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gforget |
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function [RHOP,RHOIS,RHOR] = density(TN,SN,GDEPT,ZREF) |
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% [RHOP,RHOIS,RHOR] = density(Tpot,S,P,PREF) |
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% |
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% Adapted from OPA, subroutine EOS.F (bferron@ifremer.fr) |
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% |
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% ROUTINE EOS |
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% ******************* |
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% |
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% PURPOSE : |
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% ------- |
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% COMPUTE THE POTENTIAL DENSITY RHOP, IN SITU DENSITY RHOIS, AND, IF A |
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% REFERENCE LEVEL PREF IS SPECIFIED, THE DENSITY RHOR REFERENCED TO PREF |
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% FROM POTENTIAL TEMPERATURE AND SALINITY FIELDS. |
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% |
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% IMPORTANT NOTE: This version minimize the deviations of in-situ |
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% density compared to the UNESCO equation within |
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% [0-4500]dbars!!!!!! It is the version used in OPA |
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% (differences < 2e-4 kg/m3) |
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% Below 6000 dbar , differences are > 1e-3 kg/m-3 |
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% |
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% METHOD : |
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% ------ |
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% JACKETT AND McDOUGALL (1994) EQUATION OF STATE |
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% ********************* |
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% THE IN SITU DENSITY IS COMPUTED DIRECTLY AS A FUNCTION OF |
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% POTENTIAL TEMPERATURE RELATIVE TO THE SURFACE, SALT AND PRESSURE |
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% |
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% |
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% RHO(T,S,P) |
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% |
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% WITH PRESSURE P DECIBARS |
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% POTENTIAL TEMPERATURE T DEG CELSIUS |
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% SALINITY S PSU |
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% DENSITY RHO KG/M**3 |
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% |
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% CHECK VALUE: RHO = 1.04183326 KG/M**3 FOR P=10000 DBAR, |
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% T = 40 DEG CELCIUS, S=40 PSU |
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% |
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% |
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% JACKETT AND McDOUGALL (1994) FORMULATION |
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%-------------------------------------------- |
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% |
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%... potential temperature, salinity and depth |
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ZT = TN; |
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ZS = SN; |
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if size(TN,2)>1 & size(TN,1)>1 & size(TN,1)==length(GDEPT) |
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ZH = GDEPT*ones(1,size(ZT,2)); % comented 13/04/99 for WHP Thorpe calc. |
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elseif size(TN,2)>1 & size(TN,1)>1 & size(TN,2)==length(GDEPT) |
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ZH = ones(size(ZT,1),1) *GDEPT'; |
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elseif sum(size(TN))==2 |
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ZH = ones(size(TN))*GDEPT; |
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else |
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ZH = GDEPT; % Added 13/04/99 for WHP Thorpe calc. |
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end |
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%... square root salinity |
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ZSR= sqrt(ZS); |
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%... compute density pure water at atm pressure |
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ZR1= ((((6.536332E-9*ZT-1.120083E-6).*ZT+1.001685E-4).*ZT ... |
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-9.095290E-3).*ZT+6.793952E-2).*ZT+999.842594; |
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%... seawater density atm pressure |
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ZR2= (((5.3875E-9*ZT-8.2467E-7).*ZT+7.6438E-5).*ZT ... |
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-4.0899E-3).*ZT+0.824493; |
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ZR3= (-1.6546E-6*ZT+1.0227E-4).*ZT-5.72466E-3; |
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ZR4= 4.8314E-4; |
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% |
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%... potential density (referenced to the surface) |
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RHOP= (ZR4*ZS + ZR3.*ZSR + ZR2).*ZS + ZR1; |
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% |
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%... add the compression terms |
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ZE = (-3.508914E-8*ZT-1.248266E-8).*ZT-2.595994E-6; |
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ZBW= ( 1.296821E-6*ZT-5.782165E-9).*ZT+1.045941E-4; |
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ZB = ZBW + ZE .* ZS; |
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% |
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ZD = -2.042967E-2; |
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ZC = (-7.267926E-5*ZT+2.598241E-3).*ZT+0.1571896; |
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ZAW= ((5.939910E-6*ZT+2.512549E-3).*ZT-0.1028859).*ZT-4.721788; |
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ZA = ( ZD*ZSR + ZC).*ZS + ZAW; |
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% |
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ZB1= (-0.1909078*ZT+7.390729).*ZT-55.87545; |
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ZA1= ((2.326469E-3*ZT+1.553190).*ZT-65.00517).*ZT+1044.077; |
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ZKW= (((-1.361629E-4*ZT-1.852732E-2).*ZT-30.41638).*ZT ... |
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+2098.925).*ZT+190925.6; |
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ZK0= (ZB1.*ZSR + ZA1).*ZS + ZKW; |
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% |
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%... in situ density |
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RHOIS = RHOP ./ (1.0-ZH./(ZK0-ZH.*(ZA-ZH.*ZB))); |
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%... density referenced to level ZREF |
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if nargin==4 |
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RHOR = RHOP ./ (1.0-ZREF./(ZK0-ZREF.*(ZA-ZREF.*ZB))); |
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end |
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