SUBROUTINE biology (ng,tile) ! !svn $Id: npzd_Franks.h 889 2018-02-10 03:32:52Z arango $ !************************************************** Hernan G. Arango *** ! Copyright (c) 2002-2019 The ROMS/TOMS Group Craig V. Lewis ! ! Licensed under a MIT/X style license ! ! See License_ROMS.txt ! !*********************************************************************** ! ! ! Nutrient-Phytoplankton-Zooplankton-Detritus Model. ! ! ! ! This routine computes the biological sources and sinks and adds ! ! then the global biological fields. ! ! ! ! Reference: ! ! ! ! Franks et al, 1986: Behavior of simple plankton model with ! ! food-level acclimation by herbivores, Marine Biology, 91, ! ! 121-129. ! ! ! ! Adapted from code written originally by Craig V. Lewis. ! ! ! !*********************************************************************** ! USE mod_param USE mod_grid USE mod_ncparam USE mod_ocean USE mod_stepping ! ! Imported variable declarations. ! integer, intent(in) :: ng, tile ! ! Local variable declarations. ! #include "tile.h" ! ! Set header file name. ! #ifdef DISTRIBUTE IF (Lbiofile(iNLM)) THEN #else IF (Lbiofile(iNLM).and.(tile.eq.0)) THEN #endif Lbiofile(iNLM)=.FALSE. BIONAME(iNLM)=__FILE__ END IF ! #ifdef PROFILE CALL wclock_on (ng, iNLM, 15, __LINE__, __FILE__) #endif CALL biology_tile (ng, tile, & & LBi, UBi, LBj, UBj, N(ng), NT(ng), & & IminS, ImaxS, JminS, JmaxS, & & nstp(ng), nnew(ng), & #ifdef MASKING & GRID(ng) % rmask, & #endif & GRID(ng) % Hz, & & GRID(ng) % z_r, & & GRID(ng) % z_w, & & OCEAN(ng) % t) #ifdef PROFILE CALL wclock_off (ng, iNLM, 15, __LINE__, __FILE__) #endif RETURN END SUBROUTINE biology ! !----------------------------------------------------------------------- SUBROUTINE biology_tile (ng, tile, & & LBi, UBi, LBj, UBj, UBk, UBt, & & IminS, ImaxS, JminS, JmaxS, & & nstp, nnew, & #ifdef MASKING & rmask, & #endif & Hz, z_r, z_w, & & t) !----------------------------------------------------------------------- ! USE mod_param USE mod_biology USE mod_ncparam USE mod_scalars ! ! Imported variable declarations. ! integer, intent(in) :: ng, tile integer, intent(in) :: LBi, UBi, LBj, UBj, UBk, UBt integer, intent(in) :: IminS, ImaxS, JminS, JmaxS integer, intent(in) :: nstp, nnew #ifdef ASSUMED_SHAPE # ifdef MASKING real(r8), intent(in) :: rmask(LBi:,LBj:) # endif real(r8), intent(in) :: Hz(LBi:,LBj:,:) real(r8), intent(in) :: z_r(LBi:,LBj:,:) real(r8), intent(in) :: z_w(LBi:,LBj:,0:) real(r8), intent(inout) :: t(LBi:,LBj:,:,:,:) #else # ifdef MASKING real(r8), intent(in) :: rmask(LBi:UBi,LBj:UBj) # endif real(r8), intent(in) :: Hz(LBi:UBi,LBj:UBj,UBk) real(r8), intent(in) :: z_r(LBi:UBi,LBj:UBj,UBk) real(r8), intent(in) :: z_w(LBi:UBi,LBj:UBj,0:UBk) real(r8), intent(inout) :: t(LBi:UBi,LBj:UBj,UBk,3,UBt) #endif ! ! Local variable declarations. ! integer, parameter :: Nsink = 1 integer :: Iter, i, ibio, isink, itrc, itrmx, j, k, ks integer, dimension(Nsink) :: idsink real(r8), parameter :: eps = 1.0e-16_r8 real(r8) :: cff, cff1, cff2, cff3, dtdays real(r8) :: cffL, cffR, cu, dltL, dltR real(r8), dimension(Nsink) :: Wbio