# Evaluation of HY-2 Series Satellites Mapping Capability on Mesoscale Eddies
## 3 Results
### Comparing Identified Mesoscale Eddies
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline  & & \multicolumn{3}{c}{**High Latitudes**} & \multicolumn{3}{c}{**Middle Latitudes**} & \multicolumn{3}{c}{**Low Latitudes**} \\ \hline  & **Model** & **Reference** & **Evaluation** & **Model** & **Reference** & **Evaluation** & **Model** & **Reference** & **Evaluation** \\  & **Group** & **Group** & **Group** & **Group** & **Group** & **Group** & **Group** & **Group** \\ \hline Ed. Amount & 114 & 110 & 108 & 291 & 306 & 304 & 117 & 52 & 55 \\ Ed. Radius/km & 25.10 & 32.20 & 32.64 & 69.04 & 73.20 & 72.42 & 56.19 & 109.03 & 104.96 \\ Ed. Amplitude/cm & \(-\)4.15 & \(-\)4.67 & \(-\)4.70 & \(-\)10.53 & \(-\)17.64 & \(-\)21.62 & 4.26 & 5.11 & 4.84 \\ \hline \end{tabular}
\end{table} 
Table 3: Eddy amount, radius and amplitude for models, reference groups and evaluation groups at high, middle and low latitudes. Unit of radius is km and unit of amplitude is m.  
Figure 5: Statistical histograms of radius at (**a**) high latitudes, (**b**) middle latitudes, and (**c**) low latitudes. Statistical histograms of amplitude at (**d**) high latitudes, (**e**) middle latitudes, and (**f**) low latitudes. Red boxes are for the model datasets, blue boxes for reference groups and green boxes for evaluation groups. Unit of radius is km and unit of amplitude is m.  
Figure 6: Distribution of eddies amount generated from models, reference groups and evaluation groups at (**a**–**c**) high latitudes, (**d**–**f**) middle latitudes, and (**g**–**i**) low latitudes. The resolution of the grid is 0.25\({}^{\circ}\)\(\times\) 0.25\({}^{\circ}\). The distribution of eddy radius is shown in Figure 7, and the value of each grid represents the average eddy radius identified in this location. As can be seen from Figure 7, the spatial distribution of eddy radius is very well represented at high latitudes. However, for other regions, in the case of middle latitudes with a similar orbital density to low latitudes, middle latitudes have better eddy fields, but low latitudes do not reconstruct satisfactory eddy fields. At low latitudes, the eddy radius in gridded SSH fields is larger than in the model, indicating that some smaller mesoscale eddies are captured as bigger structures. The distribution of eddy amplitude is shown in Figure 8, and the value of each grid represents the average eddy amplitude identified in this location. The spatial distribution of eddy amplitude variation is well reconstructed at both high latitudes and middle latitudes, while at low latitudes, both eddy datasets from gridded products are not able to capture enough eddies with small amplitude. However, the evaluation groups add more information on the amplitude of the eddy field than the reference groups to alleviate eddy underestimation. Figure 7: Distribution of eddies radius generated from models, reference groups and evaluation groups at (**a–c**) high latitudes, (**d–f**) middle latitudes, and (**g–i**) low latitudes. The resolution of the grid is \(0.25^{\circ}\)\(\times\)\(0.25^{\circ}\). Unit of radius in km.