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

The intercomparison of vertically integrated total ozone columns (Ω_o) 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 Ω_o values are systematically compared with total ozone column values from satellite measurements(collectively referred to as Ω_s) and reanalysis datasets (collectively referred to as Ω_r). 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 Ω_o can reflect the characteristics of four regions with latitude. The range of Ω_o 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 Ω_s, the average relative deviation of Ω_o from CYT-1 ozonesonde ranges from 0.3% to 3.5% in Altay; compared with Ω_r, the average relative deviations of Ω_o 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 C_ef(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 Ω_o and Ω_s, Ω_r become larger in low-latitude regions such as Shanghai and Sanya. In addition, it is suggested that detailed tests and analyses of C_ef(Z) for CYT-1 ozonesondes should be carried out in the future. The accuracy and stability of C_ef(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.