# Retrieval of Cloud Ice Water Path from FY-3F MWTS and MWHS
## 4 Results
### Comparison Between FY-3F Retrieval Results and ERA5 Data
As illustrated in Figure 8,  
Figure 7: IWP retrieval results in tropical and extratropical cyclones: (**a**) IWP from FY-3F observation data in tropical cyclone, (**b**) IWP from FY-3F observation data in extratropical cyclone, (**c**) IWP from ERA5 data in tropical cyclone, and (**d**) IWP from ERA5 data in extratropical cyclone. the blue line represents IWP retrieved using FY-3F data, while the green line represents IWP data from ERA5. The results indicate that both datasets exhibit similar numerical distribution characteristics, with values concentrated in the low-value range and relatively sparse in the high-value range. However, ERA5 IWP data are more tightly concentrated in the low-value range compared to FY-3F retrievals. This discrepancy may result from the lower resolution of ERA5 data, which are derived from numerical model calculations and may lack the ability to capture detailed ice cloud information. Conversely, FY-3F IWP retrievals, based on a higher-resolution physical retrieval algorithm, provide more detailed and accurate representations of ice clouds, leading to more realistic outcomes. Figure 9 displays the histogram distributions of the differences between IWP retrievals using FY-3F data and ERA5 reanalysis data. Panel (a) shows the difference distribution over ocean regions, while panel (b) illustrates the distribution over land regions. Panel (c) and (d) illustrate the distributions of differences between the two datasets for high and low IWP values in oceanic regions, respectively. As observed in Figure 7, despite employing different methods to estimate the brightness temperature at the base of ice clouds over oceans and land, the IWP retrievals from FY-3F data closely align with ERA5 data in both regions. The differences are predominantly centered around zero, with most values falling within the range of \(-\)0.25 to 0.25 kg/m\({}^{2}\), and only a few outliers displaying significant discrepancies. Additionally, the histogram distributions of both datasets follow a normal distribution. Over oceans, the mean IWP retrieved from FY-3F data is 0.21 kg/m\({}^{2}\), compared to 0.15 kg/m\({}^{2}\) from ERA5 data. Over land, the mean IWP from FY-3F data is 0.06 kg/m\({}^{2}\), compared to 0.08 kg/m\({}^{2}\) from ERA5 data. These findings indicate a high level of consistency between IWP retrievals from FY-3F satellite observations and ERA5 reanalysis data across both oceanic and terrestrial regions. Figure 8: Probability density distribution and cumulative distribution function curves of IWP: **(left)** 30\({}^{\circ}\)N–60\({}^{\circ}\)N, **(middle)** 30\({}^{\circ}\)N–30\({}^{\circ}\)S, and **(right)** 30\({}^{\circ}\)S–60\({}^{\circ}\)S. The blue bars represent the probability density distribution, and the blue lines represent the cumulative distribution function curves retrieved from FY-3F observations, while the cyan bars and lines represent corresponding values from ERA5 reanalysis data. The red and yellow bars represent the probability density distributions of IWP values equal to zero from FY-3F and ERA5, respectively, while the orange bars indicate their overlapping areas.