earthkit.meteo.thermo.array.dewpoint_from_specific_humidity
===========================================================

.. py:function:: earthkit.meteo.thermo.array.dewpoint_from_specific_humidity(q, p)

   Compute the dewpoint temperature from specific humidity.

   :param q: Specific humidity (kg/kg)
   :type q: :class:`array-like`
   :param p: Pressure (Pa)
   :type p: :class:`array-like`

   :returns: Dewpoint temperature (K). For zero ``q`` values returns nan.
   :rtype: :class:`array-like`

   The computation starts with determining the the saturation vapour pressure over
   water at the dewpoint temperature:

   .. math::

       e_{wsat}(td) = e(q, p)

   where:

       * :math:`e` is the vapour pressure (see :func:`vapour_pressure_from_specific_humidity`)
       * :math:`e_{wsat}` is the :func:`saturation_vapour_pressure` over water
       * :math:`td` is the dewpoint

   Then :math:`td` is computed from :math:`e_{wsat}(td)` by inverting the equations
   used in :func:`saturation_vapour_pressure`.