Validation and Correction of In-Orbit Tangent Height for the Ozone Monitoring Suite-Limb onboard FY-3F

Limb sounding can provide fine vertical profiles of atmospheric constituents, while 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 (FY-3F) satellite cannot provide direct geometric references for TH validation, making it difficult to quantify the TH offsets. In this paper, an in-orbit TH validation and correction algorithm is developed for OMS-L based on the vertical structure of ultraviolet limb-scattered radiance (LSR) profiles. The knee of the LSR profile at 305 nm is employed as an equivalent TH reference, enabling rapid determination and correction of TH offsets. Sensitivity analysis indicates that the algorithm accuracy is within ±300 m, and the impact of algorithm uncertainty on the 320-nm LSR simulations and the ozone profile retrievals is within ±4% and ±8%, respectively. The above algorithm is applied to OMS-L TH data from November 2024 to March 2025. The results show that OMS-L TH offsets generally remain within ±1 km. After TH correction, the LSR simulations show better agreement with the measurements, with a correlation coefficient of 0.973.