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Modified observation errors for radar-reflectivity observations in precipitation #650

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Nov 7, 2023
Merged

Modified observation errors for radar-reflectivity observations in precipitation #650

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159a90d
Changes for reducing the influence of reflectivity observations in pr…
daviddowellNOAA Nov 1, 2023
5e4a49a
add namelist parameter for inflating dbz observation errors
daviddowellNOAA Nov 6, 2023
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8 changes: 6 additions & 2 deletions src/gsi/gsimod.F90
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Expand Up @@ -26,7 +26,7 @@ module gsimod
use obsmod, only: doradaroneob,dofedoneob,oneoblat,oneoblon,oneobheight,oneobvalue,oneobddiff,oneobradid,&
radar_no_thinning,ens_hx_dbz_cut,static_gsi_nopcp_dbz,rmesh_dbz,&
rmesh_vr,zmesh_dbz,zmesh_vr,if_vterminal, if_model_dbz,if_model_fed,innov_use_model_fed,if_vrobs_raw,if_use_w_vr,&
minobrangedbz,maxobrangedbz,maxobrangevr,maxtiltvr,missing_to_nopcp,&
minobrangedbz,maxobrangedbz,maxobrangevr,maxtiltvr,inflate_dbz_obserr,missing_to_nopcp,&
ntilt_radarfiles,whichradar,&
minobrangevr,maxtiltdbz,mintiltvr,mintiltdbz,l2rwthin,hurricane_radar,&
r_hgt_fed
Expand Down Expand Up @@ -744,6 +744,10 @@ module gsimod
! optconv - downweighting option for iasi and cris for moisture channels to
! improve convergence. default 0.0 (no change). Larger number improves
! convergence.
! inflate_dbz_obserr - logical that controls inflation of reflectivity ob error
! for obs that exceed gross error magnitude
! if true, inflate ob error
! if false, reject ob
!
! NOTE: for now, if in regional mode, then iguess=-1 is forced internally.
! add use of guess file later for regional mode.
Expand Down Expand Up @@ -779,7 +783,7 @@ module gsimod
use_gfs_stratosphere,pblend0,pblend1,step_start,diag_precon,lrun_subdirs,&
use_sp_eqspace,lnested_loops,lsingleradob,thin4d,use_readin_anl_sfcmask,&
luse_obsdiag,id_drifter,id_ship,verbose,print_obs_para,lsingleradar,singleradar,lnobalance, &
missing_to_nopcp,minobrangedbz,minobrangedbz,maxobrangedbz,&
inflate_dbz_obserr,missing_to_nopcp,minobrangedbz,minobrangedbz,maxobrangedbz,&
maxobrangevr,maxtiltvr,whichradar,doradaroneob,dofedoneob,oneoblat,&
oneoblon,oneobheight,oneobvalue,oneobddiff,oneobradid,&
rmesh_vr,zmesh_dbz,zmesh_vr, ntilt_radarfiles, whichradar,&
Expand Down
8 changes: 5 additions & 3 deletions src/gsi/obsmod.F90
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Expand Up @@ -480,7 +480,8 @@ module obsmod
! ==== DBZ DA ===
public :: ntilt_radarfiles
public :: whichradar
public :: vr_dealisingopt, if_vterminal, if_model_dbz, inflate_obserr, if_vrobs_raw, if_use_w_vr, l2rwthin
public :: vr_dealisingopt, if_vterminal, if_model_dbz, if_vrobs_raw, if_use_w_vr, l2rwthin
public :: inflate_dbz_obserr

public :: doradaroneob,oneoblat,oneoblon
public :: oneobddiff,oneobvalue,oneobheight,oneobradid
Expand Down Expand Up @@ -634,7 +635,8 @@ module obsmod

logical :: ta2tb
logical :: doradaroneob,dofedoneob
logical :: vr_dealisingopt, if_vterminal, if_model_dbz,if_model_fed, innov_use_model_fed,inflate_obserr, if_vrobs_raw, if_use_w_vr, l2rwthin
logical :: vr_dealisingopt, if_vterminal, if_model_dbz,if_model_fed, innov_use_model_fed, if_vrobs_raw, if_use_w_vr, l2rwthin
logical :: inflate_dbz_obserr
character(4) :: whichradar,oneobradid
real(r_kind) :: oneoblat,oneoblon,oneobddiff,oneobvalue,oneobheight
logical :: radar_no_thinning
Expand Down Expand Up @@ -769,7 +771,7 @@ subroutine init_obsmod_dflts
if_model_dbz=.false.
if_model_fed=.false.
innov_use_model_fed=.false.
inflate_obserr=.false.
inflate_dbz_obserr=.false.
whichradar="KKKK"

oneobradid="KKKK"
Expand Down
12 changes: 9 additions & 3 deletions src/gsi/read_dbz_nc.f90
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Expand Up @@ -412,9 +412,15 @@ subroutine read_dbz_nc(nread,ndata,nodata,infile,lunout,obstype,sis,hgtl_full,no
! changed to hard-coded value for now; dbznoise used for two different purposes in this subroutine:
! (1) threshold for lowest reflectivity value considered to be an observation and
! (2) ob error
thiserr = 5.0_r_kind



! Specify a larger error standard deviation for reflectivity observations in precipitation
! than for reflectivity observations that indicate a lack of preciptation.
if( dbzQC(i,j,k) < 5.0_r_kind ) then
thiserr = 5.0_r_kind
else
thiserr = 10.0_r_kind
end if

nread = nread + 1

!#################### Data thinning ###################
Expand Down
9 changes: 6 additions & 3 deletions src/gsi/setupdbz.f90
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Expand Up @@ -150,7 +150,7 @@ subroutine setupdbz(obsLL,odiagLL,lunin,mype,bwork,awork,nele,nobs,is,radardbz_d
use convinfo, only: nconvtype,cermin,cermax,cgross,cvar_b,cvar_pg,ictype
use convinfo, only: icsubtype
use m_dtime, only: dtime_setup, dtime_check
use obsmod, only : if_model_dbz, inflate_obserr
use obsmod, only : if_model_dbz, inflate_dbz_obserr
use setupdbz_lib, only:hx_dart,jqr_dart,jqs_dart,jqg_dart
use gridmod, only: wrf_mass_regional,nems_nmmb_regional, fv3_regional
use sparsearr, only: sparr2, new, size, writearray, fullarray
Expand Down Expand Up @@ -1260,8 +1260,11 @@ subroutine setupdbz(obsLL,odiagLL,lunin,mype,bwork,awork,nele,nobs,is,radardbz_d
end if

else
if (ratio > cgross(ikx) .or. ratio_errors < tiny_r_kind) then
if ( inflate_obserr .and. (ratio-cgross(ikx)) <= cgross(ikx) .and. ratio_errors >= tiny_r_kind) then

! Apply gross error check only to reflectivity observations in precipitation (>= 5 dBZ).
if ( ( (data(idbzob,i) >= 5_r_kind) .and. (ratio > cgross(ikx)) ) .or. (ratio_errors < tiny_r_kind) ) then

if ( inflate_dbz_obserr .and. (ratio-cgross(ikx)) <= cgross(ikx) .and. ratio_errors >= tiny_r_kind) then
! Since radar reflectivity can be very different from the model background
! good observations may be rejected during this QC step. However, if these observations
! are allowed through, they can yield problems with convergence. Therefore the error
Expand Down