## 4 Results
### Seasonal Variation at Various Locations  
The seasonal variations of the derived dielectric constant are examined in this section, which is necessary for speculating how adequately the dielectric constants are estimated by using reflected GNSS signals. This analysis is used to understand the effect of the environmental change on dielectric constant, as well as vegetation effects. Figure 8 through 10 illustrate the scattering plots separated by the four seasons. The dielectric constants used in analysis are calculated from CYGNSS and SMAP exactly as per the previous section. Each dataset is separated into four seasons: March Equinox, June Solstice, September Equinox, and December Solstice while following the described sequence: (1) determine the Solstice and Equinox dates in each year; (2) gather data from 45 days prior to 45 days after each Solstice/Equinox; (3) apply the data collection process to other years of data; (4) merge the yearly separated data to one variable according to the Solstice and Equinox event; and, finally, (5) draw correlation plots in terms of each season. The entire \begin{table}
\begin{tabular}{c c c c} \hline  & **Yanco** & **TxSON** & **L.W.** \\ \hline RMSE (a) & 5.73 & 6.74 & 6.40 \\ RMSE (b) & 0.13 & 0.18 & 0.17 \\ \hline ubRMSE (a) & 3.31 & 2.08 & 2.32 \\ ubRMSE (b) & 0.07 & 0.04 & 0.05 \\ \hline C.C. (a) & 0.4495 & 0.4680 & 0.4714 \\ C.C. (b) & 0.4116 & 0.4687 & 0.4494 \\ \hline \end{tabular}
\end{table} 
Table 1: The RMSE, ubRMSE, and correlation coefficient results from the scattering plots for measurements at Yanco TxSON and Little Washita (L.W.). separation process is repeated for the same core SMAP validation sites: Yanco, TxSON, and Little Washita. Additionally, it is noted that SMAP Level 3 products are not available from mid-June 2019 to the end of July 2019. On the evening of 19 June 2019, the SMAP satellite turned into safe mode, which is a state of shutting down all instruments and, therefore, data collection was disrupted. After several recovery attempts, SMAP returned to science mode and resumed science data collection on 23 July 2019 [51]. With this absence of observations, the analysis results in June for every seasonal plot will be statistically insufficient and, therefore, cause errors. The dielectric constant that is determined from CYGNSS is correlated with dielectric constant from SMAP in every season, as shown in Figure 8 through 10. RMSE has been calculated for every season in order to evaluate the variance of the derived dielectric constant when compared with this reference. Table 2 lists the results of RMSE, ubRMSE, and correlation coefficient statistics using the dielectric constant measured at Yanco, TxSON, and Little Washita. The equivalent data used to draw Figures 8-10 are adapted to calculate Table 2.  
Figure 8: Seasonal scattering plots centered on the spring and fall equinoxes and summer and winter solstices using the dielectric constant estimated from CYGNSS with the new technique and measured by SMAP at Yanco, Australia. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **RMSE Yanco** & **RMSE TxSON** & **RMSE L.W.** \\ \hline March & 4.32 & 6.43 & 6.23 \\ June & 6.33 & 6.17 & 6.78 \\ September & 6.57 & 6.20 & 5.72 \\ December & 4.65 & 7.69 & 6.56 \\ \hline  & \multicolumn{2}{c}{ubRMSE Yanco} & \multicolumn{2}{c}{ubRMSE TxSON} & \multicolumn{2}{c}{ubRMSE L.W.} \\ \hline March & 2.82 & 1.52 & 2.23 \\ June & 2.77 & 1.75 & 2.69 \\ September & 3.29 & 2.16 & 2.44 \\ December & 2.77 & 2.12 & 2.02 \\ \hline  & C.C. Yanco & C.C. TxSON & C.C. L.W. \\ \hline March & 0.4904 & 0.5010 & 0.5538 \\ June & 0.5944 & 0.4955 & 0.5759 \\ September & 0.6465 & 0.3875 & 0.6279 \\ December & 0.5492 & 0.5217 & 0.6738 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: RMSE, ubRMSE, and correlation coefficient results from the seasonal scattering plots for measurements at Yanco, TxSON, and Little Washita (L.W.).