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subroutine da_legtra_inv(jds, jde, jts, jte, max_wavenumber, alp_size, m, & 1,2
alp, v, r_leg)
!-----------------------------------------------------------------------
! Purpose: TBD
!-----------------------------------------------------------------------
implicit none
integer, intent(in) :: jds, jde ! Number of latitudes.
integer, intent(in) :: jts, jte ! Number of latitudes.
integer, intent(in) :: max_wavenumber ! Maximum wavenumber.
integer, intent(in) :: alp_size ! Dimension of ALPs.
integer, intent(in) :: m ! Zonal wavenumber.
real, intent(in) :: alp(1:alp_size) ! Associated Legendre Polynomials
complex, intent(in) :: v(m:max_wavenumber) ! Output spectral coefficient.
complex, intent(out) :: r_leg(jts:jte) ! Field to transform.
integer :: l, j, js, je ! Loop counters.
integer :: index_m, index_j
complex :: sum_legtra ! Summation scalars.
integer :: jc, iequator
if (trace_use) call da_trace_entry
("da_legtra_inv")
index_m = m * (max_wavenumber + 1 - m) + m * (m + 1) / 2 + 1 - m
jc = (jde-jds+1)/2
iequator = mod(jde-jds+1, 2)
je = min(jc+iequator, jte)
do j = jts, je
index_j = (j - 1) * (max_wavenumber + 1) * (max_wavenumber + 2) / 2
r_leg(j) = sum(v(m:max_wavenumber) * &
alp(index_j+index_m+m:index_j+index_m+max_wavenumber))
end do
js = max(jts, jc+iequator+1)
do j = js, jte
index_j = (jds+jde - j - 1) * (max_wavenumber + 1) * (max_wavenumber + 2) / 2
sum_legtra = da_zero_complex
do l = m, max_wavenumber
! Calculate second quadrant values:
if(mod(l+m,2) == 1) then
sum_legtra = sum_legtra - v(l) * alp(index_j + index_m + l)
else
sum_legtra = sum_legtra + v(l) * alp(index_j + index_m + l)
end if
end do
r_leg(j) = sum_legtra
end do
if (trace_use) call da_trace_exit("da_legtra_inv")
end subroutine da_legtra_inv