integer, dimension(IminS:ImaxS,N(ng)) :: ksource real(r8), dimension(IminS:ImaxS,N(ng),NT(ng)) :: Bio real(r8), dimension(IminS:ImaxS,N(ng),NT(ng)) :: Bio_old real(r8), dimension(IminS:ImaxS,0:N(ng)) :: FC real(r8), dimension(IminS:ImaxS,N(ng)) :: Hz_inv real(r8), dimension(IminS:ImaxS,N(ng)) :: Hz_inv2 real(r8), dimension(IminS:ImaxS,N(ng)) :: Hz_inv3 real(r8), dimension(IminS:ImaxS,N(ng)) :: WL real(r8), dimension(IminS:ImaxS,N(ng)) :: WR real(r8), dimension(IminS:ImaxS,N(ng)) :: bL real(r8), dimension(IminS:ImaxS,N(ng)) :: bR real(r8), dimension(IminS:ImaxS,N(ng)) :: qc #include "set_bounds.h" ! !----------------------------------------------------------------------- ! Add biological Source/Sink terms. !----------------------------------------------------------------------- ! ! Avoid computing source/sink terms if no biological iterations. ! IF (BioIter(ng).le.0) RETURN ! ! Set time-stepping according to the number of iterations. ! dtdays=dt(ng)*sec2day/REAL(BioIter(ng),r8) ! ! Set vertical sinking indentification vector. ! idsink(1)=iSDet ! Small detritus ! ! Set vertical sinking velocity vector in the same order as the ! identification vector, IDSINK. ! Wbio(1)=wDet(ng) ! Small detritus ! ! Compute inverse thickness to avoid repeated divisions. ! J_LOOP : DO j=Jstr,Jend DO k=1,N(ng) DO i=Istr,Iend Hz_inv(i,k)=1.0_r8/Hz(i,j,k) END DO END DO DO k=1,N(ng)-1 DO i=Istr,Iend Hz_inv2(i,k)=1.0_r8/(Hz(i,j,k)+Hz(i,j,k+1)) END DO END DO DO k=2,N(ng)-1 DO i=Istr,Iend Hz_inv3(i,k)=1.0_r8/(Hz(i,j,k-1)+Hz(i,j,k)+Hz(i,j,k+1)) END DO END DO ! ! Extract biological variables from tracer arrays, place them into ! scratch arrays, and restrict their values to be positive definite. ! At input, all tracers (index nnew) from predictor step have ! transport units (m Tunits) since we do not have yet the new ! values for zeta and Hz. These are known after the 2D barotropic ! time-stepping. ! DO itrc=1,NBT ibio=idbio(itrc) DO k=1,N(ng) DO i=Istr,Iend Bio_old(i,k,ibio)=t(i,j,k,nstp,ibio) END DO END DO END DO ! ! Determine Correction for negativity. ! DO k=1,N(ng) DO i=Istr,Iend cff1=MAX(0.0_r8,eps-Bio_old(i,k,iNO3_))+ & & MAX(0.0_r8,eps-Bio_old(i,k,iPhyt))+ & & MAX(0.0_r8,eps-Bio_old(i,k,iZoop))+ & & MAX(0.0_r8,eps-Bio_old(i,k,iSDet)) ! ! If correction needed, determine the largest pool to debit. ! IF (cff1.gt.0.0) THEN itrmx=idbio(1) cff=t(i,j,k,nstp,itrmx) DO ibio=idbio(2),idbio(NBT) IF (t(i,j,k,nstp,ibio).gt.cff) THEN itrmx=ibio cff=t(i,j,k,nstp,ibio) END IF END DO ! ! Update new values. ! DO itrc=1,NBT ibio=idbio(itrc) Bio(i,k,ibio)=MAX(eps,Bio_old(i,k,ibio))- & & cff1*(SIGN(0.5_r8, & & REAL(itrmx-ibio,r8)**2)+ & & SIGN(0.5_r8, & & -REAL(itrmx-ibio,r8)**2)) END DO ELSE DO itrc=1,NBT ibio=idbio(itrc) Bio(i,k,ibio)=Bio_old(i,k,ibio) END DO END IF END DO END DO ! !======================================================================= ! Start internal iterations to achieve convergence of the nonlinear ! backward-implicit solution. !