#include <misc.h>#include <params.h>subroutine hordif1(rearth,phi)!----------------------------------------------------------------------- ! ! Purpose: ! Horizontal diffusion of z,d,t,q! ! Method: ! 1. implicit del**2 form above level kmnhd4! 2. implicit del**4 form at level kmnhd4 and below! 3. courant number based truncation at level kmxhdc and above! 4. increased del**2 coefficient at level kmxhd2 and above!! Computational note: this routine is multitasked by level, hence it ! is called once for each k!! Note: Most of the "ifdef" constructs employed in this routine are related! to the fact that storage order for spectral coefficients is different! depending upon whether the target architecture is PVP or not.! ! Author: ! !-----------------------------------------------------------------------!! $Id: hordif1.F90,v 1.1 2001/11/06 18:42:48 erik Exp $! $Author: erik $!!-----------------------------------------------------------------------  use precision  use pmgrid  use pspect  use comspe  implicit none!------------------------------Arguments--------------------------------  real(r8), intent(in)    :: rearth     ! radius of earth  real(r8), intent(inout) :: phi(psp)   ! used in spectral truncation of phis!-----------------------------------------------------------------------!---------------------------Local workspace-----------------------------#if ( defined PVP )  real(r8) tqfac(2*pnmax)  ! time-split implicit diffusion factors (t,q)  integer isp              ! spectral pointer  integer ne               ! spectral pointer#else  integer ir,ii            ! spectral indices         integer mr,mc            ! spectral indices#endif  real(r8) k42             ! Nominal  Del^4 diffusion coeff at T42  real(r8) k63             ! Nominal  Del^4 diffusion coeff at T63  real(r8) knn             ! Computed Del^4 diffusion coeff at TNN  real(r8) tmp             ! temp space  real(r8) hdfst4(pnmax)  integer  expon  integer  m,n             ! spectral indices!-----------------------------------------------------------------------!! Compute Del^4 diffusion coefficient!  k42   = 1.e+16  k63   = 2.e+15  expon = 25  if(pmax-1 <= 42) then     knn = k42  elseif(pmax-1 == 63) then     knn = k63  else     if(pmax-1 < 63) then        tmp = log(k42/k63)/log(63._r8*64._r8/42._r8/43._r8)     else        tmp = 2.     endif     knn = k63*(63._r8*64._r8/float(pmax)/float(pmax-1))**tmp  endif!! Set the Del^4 diffusion coefficients for each wavenumber!  hdfst4(1) = 0.  do n=2,pnmax     hdfst4(n) = knn * (n*(n-1)*n*(n-1)  ) / rearth**4  end do!! Set the horizontal diffusion factors for each wavenumer at this level! del^4 diffusion is to be applied and compute time-split implicit! factors.!#if ( defined PVP )  do n = 1, pnmax     tqfac(2*n)   = 1./(1. + 3600.*hdfst4(n))     tqfac(2*n-1) = 1./(1. + 3600.*hdfst4(n))  end do!! Apply the horizontal diffusion!  do n=1,pmax     isp = nco2(n) - 2     ne = 2*(n-1)     do m=1,2*nm(n)        phi(isp+m)  = phi(isp+m)*tqfac(ne+m)**expon     end do  end do#else  do m=1,pmmax     mr = nstart(m)     mc = 2*mr     do n=1,nlen(m)        ir = mc + 2*n - 1        ii = ir + 1        phi(ir)  = phi(ir)/(1. + 3600.*hdfst4(n+m-1))**expon        phi(ii)  = phi(ii)/(1. + 3600.*hdfst4(n+m-1))**expon     end do  end do#endif  returnend subroutine hordif1