Data Quality Analysis of Wet Atmospheric Temperature Profiles from the YunYao Meteorological Constellation Radio Occultation

Radio occultation offers high vertical resolution, global coverage, and low sensitivity to clouds and precipitation, making it a useful complement to existing atmospheric sounding techniques. The YunYao constellation, the first commercial meteorological remote sensing constellation of China, supplies a large number of GNSS-RO temperature profile products, yet the quality of its wet atmospheric profiles remains undocumented. Using operational radiosonde data from 43 stations over southern China (97–123°E, 17–31°N) during boreal winter and early spring (1 November 2025 to 31 March 2026) as reference, this study evaluates the accuracy, error characteristics, and applicability of the YunYao wet atmospheric temperature profile product, with COSMIC-2 as an independent benchmark. YunYao yields 4.77 times the matched sample volume of COSMIC-2 over the same domain and period, while its RMSE is only 0.20–0.42 °C higher. Within 50–925 hPa, the YunYao profiles agree closely with radiosondes, with RMSE generally within 1–2 °C, a weak, spatially uniform cold bias, and small diurnal differences. Below 925 hPa, near-surface error grows markedly, dominated by enhanced random error rather than systematic error, with inland cold and coastal warm bias. A January maximum of random error is possibly related to super-refraction during peak winter monsoon cold surges, and a March sign reversal of the bias possibly related to the seasonal increase in boundary layer moisture ahead of the pre-flood season. With weak cold bias correction, YunYao temperature profiles are highly usable within 50–925 hPa, while data below 925 hPa require strict quality control.