Abstract
Onboard the Chinese GaoFen-5 (GF5) satellite, the Environmental trace gases Monitoring Instrument (EMI) is a nadir-viewing wide-field spectrometer that was launched on May 9, 2018. EMI measures the back-scattered earthshine solar radiance in the ultraviolet and visible spectral range. By using the differential optical absorption spectrometry (DOAS) method and the EMI measurements in the VIS1 band (405–465 nm), we performed retrievals of NO2. Some first retrieval results of NO2 from EMI and a comparison with OMI and TROPOMI products are presented in this paper. The monthly mean total vertical column densities (VCD) of NO2 show similar spatial distributions to OMI and TROPOMI (r > 0.88) and their difference is less than 27%. A comparison of the daily total VCD shows that EMI could detect the NO2 patterns in good agreement with OMI (r = 0.93) and TROPOMI (r = 0.95). However, the slant column density (SCD) uncertainty (0.79 × 1015 molec cm−2) of the current EMI algorithm is relatively larger than OMI. The daily variation pattern of NO2 from EMI in Beijing in January 2019 is consistent with TROPOMI (r = 0.96). The spatial distribution correlation of the tropospheric NO2 VCD of EMI with OMI and TROPOMI is 0.88 and 0.89, respectively, but shows an overestimate compared to OMI (15%) and TROPOMI (23%), respectively. This study demonstrates the capability of using EMI for global NO2 monitoring.
Highlights
Nitrogen oxides (NOx=NO+NO2) play a key role in both stratospheric and tropospheric chemistry
In order to further monitor the air pollution, as well as improve the air quality on a global scale, the Environmental trace gases Monitoring Instrument (EMI), which is the main focus of this study, is located onboard the Chinese GaoFen-5 (GF5) satellite launched on 9 May, 2018 [21,22]
The selection of this date is due to the severe NO2 pollution on this day, and it is clear, so there are few pixels contaminated by cloud and few Ozone Monitoring Instrument (OMI) pixels affected by “row anomaly”
Summary
Nitrogen oxides (NOx=NO+NO2) play a key role in both stratospheric and tropospheric chemistry. In order to further monitor the air pollution, as well as improve the air quality on a global scale, the Environmental trace gases Monitoring Instrument (EMI), which is the main focus of this study, is located onboard the Chinese GaoFen-5 (GF5) satellite launched on 9 May, 2018 [21,22] It is the first sensor designed in China for trace gas monitoring with a relatively higher spatial resolution (13 × 12 km2) than OMI. The a priori NO2 profiles used in the AMF calculations are from the GMI, which is a three-dimensional CTM, with 72 atmospheric vertical levels from the surface to 0.01 hPa. The stratosphere-troposphere separation (STS) adopted in the current NASA algorithm is the modified reference sector method (MRSM) proposed by Bucsela et al (2013). The baseline STS method for TROPOMI includes the data assimilation of slant columns in the TM5-MP CTM, which provides an estimate of the stratospheric contribution to the NO2 slant columns
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
