Intercomparison of Total Column Ozone Between Ozonesonde Observations and Multi-source Products Across 4 Regions

The intercomparison of vertically integrated total ozone columns (Ωo) derived from 212 CYT-1 ozonesonde observations is conducted at 4 representative Chinese sites: Altay (Xinjiang, 47.7°N), Nenjiang (Heilongjiang, 49.1°N), Shanghai (31.4°N), and Sanya (Hainan, 18.2°N), from September 2022 to April 2023, with multi-source products. Through bias analysis and Pearson correlation analysis, the ozonesonde-derived Ωo values are systematically compared with total ozone column values from satellite measurements(collectively referred to as Ωs) and reanalysis datasets (collectively referred to as Ωr). The satellite products include TROPOMI, Suomi-NPP, GOME-2B, GOME-2C, OMI-TOMS, and OMI-DOAS, and the reanalysis datasets include ERA5, MERRA-2, and MSR. Since total ozone columns predominantly reflect stratospheric ozone concentrations, this intercomparison is considered important for validating the measurement accuracy of CYT-1 ozonesonde in stratosphere. Findings indicate that the peak of the ozone layer and the height of occurrence change with latitude, and Ωo can reflect the characteristics of four regions with latitude. The range of Ωo is found to be 250-350 DU in Altay, 300-500 DU in Nenjiang, 220-300 DU in Shanghai, and 200-250 DU in Sanya. Compared with Ωs, the average relative deviation of Ωo from CYT-1 ozonesonde ranges from 0.3% to 3.5% in Altay; compared with Ωr, the average relative deviations of Ωo from CYT-1 ozonesonde are -5.1% to -1.5% in Nenjiang, -8% to -4.2% in Shanghai, and -10.5% to -6.5% in Sanya. It indicates that a larger negative averaged bias is observed at lower latitudes. Correlation coefficients are greater than 0.7 at mid- high-latitude sites (Altay, Nenjiang, Shanghai), but they decrease below 0.5 at low-latitude site (Sanya), which shows weaker agreement. In stratosphere, the pump efficiency coefficient of the ozonesonde (collectively referred to as Cef(Z)) is affected by decreasing air pressure, and instability is observed. As a result, deviations of ozone measurements in stratosphere are caused. This is considered to be a possible cause why deviations between Ωo and Ωs, Ωr become larger in low-latitude regions such as Shanghai and Sanya. In addition, it is suggested that detailed tests and analyses of Cef(Z) for CYT-1 ozonesondes should be carried out in the future. The accuracy and stability of Cef(Z) in stratosphere can be improved through improvements in mechanical design or updates to correction algorithms. Further improvements are expected to reduce measurement bias and enhance data reliability under varying atmospheric conditions.