Limit negative values of biological variables

[gresendiz]

Hi everybody!

I'm running the NPZD_Powell model but the output of biological variables have negatives values. I see in the forum that the TS_MPDATA advection scheme is a solution for the problem but I can't use because I'm working in a workstation with OpenMP. Do you have any other idea about how limit the values ​​of biological variables?

Thanks!