## 4 Results
### Definition of Snowpack Wet-Snow Dynamics
#### 4.1.2 Catchment Scale: Melting Runoff Onset Maps  
The plot scale results were extrapolated at the catchment scale. The individual analysis carried out for a single pixel was performed in each of the pixels of the selected catchment for the 3 hydrological years analyzed (Figure 6a,b, Figure 7a,b and Figure 8a,b). First, melting cycles were identified following the methodology proposed in Section 3.1.3. Three melting cycles were defined for the first 2 hydrological years, while four melting cycles  
Figure 5: Definition of four types of Local Minima (red dots) identified for a Mediterranean mountain area. VH represents the theoretical distribution of the \(\Delta\) dB of S-1 SAR backscattering of the cross-polarization VH. FSC represents the temporal distribution of snow cover fraction. Blue dots represent the maximum snow cover fraction. Periods without snow or with dry snow are also specified on the upper axis. The x-axis represents the temporal variation over a hydrological year (September–August) of the different variables, the y-axis represents the corresponding value of the \(\Delta\) dB of S-1 SAR backscattering (left y-axis), and snow cover fraction (right y-axis). were defined in the third hydrological year analyzed (Table 3). The duration of these cycles varied within the year (Table 3). While for the years 2016-2017 and 2017-2018, a long-lasting spring melting cycle was identified (C-3 in each year), and in the case of last year, 2018-2019, three were the melting cycle with longer duration (C-2, C-3 and C-4). Each of these cycles was associated with an increasing event of baseflow in the outlet of the catchment, which was delayed a certain number of days depending on the cycle (Figure 6c, Figure 7c and Figure 8c). A deeper connection between streamflow and melting cycle is analyzed in Section 4.2. For each of these cycles, the Lmo in each pixel was identified as the melting runoff onset over the catchment to produce individual maps of Lmo distribution (Figures 6-8, bottom panels). The first cycle of the year 2016-2017 (Figure 6(c-1)) showed that pixels at a low elevation reached first the Lmo. These Lmos were identified as an LM Type III, that is, they corresponded to shallow snowpack where melting takes place due to an energy exchange between the snowpack and the ground. Pixels at high elevation were distributed without a clear pattern along the other three dates of the cycle. In this case, the melting took place as a consequence of an increase in temperature and radiation (Figure A5, see Appendix A). The Lmo map for the second melting cycle of this year (Figure 6(c-2)) took place during the winter months. Therefore, the colder temperature during this month reduced the number of wet snow pixels during this cycle (non-white pixels in the Lmo maps). Again, the pixels at a lower elevation were those which contributed first to the melting runoff. These LMs were classified also as LM Type III. It is interesting to highlight that some pixels at high elevation also reached their Lmo at the beginning of the melting cycle. This Lmo was classified as Type II, that is, the LM is reached just after the snowfall, but the melting process stopped by a colder temperature that refreezes the liquid water in the snowpack. Finally, the third cycle (Figure 6(c-3)) showed the expected behavior of a spring melting cycle with a clear increase in radiation and temperature during the melting cycle (Figure A5, see Appendix A). The Lmo was delayed with elevation, and the later the Lmo took place the higher its location was. All Lmos in this cycle corresponded to LM Type I. The behavior of the melting cycles of the hydrological year 2017-2018 differed from those described for 2016-2017. In this case, three complete snow cycles took place, that is, snow completely disappeared after each of them. Snowfall took place at the beginning of each cycle followed by an increasing pattern in radiation and temperature that favored the melting (Figure A5, see Appendix A).