## 5 Conclusions  
Nowadays, most of radiometric soil moisture (SM) retrieval and disaggregation algorithms employ the instantaneous land surface temperature (LST) in their approaches. Nevertheless, alternative LST-derived parameters, such as the daily maximum LST, may provide a better representation of the SM-LST relationship than the instantaneous LST. In order to analyze this hypothesis, we evaluated the SM and LST dynamics at daily and seasonal scales using four years of data (2011-2014) from both in situ and satellite observations acquired over the REMEDHUS network, located at the central part of the river Duero basin in Spain. The main objective was to better understand the fundamental link between the instantaneous SM (at the SMOS passes over this region) and several LST-derived parameters, and assess this relationship through the SM-LST coupling/decoupling, the evapotranspiration process and the thermal inertia. Furthermore, the SM-LST interaction was studied with the direct variables in absolute values and with their anomalies, subtracting the mean seasonal cycle of each variable (or climatology), to separate out seasonality. Considering the entire study period, SM and LST are, as expected, anticorrelated. At the daily scale, results from in situ data show that instantaneous SM exhibits stronger anticorrelation to daily maximum LST (R \(\approx-0.7\)) than to the other LST-derived parameters (i.e., instantaneous LST, daily mean LST, daily median LST, daily minimum LST and LST diurnal range). When using satellite data, stronger anticorrelation is obtained between SMOS SM and MODIS LST Aqua (or Terra) day (R \(\approx-0.7\)) than night (R \(\approx-0.4\) to \(-0.5\)). This is consistent with the in situ analysis, since the time of MODIS LST Aqua (or Terra) day is closer to the time of daily maximum LST, which is also the time of maximum potential evapotranspiration (i.e., when there is a higher atmospheric demand of water). For the anomaly time-series, results from in situ data show that LST diurnal range presents the strongest anticorrelation with SM (R \(\approx-0.3\)), followed by daily maximum LST (R \(\approx-0.3\)). This indicates that maximum LST and LST diurnal range provide complementary information of the SM-LST relationship. When using satellite data, the strongest anticorrelation is obtained with MODIS LST Aqua (or Terra) day (R \(\approx-0.5\)). Further research using a geostationary satellite such as MSG SEVIRI with a temporal resolution of 15 min. would be needed to further evaluate the relationship of SM with LST diurnal range. In addition, the SM-LST space of the normalized occurrence frequency density diagrams display a triangular shape in both ground-based and spaceborne observations. The seasonal dependency of the correlation was also studied. Results from in situ data show a strong anticorrelation between instantaneous SM and daily maximum LST in spring, summer and autumn seasons (R \(\approx-0.5\) to \(-0.7\)), revealing a SM-LST coupling. By contrast, a very low correlation is obtained in winter (R \(\approx\) +0.3), which indicates a clear SM-LST decoupling. When using satellite data, results confirm a SM-LST coupling in spring, summer and autumn (R \(\approx-0.4\) to \(-0.7\)), and a SM-LST decoupling in winter (R \(\approx-0.3\)). For the anomaly time-series, the highest correlation is obtained in summer for in situ data (R \(\approx-0.5\)). This can be to the related to the fact that an increase