First Observation of Ozone in the Troposphere Using the GaoFen-5 Satellite's Environmental Trace Gases Monitoring Instrument 2

The Environmental Trace Gases Monitoring Instrument 2 (EMI-02) payload, embarked on a hyperspectral observation satellite, was launched on September 7, 2021. The satellite's transit time is 10:30 local time. This article, drawing on data from EMI-02, introduces a methodology for measuring the tropical tropospheric ozone column (TOC) using the convective-cloud-differential method. We successfully applied this method to derive TOC in tropical regions from the EMI-02 data. The results indicate a general consistency between the EMI-02 TOC and TROPOspheric Monitoring Instrument (TROPOMI) TOC. However, owing to the difference in transit times, the TOC observed by TROPOMI at 13:30 is higher than that observed by EMI-02 at 10:30. Comparisons with ozonesonde data revealed discrepancies attributed to varying observation times, but nonetheless presented a high degree of consistency. These findings affirm the efficacy of our algorithm in providing reliable and precise TOC data. This capability is instrumental in understanding the diurnal variations of tropical TOC, where concentrations are higher in the afternoon than in the morning. The characteristics of tropical TOC varied by month. From June to October, the tropical TOC predominantly accumulated over the South Atlantic region, whereas, it tended to disperse and distribute near the 20°N latitude from November to May.