Inspection of FY-3D Satellite Temperature Data Based on Horizontal Drift Round-trip Sounding Data

The horizontal drift round-trip sounding observation is a new sounding technology developed by China Meteorological Administration. By releasing one sounding balloon with this technology, three sections of observations can be obtained, including two sections of vertical tropospheric sounding(ascending and descending) with an interval of about 6 hours and a 4-hour horizontal sounding within the stratosphere. This technology effectively makes up for the insufficiency of conventional soundings, improving the time and space resolution of radiosonde data at a lower cost. The detection system adopts Beidou radiosonde, which significantly improves the accuracy of sounding and wind measurements. In addition, the drift section of horizontal drift round-trip sounding observation fills the gap of the stratospheric temperature detection technology in China. Therefore, horizontal drift round-trip sounding data can be used to verify the temperature profile and stratosphere temperature data of meteorological satellite.Fengyun series meteorological satellites are widely used in China, supporting the meteorological forecast in the Eastern Hemisphere. Among Fengyun satellites in use, FY-3D has the longest years of service. To test the accuracy of FY-3D satellite temperature products, an algorithm is designed according to the characteristics of the horizontal drift round-trip sounding data and satellite data, and the temporal and spatial thresholds are calculated. Based on this algorithm, FY-3D satellite retrieved atmospheric temperature data are verified using the horizontal drift round-trip sounding data in the middle and lower reaches of the Yangtze from March to September in 2021. It can be concluded from the inspection results that the temperature data of FY-3D satellite has a high accuracy, with an average absolute deviation of about 1.34℃ from the data of ascending section and 1.9℃ from the data of descending section. Above 100 hPa and below 850 hPa, the temperature errors of satellite data are 0.59℃ and 0.33℃ larger, respectively. The average absolute deviation of the stratosphere is about 3.92℃, which is slightly larger than the ascending section and descending section. Compared with the sounding profile, the satellite temperature profile has lower vertical resolution and smoother trend, so it cannot show more details of atmospheric vertical variation.