): Set to True to use fill values for cloud free regions rather than surface temperature. Default is False.

missing (float): The fill value to use when fill_nocloud is True.

opt_thresh (float): The optical depth required to trigger the cloud top temperature calculation. Default is 1.0.

units (str) : Set to desired units. Default is ‘degC’.

cloudfrac

Cloud Fraction

%

vert_type (str): The vertical coordinate type for the cloud thresholds. Must be ‘height_agl’, ‘height_msl’, or ‘pres’. Default is ‘height_agl’.

low_thresh (float): The low cloud threshold (meters for ‘height_agl’ and ‘height_msl’, pascals for ‘pres’). Default is 300 m (97000 Pa)

mid_thresh (float): The mid cloud threshold (meters for ‘height_agl’ and ‘height_msl’, pascals for ‘pres’). Default is 2000 m (80000 Pa)

high_thresh (float): The high cloud threshold (meters for ‘height_agl’ and ‘height_msl’, pascals for ‘pres’). Default is 6000 m (45000 Pa)

dbz

Reflectivity

dBZ

do_variant (boolean): Set to True to enable variant calculation. Default is False.

do_liqskin (boolean): Set to True to enable liquid skin calculation. Default is False.

mdbz

Maximum Reflectivity

dBZ

do_variant (boolean): Set to True to enable variant calculation. Default is False.

do_liqskin (boolean): Set to True to enable liquid skin calculation. Default is False.

geopt/geopotential

Geopotential for the Mass Grid

m2 s-2

geopt_stag

Geopotential for the Vertically Staggered Grid

m2 s-2

helicity

Storm Relative Helicity

m2 s-2

top (float): The top level for the calculation in meters. Default is 3000.0.

lat

Latitude

decimal degrees

lon

Longitude

decimal degrees

omg/omega

Omega

Pa s-1

p/pres

Full Model Pressure

(in specified units)

Pa

hPa

mb

torr

mmhg

atm

units (str) : Set to desired units. Default is ‘Pa’.

pressure

Full Model Pressure (hPa)

hPa

pvo

Potential Vorticity

PVU

pw

Precipitable Water

kg m-2

rh

Relative Humidity

%

rh2

2m Relative Humidity

%

slp

Sea Level Pressure

hPa

hPa

mb

torr

mmhg

atm

units (str) : Set to desired units. Default is ‘hPa’.

T2

2m Temperature

K

ter

Model Terrain Height

m

km

dm

ft

mi

units (str) : Set to desired units. Default is ‘m’.

td2

2m Dew Point Temperature

degC

K

degF

units (str) : Set to desired units. Default is ‘degC’.

td

Dew Point Temperature

degC

K

degF

units (str) : Set to desired units. Default is ‘degC’.

tc

Temperature in Celsius

degC

th/theta

Potential Temperature

K

degC

degF

units (str) : Set to desired units. Default is ‘K’.

temp

Temperature (in specified units)

K

degC

degF

units (str) : Set to desired units. Default is ‘K’.

tk

Temperature in Kelvin

K

times

Times in the File or Sequence

xtimes

XTIME Coordinate

(if applicable)

minutes since

start of

model run

tv

Virtual Temperature

K

degC

degF

units (str) : Set to desired units. Default is ‘K’.

twb

Wet Bulb Temperature

K

degC

degF

units (str) : Set to desired units. Default is ‘K’.

updraft_helicity

Updraft Helicity

m2 s-2

bottom (float): The bottom level for the calculation in meters. Default is 2000.0.

top (float): The top level for the calculation in meters. Default is 5000.0.

ua

U-component of Wind on Mass Points

m s-1

km h-1

mi h-1

kt

ft s-1

units (str) : Set to desired units. Default is ‘m s-1’.

va

V-component of Wind on Mass Points

m s-1

km h-1

mi h-1

kt

ft s-1

units (str) : Set to desired units. Default is ‘m s-1’.

