EMI 云量反演及与TROPOMI 的对比研究

云参数是痕量气体反演过程中重要的输入参数, 对其准确反演具有重要意义。基于 2019 年 3 月大气痕量气 体差分吸收光谱仪 EMI 的观测数据, 利用 O4 在 477 nm 处的吸收特性进行有效云量的反演。为验证 EMI 云量反演的 准确性, 将 EMI 与 TROPOMI 的反演结果进行对比分析, 并对 2019 年 3 月 2 日、 6 日、 9 日和 10 日 EMI 和 TROPOMI 整天的云量进行了相关性分析, 相关性 R 分别为 0.752、 0.712、 0.764 和 0.762, 表明二者具有良好的相关性。进一步 选取了沙漠、海洋、陆地三个不同区域的云量分析了不同下垫面情况云量的分布特征, 发现在这三个区域, EMI 和 TROPOMI 的云量都具有较好的一致性, 并且海洋上空云量较低, 陆地上空云量较高, 而沙漠上空云量变化频繁。

Cloud Fraction Retrieval of EMI and Comparison With TROPOMI

As cloud parameters are important input parameters for retrieval of trace gases, it is of great significance for their accurate acquisition. Based on environmental trace gas monitoring instrument (EMI) observation on March 2019, the effective cloud fraction is retrieved by using the absorption feature of O4 at 477 nm. To verify the accuracy of EMI cloud algorithm, the retrieval cloud fraction of EMI is compared with TROPOMI cloud products, and the correlation analysis of EMI and TROPOMI cloud fraction on March 2, 6, 9 and 10, 2019 is carried out, and the cloud fraction correlation coefficient (R) is 0.752, 0.712, 0.764, and 0.762 respectively, indicating that the two results have good correlation. Furthermore, the cloud fractions of three different regions of desert, ocean, and land are selected to study the distribution characteristics of cloud fraction in different underlying surface. It is found that the cloud fractions of EMI and TROPOMI in the three regions are consistent, and the cloud fraction over the ocean is relatively low, the cloud fraction over the land is relatively high, and the cloud fraction over the desert changes frequently.