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Fix divide-by-zero in domain_def_clm for degenerate 1x1 domains #65

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Merged
zhao7777 merged 1 commit into from
Apr 1, 2026
+18 −1
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Fix divide-by-zero in domain_def_clm for degenerate 1x1 domains #65

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19 changes: 18 additions & 1 deletion interface/model/eclm/enkf_clm_mod_5.F90
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Original file line number Diff line number Diff line change
Expand Up @@ -1313,6 +1313,8 @@ subroutine domain_def_clm(lon_clmobs, lat_clmobs, dim_obs, &
integer :: ncols, counter
integer :: npatches, ncohorts
real :: minlon, minlat, maxlon, maxlat
real(r8) :: dlon_span, dlat_span
real(r8), parameter :: tol_degen = 1.0e-6_r8
real(r8), pointer :: lon(:)
real(r8), pointer :: lat(:)
integer :: begg, endg ! per-proc gridcell ending gridcell indices
Expand Down Expand Up @@ -1371,14 +1373,28 @@ subroutine domain_def_clm(lon_clmobs, lat_clmobs, dim_obs, &
maxlon = MAXVAL(lon(:) + 180)
minlat = MINVAL(lat(:) + 90)
maxlat = MAXVAL(lat(:) + 90)

! Degenerate horizontal domain (e.g. 1x1 grid): min==max => zero span;
! Avoid dividing by (maxlon-minlon) or (maxlat-minlat).
dlon_span = maxval(lon(:) + 180._r8) - minval(lon(:) + 180._r8)
dlat_span = maxval(lat(:) + 90._r8) - minval(lat(:) + 90._r8)

if(allocated(longxy_obs)) deallocate(longxy_obs)
allocate(longxy_obs(dim_obs), stat=ier)
if(allocated(latixy_obs)) deallocate(latixy_obs)
allocate(latixy_obs(dim_obs), stat=ier)

do i = 1, dim_obs
if(((lon_clmobs(i) + 180) - minlon) /= 0 .and. &
if (dlon_span <= tol_degen .and. dlat_span <= tol_degen) then
longxy_obs(i) = 1
latixy_obs(i) = 1
else if (dlon_span <= tol_degen) then
longxy_obs(i) = 1
latixy_obs(i) = ceiling(((lat_clmobs(i) + 90) - minlat) * nj / (maxlat - minlat))
else if (dlat_span <= tol_degen) then
longxy_obs(i) = ceiling(((lon_clmobs(i) + 180) - minlon) * ni / (maxlon - minlon))
latixy_obs(i) = 1
else if(((lon_clmobs(i) + 180) - minlon) /= 0 .and. &
((lat_clmobs(i) + 90) - minlat) /= 0) then
longxy_obs(i) = ceiling(((lon_clmobs(i) + 180) - minlon) * ni / (maxlon - minlon)) !+ 1
latixy_obs(i) = ceiling(((lat_clmobs(i) + 90) - minlat) * nj / (maxlat - minlat)) !+ 1
Expand All @@ -1395,6 +1411,7 @@ subroutine domain_def_clm(lon_clmobs, lat_clmobs, dim_obs, &
latixy_obs(i) = 1
endif
end do

! deallocate temporary arrays
!deallocate(longxy)
!deallocate(latixy)
Expand Down