(a): sketch of a depth profile derived by the exponential approach. Node distances and volume sizes increase in an exponential manner with greater depths. (b): comparison of the upper 10 cm (≈16 nodes) of the exponential 29-nodes approach adopted for this study and the irregular 29-nodes approach in the previous study of Gläser & Gläser (2019). We note the higher node density close to the surface in the new approach leading to finer resolution of the nonlinear behavior of the temperature distribution.