wrf.udhel¶
-
wrf.
udhel
(zstag, mapfct, u, v, wstag, dx, dy, bottom=2000.0, top=5000.0, meta=True)¶ Return the updraft helicity.
This function calculates updraft helicity to detect rotating updrafts. The formula follows Kain et al., 2008, Wea. and Forecasting, 931-952, but this version has controls for the limits of integration, bottom to top, in m AGL. Kain et al used 2000 to 5000 m. The expected range is 25 to 250 m-2/s-2. Keith Brewster, CAPS/Univ. of Oklahoma ; March, 2010
This is the raw computational algorithm and does not extract any variables from WRF output files. Use
wrf.getvar()
to both extract and compute diagnostic variables.Parameters: - zstag (
xarray.DataArray
ornumpy.ndarray
) – Geopotential height in [m] that is at least three dimensions with a staggered vertical dimension. The rightmost dimensions are bottom_top_stag x south_north x west_east. - mapfct (
xarray.DataArray
ornumpy.ndarray
) – The map scale factor on the mass grid. An array of at least two dimensions, whose rightmost two dimensions must be south_north x west_east. If this array is more than two dimensions, they must be the same as zstag’s leftmost dimensions. - u (
xarray.DataArray
ornumpy.ndarray
) –The u component of the wind [m s-1] whose rightmost three dimensions must be bottom_top x south_north x west_east. The leftmost dimensions must be the same as zp’s leftmost dimensions.
Note
This variable must be supplied as a
xarray.DataArray
in order to copy the dimension names to the output. Otherwise, default names will be used. - v (
xarray.DataArray
ornumpy.ndarray
) – The v component of the wind [m s-1] whose rightmost three dimensions must be bottom_top x south_north x west_east. The leftmost dimensions must be the same as zstag’s leftmost dimensions. - wstag (
xarray.DataArray
ornumpy.ndarray
) – The z component of the wind [m s-1] with the same dimensionality as zstag. - dx (
float
) – The distance between x grid points. - dy (
float
) – The distance between y grid points. - bottom (
float
, optional) – The bottom limit of integration. Default is 2000.0. - top (
float
, optional) – The upper limit of integration. Default is 5000.0. - meta (
bool
) – Set to False to disable metadata and returnnumpy.ndarray
instead ofxarray.DataArray
. Default is True.
Warning
The input arrays must not contain any missing/fill values or
numpy.nan
values.Returns: The updraft helicity. If xarray is enabled and the meta parameter is True, then the result will be an xarray.DataArray
object. Otherwise, the result will be anumpy.ndarray
object with no metadata.Return type: xarray.DataArray
ornumpy.ndarray
See also
- zstag (