\begin{equation}
avail_{crit}(i) = min_{moi,ly}(i,j) + hum_{frac}(j) * ( max_{moi,ly}(i,j) - min_{moi,ly}(i,j))
\end{equation}
where $min_{moi,ly}$ and $max_{moi,ly}$ are last year's minimum and maximum moisture availability, and $hum_{frac}$ is the 
parameter ::$pheno_crit\%hum\_frac$.
