# Retrieval of Cloud Ice Water Path from FY-3F MWTS and MWHS
## 4 Results  
### Spatio-Temporal Evolution Characteristics of IWP Retrieval Products  
Figure 4 illustrates the daily mean values and differences in IWP retrieved from two satellite datasets (FY-3F and METOP-C) over global, oceanic, and terrestrial regions from June to July 2024. Figure 3: Scatter plots illustrating the statistical relationship between the brightness temperatures at the 89 GHz (**a**) and 166 GHz (**b**) channels, derived from the 23.8 GHz and 31.4 GHz channel data, and the corresponding observed brightness temperatures at these channels. The black line denotes the 1:1 reference line, while the red line represents the fitted regression line between the two datasets. The Figure 4 shows that the IWP retrieved from FY-3F and METOP-C data exhibit a consistent global variation, with a small difference between the two datasets. The average difference in IWP is approximately 0.021 kg/m\({}^{2}\), with a maximum difference of 0.092 kg/m\({}^{2}\). In oceanic and terrestrial regions, the IWP values also follow a consistent variation, with differences of 0.035 kg/m\({}^{2}\) and \(-\)0.027 kg/m\({}^{2}\), respectively. The maximum differences between the two datasets in these regions are 0.063 kg/m\({}^{2}\) in oceanic regions and \(-\)0.062 kg/m\({}^{2}\) in terrestrial regions. Despite the use of different retrieval algorithms for IWP in oceanic and terrestrial regions, the results show a high degree of accuracy. However, the IWP retrieved from FY-3F data is slightly lower than that from METOP-C data in terrestrial regions, while the reverse is observed in oceanic regions. This discrepancy may be related to differences in satellite observation times, instrument characteristics, and algorithmic variations, warranting further investigation. In summary, despite the use of distinct algorithms for oceanic and terrestrial regions, the accuracy of the IWP retrieved from both datasets is relatively consistent, demonstrating that FY-3F data can effectively retrieve IWP globally. To analyze the seasonal variations in IWP, this study used FY-3F data from June and July 2024. The retrieved IWP values were averaged daily to investigate long-term variations. Figure 5 depicts the daily average IWP variations over oceanic regions. To validate these findings, a comparative analysis was performed using concurrent ERA5 data and METOP-C products. Figure 5 presents the variations of IWP across different latitude  
Figure 4: Daily mean changes and differences in IWP over global, oceanic, and terrestrial regions based on data from FY-3F and METOP-C satellites between June and July 2024.  
ranges over oceanic regions. The IWP values retrieved from satellite data show a high degree of consistency with ERA5 variations in low-latitude regions (30\({}^{\circ}\)S-30\({}^{\circ}\)N). However, in mid-to-high latitude regions (30-60\({}^{\circ}\)N and 30-60\({}^{\circ}\)S), the IWP values from ERA5 are generally higher than those retrieved from satellite data. This aligns with [PERSON] et al., who observed that ERA5 struggles to accurately simulate the spatial distribution of atmospheric ice clouds at mid-to-high latitudes and often overestimates cloud ice in these regions [23]. Additionally, discrepancies between satellite-retrieved IWP and ERA5 data differ between the Northern and Southern Hemispheres. In the Northern Hemisphere, the average IWP value from ERA5 is 0.18 kg/m\({}^{2}\), significantly higher than the satellite-retrieved value of 0.12 kg/m\({}^{2}\). Conversely, in the Southern Hemisphere, the average IWP value from ERA5 is 0.17 kg/m\({}^{2}\), with a smaller difference from the retrieved value of 0.14 kg/m\({}^{2}\). [PERSON] and [PERSON] noted that ice cloud content is higher in winter than in summer, a pattern consistent with our retrieval results [30]. In comparison, ERA5 exhibits less pronounced seasonal variations in IWP, suggesting that our IWP retrieval more accurately captures expected seasonal variations.