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seawater.F
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C $Header: /u/gcmpack/MITgcm/model/src/seawater.F,v 1.11 2015/02/26 17:17:56 mlosch Exp $
C $Name: $
#include "CPP_OPTIONS.h"
C-- File seawater.F: routines that compute quantities related to seawater.
C-- Contents
C Seawater (SW) librabry routines
C-- o SW_PTMP: function to compute potential temperature
C-- o SW_TEMP: function to compute in-situ temperature from pot. temp.
C-- o SW_ADTG: function to compute adiabatic temperature gradient
C-- (used by both SW_PTMP & SW_TEMP)
C---+----1----+----2----+----3----+----4----+----5----+----6----+----7-|--+----|
CBOP
C !ROUTINE: SW_PTMP
C !INTERFACE:
_RL FUNCTION SW_PTMP (S,T,P,PR)
C !DESCRIPTION: \bv
C *=============================================================*
C | S/R SW_PTMP
C | o compute potential temperature as per UNESCO 1983 report.
C *=============================================================*
C
C started:
C Armin Koehl akoehl@ucsd.edu
C
C ==================================================================
C SUBROUTINE SW_PTMP
C ==================================================================
C S :: salinity [psu (PSS-78) ]
C T :: temperature [degree C (IPTS-68)]
C P :: pressure [db]
C PR :: Reference pressure [db]
C \ev
C !USES:
IMPLICIT NONE
C !INPUT/OUTPUT PARAMETERS:
_RL S,T,P,PR
C !FUNCTIONS:
_RL sw_adtg
EXTERNAL sw_adtg
C !LOCAL VARIABLES
_RL del_P ,del_th, th, q
_RL onehalf, two, three
PARAMETER ( onehalf = 0.5 _d 0, two = 2. _d 0, three = 3. _d 0 )
CEOP
C theta1
del_P = PR - P
del_th = del_P*sw_adtg(S,T,P)
th = T + onehalf*del_th
q = del_th
C theta2
del_th = del_P*sw_adtg(S,th,P+onehalf*del_P)
th = th + (1 - 1/sqrt(two))*(del_th - q)
q = (two-sqrt(two))*del_th + (-two+three/sqrt(two))*q
C theta3
del_th = del_P*sw_adtg(S,th,P+onehalf*del_P)
th = th + (1 + 1/sqrt(two))*(del_th - q)
q = (two + sqrt(two))*del_th + (-two-three/sqrt(two))*q
C theta4
del_th = del_P*sw_adtg(S,th,P+del_P)
SW_PTMP = th + (del_th - two*q)/(two*three)
RETURN
END
C---+----1----+----2----+----3----+----4----+----5----+----6----+----7-|--+----|
CBOP
C !ROUTINE: SW_TEMP
C !INTERFACE:
_RL FUNCTION SW_TEMP( S, T, P, PR )
C !DESCRIPTION: \bv
C *=============================================================*
C | S/R SW_TEMP
C | o compute in-situ temperature from potential temperature
C *=============================================================*
C
C REFERENCES:
C Fofonoff, P. and Millard, R.C. Jr
C Unesco 1983. Algorithms for computation of fundamental properties of
C seawater, 1983. _Unesco Tech. Pap. in Mar. Sci._, No. 44, 53 pp.
C Eqn.(31) p.39
C
C Bryden, H. 1973.
C New Polynomials for thermal expansion, adiabatic temperature gradient
C and potential temperature of sea water.
C DEEP-SEA RES., 1973, Vol20,401-408.
C \ev
C !USES:
IMPLICIT NONE
C === Global variables ===
C !INPUT/OUTPUT PARAMETERS:
C === Routine arguments ===
C S :: salinity
C T :: potential temperature
C P :: pressure
C PR :: reference pressure
_RL S, T, P, PR
CEOP
C !FUNCTIONS:
_RL sw_ptmp
EXTERNAL sw_ptmp
SW_temp = SW_PTMP (S,T,PR,P)
RETURN
END
C---+----1----+----2----+----3----+----4----+----5----+----6----+----7-|--+----|
CBOP
C !ROUTINE: SW_ADTG
C !INTERFACE:
_RL FUNCTION SW_ADTG (S,T,P)
C !DESCRIPTION: \bv
C *=============================================================*
C | S/R SW_ADTG
C | o compute adiabatic temperature gradient as per UNESCO 1983 routines.
C *=============================================================*
C
C started:
C Armin Koehl akoehl@ucsd.edu
C \ev
C !USES:
IMPLICIT NONE
C !INPUT/OUTPUT PARAMETERS:
_RL S,T,P
C !LOCAL VARIABLES:
_RL a0,a1,a2,a3,b0,b1,c0,c1,c2,c3,d0,d1,e0,e1,e2
_RL sref
CEOP
sref = 35. _d 0
a0 = 3.5803 _d -5
a1 = +8.5258 _d -6
a2 = -6.836 _d -8
a3 = 6.6228 _d -10
b0 = +1.8932 _d -6
b1 = -4.2393 _d -8
c0 = +1.8741 _d -8
c1 = -6.7795 _d -10
c2 = +8.733 _d -12
c3 = -5.4481 _d -14
d0 = -1.1351 _d -10
d1 = 2.7759 _d -12
e0 = -4.6206 _d -13
e1 = +1.8676 _d -14
e2 = -2.1687 _d -16
SW_ADTG = a0 + (a1 + (a2 + a3*T)*T)*T
& + (b0 + b1*T)*(S-sref)
& + ( (c0 + (c1 + (c2 + c3*T)*T)*T) + (d0 + d1*T)*(S-sref) )*P
& + ( e0 + (e1 + e2*T)*T )*P*P
RETURN
END

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