geostrophic_wind.rst

geostrophic_wind

.. py:function::  geostrophic_wind(z, coriolis=None)

   Computes the geostrophic wind from geopotential on pressure levels.

   :param z: input fieldset (geopotential on pressure levels)
   :type fs: :class:`Fieldset`
   :param coriolis: set a constant Coriolis parameter value (1/s) for the computations. If it is None (the default) the real Coriolis parameter is computed for each gridpoint.
   :type coriolis: number or None
   :rtype: :class:`Fieldset`

   For a given z geopotential field the computation of the geostrophic wind components is based on the following formulas:

   .. math::

      u_g = -\frac{1}{f} \frac{1}{R}\frac{\partial z}{\partial \phi}

      v_g = \frac{1}{f} \frac{1}{R \ cos\phi}\frac{\partial z}{\partial \lambda}

   where:

   * R is the radius of the Earth
   * :math:`\phi` is the latitude
   * :math:`\lambda` is the longitude.
   * :math:`f=2\Omega sin\phi` is the Coriolis parameter, where :math:`\Omega` is the Earth's angular velocity. When ``coriolis`` is set a constant value is used for f.

   The derivatives are computed with a second order finite-difference approximation. The resulting fieldset contains two fields for each input field: the u and v geostrophic wind components. In each output field the points close to the poles and the Equator are bitmapped (they contain missing values).

   .. warning::

      :func:`geostrophic_wind` is only implemented for regular latitude-longitude grids.

   .. note::

      See also :func:`q_vector`.

.. mv-minigallery:: geostrophic_wind