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subroutine da_balance_geoterm_nl (domain, k, u, v, term_x, term_y),2
!---------------------------------------------------------------------------
! Purpose: calculates nonlinear geostrophic term in balance equation.
!
! method: term is k x rho f u on a single level.
!---------------------------------------------------------------------------
implicit none
type(domain), intent(in) :: grid
integer, intent(in) :: k ! Model level.
real, intent(in) :: u(:,:) ! u wind comp. (dot pts)
real, intent(in) :: v(:,:) ! v wind comp. (dot pts)
real, intent(out) :: term_x(:,:) ! x component of term.
real, intent(out) :: term_y(:,:) ! y component of term.
if (trace_use) call da_trace_entry
("da_balance_geoterm_nl")
!---------------------------------------------------------------------------
! [1.0] Initialise:
!---------------------------------------------------------------------------
term_x(:,:) = 0.0
term_y(:,:) = 0.0
!---------------------------------------------------------------------------
! [2.0] Calculate term_x = -f rho v~:
!---------------------------------------------------------------------------
term_x(its:ite, jts:jte) = -grid%xb%rho(its:ite, jts:jte, k) &
* grid%xb% v(its:ite, jts:jte, k) * grid%xb%cori(its:ite, jts:jte)
!---------------------------------------------------------------------------
! [3.0] Calculate term_y = f rho u~:
!---------------------------------------------------------------------------
term_y(its:ite, jts:jte) = grid%xb%rho(its:ite, jts:jte, k) &
* grid%xb% u(its:ite, jts:jte, k) * grid%xb%cori(its:ite, jts:jte)
if (trace_use) call da_trace_exit("da_balance_geoterm_nl")
end subroutine da_balance_geoterm_nl