vorticity

metpy.calc.vorticity(u, v, *, dx=None, dy=None, x_dim=- 1, y_dim=- 2, parallel_scale=None, meridional_scale=None, latitude=None, longitude=None, crs=None)

Calculate the vertical vorticity of the horizontal wind.

Parameters

• u ((…, M, N) xarray.DataArray or pint.Quantity) – x component of the wind

• v ((…, M, N) xarray.DataArray or pint.Quantity) – y component of the wind

• dx (pint.Quantity, optional) – The grid spacing(s) in the x-direction. If an array, there should be one item less than the size of u along the applicable axis. Optional if xarray.DataArray with latitude/longitude coordinates used as input. Also optional if one-dimensional longitude and latitude arguments are given for your data on a non-projected grid. Keyword-only argument.

• dy (pint.Quantity, optional) – The grid spacing(s) in the y-direction. If an array, there should be one item less than the size of u along the applicable axis. Optional if xarray.DataArray with latitude/longitude coordinates used as input. Also optional if one-dimensional longitude and latitude arguments are given for your data on a non-projected grid. Keyword-only argument.

• x_dim (int, optional) – Axis number of x dimension. Defaults to -1 (implying […, Y, X] order). Automatically parsed from input if using xarray.DataArray. Keyword-only argument.

• y_dim (int, optional) – Axis number of y dimension. Defaults to -2 (implying […, Y, X] order). Automatically parsed from input if using xarray.DataArray. Keyword-only argument.

• parallel_scale (pint.Quantity, optional) – Parallel scale of map projection at data coordinate. Optional if xarray.DataArray with latitude/longitude coordinates and MetPy CRS used as input. Also optional if longitude, latitude, and crs are given. If otherwise omitted, calculation will be carried out on a Cartesian, rather than geospatial, grid. Keyword-only argument.

• meridional_scale (pint.Quantity, optional) – Meridional scale of map projection at data coordinate. Optional if xarray.DataArray with latitude/longitude coordinates and MetPy CRS used as input. Also optional if longitude, latitude, and crs are given. If otherwise omitted, calculation will be carried out on a Cartesian, rather than geospatial, grid. Keyword-only argument.

• latitude (pint.Quantity, optional) – Latitude of data. Optional if xarray.DataArray with latitude/longitude coordinates used as input. Also optional if parallel_scale and meridional_scale are given. If otherwise omitted, calculation will be carried out on a Cartesian, rather than geospatial, grid. Keyword-only argument.

• longitude (pint.Quantity, optional) – Longitude of data. Optional if xarray.DataArray with latitude/longitude coordinates used as input. Also optional if parallel_scale and meridional_scale are given. If otherwise omitted, calculation will be carried out on a Cartesian, rather than geospatial, grid. Keyword-only argument.

• crs (pyproj.crs.CRS, optional) – Coordinate Reference System of data. Optional if xarray.DataArray with MetPy CRS used as input. Also optional if parallel_scale and meridional_scale are given. If otherwise omitted, calculation will be carried out on a Cartesian, rather than geospatial, grid. Keyword-only argument.

Returns

(…, M, N) xarray.DataArray or pint.Quantity – vertical vorticity

See also

divergence, absolute_vorticity

Notes

This implements a numerical version of the typical vertical vorticity equation:

\[\zeta = \frac{\partial v}{\partial x} - \frac{\partial u}{\partial y}\]

If sufficient grid projection information is provided, these partial derivatives are taken from the projection-correct derivative matrix of the vector wind. Otherwise, they are evaluated as scalar derivatives on a Cartesian grid.

Changed in version 1.0: Changed signature from (u, v, dx, dy)

Examples using metpy.calc.vorticity

Vorticity

Vorticity

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