Abstract：
In 2019, South Korea launched the Geostationary Environment Monitoring Spectrometer (GEMS) to observe trace gases with an hourly temporal resolution. Compared to previous payloads on polar-orbiting satellites, the GEMS payload has significant advantages in detecting the diurnal variation characteristics of NO2. However, there is still a lack of ground-based validations regarding the overall accuracy of GEMS in the Chinese region. In this study, we conducted a systematic ground validation of GEMS NO2 data in China for the first time. We validated the accuracy of GEMS NO2 data in four typical pollution regions in China, namely the Beijing-Tianjin-Hebei region (JJJ), the Yangtze River Delta region (YRD), the Pearl River Delta region (PRD), and the Sichuan Basin region (SCB), based on MAX-DOAS and CNEMC data. The averaged correlations using the two datasets for validation were 0.81 and 0.57, respectively, indicating a high level of accuracy for the data in China. Using the GEMS seasonal averaged NO2 data, we studied the distribution of NO2 levels in the four regions. We found that the highest NO2 in all four regions occurred during winter with concentrations of 1.84 × 1016 molecules cm-2, 1.59 × 1016 molecules cm-2, 1.58 × 1016 molecules cm-2 and 9.47 × 1015 molecules cm-2, respectively. The distribution of NO2 was closely related to the terrain. Additionally, we observed a significant underestimation issue with TROPOMI, exceeding 30 % in many regions. Based on MAX-DOAS, we investigated the vertical distribution of NO2 in the four regions and found that NO2 was mainly concentrated below 0.5 km. with the HNU station having the lowest concentration, averaging only 2.12 ppb, which was approximately 41 % of the highest concentration recorded at the CQ station. Furthermore, we conducted a study on regional and cross-regional transport using a combination of MAX-DOAS and GEMS data. We found that the transport flux of NO2 could increase by over 500 % within 1 h, making a significant contribution to local NO2 concentrations. The joint observations of GEMS and MAX-DOAS will provide reliable data support for NO2 research and control in China, making a substantial contribution to environmental protection and sustainable development.
摘要：
2019年，韩国推出了地球静止环境监测光谱仪（GEMS），以每小时的时间分辨率观测痕量气体。与以前极地轨道卫星上的有效载荷相比，GEMS有效载荷在检测NO2的日变化特征方面具有显著优势。然而,关于GEMS在中国地区的总体准确性，仍然缺乏地面验证。在这项研究中,我们首次对中国GEMSNO2数据进行了系统的地面验证。我们验证了GEMSNO2数据在中国四个典型污染区域的准确性，即京津冀地区(JJJ)，长江三角洲地区（YRD），珠江三角洲地区（PRD），和四川盆地地区（SCB），基于MAX-DOAS和CNEMC数据。使用两个数据集进行验证的平均相关性分别为0.81和0.57，这表明中国的数据具有很高的准确性。使用GEMS季节性平均NO2数据，我们研究了四个区域中NO2水平的分布。我们发现，所有四个区域中最高的NO2发生在冬季，浓度分别为1.84×1016分子cm-2，1.59×1016分子cm-2，1.58×1016分子cm-2和9.47×1015分子cm-2。NO2的分布与地形密切相关。此外,我们观察到TROPOMI存在严重的低估问题，在许多地区超过30%。基于MAX-DOAS,我们调查了四个地区NO2的垂直分布，发现NO2主要集中在0.5km以下。HNU站的浓度最低，平均只有2.12ppb，约为CQ站记录的最高浓度的41%。此外，我们结合MAX-DOAS和GEMS数据对区域和跨区域运输进行了研究。我们发现NO2的传输通量可以在1小时内增加500%以上，对当地NO2浓度有显著贡献。GEMS和MAX-DOAS的联合观测将为中国的NO2研究和控制提供可靠的数据支持，为环境保护和可持续发展做出重大贡献。
