# Retrieval of Cloud Ice Water Path from FY-3F MWTS and MWHS
###### Abstract  
Microwave sounding observations obtained from the National Oceanic and Atmospheric Administration (NOAA) and the European Meteorological Operational Satellite Program (METOP) satellites have been used for retrieving the cloud ice water path (IWP). However, the IWP algorithms developed in the past cannot be applied to the Fengyun-3F (FY-3F) microwave radiometers due to the differences in frequency of the primary channels and the fields of view. In this study, the IWP algorithm was tailored for the FY-3F satellite, and the retrieved IWP was compared with the fifth generation of reanalysis data from the European Centre for Medium-Range Weather Forecasts (ERA5) and the Meteorological Operational Satellite-C (METOP-C) products. The results indicate that the IWP distribution retrieved from FY-3F observations demonstrates strong consistency with the cloud ice distributions in ERA5 data and METOP-C products in low-latitude regions. However, discrepancies are observed among the three datasets in mid- to high-latitude regions. ERA5 data underestimate the frequency of high IWP values and overestimate the frequency of low IWP values. The IWP retrieval results from satellite datasets demonstrate a high level of consistency. Furthermore, an analysis of the IWP time series reveals that the retrieval algorithm used in this study better captures variability and seasonal characteristics of IWP compared to ERA5 data. Additionally, a comparison of FY-3F retrieval results with METOP-C products shows a high correlation and generally consistent distribution characteristics across latitude bands. These findings confirm the high accuracy of IWP retrieval from FY-3F data, which holds significant value for advancing IWP research in China. cloud ice water; microwave sounding; FY-3F; METOP-C 20251717981717981717981717981717981  
for understanding the Earth's climate system. Satellite remote sensing utilizes various observational wavelengths to measure distinct cloud microphysical properties. For clouds with relatively low optical thickness, the IWP can be measured using visible light sensors [4]. For thicker ice clouds, microwave sensors provide more accurate IWP measurements [5]. Algorithms for retrieving IWP using dual-channel microwave measurements from airborne millimeter-wave imaging radiometers have been under development for some time [6]. [PERSON] and [PERSON] demonstrated that, for a given particle volume density, the relationship between IWP and the effective diameter of ice particles can be derived using a two-stream model, and both variables can be retrieved from microwave measurements at two distinct frequencies [7]. However, since most retrieval algorithms rely on in-situ measurements over tropical oceans using aircraft, the distinction between atmospheric ice clouds and surface scatterers has not been thoroughly analyzed. To address this, [PERSON] and [PERSON] proposed a new algorithm for retrieving IWP from Advanced Microwave Sounding Unit-A (AMSU-A) measurements at 89 GHz and 150 GHz, improving its suitability for satellite-based observations [8]. Both IWP and the effective diameter of ice particles are related to the scattering parameters of ice particles, which are measured at two frequency channels (89 GHz and 150 GHz) of AMSU-A. The ratio of the scattering parameters at these frequencies directly yields the effective diameter of ice particles. With the particle volume density known, the IWP can then be derived from the scattering parameter at 150 GHz. This improved algorithm enables more accurate global retrieval of the effective diameter of ice particles and IWP from satellite data [8]. [PERSON] et al. noted that millimeter-wave frequency radiometers are sensitive to heavier precipitation, whereas sub-millimeter-wave frequencies are more responsive to smaller ice particles [9]. [PERSON] and [PERSON] expanded the two-stream radiation model and utilized the constant scanning angle along the scan line of the satellite-borne MISR/VSI to retrieve ice cloud parameters [10]. [PERSON] et al.