wa

W-component of Wind on Mass Points

m s-1

km h-1

mi h-1

kt

ft s-1

units (str) : Set to desired units. Default is ‘m s-1’.

uvmet10

10 m U and V Components of Wind

Rotated to Earth Coordinates

m s-1

km h-1

mi h-1

kt

ft s-1

units (str) : Set to desired units. Default is ‘m s-1’.

uvmet

U and V Components of Wind

Rotated to Earth Coordinates

m s-1

km h-1

mi h-1

kt

ft s-1

units (str) : Set to desired units. Default is ‘m s-1’.

wspd_wdir

Wind Speed and Direction (wind_from_direction)

in Grid Coordinates

m s-1

km h-1

mi h-1

kt

ft s-1

units (str) : Set to desired units. Default is ‘m s-1’.

wspd_wdir10

10m Wind Speed and Direction (wind_from_direction)

in Grid Coordinates

m s-1

km h-1

mi h-1

kt

ft s-1

units (str) : Set to desired units. Default is ‘m s-1’.

uvmet_wspd_wdir

Wind Speed and Direction (wind_from_direction)

Rotated to Earth Coordinates

m s-1

km h-1

mi h-1

kt

ft s-1

units (str) : Set to desired units. Default is ‘m s-1’.

uvmet10_wspd_wdir

10m Wind Speed and Direction (wind_from_direction)

Rotated to Earth Coordinates

m s-1

km h-1

mi h-1

kt

ft s-1

units (str) : Set to desired units. Default is ‘m s-1’.

z/height

Model Height for Mass Grid

m

km

dm

ft

mi

msl (boolean): Set to False to return AGL values. True is for MSL. Default is True.

units (str) : Set to desired units. Default is ‘m’.

height_agl

Model Height for Mass Grid (AGL)

m

km

dm

ft

mi

units (str) : Set to desired units. Default is ‘m’.

zstag

Model Height for Vertically Staggered Grid

m

km

dm

ft

mi

msl (boolean): Set to False to return AGL values. True is for MSL. Default is True.

units (str) : Set to desired units. Default is ‘m’.
Parameters:

  • wrfin (netCDF4.Dataset, Nio.NioFile, or an iterable) – WRF-ARW NetCDF data as a netCDF4.Dataset, Nio.NioFile or an iterable sequence of the aforementioned types.

  • varname (str) – The variable name.

  • timeidx (int or wrf.ALL_TIMES, optional) – The desired time index. This value can be a positive integer, negative integer, or wrf.ALL_TIMES (an alias for None) to return all times in the file or sequence. The default is 0.

  • method (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 (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 (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 (bool, optional) – Set to False to disable metadata and return numpy.ndarray instead of xarray.DataArray. Default is True.

  • **kwargs – Optional keyword arguments for certain diagnostics. See table above.

Returns:

If xarray is enabled and the meta parameter is True, then the result will be a xarray.DataArray object. Otherwise, the result will be a numpy.ndarray object with no metadata.

Return type:

xarray.DataArray or numpy.ndarray

Raises:

  • ValueError – Raised when an invalid diagnostic type or keyword argument is passed to the routine.

  • FortranError – Raised when a problem occurs during a Fortran calculation.

See also

numpy.ndarray, xarray.DataArray

Examples

Using netCDF4

from netCDF4 import Dataset
from wrf import getvar

wrfnc = Dataset("wrfout_d02_2010-06-13_21:00:00")
slp = getvar(wrfnc, "slp")

Using PyNIO

from Nio import open_file
from wrf import getvar

wrfnc = open_file("wrfout_d02_2010-06-13_21:00:00"+".nc", "r")
slp = getvar(wrfnc, "slp")

Using Iterables:

import os
from netCDF4 import Dataset
from wrf import getvar

filedir = "/path/to/wrf/files"
wrfin = [Dataset(f) for f in os.listdir(filedir)
        if f.startswith("wrfout_d02_")]

uvmet = getvar(wrfin, "uvmet", timeidx=3, units="kt")