Light formulation in npzd_Powell.h without SPITZ cpp flag

[dwhitt]

I'm following up on a forum post entitled NPZD_POWELL without SPITZ CPP option dated Nov 27 2013. This ​post discusses a bug that has gone unfixed as of January 14 2015 when I downloaded the version of ROMS I am currently working with.

To reiterate:

The option to run NPZD_POWELL without SPITZ flag produces an error in the phytoplankton growth rate. Perhaps make the SPITZ option activated by default as that follows Powell et al. 2006, delete the alternative code, and delete the SPITZ CPP option?

For example, in npzd_Powell.h replace the following:

#ifdef SPITZ
          cff1=dtdays*Vm_NO3(ng)*PhyIS(ng)
          cff2=Vm_NO3(ng)*Vm_NO3(ng)
          cff3=PhyIS(ng)*PhyIS(ng)
#else
          cff1=dtdays*Vm_NO3(ng)
#endif
          DO k=1,N(ng)
            DO i=Istr,Iend
#ifdef SPITZ
              cff4=1.0_r8/SQRT(cff2+cff3*Light(i,k)*Light(i,k))
              cff=Bio(i,k,iPhyt)*                                       &
     &            cff1*cff4*Light(i,k)/                                 &
     &            (K_NO3(ng)+Bio(i,k,iNO3_))
#else
              cff=Bio(i,k,iPhyt)*                                       &
     &            cff1*Light(i,k)/                                      &
     &            (K_NO3(ng)+Bio(i,k,iNO3_))
#endif
              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

with:

          cff1=dtdays*Vm_NO3(ng)*PhyIS(ng)
          cff2=Vm_NO3(ng)*Vm_NO3(ng)
          cff3=PhyIS(ng)*PhyIS(ng)
          DO k=1,N(ng)
            DO i=Istr,Iend
              cff4=1.0_r8/SQRT(cff2+cff3*Light(i,k)*Light(i,k))
              cff=Bio(i,k,iPhyt)*                                       &
     &            cff1*cff4*Light(i,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

[arango]

Yes, thank you for bringing this to my attention. I missed this forum message. I also corrected that tangent linear, representer, and adjoint versions of this routine.