NODES defines the number of soil thermal nodes used by the model to explicitly solve soil thermal fluxes. At this time the explicit solution of the soil thermal fluxes occurs only when the model is run with the frozen soil algorithm activated. The model uses a node at the surface, a node at the bottom of the thin (5-15cm) top layer, and a node at the damping depth. If more nodes are defined they are distributed evenly between the bottom of the top layer and the damping depth. More nodes improves the accuracy of the soil heat flux solution, but also increases the computational time. I reccommend at least 5 nodes.