absolute_momentum¶

metpy.calc.absolute_momentum(u_wind, v_wind, index='index')[source]¶

Calculate cross-sectional absolute momentum (also called pseudoangular momentum).

As given in [Schultz1999], absolute momentum (also called pseudoangular momentum) is given by

\[M = v + fx\]

where \(v\) is the along-front component of the wind and \(x\) is the cross-front distance. Applied to a cross-section taken perpendicular to the front, \(v\) becomes the normal component of the wind and \(x\) the tangential distance.

If using this calculation in assessing symmetric instability, geostrophic wind should be used so that geostrophic absolute momentum \(\left(M_g\right)\) is obtained, as described in [Schultz1999].

Parameters

u_wind (xarray.DataArray) – The input DataArray of the x-component (in terms of data projection) of the wind.
v_wind (xarray.DataArray) – The input DataArray of the y-component (in terms of data projection) of the wind.

Returns

absolute_momentum (xarray.DataArray) – The absolute momentum

Notes

The coordinates of u_wind and v_wind must match.