add_noise.F90

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!SFX_LIC Copyright 1994-2014 CNRS, Meteo-France and Universite Paul Sabatier
!SFX_LIC This is part of the SURFEX software governed by the CeCILL-C licence
!SFX_LIC version 1. See LICENSE, CeCILL-C_V1-en.txt and CeCILL-C_V1-fr.txt  
!SFX_LIC for details. version 1.
SUBROUTINE add_noise(PADDTIMECORR,PASSIM_WINH,PWHITE_NOISE,PRED_NOISE)
!
USE yomhook,            ONLY : lhook,dr_hook
USE parkind1,           ONLY : jprb
!
IMPLICIT NONE
!
REAL, INTENT(IN) ::  paddtimecorr
REAL, INTENT(IN) ::  pwhite_noise
REAL, INTENT(IN) :: passim_winh
REAL, INTENT(INOUT) :: pred_noise
!
REAL :: zalpha, zmu
REAL(KIND=JPRB) :: zhook_handle
!
IF (lhook) CALL dr_hook('ADD_NOISE',0,zhook_handle)
!
! Define parameters for model error
!
! ZTAU   = 3.*86400.         ! temporal correlation (sec)
!ZSIGMA = 1.E-3/86400.      ! standard deviation of error (m3/m3/s)

zalpha = 1./(1. + ((passim_winh/24.0)/paddtimecorr))
!
zmu = sqrt(1. - zalpha**2)*pwhite_noise
!
pred_noise = zalpha*pred_noise + zmu
!
 !WGN = WGN + ZBETA*WGN_n*DT
!
IF (lhook) CALL dr_hook('ADD_NOISE',1,zhook_handle)
!
END SUBROUTINE add_noise