def saturated_vapor_pressure(t_kelvin):
if t_kelvin >= <NUM_LIT>:<EOL><INDENT>sig = <NUM_LIT:1> - (t_kelvin / <NUM_LIT>)<EOL>sig_polynomial = (-<NUM_LIT> * sig) + (<NUM_LIT> * sig ** <NUM_LIT>) +(-<NUM_LIT> * sig ** <NUM_LIT:3>) + (<NUM_LIT> * sig ** <NUM_LIT>) +(-<NUM_LIT> * sig ** <NUM_LIT:4>) + (<NUM_LIT> * sig ** <NUM_LIT>)<EOL>crit_temp = <NUM_LIT> / t_kelvin<EOL>exponent = crit_temp * sig_polynomial<EOL>p_ws = math.exp(exponent) * <NUM_LIT><EOL><DEDENT>else:<EOL><INDENT>theta = t_kelvin / <NUM_LIT><EOL>exponent = -<NUM_LIT> * (<NUM_LIT:1> - theta ** -<NUM_LIT>) +<NUM_LIT> * (<NUM_LIT:1> - theta ** -<NUM_LIT>)<EOL>p_ws = math.exp(exponent) * <NUM_LIT><EOL><DEDENT>return p_ws<EOL>
Saturated Vapor Pressure (Pa) at t_kelvin (K).

    This function accounts for the different behaviour above vs. below
    the freezing point of water.

    Note:
        [1] W. Wagner and A. Pru:" The IAPWS Formulation 1995 for the Thermodynamic
        Properties of Ordinary Water Substance for General and Scientific Use ",
        Journal of Physical and Chemical Reference Data,
        June 2002 ,Volume 31, Issue 2, pp. 387535

        [2] Vaisala. (2013) Humidity Conversion Formulas:
        Calculation Formulas for Humidity.
        www.vaisala.com/Vaisala%20Documents/Application%20notes/Humidity_Conversion_Formulas_B210973EN-F.pdf