======================================================================= ! ! During the iterative procedure a series of fractional time steps are ! performed in a chained mode (splitting by different biological ! conversion processes) in sequence of the main food chain. In all ! stages the concentration of the component being consumed is treated ! in fully implicit manner, so the algorithm guarantees non-negative ! values, no matter how strong s the concentration of active consuming ! component (Phytoplankton or Zooplankton). The overall algorithm, ! as well as any stage of it, is formulated in conservative form ! (except explicit sinking) in sense that the sum of concentration of ! all components is conserved. ! ! In the implicit algorithm, we have for example (N: nutrient, ! P: phytoplankton), ! ! N(new) = N(old) - uptake * P(old) uptake = mu * N / (Kn + N) ! {Michaelis-Menten} ! below, we set ! The N in the numerator of ! cff = mu * P(old) / (Kn + N(old)) uptake is treated implicitly ! as N(new) ! ! so the time-stepping of the equations becomes: ! ! N(new) = N(old) / (1 + cff) (1) when substracting a sink term, ! consuming, divide by (1 + cff) ! and ! ! P(new) = P(old) + cff * N(new) (2) when adding a source term, ! growing, add (cff * source) ! ! Notice that if you substitute (1) in (2), you will get: ! ! P(new) = P(old) + cff * N(old) / (1 + cff) (3) ! ! If you add (1) and (3), you get ! ! N(new) + P(new) = N(old) + P(old) ! ! implying conservation regardless how "cff" is computed. Therefore, ! this scheme is unconditionally stable regardless of the conversion ! rate. It does not generate negative values since the constituent ! to be consumed is always treated implicitly. It is also biased ! toward damping oscillations. ! ! The iterative loop below is to iterate toward an universal Backward- ! Euler treatment of all terms. So if there are oscillations in the ! system, they are only physical oscillations. These iterations, ! however, do not improve the accuaracy of the solution. ! ITER_LOOP: DO Iter=1,BioIter(ng) ! ! Nutrient uptake by phytoplankton. ! cff1=dtdays*Vm_NO3(ng) DO k=1,N(ng) DO i=Istr,Iend cff=Bio(i,k,iPhyt)* & & cff1*EXP(K_ext(ng)*z_r(i,j,k))/ & & (K_NO3(ng)+Bio(i,k,iNO3_)) Bio(i,k,iNO3_)=Bio(i,k,iNO3_)/ & & (1.0_r8+cff) Bio(i,k,iPhyt)=Bio(i,k,iPhyt)+ & & Bio(i,k,iNO3_)*cff END DO END DO ! ! Phytoplankton grazing by Zooplankton and mortality to Detritus ! (rate: PhyMR). ! cff1=dtdays*ZooGR(ng) cff2=dtdays*PhyMR(ng) cff3=K_phy(ng)*K_phy(ng) DO k=1,N(ng) DO i=Istr,Iend cff=Bio(i,k,iZoop)*Bio(i,k,iPhyt)*cff1/ & & (cff3+Bio(i,k,iPhyt)*Bio(i,k,iPhyt)) Bio(i,k,iPhyt)=Bio(i,k,iPhyt)/ & & (1.0_r8+cff+cff2) Bio(i,k,iZoop)=Bio(i,k,iZoop)+ & & Bio(i,k,iPhyt)*cff*(1.0_r8-ZooGA(ng)) Bio(i,k,iSDet)=Bio(i,k,iSDet)+ & & Bio(i,k,iPhyt)* & & (cff2+cff*(ZooGA(ng)-ZooEC(ng))) Bio(i,k,iNO3_)=Bio(i,k,iNO3_)+ & & Bio(i,k,iPhyt)*cff*ZooEC(ng) END DO END DO ! ! Zooplankton excretion to nutrients and mortality to Detritus. ! cff1=1.0_r8/(1.0_r8+dtdays*(ZooMR(ng)+ZooMD(ng))) cff2=dtdays*ZooMR(ng) cff3=dtdays*ZooMD(ng) DO k=1,N(ng) DO i=Istr,Iend Bio(i,k,iZoop)=Bio(i,k,iZoop)*cff1 Bio(i,k,iNO3_)=Bio(i,k,iNO3_)+ & & Bio(i,k,iZoop)*cff2 Bio(i,k,iSDet)=Bio(i,k,iSDet)+ & & Bio(i,k,iZoop)*cff3 END DO END DO ! ! Detritus breakdown to nutrients. ! cff1=dtdays*DetRR(ng) cff2=1.0_r8/(1.0_r8+cff1) DO k=1,N(ng) DO i=Istr,Iend Bio(i,k,iSDet)=Bio(i,k,iSDet)*cff2 Bio(i,k,iNO3_)=Bio(i,k,iNO3_)+ & & Bio(i,k,iSDet)*cff1 END DO END DO ! !