Unidata / MetPy

@exporter.export

@check_units('[pressure]', '[temperature]', '[temperature]')

def lfc(pressure, temperature, dewpt):

    r"""Calculate the level of free convection (LFC).

    This works by finding the first intersection of the ideal parcel path and

    the measured parcel temperature.

    Parameters

    ----------

    pressure : `pint.Quantity`

        The atmospheric pressure

    temperature : `pint.Quantity`

        The temperature at the levels given by `pressure`

    dewpt : `pint.Quantity`

        The dew point at the levels given by `pressure`

    Returns

    -------

    `pint.Quantity`

        The LFC pressure and temperature

    See Also

    --------

    parcel_profile

    """

    ideal_profile = parcel_profile(pressure, temperature[0], dewpt[0]).to('degC')

    # The parcel profile and data have the same first data point, so we ignore

    # that point to get the real first intersection for the LFC calculation.

    x, y = find_intersections(pressure[1:], ideal_profile[1:], temperature[1:],

                              direction='increasing')

    if len(x) == 0:

        return np.nan * pressure.units, np.nan * temperature.units

    else:

        return x[0], y[0]

@exporter.export

@check_units('[pressure]', '[temperature]', '[temperature]')

@exporter.export

@check_units('[pressure]', '[temperature]', '[temperature]')

def el(pressure, temperature, dewpt):

    r"""Calculate the equilibrium level.

    This works by finding the last intersection of the ideal parcel path and

    the measured environmental temperature. If there is one or fewer intersections, there is

    no equilibrium level.

    Parameters

    ----------

    pressure : `pint.Quantity`

        The atmospheric pressure

    temperature : `pint.Quantity`

        The temperature at the levels given by `pressure`

    dewpt : `pint.Quantity`

        The dew point at the levels given by `pressure`

    Returns

    -------

    `pint.Quantity, pint.Quantity`

        The EL pressure and temperature

    See Also

    --------

    parcel_profile

    """

    ideal_profile = parcel_profile(pressure, temperature[0], dewpt[0]).to('degC')

    x, y = find_intersections(pressure[1:], ideal_profile[1:], temperature[1:])

    # If there is only one intersection, it's the LFC and we return None.

    if len(x) <= 1:

        return np.nan * pressure.units, np.nan * temperature.units

    else:

        return x[-1], y[-1]

@exporter.export