da_get_vertical_truncation.inc

1 subroutine da_get_vertical_truncation( max_vert_var, eigenval, be_sub)
2 
3    !---------------------------------------------------------------------------
4    !  Purpose: Calculate vertical mode truncation from explained variance.
5    !
6    !  Method:  Calculate cumulative variance and compare with limit.
7    !---------------------------------------------------------------------------
8 
9    implicit none
10 
11    real, intent(in)                 :: max_vert_var    ! Vertical variance limit.
12    real, intent(in)                 :: eigenval(:)     ! Global eigenvaluess.
13    type(be_subtype), intent(inout) :: be_sub          ! Back. error sub type.
14     
15    integer                          :: kz              ! # vertical levels.
16    integer                          :: k               ! Loop counter.
17    real                             :: tot_variance    ! Total variance.
18    real                             :: cum_variance    ! Cumulative variance.
19    character(LEN = 6)              :: name            ! Variable name.
20 
21    if (trace_use_dull) call da_trace_entry("da_get_vertical_truncation")
22 
23 
24    !---------------------------------------------------------------------------
25    ! [1.0] Initialise:
26    !---------------------------------------------------------------------------
27 
28    kz = size( eigenval(:))
29    name = trim(be_sub % name)
30 
31    !---------------------------------------------------------------------------
32    ! [2.0] Calculate vertical truncation:
33    !---------------------------------------------------------------------------
34 
35    if (max_vert_var >= 100.0) then
36    
37       ! [2.1] No truncation: 
38       be_sub % mz = kz
39 
40       ! Disregard zero/-ve eigenvalues(which should be very small and only 
41       ! appear if statistics have been interpolated between domains):
42 
43       do k = 1, kz
44          if (eigenval(k) <= 0.0) then
45             be_sub % mz = k - 1
46             exit
47          end if
48       end do      
49    else
50    
51       ! [2.2] Calculate cumulative variance and truncate:
52 
53       tot_variance = sum( eigenval(1:kz))
54       cum_variance = 0.0
55       
56       do k = 1, kz
57          cum_variance = cum_variance + eigenval(k)
58          
59          if (eigenval(k) <= 0.0) then
60             be_sub % mz = k - 1
61             exit
62          end if
63          
64          if (cum_variance/tot_variance >= 0.01 * max_vert_var) then
65             be_sub % mz = k
66             exit
67          end if  
68       end do
69       
70       if (max_vert_var == 0.0) be_sub % mz = 0 
71 
72    end if
73 
74    write(unit=stdout,fmt='(A,A6,A3,I3,A1,f7.2,A2)') &
75       'Vertical truncation for ', name, &
76       ' = ', be_sub % mz, '(', &
77       max_vert_var, '%)'
78    write (unit=stdout,fmt='(A)') " "
79 
80    if (trace_use_dull) call da_trace_exit("da_get_vertical_truncation")
81                                        
82 end subroutine da_get_vertical_truncation
83 
84