earthkit.meteo.thermo.array.ept_from_dewpoint
=============================================

.. py:function:: earthkit.meteo.thermo.array.ept_from_dewpoint(t, td, p, method='ifs')

   Compute the equivalent potential temperature from dewpoint.

   :param t: Temperature (K)
   :type t: :class:`number` or :class:`array-like`
   :param td: Dewpoint (K)
   :type td: :class:`number` or :class:`array-like`
   :param p: Pressure (Pa)
   :type p: :class:`number` or :class:`array-like`
   :param method: Specifies the computation method. The possible values are: "ifs", "bolton35", "bolton39".
   :type method: :class:`str`, *optional*

   :returns: Equivalent potential temperature (K)
   :rtype: :class:`number` or :class:`array-like`

   The actual computation is based on the value of ``method``:

   * "ifs": the formula from the IFS model [IFS-CY47R3-PhysicalProcesses]_ (Chapter 6.11) is used:

       .. math::

           \Theta_{e} = \Theta\; exp(\frac{L_{v}\; q}{c_{pd}\; t_{LCL}})

   * "bolton35": Eq (35) from [Bolton1980]_ is used:


       .. math::

           \Theta_{e} = \Theta (\frac{10^{5}}{p})^{\kappa 0.28 w} exp(\frac{2675 w}{t_{LCL}})

   * "bolton39": Eq (39) from [Bolton1980]_ is used:

       .. math::

           \Theta_{e} =
           t (\frac{10^{5}}{p-e})^{\kappa} (\frac{t}{t_{LCL}})^{0.28 w} exp[(\frac{3036}{t_{LCL}} -
           1.78)w(1+0.448\; w)]

   where:

       * :math:`\Theta` is the :func:`potential_temperature`
       * :math:`t_{LCL}` is the temperature at the Lifting Condestation Level computed
         with :func:`lcl_temperature` using option:

           * method="davis" when ``method`` is "ifs"
           * method="bolton" when ``method`` is "bolton35" or "bolton39"
       * :math:`q` is the specific humidity computed with :func:`specific_humidity_from_dewpoint`
       * :math:`w`: is the mixing ratio computed with :func:`mixing_ratio_from_dewpoint`
       * :math:`e` is the vapour pressure computed with :func:`vapour_pressure_from_mixing_ratio`
       * :math:`L_{v}`: is the latent heat of vaporisation
         (see :data:`earthkit.meteo.constants.Lv`)
       * :math:`c_{pd}` is the specific heat of dry air on constant pressure
         (see :data:`earthkit.meteo.constants.c_pd`)
       * :math:`\kappa = R_{d}/c_{pd}` (see :data:`earthkit.meteo.constants.kappa`)