! this module was extracted from the GSI version operational
! at NCEP in Dec. 2007.
module constants
!$$$ module documentation block
! . . . .
! module: constants
! prgmmr: treadon org: np23 date: 2003-09-25
!
! abstract: This module contains the definition of various constants
! used in the gsi code
!
! program history log:
! 2003-09-25 treadon - original code
! 2004-03-02 treadon - allow global and regional constants to differ
! 2004-06-16 treadon - update documentation
! 2004-10-28 treadon - replace parameter tiny=1.e-12 with tiny_r_kind
! and tiny_single
! 2004-11-16 treadon - add huge_single, huge_r_kind parameters
! 2005-01-27 cucurull - add ione
! 2005-08-24 derber - move cg_term to constants from qcmod
! 2006-03-07 treadon - add rd_over_cp_mass
! 2006-05-18 treadon - add huge_i_kind
! 2006-06-06 su - add var-qc wgtlim, change value to 0.25 (ECMWF)
! 2006-07-28 derber - add r1000
!
! Subroutines Included:
! sub init_constants - compute derived constants, set regional/global constants
!
! Variable Definitions:
! see below
!
! attributes:
! language: f90
! machine: ibm RS/6000 SP
!
!$$$
use kinds, only: r_single,r_kind,i_kind
implicit none
! Declare constants
integer(i_kind) izero,ione
real(r_kind) rearth,grav,omega,rd,rv,cp,cv,cvap,cliq
real(r_kind) csol,hvap,hfus,psat,t0c,ttp,jcal,cp_mass,cg_term
real(r_kind) fv,deg2rad,rad2deg,pi,tiny_r_kind,huge_r_kind,huge_i_kind
real(r_kind) ozcon,rozcon,tpwcon,rd_over_g,rd_over_cp,g_over_rd
real(r_kind) amsua_clw_d1,amsua_clw_d2,constoz,zero,one,two,four
real(r_kind) one_tenth,quarter,three,five,rd_over_cp_mass, gamma
real(r_kind) rearth_equator,stndrd_atmos_ps,r1000
real(r_kind) semi_major_axis,semi_minor_axis,n_a,n_b
real(r_kind) eccentricity,grav_polar,grav_ratio
real(r_kind) grav_equator,earth_omega,grav_constant
real(r_kind) flattening,eccentricity_linear,somigliana
real(r_kind) dldt,dldti,hsub,psatk,tmix,xa,xai,xb,xbi
real(r_kind) eps,epsm1,omeps,wgtlim
real(r_kind) elocp,cpr,el2orc,cclimit,climit,epsq
real(r_kind) pcpeff0,pcpeff1,pcpeff2,pcpeff3,rcp,c0,delta
real(r_kind) h1000,factor1,factor2,rhcbot,rhctop,dx_max,dx_min,dx_inv
real(r_kind) h300,half,cmr,cws,ke2,row,rrow
real(r_single) zero_single,tiny_single,huge_single
real(r_single) rmw_mean_distance, roic_mean_distance
logical :: constants_initialized = .true.
! Define constants common to global and regional applications
! name value description units
! ---- ----- ----------- -----
parameter(rearth_equator= 6.37813662e6_r_kind) ! equatorial earth radius (m)
parameter(omega = 7.2921e-5_r_kind) ! angular velocity of earth (1/s)
parameter(cp = 1.0046e+3_r_kind) ! specific heat of air @pressure (J/kg/K)
parameter(cvap = 1.8460e+3_r_kind) ! specific heat of h2o vapor (J/kg/K)
parameter(csol = 2.1060e+3_r_kind) ! specific heat of solid h2o (ice)(J/kg/K)
parameter(hvap = 2.5000e+6_r_kind) ! latent heat of h2o condensation (J/kg)
parameter(hfus = 3.3358e+5_r_kind) ! latent heat of h2o fusion (J/kg)
parameter(psat = 6.1078e+2_r_kind) ! pressure at h2o triple point (Pa)
parameter(t0c = 2.7315e+2_r_kind) ! temperature at zero celsius (K)
parameter(ttp = 2.7316e+2_r_kind) ! temperature at h2o triple point (K)
parameter(jcal = 4.1855e+0_r_kind) ! joules per calorie ()
parameter(stndrd_atmos_ps = 1013.25e2_r_kind) ! 1976 US standard atmosphere ps (Pa)
! Numeric constants
parameter(izero = 0)
parameter(ione = 1)
parameter(zero_single = 0.0_r_single)
parameter(zero = 0.0_r_kind)
parameter(one_tenth = 0.10_r_kind)
parameter(quarter= 0.25_r_kind)
parameter(one = 1.0_r_kind)
parameter(two = 2.0_r_kind)
parameter(three = 3.0_r_kind)
parameter(four = 4.0_r_kind)
parameter(five = 5.0_r_kind)
parameter(r1000 = 1000.0_r_kind)
! Constants for gps refractivity
parameter(n_a=77.6_r_kind) !K/mb
parameter(n_b=3.73e+5_r_kind) !K^2/mb
! Parameters below from WGS-84 model software inside GPS receivers.
