## 4 Evaluation of Model Developments
### Evaluation of Updated Soil Parametrization  
The updated soil depth and vertical discretization is assessed with surface offline simulations forced with ERA5. A control simulation with the default 4 layers and 2.89 m depth is compared with 2 additional configurations; one using a 10-layer/8 m depth configuration for both water and temperature (OSML10_TW) and in the other, the depth is only extended for temperature while keeping the default 2.89 m depth for water (OSML10_T). Evaluated against the FluxCOM energy flux products, both 10-layer configurations show different signals for the latent and sensible heat fluxes compared to the control standard 4-layers configuration. As an illustrative example, Figure 19 shows that using the 10-layer configuration results in an increase of the sensible heat flux correlation with the FluxCOM product compared to the standard 4-layer configuration, while the latent heat flux shows a general decrease of the correlation with increase over arid areas. Note that in this case, the 10-layer configurations (OSML10_TW) and (OSML10_T) have very similar correlations for flux scores, although the configurations with 8 m for temperature and 2.89 m depth for water has different patterns in subsurface runoff (figures not shown). Following the evaluation of the Land Cover and LAI impact on the diurnal range of LST (see Figure 9, the impact of the increased vertical resolution in the soil is also assessed by evaluating the LST diurnal range. Figure 20 shows the absolute bias difference of the mean diurnal range of LST between the OSML10_TW simulation and the control simulation for JJA (top panel) and SON (bottom panel). Similarly to the reduction of the diurnal range underestimation seen in CLAI (Figure 9), the increased vertical resolution of the soil near the surface also reduces the diurnal range under-estimation over the Iberian Peninsula, South Africa and Eastern South America. In general, the increased vertical resolution drives an increase of the LST diurnal range, due to a reduction of the thermal inertia of the top soil layer. While this compares favourably in most of the MSG disk, in the Western Sahara and Arabian peninsula there is an increase of the bias during June-August (Figure 20a) and in SON over the Arabian peninsula (Figure 20b). This is consistent with the already existing over-estimation of the diurnal range in the control simulation, which is likely associated with limitations of the LSA-SAF product in those regions due to Aerosols (West Sahara) and directional effects (Arabian Peninsula). Both changes in land cover, LAI and vertical resolution in the soil show a positive impact on the LST diurnal range. Further research is needed to understand if these two are additive and to assess the benefits (and limitations) of these two changes in the representation of the LST diurnal cycle. Figure 19: Difference in correlation with FluxCom energy fluxes between the 10-layers soil experiment (OSML10_TW) and the standard 4-layers experiment (**a**) Sensible heat flux; (**b**) Latent heat flux. The impact on soil moisture is evaluated with the ESA-CCI soil moisture product ([PERSON] et al. [83], [PERSON] et al. [84] and [PERSON] et al. [85]). Figure 21 shows the difference of the surface soil moisture correlation with regards to the ESA-CCI surface soil moisture product between simulations using the 10-layer configuration and the current 4-layer configuration for JJA 2018. It is shown that during dry season, the surface soil moisture of the 10-layer configuration correlates better with the ESA-CCI soil moisture as the satellite observation depth matches better the surface layer depth of the 10-layer configuration. Figure 21: Difference of the surface soil moisture correlation with regards to the ESA-CCI surface soil moisture product between simulations using the 10-layer configuration and the current 4-layer configuration for JJA.