earthkit.meteo.wind.xarray.direction

earthkit.meteo.wind.xarray.direction(u, v, convention='meteo', to_positive=True)

Compute the direction/angle of a vector quantity.

Parameters:

• u (xarray.DataArray) – u wind/x vector component

• v (xarray.DataArray) – v wind/y vector component (same units as u)

• convention (str, optional) –

  Specify how the direction/angle is interpreted. The possible values are as follows:

  • ”meteo”: the direction is the meteorological wind direction (see below for explanation)

  • ”polar”: the direction is measured anti-clockwise from the x axis (East/right) to the vector

• to_positive (bool, optional) – If True, the resulting values are mapped into the [0, 360] range when convention is “polar”. Otherwise they lie in the [-180, 180] range.

Returns:

Direction/angle (degrees)

Return type:

xarray.DataArray

Notes

The meteorological wind direction is the direction from which the wind is blowing. Wind direction increases clockwise such that a northerly wind is 0°, an easterly wind is 90°, a southerly wind is 180°, and a westerly wind is 270°. The figure below illustrates how it is related to the actual orientation of the wind vector: