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 (number) – Depth of the layer
bottom (number) – Height of layer bottom AGL (default is surface)
storm_u (number) – U component of storm motion (default is 0 m/s)
storm_v (number) – V component of storm motion (default is 0 m/s)

Returns

pint.Quantity – Positive storm-relative helicity
pint.Quantity – Negative storm-relative helicity
pint.Quantity – Total storm-relative helicity

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

significant_tornado

supercell_composite