parameter(semi_major_axis = 6378.1370e3_r_kind) ! (m)
parameter(semi_minor_axis = 6356.7523142e3_r_kind) ! (m)
parameter(grav_polar = 9.8321849378_r_kind) ! (m/s2)
parameter(grav_equator = 9.7803253359_r_kind) ! (m/s2)
parameter(earth_omega = 7.292115e-5_r_kind) ! (rad/s)
parameter(grav_constant = 3.986004418e14_r_kind) ! (m3/s2)
! Derived geophysical constants
parameter(flattening = (semi_major_axis-semi_minor_axis)/semi_major_axis)!()
parameter(somigliana = &
(semi_minor_axis/semi_major_axis) * (grav_polar/grav_equator) - one)!()
parameter(grav_ratio = (earth_omega*earth_omega * &
semi_major_axis*semi_major_axis * semi_minor_axis) / grav_constant) !()
! Derived thermodynamic constants
parameter ( dldti = cvap-csol )
parameter ( hsub = hvap+hfus )
parameter ( psatk = psat*0.001_r_kind )
parameter ( tmix = ttp-20._r_kind )
parameter ( elocp = hvap/cp )
parameter ( rcp = one/cp )
! Constants used in GFS moist physics
parameter ( h300 = 300._r_kind )
parameter ( half = 0.5_r_kind )
parameter ( cclimit = 0.001_r_kind )
parameter ( climit = 1.e-20_r_kind)
parameter ( epsq = 2.e-12_r_kind )
parameter ( h1000 = 1000.0_r_kind)
parameter ( rhcbot=0.85_r_kind )
parameter ( rhctop=0.85_r_kind )
parameter ( dx_max=-8.8818363_r_kind )
parameter ( dx_min=-5.2574954_r_kind )
parameter ( dx_inv=one/(dx_max-dx_min) )
parameter ( c0=0.002_r_kind )
parameter ( delta=0.6077338_r_kind )
parameter ( pcpeff0=1.591_r_kind )
parameter ( pcpeff1=-0.639_r_kind )
parameter ( pcpeff2=0.0953_r_kind )
parameter ( pcpeff3=-0.00496_r_kind )
parameter ( cmr = one/0.0003_r_kind )
parameter ( cws = 0.025_r_kind )
parameter ( ke2 = 0.00002_r_kind )
parameter ( row = 1000._r_kind )
parameter ( rrow = one/row )
! Constant used to process ozone
parameter ( constoz = 604229.0_r_kind)
! Constants used in cloud liquid water correction for AMSU-A
! brightness temperatures
parameter ( amsua_clw_d1 = 0.754_r_kind )
parameter ( amsua_clw_d2 = -2.265_r_kind )
! Constants used for variational qc
parameter ( wgtlim = 0.25_r_kind) ! Cutoff weight for concluding that obs has been
! rejected by nonlinear qc. This limit is arbitrary
! and DOES NOT affect nonlinear qc. It only affects
! the printout which "counts" the number of obs that
! "fail" nonlinear qc. Observations counted as failing
! nonlinear qc are still assimilated. Their weight
! relative to other observations is reduced. Changing
! wgtlim does not alter the analysis, only
! the nonlinear qc data "count"
! Constants describing the Extended Best-Track Reanalysis [Demuth et
! al., 2008] tropical cyclone (TC) distance for regions relative to TC
! track position; units are in kilometers
parameter (rmw_mean_distance = 64.5479412)
parameter (roic_mean_distance = 338.319656)
contains
subroutine init_constants_derived
!$$$ subprogram documentation block
! . . . .
