ocean_wave_speed_destroy Subroutine

   subroutine ocean_wave_speed_destroy(this)
      class(ocean_wave_speed_t), intent(inout) :: this
      this%is_init = .false.
      if (allocated(this%f_centre)) deallocate (this%f_centre)
      if (allocated(this%beta_centre)) deallocate (this%beta_centre)
      if (allocated(this%cg1)) deallocate (this%cg1)
      if (allocated(this%rd)) deallocate (this%rd)
      if (allocated(this%rd_over_dx)) deallocate (this%rd_over_dx)
   end subroutine ocean_wave_speed_destroy