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Update Schmidt Transform for higher resolution #229

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Update Schmidt Transform for higher resolution #229

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44 changes: 25 additions & 19 deletions src/Infrastructure/Util/src/ESMF_UtilCubedSphere.F90
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Original file line number Diff line number Diff line change
Expand Up @@ -35,7 +35,7 @@ module ESMF_UtilCubedSphereMod
real(ESMF_KIND_R8) , parameter:: torad = pi/180.0 ! convert to radians
real(ESMF_KIND_R8) , parameter:: missing = 1.e25
real(ESMF_KIND_R8), parameter :: JAPAN_SHIFT = pi/18
integer, parameter:: f_p = selected_real_kind(15)
integer, parameter:: f_p = maxval(selected_real_kind(15),selected_real_kind(20))
real(ESMF_KIND_R8) :: stretch ! Optional stretching factor for the grid
logical :: dxdy_area = .false. ! define area using dx*dy else spherical excess formula
logical :: latlon = .false.
Expand Down Expand Up @@ -1068,10 +1068,12 @@ subroutine direct_transform(stretch_factor, lon_p, lat_p, lon, lat)
! 0 <= lon <= 2*pi ; -pi/2 <= lat <= pi/2
real(ESMF_KIND_R8), intent(inout) :: lon(:,:), lat(:,:)
!
real(ESMF_KIND_R8) :: lat_t, sin_p, cos_p, sin_lat, cos_lat, sin_o, p2, two_pi
real(ESMF_KIND_R8) :: c2p1, c2m1
real(f_p) :: lat_t, sin_p, cos_p, sin_lat, cos_lat, sin_o, p2, two_pi
real(f_p) :: c2p1, c2m1, one, near_zero, f_p_lon, f_p_lat
integer:: i, j

one = 1.d0
near_zero = tiny(near_zero)
p2 = 0.5d0*pi
two_pi = 2.d0*pi

Expand All @@ -1083,28 +1085,32 @@ subroutine direct_transform(stretch_factor, lon_p, lat_p, lon, lat)

do j=1,size(lon,2)
do i=1,size(lon,1)
if ( abs(c2m1) > 1.d-7 ) then
sin_lat = sin(lat(i,j))
f_p_lon = lon(i,j)
f_p_lat = lat(i,j)
if ( abs(c2m1) > near_zero ) then
sin_lat = sin(f_p_lat)
lat_t = asin( (c2m1+c2p1*sin_lat)/(c2p1+c2m1*sin_lat) )
else ! no stretching
lat_t = lat(i,j)
lat_t = f_p_lat
endif
sin_lat = sin(lat_t)
cos_lat = cos(lat_t)
sin_o = -(sin_p*sin_lat + cos_p*cos_lat*cos(lon(i,j)))
if ( (1.-abs(sin_o)) < 1.d-7 ) then ! poles
lon(i,j) = 0.d0
lat(i,j) = sign( p2, sin_o )
sin_lat = sin(lat_t)
cos_lat = cos(lat_t)
sin_o = -(sin_p*sin_lat + cos_p*cos_lat*cos(f_p_lon))
if ( (one-abs(sin_o)) < near_zero ) then ! poles
f_p_lon = 0.d0
f_p_lat = sign( p2, sin_o )
else
lat(i,j) = asin( sin_o )
lon(i,j) = lon_p + atan2( -cos_lat*sin(lon(i,j)), &
-sin_lat*cos_p+cos_lat*sin_p*cos(lon(i,j)))
if ( lon(i,j) < 0.d0 ) then
lon(i,j) = lon(i,j) + two_pi
elseif( lon(i,j) >= two_pi ) then
lon(i,j) = lon(i,j) - two_pi
f_p_lat = asin( sin_o )
f_p_lon = lon_p + atan2( -cos_lat*sin(f_p_lon), &
-sin_lat*cos_p+cos_lat*sin_p*cos(f_p_lon))
if ( f_p_lon < 0.d0 ) then
f_p_lon = f_p_lon + two_pi
elseif( f_p_lon >= two_pi ) then
f_p_lon = f_p_lon - two_pi
endif
endif
lon(i,j) = f_p_lon
lat(i,j) = f_p_lat
enddo
enddo

Expand Down