PRO cc2stock, z_ib, c_i, S_i

;==================================================================================================
;
; this gorgeous script integrates a concentration c_i (./m3) into a stock S_i (./m2)
; by integrating vertically on any grid
; (c) Martouf, Helsinki, Aug 2014
;
;==================================================================================================
;
;--------------------------------------------------------------------------------------------------
; extract number of layers and time steps
;--------------------------------------------------------------------------------------------------

zsize = SIZE(c_i)

nlay = zsize(1)   ; number of layers
nts  = zsize(2)   ; number of time steps

S_i = FLTARR(nts)

;--------------------------------------------------------------------------------------------------
; Compute layer depths
;--------------------------------------------------------------------------------------------------
dz = FLTARR(nlay,nts)

FOR i = 0, nts - 1 DO BEGIN
   zz = 0. 
   FOR jk = 0, nlay - 1 DO BEGIN
      dz(jk,i) = 2.* ( z_ib(jk,i) - zz )
      zz       = z_ib(jk,i) + dz(jk,i) / 2.
   ENDFOR
ENDFOR

;--------------------------------------------------------------------------------------------------
; Compute the weighted vertical average
;--------------------------------------------------------------------------------------------------

S_i[*] = 0.
FOR i = 0, nts - 1 DO BEGIN
    FOR k = 0, nlay - 1 DO BEGIN
       S_i(i) = S_i(i) + dz(k,i) * c_i(k,i)
    ENDFOR
ENDFOR

;--------------------------------------------------------------------------------------------------

END