C $Header: /u/gcmpack/MITgcm/pkg/sbo/sbo_calc.F,v 1.8 2004/06/18 16:59:00 edhill Exp $
C $Name: $
#include "SBO_OPTIONS.h"
CBOP
C !ROUTINE: SBO_CALC
C !INTERFACE: ==========================================================
SUBROUTINE SBO_CALC( myCurrentTime, myIter, myThid )
C !DESCRIPTION: \bv
C /==========================================================\
C | SUBROUTINE SBO_CALC |
C | o Do SBO diagnostic output. |
C |==========================================================|
C | NOTE: The following subtleties are ignored for time |
C | being but may need revisiting at some point in time. |
C | 1) The model is volume-preserving and Boussinesq so |
C | quantities like oceanic mass need to be interpreted |
C | with some care. |
C | 2) The sea surface height variable etaN lags other |
C | prognostic variables by half a time step. This lag |
C | is ignored in SBO computations. |
C | 3) Density is computed using function SBO_RHO which is |
C | not exaclty equivalent to the model s FIND_RHO. |
C \==========================================================/
IMPLICIT NONE
c=======================================================================
c
c Written by Richard Gross (Richard.Gross@jpl.nasa.gov)
c June 10, 2001: Modified for online computations in MIT GCM UV
c by Dimitris Menemenlis (Menemenlis@jpl.nasa.gov)
c
c Purpose
c calc_sbo calculates the core products of the IERS Special Bureau
c for the Oceans including oceanic mass, center-of-mass, angular
c momentum, and bottom pressure.
c
c Usage
c 1. calc_sbo must be called, and the results saved, at each time step
c in order to create a time series of the IERS SBO core products
c 2. it is suggested that after the time series have been generated
c and before saving the results to a file, time-mean values be
c computed and removed from all of the calculated core products
c and that the mean values be reported along with the demeaned
c time series
c
c Availability
c ftp://euler.jpl.nasa.gov/sbo/software/calc_sbo.f
c
c Reference
c Gross, R. S., F. O. Bryan, Y. Chao, J. O. Dickey, S. L. Marcus,
c R. M. Ponte, and R. Tokmakian, The IERS Special Bureau for the
c Oceans, in IERS Technical Note on the IERS Global Geophysical
c Fluids Center, edited by B. Chao, in press, Observatoire de Paris,
c Paris, France, 2000.
c
c Required inputs
c gridded values of horizontal velocity (u,v), temperature,
c salinity, and sea surface height along with the latitude,
c and longitude of the grid points and the thicknesses of the
c vertical layers
c
c External routines called by calc_sbo
c real function rho1(s, t)
c returns density of sea water given salinity s and temperature t
c (a default version of rho1 has been included with calc_sbo,
c however in general this should be replaced by a function that
c returns the density of the model ocean so that the same density
c as the model s is used to compute the sbo products)
c
c Assumptions
c 1. the input velocity, temperature, salinity, and sea surface
c height fields are assumed to be defined on the same grid
c 2. the horizontal grid is assumed to be equally spaced in
c latitude and longitude
c 3. land is flagged in the input quantities by a salinity or
c temperature value greater than or equal to 999.99
c 4. input quantities are assumed to have the following units:
c salinity (s) parts per thousand
c temperature (t) degrees centigrade
c eastwards velocity (u) centimeters per second
c northwards velocity (v) centimeters per second
c sea surface height (ssh) meters
c latitude of grid point degrees N
c longitude of grid point degrees E
c thickness of layer meters
c 5. input quantities are passed to calc_sbo via common blocks
c /ogcm/ and /vgrid/
c 6. land is flagged in the output ocean-bottom pressure (obp)
c by a value of -999.99
c 7. calulated products have the units:
c mass of oceans (mass) kilograms (kg)
c center-of-mass of oceans (com) meters (m)
c oceanic angular momentum (oam) kg-m**2/second
c ocean-bottom pressure (obp) Pascals (Newton/m**2)
c 8. calculated products are passed out of calc_sbo via common
c block /sbo/
c 9. the sea surface height layer is assumed to have the same
c velocity, temperature, and salinity as the first depth layer
c
c For questions regarding calc_sbo or the IERS SBO, please contact:
c Richard Gross Richard.Gross@jpl.nasa.gov
c Jet Propulsion Laboratory ph. +1 818-354-4010
c Mail Stop 238-332 fax +1 818-393-6890
c 4800 Oak Grove Drive
c Pasadena, Ca 91109-8099
c USA
c
c=======================================================================
c \ev
C !USES: ===============================================================
C === Global variables ===
#include "SIZE.h"
#include "EEPARAMS.h"
