An In-Orbit Tangent Height Validation and Correction Method for OMS-L/FY-3F

Tangent height (TH) offsets are the primary source of uncertainty in limb sounding. Due to the absence of a star tracker, the Ozone Monitoring Suite-Limb (OMS-L) aboard the Fengyun-3F satellite cannot provide a direct and accurate reference for TH validation, making it difficult to quantify the TH offsets. In this paper, an in-orbit TH validation and correction algorithm was established for OMS-L based on the vertical structure of ultraviolet limb-scattered radiance (LSR) profiles. The knee of the LSR profile at 305 nm was employed as an equivalent TH reference, enabling rapid determination and correction of TH offsets. Sensitivity analysis indicated that the algorithm accuracy was within ±300 m, and the impact of algorithm uncertainty on the 320 nm LSR simulations and the ozone profile retrievals did not exceed ±4% and ±8%, respectively. The above algorithm was applied to OMS-L TH data from November 2024 to March 2025. The results showed that OMS-L TH offsets generally remained within ±1 km. After TH correction, the LSR simulations were more accurate and consistent with measurements, with a correlation coefficient of 0.973.