absolute_momentum#

metpy.calc.absolute_momentum(u, v, index='index')[source]#

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

The cross-sectional absolute momentum is calculated given u- and v-components of the wind along a 2 dimensional vertical cross-section. The coordinates of u and v must match.

Parameters:

• u (xarray.DataArray) – The input DataArray of the x-component (in terms of data projection) of the wind.

• v (xarray.DataArray) – The input DataArray of the y-component (in terms of data projection) of the wind.

• index (str or int, optional) – Denotes the index coordinate of the cross-section, defaults to ‘index’ as set by metpy.interpolate.cross_section

Returns:

absolute_momentum (xarray.DataArray) – Absolute momentum

See also

metpy.interpolate.cross_section, cross_section_components

Notes

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].

Changed in version 1.0: Renamed u_wind, v_wind parameters to u, v