Successful Derivation of Absorbing Aerosol Index from the Environmental Trace Gases Monitoring Instrument (EMI)

We retrieved the absorbing aerosol index (AAI) based on the measured reflectance from the Environmental Trace Gases Monitoring Instrument (EMI) for the first time. EMI is a push-broom spectrometer onboard the Chinese GeoFen-5 satellite launched on 9 May 2018, which was initially developed to determine the global distribution of atmospheric composition. The EMI initial AAI results were corrected from physical stripes and yielded an offset of 5.92 as calibration errors from a background value based on the statistical method that count the EMI AAI over the Pacific Ocean under cloudless scenes. We also evaluated the consistency of the EMI AAI and data with the TROPOspheric Monitoring Instrument (TROPOMI) observations. A comparison between the monthly average EMI AAI data and TROPOMI AAI revealed regional consistencies between these instruments with a similar spatial distribution of AAI (correlation coefficient, r > 0.9). The daily-scale results demonstrated that EMI was also consistent with TROPOMI AAI (r = 0.9). The spatial distribution of EMI AAI is consistent with Aerosol Optical Depth (AOD) from TROPOMI. The daily variation of EMI AAI in an Australian wildfire event was consistent with TROPOMI (r = 0.92). Overall, we demonstrated that EMI AAI can be efficiently used to detect large aerosol events for reconstructing the spatial variability of Ultraviolet (UV) absorbing aerosols.

Automated summary

This study presented the retrieval of absorbing aerosol index (AAI) for the first time using the Environmental Trace Gases Monitoring Instrument (EMI) on the Chinese GeoFen-5 satellite. The results showed that EMI AAI was consistent with TROPOMI AAI, both in terms of regional distribution and daily variations. The study demonstrated that EMI AAI can be effectively used to detect large aerosol events and reconstruct the spatial variability of UV absorbing aerosols.