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!**********************************************************************
! Copyright 1998,1999,2000,2001,2002,2005,2007,2008,2009,2010 *
! Andreas Stohl, Petra Seibert, A. Frank, Gerhard Wotawa, *
! Caroline Forster, Sabine Eckhardt, John Burkhart, Harald Sodemann *
! *
! This file is part of FLEXPART. *
! *
! FLEXPART is free software: you can redistribute it and/or modify *
! it under the terms of the GNU General Public License as published by*
! the Free Software Foundation, either version 3 of the License, or *
! (at your option) any later version. *
! *
! FLEXPART is distributed in the hope that it will be useful, *
! but WITHOUT ANY WARRANTY; without even the implied warranty of *
! MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
! GNU General Public License for more details. *
! *
! You should have received a copy of the GNU General Public License *
! along with FLEXPART. If not, see <http://www.gnu.org/licenses/>. *
!**********************************************************************
!##################################################################
!##################################################################
!###### ######
!###### Developed by ######
!###### Center for Analysis and Prediction of Storms ######
!###### University of Oklahoma ######
!###### ######
!##################################################################
!##################################################################
function f_qvsat( p, t )
!PURPOSE:
!
!Calculate the saturation specific humidity using enhanced Teten's
!formula.
!
!AUTHOR: Yuhe Liu
!01/08/1998
!
!MODIFICATION HISTORY:
!
!INPUT :
! p Pressure (Pascal)
! t Temperature (K)
!OUTPUT:
! f_qvsat Saturation water vapor specific humidity (kg/kg).
!
!Variable Declarations.
!
implicit none
real :: p ! Pressure (Pascal)
real :: t ! Temperature (K)
real :: f_qvsat ! Saturation water vapor specific humidity (kg/kg)
real :: f_esl,f_esi,fespt
real,parameter :: rd = 287.0 ! Gas constant for dry air (m**2/(s**2*K))
real,parameter :: rv = 461.0 ! Gas constant for water vapor (m**2/(s**2*K)).
real,parameter :: rddrv = rd/rv
! Change by A. Stohl to save computation time:
! IF ( t.ge.273.15 ) THEN ! for water
if ( t.ge.253.15 ) then ! modification Petra Seibert
! (supercooled water may be present)
fespt=f_esl(p,t)
else
fespt=f_esi(p,t)
endif
!!$ f_qvsat = rddrv * fespt / (p-(1.0-rddrv)*fespt) !old
if (p-(1.0-rddrv)*fespt == 0.) then !bugfix
f_qvsat = 1.
else
f_qvsat = rddrv * fespt / (p-(1.0-rddrv)*fespt)
end if
return
end function f_qvsat
function f_esl( p, t )
implicit none
real :: p ! Pressure (Pascal)
real :: t ! Temperature (K)
real :: f_esl ! Saturation water vapor pressure over liquid water
real :: f
!#######################################################################
!
!Saturation specific humidity parameters used in enhanced Teten's
!formula. (See A. Buck, JAM 1981)
!
!#######################################################################
real,parameter :: satfwa = 1.0007
real,parameter :: satfwb = 3.46e-8 ! for p in Pa
real,parameter :: satewa = 611.21 ! es in Pa
real,parameter :: satewb = 17.502
real,parameter :: satewc = 32.18
real,parameter :: satfia = 1.0003
real,parameter :: satfib = 4.18e-8 ! for p in Pa
real,parameter :: sateia = 611.15 ! es in Pa
real,parameter :: sateib = 22.452
real,parameter :: sateic = 0.6
f = satfwa + satfwb * p
f_esl = f * satewa * exp( satewb*(t-273.15)/(t-satewc) )
return
end function f_esl
function f_esi( p, t )
implicit none
real :: p ! Pressure (Pascal)
real :: t ! Temperature (K)
real :: f_esi ! Saturation water vapor pressure over ice (Pa)
real :: f
!#######################################################################
!
!Saturation specific humidity parameters used in enhanced Teten's
!formula. (See A. Buck, JAM 1981)
!
!#######################################################################
!
real,parameter :: satfwa = 1.0007
real,parameter :: satfwb = 3.46e-8 ! for p in Pa
real,parameter :: satewa = 611.21 ! es in Pa
real,parameter :: satewb = 17.502
real,parameter :: satewc = 32.18
real,parameter :: satfia = 1.0003
real,parameter :: satfib = 4.18e-8 ! for p in Pa
real,parameter :: sateia = 611.15 ! es in Pa
real,parameter :: sateib = 22.452
real,parameter :: sateic = 0.6
f = satfia + satfib * p
f_esi = f * sateia * exp( sateib*(t-273.15)/(t-sateic) )
return
end function f_esi
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