fix for 4diau with iau_filter_increments=T (#167)

* fix for 4diau with iau_filter_increments=T

* fix time interval for 3DIAU

* fix typo in comment

* fix bug found in review by @MingjingTong-NOAA

* change tnext to integer variable itnext

Co-authored-by: jswhit2 <Jeffrey.S.Whitaker@noaa.gov>

Author: jswhit

tools/fv_iau_mod.F90

@@ -253,6 +253,7 @@ subroutine IAU_initialize (IPD_Control, IAU_Data,Init_parm)
     allocate (iau_state%inc1%tracer_inc(is:ie, js:je, km,ntracers))
     iau_state%hr1=IPD_Control%iaufhrs(1)
     iau_state%wt = 1.0 ! IAU increment filter weights (default 1.0)
+    iau_state%wt_normfact = 1.0
     if (IPD_Control%iau_filter_increments) then
        ! compute increment filter weights, sum to obtain normalization factor
        dtp=IPD_control%dtp
@@ -298,26 +299,31 @@ subroutine getiauforcing(IPD_Control,IAU_Data)
    type (IPD_control_type), intent(in) :: IPD_Control
    type(IAU_external_data_type),  intent(inout) :: IAU_Data
    real(kind=kind_phys) t1,t2,sx,wx,wt,dtp
-   integer n,i,j,k,sphum,kstep,nstep
+   integer n,i,j,k,sphum,kstep,nstep,itnext
 
    IAU_Data%in_interval=.false.
    if (nfiles.LE.0) then
        return
    endif
 
-   t1=iau_state%hr1 - IPD_Control%iau_delthrs*0.5
-   t2=iau_state%hr1 + IPD_Control%iau_delthrs*0.5
+   if (nfiles .eq. 1) then 
+       t1 = IPD_Control%iaufhrs(1)-0.5*IPD_Control%iau_delthrs
+       t2 = IPD_Control%iaufhrs(1)+0.5*IPD_Control%iau_delthrs
+   else
+       t1 = IPD_Control%iaufhrs(1)
+       t2 = IPD_Control%iaufhrs(nfiles)
+   endif
    if (IPD_Control%iau_filter_increments) then
       ! compute increment filter weight
-      ! t1 beginning of window, t2 end of window
+      ! t1 is beginning of window, t2 end of window
       ! IPD_Control%fhour current time
       ! in window kstep=-nstep,nstep (2*nstep+1 total)
       ! time step IPD_control%dtp
       dtp=IPD_control%dtp
       nstep = 0.5*IPD_Control%iau_delthrs*3600/dtp
       ! compute normalized filter weight
-      kstep = (IPD_Control%fhour-(t1+IPD_Control%iau_delthrs*0.5))*3600./dtp
-      if (kstep .ge. -nstep .and. kstep .le. nstep) then
+      kstep = ((IPD_Control%fhour-t1) - 0.5*IPD_Control%iau_delthrs)*3600./dtp
+      if (IPD_Control%fhour >= t1 .and. IPD_Control%fhour < t2) then
          sx     = acos(-1.)*kstep/nstep
          wx     = acos(-1.)*kstep/(nstep+1)
          if (kstep .ne. 0) then
@@ -326,7 +332,7 @@ subroutine getiauforcing(IPD_Control,IAU_Data)
             wt = 1.
          endif
          iau_state%wt = iau_state%wt_normfact*wt
-         if (is_master()) print *,'filter wt',kstep,IPD_Control%fhour,iau_state%wt
+         !if (is_master()) print *,'kstep,t1,t,t2,filter wt=',kstep,t1,IPD_Control%fhour,t2,iau_state%wt/iau_state%wt_normfact
       else
          iau_state%wt = 0.
       endif
@@ -340,31 +346,32 @@ subroutine getiauforcing(IPD_Control,IAU_Data)
          IAU_Data%in_interval=.false.
       else
          if (IPD_Control%iau_filter_increments) call setiauforcing(IPD_Control,IAU_Data,iau_state%wt)
-         if (is_master()) print *,'apply iau forcing',t1,IPD_Control%fhour,t2
+         if (is_master()) print *,'apply iau forcing t1,t,t2,filter wt=',t1,IPD_Control%fhour,t2,iau_state%wt/iau_state%wt_normfact
          IAU_Data%in_interval=.true.
       endif
       return
    endif
 
    if (nfiles > 1) then
-      t2=2
-      if (IPD_Control%fhour < IPD_Control%iaufhrs(1) .or. IPD_Control%fhour >= IPD_Control%iaufhrs(nfiles)) then
+      itnext=2
+      if (IPD_Control%fhour < t1 .or. IPD_Control%fhour >= t2) then
 !         if (is_master()) print *,'no iau forcing',IPD_Control%iaufhrs(1),IPD_Control%fhour,IPD_Control%iaufhrs(nfiles)
          IAU_Data%in_interval=.false.
       else
+         if (is_master()) print *,'apply iau forcing t1,t,t2,filter wt=',t1,IPD_Control%fhour,t2,iau_state%wt/iau_state%wt_normfact
          IAU_Data%in_interval=.true.
          do k=nfiles,1,-1
             if (IPD_Control%iaufhrs(k) > IPD_Control%fhour) then
-               t2=k
+               itnext=k
             endif
          enddo
-!         if (is_master()) print *,'t2=',t2
+!         if (is_master()) print *,'itnext=',itnext
          if (IPD_Control%fhour >= iau_state%hr2) then ! need to read in next increment file
             iau_state%hr1=iau_state%hr2
-            iau_state%hr2=IPD_Control%iaufhrs(int(t2))
+            iau_state%hr2=IPD_Control%iaufhrs(itnext)
             iau_state%inc1=iau_state%inc2
-            if (is_master()) print *,'reading next increment file',trim(IPD_Control%iau_inc_files(int(t2)))
-            call read_iau_forcing(IPD_Control,iau_state%inc2,'INPUT/'//trim(IPD_Control%iau_inc_files(int(t2))))
+            if (is_master()) print *,'reading next increment file',trim(IPD_Control%iau_inc_files(itnext))
+            call read_iau_forcing(IPD_Control,iau_state%inc2,'INPUT/'//trim(IPD_Control%iau_inc_files(itnext)))
          endif
          call updateiauforcing(IPD_Control,IAU_Data,iau_state%wt)
       endif