! subprogram: init_constants_derived set derived constants
! prgmmr: treadon org: np23 date: 2004-12-02
!
! abstract: This routine sets derived constants
!
! program history log:
! 2004-12-02 treadon
! 2005-03-03 treadon - add implicit none
!
! input argument list:
!
! output argument list:
!
! attributes:
! language: f90
! machine: ibm rs/6000 sp
!
!$$$
implicit none
! Trigonometric constants
pi = acos(-one)
deg2rad = pi/180.0_r_kind
rad2deg = one/deg2rad
cg_term = (sqrt(two*pi))/two ! constant for variational qc
tiny_r_kind = tiny(zero)
huge_r_kind = huge(zero)
tiny_single = tiny(zero_single)
huge_single = huge(zero_single)
huge_i_kind = huge(izero)
! Geophysical parameters used in conversion of geopotential to
! geometric height
eccentricity_linear = sqrt(semi_major_axis**2 - semi_minor_axis**2)
eccentricity = eccentricity_linear / semi_major_axis
constants_initialized = .true.
return
end subroutine init_constants_derived
subroutine init_constants(regional)
!$$$ subprogram documentation block
! . . . .
! subprogram: init_constants set regional or global constants
! prgmmr: treadon org: np23 date: 2004-03-02
!
! abstract: This routine sets constants specific to regional or global
! applications of the gsi
!
! program history log:
! 2004-03-02 treadon
! 2004-06-16 treadon, documentation
! 2004-10-28 treadon - use intrinsic TINY function to set value
! for smallest machine representable positive
! number
! 2004-12-03 treadon - move derived constants to init_constants_derived
! 2005-03-03 treadon - add implicit none
!
! input argument list:
! regional - if .true., set regional gsi constants;
! otherwise (.false.), use global constants
!
! output argument list:
!
! attributes:
! language: f90
! machine: ibm rs/6000 sp
!
!$$$
implicit none
logical regional
real(r_kind) reradius,g,r_d,r_v,cliq_wrf
gamma = 0.0065
! Define regional constants here
if (regional) then
! Name given to WRF constants
reradius = one/6370.e03_r_kind
g = 9.81_r_kind
r_d = 287.04_r_kind
r_v = 461.6_r_kind
cliq_wrf = 4190.0_r_kind
cp_mass = 1004.67_r_kind
! Transfer WRF constants into unified GSI constants
rearth = one/reradius
grav = g
rd = r_d
rv = r_v
cv = cp-r_d
cliq = cliq_wrf
rd_over_cp_mass = rd / cp_mass
! Define global constants here
else
rearth = 6.3712e+6_r_kind
grav = 9.80665e+0_r_kind
rd = 2.8705e+2_r_kind
rv = 4.6150e+2_r_kind
cv = 7.1760e+2_r_kind
cliq = 4.1855e+3_r_kind
cp_mass= zero
rd_over_cp_mass = zero
endif
! Now define derived constants which depend on constants
! which differ between global and regional applications.
! Constants related to ozone assimilation
ozcon = grav*21.4e-9_r_kind
rozcon= one/ozcon
! Constant used in vertical integral for precipitable water
tpwcon = 100.0_r_kind/grav
! Derived atmospheric constants
fv = rv/rd-one ! used in virtual temperature equation
dldt = cvap-cliq
xa = -(dldt/rv)
xai = -(dldti/rv)
xb = xa+hvap/(rv*ttp)
xbi = xai+hsub/(rv*ttp)
eps = rd/rv
epsm1 = rd/rv-one
omeps = one-eps
factor1 = (cvap-cliq)/rv
factor2 = hvap/rv-factor1*t0c
cpr = cp*rd
el2orc = hvap*hvap/(rv*cp)
rd_over_g = rd/grav
rd_over_cp = rd/cp
g_over_rd = grav/rd
return
end subroutine init_constants
end module constants