#include "PARAMS.h"
#include "GRID.h"
#include "DYNVARS.h"
#include "CG2D.h"
#include "SBO.h"
C !INPUT PARAMETERS: ===================================================
C == Routine arguments ==
C myCurrentTime - Current time of simulation ( s )
C myIter - Iteration number
C myThid - Number of this instance of SBO_CALC
_RL myCurrentTime
INTEGER myIter, myThid
#ifdef ALLOW_SBO
C !LOCAL VARIABLES: ====================================================
c external function called by calc_sbo
c returns density of sea water
_RL sbo_rho
c internal variables
c bi, bj - array indices
c I - index over longitude grid points
c J - index over latitude grid points
c K - index over layers
c lat - latitude of grid point (radians)
c lat_deg - latitude of grid point (degrees)
c lon - longitude of grid point (radians)
c radius - radius of bottom of layer (m)
c darea - element of surface area (unit radius)
c dradius - element of radius (m)
c dvolume - element of volume (m**3)
c s - salinity at grid point (ppt)
c t - temperature at grid point (deg C)
c u - eastward velocity at grid point (m/s)
c v - northward velocity at grid point (m/s)
c density - density at grid point (kg/m**3)
c ae - earth s mean radius (m) (PREM value)
c grav - earth s mean gravity (m/s**2) (PREM)
c sbo_omega - earth s mean angular velocity (rad/s)
integer bi, bj, I, J, K
_RL lat, lat_deg, lon, radius, darea, dradius, dvolume, depth
_RL s, t, u, v, density
_RL ae, grav, sbo_omega
PARAMETER ( ae = 6.3710 _d 6 )
PARAMETER ( grav = 9.8156 )
PARAMETER ( sbo_omega = 7.292115 _d -5 )
CEOP
c initialize variables to be computed
xoamc = 0.0
yoamc = 0.0
zoamc = 0.0
xoamp = 0.0
yoamp = 0.0
zoamp = 0.0
mass = 0.0
xcom = 0.0
ycom = 0.0
zcom = 0.0
DO bj = myByLo(myThid), myByHi(myThid)
DO bi = myBxLo(myThid), myBxHi(myThid)
DO J = 1-OLy, sNy+OLy
DO I = 1-OLx, sNx+OLx
obp(I,J,bi,bj) = 0.0
ENDDO
ENDDO
ENDDO
ENDDO
c loop over all grid points, accumulating mass, com, oam, and obp
do bj = myByLo(myThid), myByHi(myThid)
do bi = myBxLo(myThid), myBxHi(myThid)
do J = 1, sNy
do I = 1, sNx
c latitude (rad)
lat_deg = yC(I,J,bi,bj)
lat = yC(I,J,bi,bj) * pi / 180.0
c longitude (rad)
lon = xC(I,J,bi,bj) * pi / 180.0
c unit radius
darea = dyF(I,J,bi,bj) * dxF(I,J,bi,bj) / ae / ae
do K = 0, Nr
c K=0 => ssh
if (K .eq. 0) then
c if land, flag it in obp and skip it
if (_hFacC(i,j,1,bi,bj).eq.0.) then
obp(I,J,bi,bj) = -999.99
goto 1010
end
if
radius = ae
dradius = etaN(I,J,bi,bj)
c assume surface has same vel and density as first layer
s = salt(I,J,1,bi,bj)
t = theta(I,J,1,bi,bj)
u =(uvel(I,J,1,bi,bj)+uvel(I+1,J,1,bi,bj))/2.
v =(vvel(I,J,1,bi,bj)+vvel(I,J+1,1,bi,bj))/2.
else
c if land, skip it
if (_hFacC(i,j,k,bi,bj).eq.0.) goto 1010
c radius to center of cell (m)
radius = ae - abs(rC(K))
dradius = drF(K)
s = salt(I,J,K,bi,bj)
t = theta(I,J,K,bi,bj)
u =(uvel(I,J,K,bi,bj)+uvel(I+1,J,K,bi,bj))/2.
v =(vvel(I,J,K,bi,bj)+vvel(I,J+1,K,bi,bj))/2.
end
if
c cell volume (m**3)
dvolume = darea * radius**2 * dradius
c get density
depth = ae - radius
density = sbo_rho(depth,lat_deg,s,t)
c accumulate mass of oceans
mass = mass + density * dvolume
c accumulate center-of-mass of oceans
xcom = xcom + density * cos(lat) * cos(lon)
& * radius * dvolume
ycom = ycom + density * cos(lat) * sin(lon)
& * radius * dvolume
zcom = zcom + density * sin(lat) *
& radius * dvolume
c accumulate oceanic angular momentum due to currents
xoamc = xoamc + ( v*sin(lon)-u*sin(lat)*cos(lon))
& * density * radius * dvolume
yoamc = yoamc + (-v*cos(lon)-u*sin(lat)*sin(lon))
& * density * radius * dvolume
zoamc = zoamc + u*cos(lat)
& * density * radius * dvolume
c accumulate oceanic angular momentum due to pressure
xoamp = xoamp - sin(lat) * cos(lat) * cos(lon)
& * sbo_omega * density * radius**2 * dvolume
yoamp = yoamp - sin(lat) * cos(lat) * sin(lon)
& * sbo_omega * density * radius**2 * dvolume
zoamp = zoamp + cos(lat)**2
& * sbo_omega * density * radius**2 * dvolume
c accumulate ocean-bottom pressure
obp(I,J,bi,bj) = obp(I,J,bi,bj) +
& grav * density * dradius
c end loop over depth
end
do
1010 continue
c end loop over longitude
end
do
c end loop over latitude
end
do
c end loop over bi
end
do
c end loop over bj
end
do
c sum all values across model tiles
_GLOBAL_SUM_R8( mass , myThid )
_GLOBAL_SUM_R8( xcom , myThid )
_GLOBAL_SUM_R8( ycom , myThid )
_GLOBAL_SUM_R8( zcom , myThid )
_GLOBAL_SUM_R8( xoamc , myThid )
_GLOBAL_SUM_R8( yoamc , myThid )
_GLOBAL_SUM_R8( zoamc , myThid )
_GLOBAL_SUM_R8( xoamp , myThid )
_GLOBAL_SUM_R8( yoamp , myThid )
_GLOBAL_SUM_R8( zoamp , myThid )
c finish calculating center-of-mass of oceans
xcom = xcom / mass
ycom = ycom / mass
zcom = zcom / mass
#endif /* ALLOW_SBO */
return
end