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subroutine da_asslegpol (l, m, sinlat, coslat, alp) 10
!-----------------------------------------------------------------------
! Purpose: TBD
!-----------------------------------------------------------------------
implicit none
integer, intent(in) :: l ! Legendre wavenumber.
integer, intent(in) :: m ! Fourier wavenumber.
real, intent(in) :: sinlat ! sin(latitude).
real, intent(in) :: coslat ! cos(latitude).
real, intent(out) :: alp ! Associated Legendre Polynomial.
integer :: i, loop
real :: half_co
real :: alp1, alp2
half_co = 0.5 * coslat
! Calculate ALP:
if (l < m) then
alp = 0.0
else
alp = 1.0
do i = m+1, 2*m
alp = alp * real(i) * half_co
end do
if (mod(m,2) /= 0) then
alp = -alp
end if
if (l > m) then
alp1 = alp
alp = real(2*m+1) * sinlat * alp1
if (l /= m+1) then
do loop = m+2,l
alp2 = alp1
alp1 = alp
alp = (real(2*loop-1) * sinlat * alp1 - real(loop-1+m) * alp2) &
/ real(loop-m)
end do
end if
end if
end if
end subroutine da_asslegpol