SUBROUTINE FCULZD_HPA (LATITUDE, ELLIP_HT, PRESSURE, WVP,
. LAMBDA_UM, FCUL_ZTD, FCUL_ZHD, FCUL_ZWD)
*+
* - - - - - - - - - - - -
* F C U L Z D _ H P A
* - - - - - - - - - - - -
*
* This routine is part of the International Earth Rotation and
* Reference Systems Service (IERS) Conventions software collection.
*
* This subroutine determines the total zenith delay following (Mendes and Pavlis, 2004).
*
* In general, Class 1, 2, and 3 models represent physical effects that
* act on geodetic parameters while canonical models provide lower-level
* representations or basic computations that are used by Class 1, 2, or
* 3 models.
*
* Status: Class 1 model
*
* Class 1 models are those recommended to be used a priori in the
* reduction of raw space geodetic data in order to determine
* geodetic parameter estimates.
* Class 2 models are those that eliminate an observational
* singularity and are purely conventional in nature.
* Class 3 models are those that are not required as either Class
* 1 or 2.
* Canonical models are accepted as is and cannot be classified as a
* Class 1, 2, or 3 model.
*
* Given:
* LATITUDE d Geodetic Latitude given in degrees (North Latitude)
* ELLIP_HT d Height above ellipsoid given in meters
* PRESSURE d Surface pressure given in hPa (mbars) (Note 1)
* WVP d Water vapor pressure in hPa (mbars) (Note 1)
* LAMBDA_UM d Laser wavelength (micrometers)
*
* Returned:
* FCUL_ZTD d Zenith total delay in meters
* FCUL_ZHD d Zenith hydrostatic delay in meters
* FCUL_ZWD d Zenith non-hydrostatic delay in meters
*
* Notes:
*
* 1) The surface pressure provided was converted from inches Hg.
* The water vapor pressure was calculated from the surface
* temperature (Celsius) and Relative Humidity (% R.H.) at the station.
*
* Test case:
* given input: LATITUDE = 30.67166667D0 degrees (McDonald Observatory)
* ELLIP_HT = 2010.344D0 meters
* PRESSURE = 798.4188D0 hPa (August 14, 2009)
* WVP = 14.322D0 hPa (August 14, 2009)
* LAMBDA_UM = 0.532D0 micrometers (See Mendes et al.)
* expected output: FCUL_ZTD = 1.935225924846803114D0 m
* FCUL_ZHD = 1.932992176591644462D0 m
* FCUL_ZWD = 0.2233748255158703871D-02 m
*
* References:
* Mendes, V.B. and E.C. Pavlis, 2004,
* "High-accuracy zenith delay prediction at optical wavelengths,"
* Geophysical Res. Lett., 31, L14602, doi:10.1029/2004GL020308, 2004
*
* Petit, G. and Luzum, B. (eds.), IERS Conventions (2010),
* IERS Technical Note No. 36, BKG (2010)
*
* Revisions:
* 2000 March 31 V.B. Mendes Original code
* 2009 August 14 B.E. Stetzler Added header and copyright
* 2009 August 14 B.E. Stetzler Use of DOUBLE PRECISION
* 2009 August 14 B.E. Stetzler Provided test case
* 2009 August 14 B.E. Stetzler Capitalized all variables for FORTRAN 77
* compatibility and provided more comments
*-----------------------------------------------------------------------
IMPLICIT NONE
DOUBLE PRECISION C, PI, ELLIP_HT, LATITUDE, F, PRESSURE, WVP
DOUBLE PRECISION K0, K1, K2, K3
DOUBLE PRECISION XC, CORR
DOUBLE PRECISION SIGMA, W0, W1, W2, W3, FH, FNH
DOUBLE PRECISION LAMBDA_UM
DOUBLE PRECISION FCUL_ZHD, FCUL_ZWD, FCUL_ZTD
PARAMETER ( C = 2.99792458D8) ! speed of light in vacuum (m/s)
PARAMETER ( PI = 3.1415926535897932384626433D0 )
* CO2 content in ppm
XC = 375.0D0
* constant values to be used in Equation (20)
* k1 and k3 are k1* and k3*
K0 = 238.0185D0
K1 = 19990.975D0
K2 = 57.362D0
K3 = 579.55174D0
* constant values to be used in Equation (32)
W0 = 295.235D0
W1 = 2.6422D0
W2 = -0.032380D0
W3 = 0.004028D0
* Wave number
SIGMA = 1/LAMBDA_UM
* correction factor - Equation (24)
F = 1 - 0.00266*COS(2*PI/180*LATITUDE) - 0.00028D-3*ELLIP_HT
* correction for CO2 content
CORR = 1.0D0 + 0.534D-6*(XC-450)
* dispersion equation for the hydrostatic component - Equation (20)
FH = 0.01D0*CORR*((K1*(K0+SIGMA**2))/((K0-SIGMA**2)**2) +
. K3*(K2+SIGMA**2)/((K2-SIGMA**2)**2))
* computation of the hydrostatic component - Equation (26)
* caution: pressure in hectoPascal units
FCUL_ZHD = 2.416579D-3*FH*PRESSURE/F
* dispersion equation for the non-hydrostatic component - Equation (32)
FNH = 0.003101D0*(W0+3.0*W1*SIGMA**2 +
. 5.0*W2*SIGMA**4+7.0*W3*SIGMA**6)
* computation of the non-hydrostatic component - Equation (38)
* caution: pressure in hectoPascal units
FCUL_ZWD = 1.D-4*(5.316D0*FNH-3.759*FH)*WVP/F
* compute the zenith total delay
FCUL_ZTD = FCUL_ZHD + FCUL_ZWD
RETURN
* Finished.
*+----------------------------------------------------------------------
*
* Copyright (C) 2008
* IERS Conventions Center
*
* ==================================
* IERS Conventions Software License
* ==================================
*
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*
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*
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* Correspondence concerning IERS Conventions software should be
* addressed as follows:
*
* Gerard Petit
* Internet email: gpetit[at]bipm.org
* Postal address: IERS Conventions Center
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*
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*
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*-----------------------------------------------------------------------
end