----------------------------------------------------------------------- ! Vertical sinking terms. !----------------------------------------------------------------------- ! ! Reconstruct vertical profile of selected biological constituents ! "Bio(:,:,isink)" in terms of a set of parabolic segments within each ! grid box. Then, compute semi-Lagrangian flux due to sinking. ! SINK_LOOP: DO isink=1,Nsink ibio=idsink(isink) ! ! Copy concentration of biological particulates into scratch array ! "qc" (q-central, restrict it to be positive) which is hereafter ! interpreted as a set of grid-box averaged values for biogeochemical ! constituent concentration. ! DO k=1,N(ng) DO i=Istr,Iend qc(i,k)=Bio(i,k,ibio) END DO END DO ! DO k=N(ng)-1,1,-1 DO i=Istr,Iend FC(i,k)=(qc(i,k+1)-qc(i,k))*Hz_inv2(i,k) END DO END DO DO k=2,N(ng)-1 DO i=Istr,Iend dltR=Hz(i,j,k)*FC(i,k) dltL=Hz(i,j,k)*FC(i,k-1) cff=Hz(i,j,k-1)+2.0_r8*Hz(i,j,k)+Hz(i,j,k+1) cffR=cff*FC(i,k) cffL=cff*FC(i,k-1) ! ! Apply PPM monotonicity constraint to prevent oscillations within the ! grid box. ! IF ((dltR*dltL).le.0.0_r8) THEN dltR=0.0_r8 dltL=0.0_r8 ELSE IF (ABS(dltR).gt.ABS(cffL)) THEN dltR=cffL ELSE IF (ABS(dltL).gt.ABS(cffR)) THEN dltL=cffR END IF ! ! Compute right and left side values (bR,bL) of parabolic segments ! within grid box Hz(k); (WR,WL) are measures of quadratic variations. ! ! NOTE: Although each parabolic segment is monotonic within its grid ! box, monotonicity of the whole profile is not guaranteed, ! because bL(k+1)-bR(k) may still have different sign than ! qc(i,k+1)-qc(i,k). This possibility is excluded, ! after bL and bR are reconciled using WENO procedure. ! cff=(dltR-dltL)*Hz_inv3(i,k) dltR=dltR-cff*Hz(i,j,k+1) dltL=dltL+cff*Hz(i,j,k-1) bR(i,k)=qc(i,k)+dltR bL(i,k)=qc(i,k)-dltL WR(i,k)=(2.0_r8*dltR-dltL)**2 WL(i,k)=(dltR-2.0_r8*dltL)**2 END DO END DO cff=1.0E-14_r8 DO k=2,N(ng)-2 DO i=Istr,Iend dltL=MAX(cff,WL(i,k )) dltR=MAX(cff,WR(i,k+1)) bR(i,k)=(dltR*bR(i,k)+dltL*bL(i,k+1))/(dltR+dltL) bL(i,k+1)=bR(i,k) END DO END DO DO i=Istr,Iend FC(i,N(ng))=0.0_r8 ! NO-flux boundary condition #if defined LINEAR_CONTINUATION bL(i,N(ng))=bR(i,N(ng)-1) bR(i,N(ng))=2.0_r8*qc(i,N(ng))-bL(i,N(ng)) #elif defined NEUMANN bL(i,N(ng))=bR(i,N(ng)-1) bR(i,N(ng))=1.5_r8*qc(i,N(ng))-0.5_r8*bL(i,N(ng)) #else bR(i,N(ng))=qc(i,N(ng)) ! default strictly monotonic bL(i,N(ng))=qc(i,N(ng)) ! conditions bR(i,N(ng)-1)=qc(i,N(ng)) #endif #if defined LINEAR_CONTINUATION bR(i,1)=bL(i,2) bL(i,1)=2.0_r8*qc(i,1)-bR(i,1) #elif defined NEUMANN bR(i,1)=bL(i,2) bL(i,1)=1.5_r8*qc(i,1)-0.5_r8*bR(i,1) #else bL(i,2)=qc(i,1) ! bottom grid boxes are bR(i,1)=qc(i,1) ! re-assumed to be bL(i,1)=qc(i,1) ! piecewise constant. #endif END DO ! ! Apply monotonicity constraint again, since the reconciled interfacial ! values