Evaluations of Environmental Trace Gases Monitoring Instrument (EMI) Level 1 Data [星载痕量气体差分吸收光谱仪1级数据质量评价]

作者：Cheng L.-X.; Tao J.-H.^*; Zhou H.-J.; Yu C.; Fan M.; Wang Y.-P.; Wang Z.-B.; Chen L.-F.

来源：Spectroscopy and Spectral Analysis, 2021, 41(12): 3881-3886.

DOI：10.3964/j.issn.1000-0593(2021)12-3881-06

• Data quality
• EMI
• GF-5
• Slit function
• Wavelength calibration

The Environmental trace gases Monitoring Instrument (EMI) is the first high spectral resolution imaging spectrometer in China designed to monitor trace gas in tropospheric and stratospheric. To fully understand the instrument's characteristics and make better use of the level 1 (L1) data, comprehensive evaluations of irradiance and radiance data measured by the EMI instrument were carried out in this study. For both ultraviolet-2 and visible-1 bands, the slit function change drastically as a function of detectors in the across-track direction of charge-coupled device (CCD), which is more than 6 times larger than that of TROP(OMI). The use of different slit functions according to the row can improve the calibration accuracy. Small wavelength shifts were found in both irradiance and radiance data with an average value of 0.015 and 0.03 nm, respectively. Although they meet the requirement of the design specification (0.05 nm), wavelength calibration is still needed during the trace gas retrieval. EMI irradiance data agree highly (r>0.95) with OMI and TROPOMI and the reference solar spectrum. EMI radiance data also shows a better agreement (r>0.93) with OMI and TROPOMI by averaging the cloud-free pixels over the clean Pacific region. This study demonstrates the good quality of current EMI L1 data for trace gas retrieval, and it provides a reference for the design and data quality evaluation scheme of subsequent instruments.

• 单位
  中国科学院大学; 遥感科学国家重点实验室