def ocean(dz):
return const.rho_w * const.cw * dz<EOL>
Returns heat capacity of a unit area of water, in units J /m**2 / K.

    .. math::

        C_o = \\rho_w \\cdot c_w \\cdot dz

    where

    ==============================  ==============  ==================================================  ==================================
    variable                        value           unit                                                description
    ==============================  ==============  ==================================================  ==================================
    :math:`C_o`                     *output*        :math:`\\textrm{J} / \\textrm{m}^2 / \\textrm{K}`      heat capacity for oceanic cell
    :math:`c_w`                     :math:`4181.3`  :math:`\\textrm{J} / \\textrm{kg} / \\textrm{K}`       specific heat of liquid water
    :math:`dz`                      *input*         :math:`\\textrm{m}`                                  water depth of oceanic cell
    :math:`\\rho_w`                  :math:`1000.`   :math:`\\textrm{kg} / \\textrm{m}^3`                   density of water
    ==============================  ==============  ==================================================  ==================================

    **Function-call argument** \n

    :param array dz:    water depth of ocean cells (*unit:* m)
    :returns:           the heat capacity for ocean cells correspoding to
                        depth input (*unit:* J /m**2 / K)
    :rtype:             array

    :Example:

        Calculate atmospheric heat capacity for pressure intervals of
        1, 10, 100 m::

            >>> from climlab.utils import heat_capacity

            >>> pressure_interval = array([1,10,100]) # in m
            >>> heat_capacity.ocean(pressure_interval) # in J /m**2 / K
            array([  4.18130000e+06,   4.18130000e+07,   4.18130000e+08])