Sea Surface and Snowflakes as Natural Targets Connecting FY‐3G and GPM‐CO Dual‐Frequency Radars

• Published in: Geophysical research letters 2024-12, Vol.51 (23), p.n/a
• Main Authors: Liu, Bo, Li, Haoran, Liu, Liping, Shang, Jian, Yin, Honggang, Kuo, Kwo‐Sen
• Format: Article
• Language: English
• Subjects: Calibration; Global precipitation; Hydrometeors; Missions; Observatories; Precipitation; Precipitation measurements; Radar; Radar calibration; Radar data; Radar signatures; Reflectance; Satellite observation; Satellite tracking; Satellites; Sea surface; Snowflakes; Tracking
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2024GL110878

The Precipitation Measurement Radar (PMR) onboard FengYun‐3G consists of a Ku‐/Ka‐band radar, which is characterized by similar configurations with the Dual‐frequency Precipitation Radar (DPR) carried by Global Precipitation Measurement mission Core Observatory. However, directly comparing observations from two radars is challenging due to a scarcity of their coincidences. In this study, sea surface echoes in their track intersections were employed to cross‐calibrate PMR. Then, we show that the dual‐frequency ratio (DFR) in snow stably increases with Ku‐band reflectivity in statistics, allowing for an assessment of the consistency between PMR and DPR observations. Surprisingly, our results reveal a underestimation of DFR in DPR inner swath, while observations from PMR are in good agreement with those from DPR outer swath. This study demonstrates the novel use of natural targets for spaceborne dual‐frequency radar calibration, and presents a unique view into the connection between the two spaceborne precipitation radar missions in operation. Plain Language Summary Spaceborne cloud and precipitation radars allow global characterization of hydrometeors and have been extensively used in various disciplines. Synergistic applications of radar observations from multiple satellites largely enhance the wealth of radar data offers, while the physical interpretation of radar observations relies on assured data consistency from different platforms. Similar with the Dual‐frequency Precipitation Radar (DPR) onboard Global Precipitation Measurement mission Core Observatory satellite, FengYun‐3G (FY‐3G) carries China's first spaceborne precipitation radar, a Ku‐/Ka‐band Precipitation Measurement Radar (PMR). However, it is challenging to directly compare the radar observations from the two satellites since their tracks rarely intersect simultaneously with precipitation. Here, we show how natural targets can be used for connecting observations from the two satellite missions. First, we use sea surface echoes observed by DPR in their intersections to calibrate the radar onboard FY‐3G. Then, we show that the dual‐frequency signatures of snowflakes as observed by the Ku‐/Ka‐band radar can be used to validate the radar observations from the two satellites. This is the first comparison between dual‐frequency radar observations from the two spaceborne precipitation radar missions, laying the basis for synergetic use of their observations in the future. Key Points Sea surface ech