Finish unit test for function get_xnsum.

Fixes ufs-community#1000.

tests/orog/ftst_get_xnsum.F90

@@ -1,121 +1,115 @@
  program check_get_xnsum
 
+! Unit test for function get_xnsum, which computes the
+! the number of high-resolution orography data points
+! within a model grid box that are above the average
+! terrain height.
+
  use orog_utils, only : get_xnsum
 
  implicit none
 
- integer, parameter :: imn=360
- integer, parameter :: jmn=181
+ integer, parameter :: imn=360  ! i-dimension of high-res grid
+ integer, parameter :: jmn=181  ! j-dimension of high-res grid
 
  integer            :: j
- integer            :: zavg(imn,jmn)
- integer            :: zslm(imn,jmn)
+ integer            :: zavg(imn,jmn)  ! High-res grid terrain
+ integer            :: zslm(imn,jmn)  ! High-res grid land mask
 
- real               :: delxn=360.0/float(imn)
- real               :: glat(jmn)
+ real               :: delxn=360.0/float(imn) ! Resolution of high-res grid in degrees.
+ real               :: glat(jmn)              ! Latitude of each high-res grid row in degrees.
  real               :: lon1,lat1,lon2,lat2
  real               :: xnsum
 
- print*,"Begin test."
+ print*,"Begin test of function get_xnsum"
 
-! Set up a 'high-res' 1-degree grid.
+! The high-res grid is a global one-degree lat/lon grid. Point (1,1)
+! is the south pole/greenwich.
 
  do j = 1, jmn
    glat(j) = -90.0 + float(j-1) * delxn
-   print*,'j lat ',j,glat(j)
  enddo
 
+! Bounds of model grid box - straddles equator/greenwich.
+! There are approximately 16 high-res points located within
+! the model box.
+
+ lon1 = -2.5
+ lon2 = 2.5
+ lat1 = -1.5
+ lat2 = 1.5
+
 ! First test point. The high-res grid is all ocean. Since all points in
 ! the model grid box will be sea level, there will be no points
 ! higher than the average of 0 meters.
 
  print*,"Test point 1."
 
- zslm = 0    ! all water
- zavg = -999 ! all sea level
-
-! Bounds of model grid box - straddles greenwich.
-
- lon1 = -2.5
- lon2 = 2.5
- lat1 = -1.5
- lat2 = 1.5
+ zslm = 0    ! high-res grid all water
+ zavg = -999 ! high-res grid all sea level
 
  xnsum = get_xnsum(lon1,lat1,lon2,lat2,imn,jmn, &
                    glat, zavg, zslm, delxn)
 
  if (nint(xnsum) /= 0) stop 2
 
+! Second test point. All high-res points are land with an elevation
+! of 50 meters. There will be no points higher than the average.
+
  print*,"Test point 2."
 
- zslm = 1    ! all land
+ zslm = 1   ! high-res grid all land
  zavg = 50  ! constant elevation of 50 meters.
 
-! Bounds of model grid box - straddles greenwich.
-
- lon1 = -2.5
- lon2 = 2.5
- lat1 = -1.5
- lat2 = 1.5
-
  xnsum = get_xnsum(lon1,lat1,lon2,lat2,imn,jmn, &
                    glat, zavg, zslm, delxn)
 
  if (nint(xnsum) /= 0) stop 4
 
- print*,"Test point 3."
+! Third test point. All high-res points are land. One point is
+! 100 meters, the rest are 50 meters. Therefore, there should
+! be one point higher than the average.
 
- zslm = 1    ! all land
- zavg = 50   ! constant elevation of 50 meters.
- zavg(359,91) = 100
-
-! Bounds of model grid box - straddles greenwich.
+ print*,"Test point 3."
 
- lon1 = -2.5
- lon2 = 2.5
- lat1 = -1.5
- lat2 = 1.5
+ zslm = 1           ! all land
+ zavg = 50          ! initialize elevation to 50 meters.
+ zavg(359,91) = 100 ! one point within the model box is 100 meters.
 
  xnsum = get_xnsum(lon1,lat1,lon2,lat2,imn,jmn, &
                    glat, zavg, zslm, delxn)
 
  if (nint(xnsum) /= 1) stop 6
 
- print*,"Test point 4."
-
- zslm = 0    ! all water
- zavg = -999   ! set to sea level.
- zavg(2,93) = 20 ! this represents an inland lake above sea level.
+! Fourth test point. All high-res points are water. One point is
+! 20 meters, which represents an inland lake. The other points
+! are ocean. Therefore, there should be one point higher than the average.
 
-! Bounds of model grid box - straddles greenwich.
+ print*,"Test point 4."
 
- lon1 = -2.5
- lon2 = 2.5
- lat1 = -1.5
- lat2 = 1.5
+ zslm = 0         ! all water
+ zavg = -999      ! initialize to sea level.
+ zavg(2,93) = 20  ! this represents an inland lake above sea level.
 
  xnsum = get_xnsum(lon1,lat1,lon2,lat2,imn,jmn, &
                    glat, zavg, zslm, delxn)
 
  if (nint(xnsum) /= 1) stop 8
 
- print*,"Test point 5."
-
- zslm = 0      ! all water
- zavg = -999   ! set to sea level.
- zslm(1:2,90:93) = 1 ! half points in grid box land
- zavg(1,90:93) = 25 ! land points above sea level
- zavg(2,90) = 100 ! land points above sea level
- zavg(2,91) = 110 ! land points above sea level
- zavg(2,92) = 107 ! land points above sea level
- zavg(2,93) = 207 ! land points above sea level
+! Fifth test point. Half of the high-res points within the grid
+! box are land and half are water. Four high-res points are
+! above the average.
 
-! Bounds of model grid box - straddles greenwich.
+ print*,"Test point 5."
 
- lon1 = -2.5
- lon2 = 2.5
- lat1 = -1.5
- lat2 = 1.5
+ zslm = 0            ! Initialize to all water
+ zavg = -999         ! Initialize to sea level.
+ zslm(1:2,90:93) = 1 ! Half the points in the grid box are land.
+ zavg(1,90:93) = 25  ! Set the elevation at the
+ zavg(2,90) = 100    ! land points so that
+ zavg(2,91) = 110    ! four points are above the average.
+ zavg(2,92) = 107
+ zavg(2,93) = 207
 
  xnsum = get_xnsum(lon1,lat1,lon2,lat2,imn,jmn, &
                    glat, zavg, zslm, delxn)