may cause a non-monotonic behavior of the parabolic segments ! inside the grid box. ! DO k=1,N(ng) DO i=Istr,Iend dltR=bR(i,k)-qc(i,k) dltL=qc(i,k)-bL(i,k) cffR=2.0_r8*dltR cffL=2.0_r8*dltL IF ((dltR*dltL).lt.0.0_r8) THEN dltR=0.0_r8 dltL=0.0_r8 ELSE IF (ABS(dltR).gt.ABS(cffL)) THEN dltR=cffL ELSE IF (ABS(dltL).gt.ABS(cffR)) THEN dltL=cffR END IF bR(i,k)=qc(i,k)+dltR bL(i,k)=qc(i,k)-dltL END DO END DO ! ! After this moment reconstruction is considered complete. The next ! stage is to compute vertical advective fluxes, FC. It is expected ! that sinking may occurs relatively fast, the algorithm is designed ! to be free of CFL criterion, which is achieved by allowing ! integration bounds for semi-Lagrangian advective flux to use as ! many grid boxes in upstream direction as necessary. ! ! In the two code segments below, WL is the z-coordinate of the ! departure point for grid box interface z_w with the same indices; ! FC is the finite volume flux; ksource(:,k) is index of vertical ! grid box which contains the departure point (restricted by N(ng)). ! During the search: also add in content of whole grid boxes ! participating in FC. ! cff=dtdays*ABS(Wbio(isink)) DO k=1,N(ng) DO i=Istr,Iend FC(i,k-1)=0.0_r8 WL(i,k)=z_w(i,j,k-1)+cff WR(i,k)=Hz(i,j,k)*qc(i,k) ksource(i,k)=k END DO END DO DO k=1,N(ng) DO ks=k,N(ng)-1 DO i=Istr,Iend IF (WL(i,k).gt.z_w(i,j,ks)) THEN ksource(i,k)=ks+1 FC(i,k-1)=FC(i,k-1)+WR(i,ks) END IF END DO END DO END DO ! ! Finalize computation of flux: add fractional part. ! DO k=1,N(ng) DO i=Istr,Iend ks=ksource(i,k) cu=MIN(1.0_r8,(WL(i,k)-z_w(i,j,ks-1))*Hz_inv(i,ks)) FC(i,k-1)=FC(i,k-1)+ & & Hz(i,j,ks)*cu* & & (bL(i,ks)+ & & cu*(0.5_r8*(bR(i,ks)-bL(i,ks))- & & (1.5_r8-cu)* & & (bR(i,ks)+bL(i,ks)- & & 2.0_r8*qc(i,ks)))) END DO END DO DO k=1,N(ng) DO i=Istr,Iend Bio(i,k,ibio)=qc(i,k)+(FC(i,k)-FC(i,k-1))*Hz_inv(i,k) END DO END DO END DO SINK_LOOP END DO ITER_LOOP ! !----------------------------------------------------------------------- ! Update global tracer variables: Add increment due to BGC processes ! to tracer array in time index "nnew". Index "nnew" is solution after ! advection and mixing and has transport units (m Tunits) hence the ! increment is multiplied by Hz. Notice that we need to subtract ! original values "Bio_old" at the top of the routine to just account ! for the concentractions affected by BGC processes. This also takes ! into account any constraints (non-negative concentrations, carbon ! concentration range) specified before entering BGC kernel. If "Bio" ! were unchanged by BGC processes, the increment would be exactly ! zero. Notice that final tracer values, t(:,:,:,nnew,:) are not ! bounded >=0 so that we can preserve total inventory of nutrients ! when advection causes tracer concentration to go negative. !----------------------------------------------------------------------- ! DO itrc=1,NBT ibio=idbio(itrc) DO k=1,N(ng) DO i=Istr,Iend cff=Bio(i,k,ibio)-Bio_old(i,k,ibio) t(i,j,k,nnew,ibio)=t(i,j,k,nnew,ibio)+cff*Hz(i,j,k) END DO END DO END DO END DO J_LOOP RETURN END SUBROUTINE biology_tile