earthkit.meteo.thermo.array.vapour_pressure_from_specific_humidity
==================================================================

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

   Compute the vapour pressure from specific humidity.

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

   :returns: Vapour pressure (Pa)
   :rtype: :class:`number` or :class:`array-like`

   The computation is based on the following formula [Wallace2006]_:

   .. math::

       e = \frac{p\;q}{\epsilon\; (1 + q(\frac{1}{\epsilon} -1 ))}

   with :math:`\epsilon =  R_{d}/R_{v}` (see :data:`earthkit.meteo.constants.epsilon`).