# Joint Use of Spaceborne Microwave Sensor Data and CYGNSS Data to Observe Tropical Cyclones
## 5 Discussion  
When the SMAP radiometer and CYGNSS data were combined to estimate the position of Hurricane Florence, the black circle does not appear in some subfigures of Figure 9, for example, \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Hurricane** & **Observation Period** & **Observation Data** & **MAE** & **RMSD** & **Correlation** & **Bias (m/s)** & **Number of Samples** \\ \hline \multirow{2}{*}{ Florence} & 08 to 12 September 2018 & SMAP + CYGNSS & 13.0 & 15.6 & 0.6031 & 1.5 & 14 \\ \cline{2-7}  & \multirow{2}{*}{01 to 04 September 2019} & CYGNSS & 15.8 & 17.6 & 0.4348 & 2.0 & 12 \\ \cline{2-7}  & & SMAP + CYGNSS & 15.7 & 18.0 & 0.1782 & \(-\)3.7 & 13 \\ \cline{2-7}  & \multirow{2}{*}{08 to 10 October 2018} & CYGNSS & 6.4 & 8.8 & 0.8216 & \(-\)1.5 & 11 \\ \cline{2-7}  & & SMAP + CYGNSS & 15.1 & 16.1 & 0.2496 & 4.5 & 10 \\ \cline{2-7}  & \multirow{2}{*}{23 to 26 August 2017} & CYGNSS & 6.1 & 7.0 & 0.9745 & 1.2 & 8 \\ \cline{2-7}  & & SMAP + CYGNSS & 8.6 & 11.0 & 0.9677 & 1.0 & 11 \\ \cline{2-7}  & \multirow{2}{*}{03 to 26 August 2017} & CYGNSS & 10.0 & 11.9 & 0.9747 & 1.4 & 9 \\ \cline{2-7}  & & SMAP + CYGNSS & 12.2 & 13.4 & 0.7601 & \(-\)2.5 & 12 \\ \cline{2-7}  & \multirow{2}{*}{30 August to 02 September 2018} & CYGNSS & 12.5 & 13.9 & 0.7423 & \(-\)3.0 & 9 \\ \hline \multirow{2}{*}{ Aletta} & 07 to 09 June 2018 & SMAP + CYGNSS & 10.9 & 12.6 & 0.7385 & \(-\)3.3 & 10 \\ \cline{2-7}  & \multirow{2}{*}{05 to 09 June 2018} & CYGNSS & 11.4 & 13.2 & 0.6197 & \(-\)4.5 & 7 \\ \cline{2-7}  & \multirow{2}{*}{20 to 23 August 2018} & SMAP + CYGNSS & 11.3 & 13.4 & 0.3436 & \(-\)8.5 & 11 \\ \cline{2-7}  & \multirow{2}{*}{05 to 05 September 2018} & CYGNSS & 12.1 & 14.1 & 0.0572 & \(-\)10 & 8 \\ \cline{2-7}  & \multirow{2}{*}{27 to 30 September 2018} & SMAP + CYGNSS & 11.6 & 13.1 & 0.5229 & \(-\)6.4 & 11 \\ \cline{2-7}  & \multirow{2}{*}{05 to 05 September 2018} & CYGNSS & 12.9 & 13.6 & 0.4040 & \(-\)8.9 & 8 \\ \hline \multirow{2}{*}{ [PERSON]} & \multirow{2}{*}{16 to 19 September 2019} & SMAP + CYGNSS & 7.7 & 8.6 & 0.9034 & \(-\)1.8 & 10 \\ \cline{2-7}  & \multirow{2}{*}{05 to 05 September 2019} & CYGNSS & 9.6 & 11.1 & 0.2471 & \(-\)8.8 & 8 \\ \hline \multirow{2}{*}{ Lorenzo} & \multirow{2}{*}{27 to 29 September 2019} & SMAP + CYGNSS & 13.3 & 14.7 & 0.6040 & \(-\)5.1 & 10 \\ \cline{2-7}  & \multirow{2}{*}{05 to 05 September 2018} & CYGNSS & 15.3 & 16.6 & 0.5603 & \(-\)5.7 & 7 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparison between the estimated and NHC maximum wind speeds of observed hurricanes. Figure 12: Comparison between the estimated maximum wind speeds of Hurricane Florence and the best track peak winds estimated by the NHC from 8 to 12 September 2018. Figure 9(a2). This is due to the fact that the fusion result shown in such subfigures does not contain a complete structure of the TC, mainly because of the sparse tracks of CYGNSS satellites. As a result, the TC center-fixing algorithm cannot determine the center position of the TC. Furthermore, when our method was used to estimate the tracks of the ten hurricanes listed in Table 1 compared to the NHC best tracks, the MAE values range between 18.4 and 46 km, and the SD values vary between 15.1 and 28.2 km. To further evaluate the performance of our method, a comparison of the track of Hurricane Florence estimated with GOES-16 GeoColor images using the Automated Rotational Center Hurricane EYE Retrieval (ARCHER) TC center-fixing algorithm [38] was also made, as shown in Figure 11. We found that the MAE was 40.1 km and the SD was 25.1 km. In addition, compared to the TC center automatic determination method based on HY-2 and QuikSCAT wind vector products that is described in [39], our method achieves higher accuracy in the estimation of the TC track according to the MAE and SD values, and it can also monitor the TC track with a shorter time interval because of the combination of the CYGNSS data.