## 3 Characteristics of the Waveforms
### Contrasts in the Parameters
#### 3.4.1 Analysis of the 1 Hz Data  
This study used the daily OSI-SAF_ICETYPE dataset in order to determine the ice types of the locations at the 1 Hz data points which matched the geographic information. The ice have three classification types: 1--young ice (sea ice of not more than one winter's growth; in later sections, the AARI ice chart provide an ice type \"first year ice\" which also been defined as \"young ice\" in this study); 2--old ice (sea ice that has survived at least one summer's melt; the ice type of OSI-SAF_ICETYPE dataset called \"ice that survived a summer melt\"); 3--ambiguous ice type. **The Arctic regions:**  
The cumulative probability distributions of each parameter and case are shown in Figure 7. In this study, the four waveform parameters were calculated as follows: AGC of the C Band; AGC of the Ku Band; PP of the C Band; and the PP of the Ku Band. It was found that the more separated the distributions were from one type to another, the easier it was to identify their flags. Figure 7A-H showed that the distributions for all of the four parameters for the young ice, old ice, and ambiguous ice had closely resembled each other within the classes. However, the distributions for the open ice (for example, no ice or very open ice which were the same as seawater) had largely differed from the three ice types. The seawater had taken up a large portion of the low values of the AGC and PP. Additionally, the spread of the two parameters for the ice types was wide. Figure 7A,B,E,F showed that the AGC for the seawater and three ice types had overlaying areas. The AGC of the Ku Band from the HY-2A ALT was found to be particularly outstanding. The values from the overlay areas had resulted in errors when used for the classification process. Since the three ice types were found to be similar to each other, the relatively young ice, ice that survived a summer melt, and ambiguous ice types were categorized as one type in this study. Figure 6: Original and normalized waveforms of the Suboptimal Maximum Likelihood Estimation (SMLE) and Offset Center of Gravity (OCOG) of the diffuse surfaces. It was found in this study that the values of the ice had a wide range (Figure 8). However, the distributions of seawater were very close. The overlaying areas of the AGC from the C Band were determined to be less than those of the Ku Band. The AGC values from the Ku Band of the seawater were almost included in the value range of the sea ice. Additionally, the AGC value of the C Band of the seawater were mainly less than 35. Meanwhile, that of the seawater was consistently larger than 35. The sea ice and seawater were found to be well separated by the PP values of the three types, as detailed in Figure 8A,B,E,F. Figure 8: Histogram of the sea ice and seawater from the HY-2A/B. Note: **A–D** are the results of the HY-2A; **E–H** are the results of the HY-2B. Figure 7: Cumulative probability distributions for the four cases (seawater, young ice, old ice, and ambiguous ice) for the four waveform parameters: AGC of the C Band; AGC of the Ku Band; PP of the C band; PP of the Ku band. Note: **A–D** are the results of the HY-2A; **E–H** are the results of the HY-2B. **The Antarctic regions:**  
Figure 9 showed the cumulative probability distributions for the four different ice types for the four waveform parameters. In the Antarctic, the two different parameters were found to have good discrimination results for the seawater and sea ice. In Figure 9A,B,E,F, the seawater and sea ice have a largely overlap in the region of low value. However, there were less overlap in Figure 9A,B,E,F. These AGC values of overlapping areas has an influence on separate the sea water and sea ice. The PP values were determined to be more effective than the AGC for the classification process. It was observed at low value regions of the PP that the cumulative probability of the seawater had almost reached as high than 90%, and the rate of sea ice was very low.