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e_eq_water

PURPOSE ^

E_EQ_WATER Equilibrium water vapor pressure over liquid water

SYNOPSIS ^

function ew = e_eq_water(T)

DESCRIPTION ^

 E_EQ_WATER  Equilibrium water vapor pressure over liquid water

 Calculate the equilibrium water vapor pressure over a plane surface
 of liquid water according to Sonntag, 1994.
 
 The coefficients for units of K for temperature and Pa for the partial
 pressure are quoted in Helten et al., 1999.  I have verified that
 these coefficients are consistent with the ones given in Leiterer et
 al., 1997, with the only difference that the ones in the Leiterer et
 al. paper are for partial pressure in units of hPa.

 The temperature of 0C corresponds to 273.15K. (Not 273.16K, as stated
 in the Leiterer paper.)
 
 The formula (T in K, Ew in Pa):
 
 Ew(T) = exp[ a/T + b + cT + dT^2 + e ln(T) ]

 References:
 
 Sonntag, D., Advancements in the field of hygrometry, Meteorologische
 Zeitschrift, 3, 51-66, 1994.
 
 Helten, M. et al, In-flight comparison of MOZAIC and POLINAT water
 vapor measurements, JGR, 104, 26.087-26.096, 1999.
 
 Leiterer U. et al, Improvements in Radiosonde Humidity Profiles Using
 RS80/RS90 Radiosondes of Vaisala, Beitr. Phys. Atmosph., 70(4),
 319-336, 1997. 

 FORMAT   ew = e_eq_water(T)

 OUT       ew = Equilibrium water vapor pressure in [Pa].
 IN       T  = Temperature in [K].

CROSS-REFERENCE INFORMATION ^

This function calls: This function is called by:

DOWNLOAD ^

e_eq_water.m

SOURCE CODE ^

0001 % E_EQ_WATER  Equilibrium water vapor pressure over liquid water
0002 %
0003 % Calculate the equilibrium water vapor pressure over a plane surface
0004 % of liquid water according to Sonntag, 1994.
0005 %
0006 % The coefficients for units of K for temperature and Pa for the partial
0007 % pressure are quoted in Helten et al., 1999.  I have verified that
0008 % these coefficients are consistent with the ones given in Leiterer et
0009 % al., 1997, with the only difference that the ones in the Leiterer et
0010 % al. paper are for partial pressure in units of hPa.
0011 %
0012 % The temperature of 0C corresponds to 273.15K. (Not 273.16K, as stated
0013 % in the Leiterer paper.)
0014 %
0015 % The formula (T in K, Ew in Pa):
0016 %
0017 % Ew(T) = exp[ a/T + b + cT + dT^2 + e ln(T) ]
0018 %
0019 % References:
0020 %
0021 % Sonntag, D., Advancements in the field of hygrometry, Meteorologische
0022 % Zeitschrift, 3, 51-66, 1994.
0023 %
0024 % Helten, M. et al, In-flight comparison of MOZAIC and POLINAT water
0025 % vapor measurements, JGR, 104, 26.087-26.096, 1999.
0026 %
0027 % Leiterer U. et al, Improvements in Radiosonde Humidity Profiles Using
0028 % RS80/RS90 Radiosondes of Vaisala, Beitr. Phys. Atmosph., 70(4),
0029 % 319-336, 1997.
0030 %
0031 % FORMAT   ew = e_eq_water(T)
0032 %
0033 % OUT       ew = Equilibrium water vapor pressure in [Pa].
0034 % IN       T  = Temperature in [K].
0035 
0036 % 2003-03-28 Created by Stefan Buehler
0037 
0038 function ew = e_eq_water(T)
0039 
0040 % Coefficients for Ew:
0041 a = -6096.9385;
0042 b = 21.2409642;
0043 c = -2.711193e-2;
0044 d = 1.673952e-5;
0045 e = 2.433502;
0046 
0047 ew = exp( a./T + b + c*T + d*T.^2 + e*log(T) );

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