storm_relative_helicity#

metpy.calc.storm_relative_helicity(height, u, v, depth, *, bottom=None, storm_u=None, storm_v=None)#

Calculate storm relative helicity.

Calculates storm relative helicity following [Markowski2010] pg.230-231

\[\int\limits_0^d (\bar v - c) \cdot \bar\omega_{h} \,dz\]

This is applied to the data from a hodograph with the following summation:

\[\sum_{n = 1}^{N-1} [(u_{n+1} - c_{x})(v_{n} - c_{y}) - (u_{n} - c_{x})(v_{n+1} - c_{y})]\]
Parameters:

  • u (array-like) – U component winds

  • v (array-like) – V component winds

  • height (array-like) – Atmospheric height, will be converted to AGL

  • depth (float or int) – Depth of the layer

  • bottom (float or int) – Height of layer bottom AGL (default is surface)

  • storm_u (float or int) – U component of storm motion (default is 0 m/s)

  • storm_v (float or int) – V component of storm motion (default is 0 m/s)

Returns:

Examples

>>> from metpy.calc import storm_relative_helicity, wind_components
>>> from metpy.units import units
>>> # set needed values of pressure, height, wind direction/speed
>>> p = [1000, 925, 850, 700, 500, 400] * units.hPa
>>> h = [250, 700, 1500, 3100, 5720, 7120] * units.meters
>>> wdir = [165, 180, 190, 210, 220, 250] * units.degree
>>> sped = [5, 15, 20, 30, 50, 60] * units.knots
>>> # compute wind components
>>> u, v = wind_components(sped, wdir)
>>> # compute SRH with a storm vector
>>> storm_relative_helicity(h, u, v, depth=1 * units.km,
...                         storm_u=7 * units('m/s'), storm_v=7 * units('m/s'))
(<Quantity(49.6086162, 'meter ** 2 / second ** 2')>,
<Quantity(0.0, 'meter ** 2 / second ** 2')>,
<Quantity(49.6086162, 'meter ** 2 / second ** 2')>)

Notes

Only functions on 1D profiles (not higher-dimension vertical cross sections or grids). Since this function returns scalar values when given a profile, this will return Pint Quantities even when given xarray DataArray profiles.

Changed in version 1.0: Renamed heights parameter to height and converted bottom, storm_u, and storm_v parameters to keyword-only arguments

Examples using metpy.calc.storm_relative_helicity#

Sounding Calculation Examples

Sounding Calculation Examples